NAME
grib2.h - Header file for NCEPLIBS-g2c library.
SYNOPSIS
#include
<stdio.h>
#include <stdint.h>
Data Structures
struct gribfield
Struct for GRIB field.
struct gtemplate
Struct for GRIB template.
Macros
#define G2_VERSION
’g2clib-1.6.4’
Current version of NCEPLIBS-g2c library.
Typedefs
typedef float g2float
Float type.
typedef int64_t g2int
Long integer type.
typedef uint64_t g2intu
Unsigned long integer type.
typedef struct gribfield gribfield
Struct for GRIB field.
typedef struct gtemplate gtemplate
Struct for GRIB template.
Functions
void compack
(g2float *, g2int, g2int, g2int
*, unsigned char *, g2int *)
This subroutine packs up a data field using a complex
packing algorithm as defined in the GRIB2 documention.
gtemplate * extdrstemplate (g2int,
g2int *)
This subroutine generates the remaining octet map for a
given Data Representation Template, if required.
gtemplate * extgridtemplate (g2int,
g2int *)
This subroutine generates the remaining octet map for a
given Grid Definition Template, if required.
gtemplate * extpdstemplate (g2int,
g2int *)
This subroutine generates the remaining octet map for a
given Product Definition Template, if required.
g2int g2_addfield (unsigned char *, g2int,
g2int *, g2float *, g2int,
g2int, g2int *, g2float *,
g2int, g2int, g2int *)
This routine packs up Sections 4 through 7 for a given field
and adds them to a GRIB2 message.
g2int g2_addgrid (unsigned char *, g2int *,
g2int *, g2int *, g2int)
This routine packs up a Grid Definition Section (Section 3)
and adds it to a GRIB2 message.
g2int g2_addlocal (unsigned char *, unsigned char *,
g2int)
This routine adds a Local Use Section (Section 2) to a GRIB2
message.
g2int g2_create (unsigned char *, g2int *,
g2int *)
This routine initializes a new GRIB2 message and packs GRIB2
sections 0 (Indicator Section) and 1 (Identification
Section).
void g2_free (gribfield *)
This routine frees up memory that was allocated for struct
gribfield.
g2int g2_getfld (unsigned char *, g2int,
g2int, g2int, gribfield **)
This subroutine returns all the metadata, template values,
Bit-map (if applicable), and the unpacked data for a given
data field.
g2int g2_gribend (unsigned char *)
This routine finalizes a GRIB2 message after all grids and
fields have been added.
g2int g2_info (unsigned char *, g2int *,
g2int *, g2int *, g2int *)
This subroutine searches through a GRIB2 message and returns
the number of gridded fields found in the message and the
number (and maximum size) of Local Use Sections.
g2int g2_unpack1 (unsigned char *, g2int *,
g2int **, g2int *)
This subroutine unpacks Section 1 (Identification Section)
as defined in GRIB Edition 2.
g2int g2_unpack3 (unsigned char *, g2int *,
g2int **, g2int **, g2int *,
g2int **, g2int *)
This routine unpacks Section 3 (Grid Definition Section) as
defined in GRIB Edition 2.
g2int g2_unpack4 (unsigned char *, g2int *,
g2int *, g2int **, g2int *,
g2float **, g2int *)
This subroutine unpacks Section 4 (Product Definition
Section) as defined in GRIB Edition 2.
g2int g2_unpack5 (unsigned char *, g2int *,
g2int *, g2int *, g2int **,
g2int *)
This subroutine unpacks Section 5 (Data Representation
Section) as defined in GRIB Edition 2.
g2int g2_unpack6 (unsigned char *, g2int *,
g2int, g2int *, g2int **)
This subroutine unpacks Section 6 (Bit-Map Section) as
defined in GRIB Edition 2.
g2int g2_unpack7 (unsigned char *, g2int *,
g2int, g2int *, g2int, g2int *,
g2int, g2float **)
This subroutine unpacks Section 7 (Data Section) as defined
in GRIB Edition 2.
void gbit (unsigned char *, g2int *,
g2int, g2int)
Get bits - unpack bits: Extract arbitrary size values from a
packed bit string, right justifying each value in the
unpacked iout array.
void gbits (unsigned char *, g2int *,
g2int, g2int, g2int, g2int)
Get bits - unpack bits: Extract arbitrary size values from a
packed bit string, right justifying each value in the
unpacked iout array.
gtemplate * getdrstemplate (g2int)
This subroutine returns DRS template information for a
specified Data Representation Template 5.NN.
gtemplate * getgridtemplate (g2int)
This subroutine returns grid template information for a
specified Grid Definition Template 3.NN.
gtemplate * getpdstemplate (g2int)
This subroutine returns PDS template information for a
specified Product Definition Template 4.NN.
double int_power (double, g2int)
Function similar to C pow() power function.
void misspack (g2float *, g2int,
g2int, g2int *, unsigned char *, g2int
*)
This subroutine packs up a data field using a complex
packing algorithm as defined in the GRIB2 documention.
void mkieee (g2float *, g2int *,
g2int)
This subroutine stores a list of real values in 32-bit IEEE
floating point format.
int pack_gp (g2int *, g2int *,
g2int *, g2int *, g2int *, g2int
*, g2int *, g2int *, g2int *,
g2int *, g2int *, g2int *, g2int
*, g2int *, g2int *, g2int *,
g2int *, g2int *, g2int *, g2int
*)
Determines groups of variable size, but at least of size
minpk, the associated max (jmax( )) and min (jmin( )), the
number of bits necessary to hold the values in each group
(lbit( )), the number of values in each group (nov( )), the
number of bits necessary to pack the jmin( ) values (ibit),
the number of bits necessary to pack the lbit( ) values
(jbit), and the number of bits necessary to pack the nov( )
values (kbit).
void rdieee (g2int *, g2float *,
g2int)
This subroutine reads a list of real values in 32-bit IEEE
floating point format.
void sbit (unsigned char *, g2int *,
g2int, g2int)
Store bits - put arbitrary size values into a packed bit
string, taking the low order bits from each value in the
unpacked array.
void sbits (unsigned char *, g2int *,
g2int, g2int, g2int, g2int)
Store bits - put arbitrary size values into a packed bit
string, taking the low order bits from each value in the
unpacked array.
void seekgb (FILE *, g2int, g2int,
g2int *, g2int *)
This subprogram searches a file for the next GRIB Message.
void simpack (g2float *, g2int,
g2int *, unsigned char *, g2int *)
This subroutine packs up a data field using the simple
packing algorithm as defined in the GRIB2 documention.
Detailed Description
Header file for NCEPLIBS-g2c library.
PROGRAM HISTORY LOG:
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2002-10-25 Gilbert |
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|
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2009-01-14 Vuong Changed struct template to gtemplate |
Each element of structure gribfield is defined as:
gribfield gfld;
gfld->version
= GRIB edition number ( currently 2 )
gfld->discipline = Message Discipline ( see Code Table
0.0 )
gfld->idsect = Contains the entries in the Identification
Section ( Section 1 )
This element is a pointer to an array
that holds the data.
gfld->idsect[0] = Identification of originating Centre
( see Common Code Table C-1 )
7 - US National Weather Service
gfld->idsect[1] = Identification of originating
Sub-centre
gfld->idsect[2] = GRIB Master Tables Version Number
( see Code Table 1.0 )
0 - Experimental
1 - Initial operational version number
gfld->idsect[3] = GRIB Local Tables Version Number
( see Code Table 1.1 )
0 - Local tables not used
1-254 - Number of local tables version used
gfld->idsect[4] = Significance of Reference Time (Code
Table 1.2)
0 - Analysis
1 - Start of forecast
2 - Verifying time of forecast
3 - Observation time
gfld->idsect[5] = Year ( 4 digits )
gfld->idsect[6] = Month
gfld->idsect[7) = Day
gfld->idsect[8] = Hour
gfld->idsect[9] = Minute
gfld->idsect[10] = Second
gfld->idsect[11] = Production status of processed data
( see Code Table 1.3 )
0 - Operational products
1 - Operational test products
2 - Research products
3 - Re-analysis products
gfld->idsect[12] = Type of processed data ( see Code
Table 1.4 )
0 - Analysis products
1 - Forecast products
2 - Analysis and forecast products
3 - Control forecast products
4 - Perturbed forecast products
5 - Control and perturbed forecast products
6 - Processed satellite observations
7 - Processed radar observations
gfld->idsectlen = Number of elements in
gfld->idsect[].
gfld->local = Pointer to character array containing
contents
of Local Section 2, if included
gfld->locallen = length of array gfld->local[]
gfld->ifldnum = field number within GRIB message
gfld->griddef = Source of grid definition (see Code Table
3.0)
0 - Specified in Code table 3.1
1 - Predetermined grid Defined by originating centre
gfld->ngrdpts = Number of grid points in the defined
grid.
gfld->numoct_opt = Number of octets needed for each
additional grid points definition.
Used to define number of
points in each row ( or column ) for
non-regular grids.
= 0, if using regular grid.
gfld->interp_opt = Interpretation of list for optional
points
definition. (Code Table 3.11)
gfld->igdtnum = Grid Definition Template Number (Code
Table 3.1)
gfld->igdtmpl = Contains the data values for the
specified Grid
Definition Template ( NN=gfld->igdtnum ). Each
element of this integer array contains an entry (in
the order specified) of Grid Defintion Template 3.NN
This element is a pointer to an array
that holds the data.
gfld->igdtlen = Number of elements in gfld->igdtmpl[].
i.e. number of
entries in Grid Defintion Template 3.NN
( NN=gfld->igdtnum ).
gfld->list_opt = (Used if gfld->numoct_opt .ne. 0)
This array
contains the number of grid points contained in
each row ( or column ). (part of Section 3)
This element is a pointer to an array
that holds the data. This pointer is nullified
if gfld->numoct_opt=0.
gfld->num_opt = (Used if gfld->numoct_opt .ne. 0) The
number of entries
in array ideflist. i.e. number of rows ( or columns )
for which optional grid points are defined. This value
is set to zero, if gfld->numoct_opt=0.
gfdl->ipdtnum = Product Definition Template Number (see
Code Table 4.0)
gfld->ipdtmpl = Contains the data values for the
specified Product
Definition Template ( N=gfdl->ipdtnum ). Each element
of this integer array contains an entry (in the
order specified) of Product Defintion Template 4.N.
This element is a pointer to an array
that holds the data.
gfld->ipdtlen = Number of elements in gfld->ipdtmpl[].
i.e. number of
entries in Product Defintion Template 4.N
( N=gfdl->ipdtnum ).
gfld->coord_list = Real array containing floating point
values
intended to document the vertical discretisation
associated to model data on hybrid coordinate
vertical levels. (part of Section 4)
This element is a pointer to an array
that holds the data.
gfld->num_coord = number of values in array
gfld->coord_list[].
gfld->ndpts = Number of data points unpacked and
returned.
gfld->idrtnum = Data Representation Template Number
( see Code Table 5.0)
gfld->idrtmpl = Contains the data values for the
specified Data
Representation Template ( N=gfld->idrtnum ). Each
element of this integer array contains an entry
(in the order specified) of Product Defintion
Template 5.N.
This element is a pointer to an array
that holds the data.
gfld->idrtlen = Number of elements in gfld->idrtmpl[].
i.e. number
of entries in Data Representation Template 5.N
( N=gfld->idrtnum ).
gfld->unpacked = logical value indicating whether the
bitmap and
data values were unpacked. If false,
gfld->bmap and gfld->fld pointers are nullified.
gfld->expanded = Logical value indicating whether the
data field
was expanded to the grid in the case where a
bit-map is present. If true, the data points in
gfld->fld match the grid points and zeros were
inserted at grid points where data was bit-mapped
out. If false, the data values in gfld->fld were
not expanded to the grid and are just a consecutive
array of data points corresponding to each value of
’1’ in gfld->bmap.
gfld->ibmap = Bitmap indicator ( see Code Table 6.0 )
0 = bitmap applies and is included in Section 6.
1-253 = Predefined bitmap applies
254 = Previously defined bitmap applies to this field
255 = Bit map does not apply to this product.
gfld->bmap = integer array containing decoded bitmap,
if gfld->ibmap=0 or gfld->ibap=254. Otherwise
nullified.
This element is a pointer to an array
that holds the data.
gfld->fld = Array of gfld->ndpts unpacked data points.
This element is a pointer to an array
that holds the data.
Author
Stephen Gilbert
Date
2002-10-25
Definition in file grib2.h.
Data Type Documentation
struct gribfield
Struct for GRIB field.
Definition at line 186 of file grib2.h.
Data Fields:
g2int * bmap
g2float * coord_list
g2int discipline
g2int expanded
g2float * fld
g2int griddef
g2int ibmap
g2int idrtlen
g2int * idrtmpl
g2int idrtnum
g2int * idsect
g2int idsectlen
g2int ifldnum
g2int igdtlen
g2int * igdtmpl
g2int igdtnum
g2int interp_opt
g2int ipdtlen
g2int * ipdtmpl
g2int ipdtnum
g2int * list_opt
unsigned char * local
g2int locallen
g2int ndpts
g2int ngrdpts
g2int num_coord
g2int num_opt
g2int numoct_opt
g2int unpacked
g2int version
struct gtemplate
Struct for GRIB template.
Definition at line 165 of file grib2.h.
Data Fields:
g2int * ext num
of octets of each entry in the extension
part of the template.
g2int extlen number of entries in the template extension.
g2int *
map num of octets of each entry in the
static part of the template.
g2int
maplen number of entries in the static part
of the template.
g2int
needext indicates whether or not the template needs
to be extended.
g2int num template number.
g2int type 3=Grid Defintion Template. 4=Product Defintion Template. 5=Data Representation Template.
Macro Definition Documentation
#define
G2_VERSION ’g2clib-1.6.4’
Current version of NCEPLIBS-g2c library.
Definition at line 156 of file grib2.h.
Typedef Documentation
typedef
float g2float
Float type.
Definition at line 160 of file grib2.h.
typedef
int64_t g2int
Long integer type.
Definition at line 158 of file grib2.h.
typedef
uint64_t g2intu
Unsigned long integer type.
Definition at line 159 of file grib2.h.
typedef
struct gribfield gribfield
Struct for GRIB field.
Definition at line 160 of file grib2.h.
typedef
struct gtemplate gtemplate
Struct for GRIB template.
Definition at line 160 of file grib2.h.
Function Documentation
void compack
(g2float * fld, g2int ndpts, g2int idrsnum, g2int *
idrstmpl, unsigned char * cpack, g2int * lcpack)
This subroutine packs up a data field using a complex
packing algorithm as defined in the GRIB2 documention. It
supports GRIB2 complex packing templates with or without
spatial differences (i.e. DRTs 5.2 and 5.3). It also fills
in GRIB2 Data Representation Template 5.2 or 5.3 with the
appropriate values.
Parameters
fld Contains the data
values to pack
ndpts The number of data values in array fld
idrsnum Data Representation Template number 5.N Must
equal 2 or 3.
idrstmpl Contains the array of values for Data
Representation Template 5.2 or 5.3.
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0 Reference value - ignored on input, set my compack(). |
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1 Binary Scale Factor |
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2 Decimal Scale Factor |
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6 Missing value management |
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7 Primary missing value |
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8 Secondary missing value |
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16 Order of Spatial Differencing ( 1 or 2 ) |
Parameters
cpack The packed data
field
lcpack length of packed field cpack.
Author
Stephen Gilbert
Date
2002-11-07
Definition at line 39 of file compack.c.
References int_power(), mkieee(), pack_gp(), sbit(), and sbits().
Referenced by cmplxpack().
gtemplate*
extdrstemplate (g2int number, g2int * list)
This subroutine generates the remaining octet map for a
given Data Representation Template, if required. Some
Templates can vary depending on data values given in an
earlier part of the Template, and it is necessary to know
some of the earlier entry values to generate the full octet
map of the Template.
PROGRAM HISTORY LOG:
|
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2000-05-11 Gilbert | ||
|
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2009-01-14 Vuong Changed structure name template to gtemplate |
Parameters
number NN, indicating
the number of the Data Representation Template 5.NN that is
being requested.
list The list of values for each entry in the the Data
Representation Template 5.NN.
Returns
Pointer to the returned template struct. Returns NULL pointer, if template not found.
Author
Stephen Gilbert
Date
2000-05-11
Definition at line 104 of file drstemplates.c.
References getdrsindex(), and getdrstemplate().
Referenced by g2_unpack5().
gtemplate*
extgridtemplate (g2int number, g2int * list)
This subroutine generates the remaining octet map for a
given Grid Definition Template, if required. Some Templates
can vary depending on data values given in an earlier part
of the Template, and it is necessary to know some of the
earlier entry values to generate the full octet map of the
Template.
PROGRAM HISTORY LOG:
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2000-05-09 Gilbert | ||
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2008-07-08 Vuong Added GDT 3.32768 Rotate Lat/Lon E-grid (Arakawa) | ||
|
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2009-01-14 Vuong Changed structure name template to gtemplate | ||
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2010-05-11 Vuong Added GDT 3.32769 Rotate Lat/Lon Non-E Staggered grid (Arakawa) | ||
|
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2013-08-06 Vuong Added GDT 3.4,3.5,3.12,3.101,3.140 |
Parameters
number NN, indicating
the number of the Grid Definition Template 3.NN that is
being requested.
list The list of values for each entry in the Grid
Definition Template.
Returns
Pointer to the returned template struct. Returns NULL pointer, if template not found.
Author
Stephen Gilbert
Date
2000-05-09
Definition at line 119 of file gridtemplates.c.
References getgridindex(), and getgridtemplate().
Referenced by g2_addgrid(), and g2_unpack3().
gtemplate*
extpdstemplate (g2int number, g2int * list)
This subroutine generates the remaining octet map for a
given Product Definition Template, if required. Some
Templates can vary depending on data values given in an
earlier part of the Template, and it is necessary to know
some of the earlier entry values to generate the full octet
map of the Template.
Parameters
number NN, indicating
the number of the Product Definition Template 4.NN that is
being requested.
list The list of values for each entry in the the
Product Definition Template 4.NN.
Returns
Pointer to the returned template struct. Returns NULL pointer, if template not found.
Author
Stephen Gilbert
Date
2000-05-11
Definition at line 108 of file pdstemplates.c.
References getpdsindex(), and getpdstemplate().
Referenced by g2_addfield(), and g2_unpack4().
g2int
g2_addfield (unsigned char * cgrib, g2int ipdsnum, g2int *
ipdstmpl, g2float * coordlist, g2int numcoord, g2int
idrsnum, g2int * idrstmpl, g2float * fld, g2int ngrdpts,
g2int ibmap, g2int * bmap)
This routine packs up Sections 4 through 7 for a given field
and adds them to a GRIB2 message. They are Product
Definition Section, Data Representation Section, Bit-Map
Section and Data Section, respectively.
This routine is used with routines g2_create(), g2_addlocal(), g2_addgrid(), and g2_gribend() to create a complete GRIB2 message. g2_create() must be called first to initialize a new GRIB2 message. Also, routine g2_addgrid() must be called after g2_create() and before this routine to add the appropriate grid description to the GRIB2 message. Also, a call to g2_gribend() is required to complete GRIB2 message after all fields have been added.
PROGRAM HISTORY LOG:
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2002-11-05 Gilbert | ||
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2002-12-23 Gilbert - Added complex spherical harmonic packing | ||
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2003-08-27 Gilbert - Added support for new templates using PNG and JPEG2000 algorithms/templates. | ||
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2004-11-29 Gilbert - JPEG2000 now allowed to use WMO Template no. 5.40 PNG now allowed to use WMO Template no. 5.41 |
•
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Added check to determine if packing algorithm failed. | |||
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2005-05-10 Gilbert - Imposed minimum size on cpack, used to hold encoded bit string. | ||
|
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2009-01-14 Vuong Changed structure name template to gtemplate |
Parameters
cgrib Char array that
contains the GRIB2 message to which sections 4 through 7
should be added. Must be allocated large enough to store the
entire GRIB2 message.
ipdsnum Product Definition Template Number (see Code
Table 4.0).
ipdstmpl Contains the data values for the specified
Product Definition Template (N=ipdsnum). Each element of
this integer array contains an entry (in the order
specified) of Product Defintion Template 4.N.
coordlist Array containg floating point values intended
to document the vertical discretisation associated to model
data on hybrid coordinate vertical levels.
numcoord number of values in array coordlist.
idrsnum Data Representation Template Number (see Code
Table 5.0).
idrstmpl Contains the data values for the specified Data
Representation Template (N=idrsnum). Each element of this
integer array contains an entry (in the order specified) of
Data Representation Template 5.N. Note that some values in
this template (eg. reference values, number of bits, etc...)
may be changed by the data packing algorithms. Use this to
specify scaling factors and order of spatial differencing,
if desired.
fld Array of data points to pack.
ngrdpts- Number of data points in grid. i.e. size of fld
and bmap.
ibmap - Bitmap indicator (see Code Table 6.0)
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0 = bitmap applies and is included in Section 6. | ||
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1-253 = Predefined bitmap applies. | ||
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254 = Previously defined bitmap applies to this field. | ||
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255 = Bit map does not apply to this product. |
bmap Integer array containing bitmap to be added. (if ibmap=0).
Returns
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> 0 Current size of updated GRIB2 message | ||
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-1 GRIB message was not initialized. Need to call routine g2_create() first. | ||
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-2 GRIB message already complete. Cannot add new section. | ||
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-3 Sum of Section byte counts doesn’t add to total byte count. | ||
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-4 Previous Section was not 3 or 7. | ||
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-5 Could not find requested Product Definition Template. | ||
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-6 Section 3 (GDS) not previously defined in message. | ||
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-7 Tried to use unsupported Data Representationi Template. | ||
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-8 Specified use of a previously defined bitmap, but one does not exist in the GRIB message. | ||
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-9 GDT of one of 5.50 through 5.53 required to pack field using DRT 5.51. | ||
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-10 Error packing data field. |
Note
Note that the Sections 4 through 7 can only follow Section 3 or Section 7 in a GRIB2 message.
Author
Stephen Gilbert
Date
2002-11-05
Definition at line 103 of file g2_addfield.c.
References cmplxpack(), gtemplate::ext, gtemplate::extlen, extpdstemplate(), gbit(), getdim(), getdrstemplate(), getpdstemplate(), getpoly(), jpcpack(), gtemplate::map, gtemplate::maplen, mkieee(), gtemplate::needext, pngpack(), sbit(), sbits(), simpack(), and specpack().
g2int
g2_addgrid (unsigned char * cgrib, g2int * igds, g2int *
igdstmpl, g2int * ideflist, g2int idefnum)
This routine packs up a Grid Definition Section (Section 3)
and adds it to a GRIB2 message. It is used with routines
g2_create(), g2_addlocal(),
g2_addfield(), and g2_gribend() to create a
complete GRIB2 message. g2_create() must be called
first to initialize a new GRIB2 message.
Parameters
cgrib Char array that
contains the GRIB2 message to which section should be added.
Must be allocated large enough to store the entire GRIB2
message.
igds Contains information needed for GRIB Grid
Definition Section 3. Must be dimensioned >= 5.
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igds[0] Source of grid definition (see Code Table 3.0) | ||
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igds[1] Number of grid points in the defined grid. | ||
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igds[2] Number of octets needed for each additional grid points definition. Used to define number of points in each row (or column) for non-regular grids. = 0, if using regular grid. | ||
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igds[3] Interpretation of list for optional points definition. (Code Table 3.11) | ||
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igds[4] Grid Definition Template Number (Code Table 3.1) |
igdstmpl
Contains the data values for the specified Grid Definition
Template (NN=igds[4]). Each element of this integer array
contains an entry (in the order specified) of Grid Defintion
Template 3.NN
ideflist (Used if igds[2] != 0) This array contains the
number of grid points contained in each row (or column).
idefnum (Used if igds[2] != 0) The number of entries in
array ideflist. i.e. number of rows (or columns) for which
optional grid points are defined.
Returns
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> 0 Current size of updated GRIB2 message | ||
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-1 GRIB message was not initialized. Need to call routine gribcreate first. | ||
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-2 GRIB message already complete. Cannot add new section. | ||
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-3 Sum of Section byte counts doesn’t add to total byte count | ||
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-4 Previous Section was not 1, 2 or 7. | ||
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-5 Could not find requested Grid Definition Template. |
Note
The Grid Def Section ( Section 3 ) can only follow Section 1, 2 or Section 7 in a GRIB2 message.
PROGRAM HISTORY LOG
|
• |
2002-11-01 Gilbert | ||
|
• |
2009-01-14 Vuong Changed structure name template to gtemplate |
Author
Stephen Gilbeert
Date
2002-11-01
Definition at line 60 of file g2_addgrid.c.
References gtemplate::ext, extgridtemplate(), gtemplate::extlen, gbit(), getgridtemplate(), gtemplate::map, gtemplate::maplen, gtemplate::needext, sbit(), and sbits().
g2int
g2_addlocal (unsigned char * cgrib, unsigned char * csec2,
g2int lcsec2)
This routine adds a Local Use Section (Section 2) to a GRIB2
message. It is used with routines g2_create(),
g2_addgrid(), g2_addfield(), and
g2_gribend() to create a complete GRIB2 message.
g2_create() must be called first to initialize a new
GRIB2 message.
Parameters
cgrib Char array that
contains the GRIB2 message to which section 2 should be
added. Must be allocated large enough to store the entire
GRIB2 message.
csec2 Character array containing information to be added
in Section 2.
lcsec2 Number of bytes of character array csec2 to be
added to Section 2.
Returns
> 0 = Current size of updated GRIB2 message.
|
• |
-1 GRIB message was not initialized. Need to call routine gribcreate first. | ||
|
• |
-2 GRIB message already complete. Cannot add new section. | ||
|
• |
-3 Sum of Section byte counts doesn’t add to total byte count | ||
|
• |
-4 Previous Section was not 1 or 7. |
Note
The Local Use Section (Section 2) can only follow Section 1 or Section 7 in a GRIB2 message.
Author
Stephen Gilbeert
Date
2002-11-01
Definition at line 37 of file g2_addlocal.c.
References gbit(), and sbit().
g2int
g2_create (unsigned char * cgrib, g2int * listsec0, g2int *
listsec1)
This routine initializes a new GRIB2 message and packs GRIB2
sections 0 (Indicator Section) and 1 (Identification
Section). This routine is used with routines
g2_addlocal(), g2_addgrid(),
g2_addfield(), and g2_gribend() to create a
complete GRIB2 message. g2_create() must be called
first to initialize a new GRIB2 message. Also, a call to
g2_gribend() is required to complete GRIB2 message
after all fields have been added.
Parameters
cgrib Character array to
contain the GRIB2 message. Must be allocated large enough to
store the entire GRIB2 message.
listsec0 Contains information needed for GRIB Indicator
Section 0. Must be dimensioned >= 2.
|
• |
listsec0[0]=Discipline-GRIB Master Table Number (see Code Table 0.0) | ||
|
• |
listsec0[1]=GRIB Edition Number (currently 2) |
listsec1 Contains information needed for GRIB Identification Section 1. Must be dimensioned >= 13.
|
• |
listsec1[0] Id of orginating centre (Common Code Table C-1) | ||
|
• |
listsec1[1] Id of orginating sub-centre (local table) | ||
|
• |
listsec1[2] GRIB Master Tables Version Number (Code Table 1.0) | ||
|
• |
listsec1[3] GRIB Local Tables Version Number (Code Table 1.1) | ||
|
• |
listsec1[4] Significance of Reference Time (Code Table 1.2) | ||
|
• |
listsec1[5] Reference Time - Year (4 digits) | ||
|
• |
listsec1[6] Reference Time - Month | ||
|
• |
listsec1[7] Reference Time - Day | ||
|
• |
listsec1[8] Reference Time - Hour | ||
|
• |
listsec1[9] Reference Time - Minute | ||
|
• |
listsec1[10] Reference Time - Second | ||
|
• |
listsec1[11] Production status of data (Code Table 1.3) | ||
|
• |
listsec1[12] Type of processed data (Code Table 1.4) |
Returns
- > 0 Current size of new GRIB2 message
|
• |
-1 Tried to use for version other than GRIB Edition 2 |
This routine is intended for use with routines g2_addlocal(), g2_addgrid(), g2_addfield(), and g2_gribend() to create a complete GRIB2 message.
Author
Stephen Gilbeert
Date
2002-10-31
Definition at line 52 of file g2_create.c.
References MAPSEC1LEN, and sbit().
void g2_free
(gribfield * gfld)
This routine frees up memory that was allocated for struct
gribfield.
Parameters
gfld pointer to gribfield structure (defined in include file grib2.h) returned from routine g2_getfld().
Note
This routine must be called to free up memory used by the decode routine, g2_getfld(), when user no longer needs to reference this data.
Author
Stephen Gilbeert
Date
2002-10-28
Definition at line 24 of file g2_free.c.
g2int
g2_getfld (unsigned char * cgrib, g2int ifldnum, g2int
unpack, g2int expand, gribfield ** gfld)
This subroutine returns all the metadata, template values,
Bit-map (if applicable), and the unpacked data for a given
data field. All of the information returned is stored in a
gribfield structure, which is defined in file
grib2.h. Users of this routine will need to include
grib2.h in their source code that calls this
routine.
Since there can be multiple data fields packed into a GRIB2 message, the calling routine indicates which field is being requested with the ifldnum argument.
PROGRAM HISTORY LOG:
|
• |
2002-10-28 Gilbert | ||
|
• |
2013-08-08 Vuong Free up memory in array igds - free(igds) |
Parameters
cgrib Character pointer
to the GRIB2 message.
ifldnum Specifies which field in the GRIB2 message to
return.
unpack Boolean value indicating whether to unpack
bitmap/data field.
|
• |
1 unpack bitmap (if present) and data values. |
|||
|
• |
0 do not unpack bitmap and data values. |
expand Boolean value indicating whether the data points should be expanded to the correspond grid, if a bit-map is present. This argument is ignored if unpack == 0 OR if the returned field does not contain a bit-map.
|
• |
1 if possible, expand data field to grid, inserting zero values at gridpoints that are bitmapped out. (SEE REMARKS2) | ||
|
• |
0 do not expand data field, leaving it an array of consecutive data points for each ’1’ in the bitmap. |
gfld pointer to structure gribfield containing all decoded data for the data field.
gfld->version
= GRIB edition number ( currently 2 )
gfld->discipline = Message Discipline ( see Code Table
0.0 )
gfld->idsect = Contains the entries in the Identification
Section ( Section 1 )
This element is a pointer to an array
that holds the data.
gfld->idsect[0] = Identification of originating Centre
( see Common Code Table C-1 )
7 - US National Weather Service
gfld->idsect[1] = Identification of originating
Sub-centre
gfld->idsect[2] = GRIB Master Tables Version Number
( see Code Table 1.0 )
0 - Experimental
1 - Initial operational version number
gfld->idsect[3] = GRIB Local Tables Version Number
( see Code Table 1.1 )
0 - Local tables not used
1-254 - Number of local tables version used
gfld->idsect[4] = Significance of Reference Time (Code
Table 1.2)
0 - Analysis
1 - Start of forecast
2 - Verifying time of forecast
3 - Observation time
gfld->idsect[5] = Year ( 4 digits )
gfld->idsect[6] = Month
gfld->idsect[7) = Day
gfld->idsect[8] = Hour
gfld->idsect[9] = Minute
gfld->idsect[10] = Second
gfld->idsect[11] = Production status of processed data
( see Code Table 1.3 )
0 - Operational products
1 - Operational test products
2 - Research products
3 - Re-analysis products
gfld->idsect[12] = Type of processed data ( see Code
Table 1.4 )
0 - Analysis products
1 - Forecast products
2 - Analysis and forecast products
3 - Control forecast products
4 - Perturbed forecast products
5 - Control and perturbed forecast products
6 - Processed satellite observations
7 - Processed radar observations
gfld->idsectlen = Number of elements in
gfld->idsect[].
gfld->local = Pointer to character array containing
contents
of Local Section 2, if included
gfld->locallen = length of array gfld->local[]
gfld->ifldnum = field number within GRIB message
gfld->griddef = Source of grid definition (see Code Table
3.0)
0 - Specified in Code table 3.1
1 - Predetermined grid Defined by originating centre
gfld->ngrdpts = Number of grid points in the defined
grid.
gfld->numoct_opt = Number of octets needed for each
additional grid points definition.
Used to define number of
points in each row ( or column ) for
non-regular grids.
= 0, if using regular grid.
gfld->interp_opt = Interpretation of list for optional
points
definition. (Code Table 3.11)
gfld->igdtnum = Grid Definition Template Number (Code
Table 3.1)
gfld->igdtmpl = Contains the data values for the
specified Grid
Definition Template ( NN=gfld->igdtnum ). Each
element of this integer array contains an entry (in
the order specified) of Grid Defintion Template 3.NN
This element is a pointer to an array
that holds the data.
gfld->igdtlen = Number of elements in gfld->igdtmpl[].
i.e. number of
entries in Grid Defintion Template 3.NN
( NN=gfld->igdtnum ).
gfld->list_opt = (Used if gfld->numoct_opt .ne. 0)
This array
contains the number of grid points contained in
each row ( or column ). (part of Section 3)
This element is a pointer to an array
that holds the data. This pointer is nullified
if gfld->numoct_opt=0.
gfld->num_opt = (Used if gfld->numoct_opt .ne. 0)
The number of entries
in array ideflist. i.e. number of rows ( or columns )
for which optional grid points are defined. This value
is set to zero, if gfld->numoct_opt=0.
gfdl->ipdtnum = Product Definition Template Number(see
Code Table 4.0)
gfld->ipdtmpl = Contains the data values for the
specified Product
Definition Template ( N=gfdl->ipdtnum ). Each element
of this integer array contains an entry (in the
order specified) of Product Defintion Template 4.N.
This element is a pointer to an array
that holds the data.
gfld->ipdtlen = Number of elements in gfld->ipdtmpl[].
i.e. number of
entries in Product Defintion Template 4.N
( N=gfdl->ipdtnum ).
gfld->coord_list = Real array containing floating point
values
intended to document the vertical discretisation
associated to model data on hybrid coordinate
vertical levels. (part of Section 4)
This element is a pointer to an array
that holds the data.
gfld->num_coord = number of values in array
gfld->coord_list[].
gfld->ndpts = Number of data points unpacked and
returned.
gfld->idrtnum = Data Representation Template Number
( see Code Table 5.0)
gfld->idrtmpl = Contains the data values for the
specified Data
Representation Template ( N=gfld->idrtnum ). Each
element of this integer array contains an entry
(in the order specified) of Product Defintion
Template 5.N.
This element is a pointer to an array
that holds the data.
gfld->idrtlen = Number of elements in gfld->idrtmpl[].
i.e. number
of entries in Data Representation Template 5.N
( N=gfld->idrtnum ).
gfld->unpacked = logical value indicating whether the
bitmap and
data values were unpacked. If false,
gfld->bmap and gfld->fld pointers are nullified.
gfld->expanded = Logical value indicating whether the
data field
was expanded to the grid in the case where a
bit-map is present. If true, the data points in
gfld->fld match the grid points and zeros were
inserted at grid points where data was bit-mapped
out. If false, the data values in gfld->fld were
not expanded to the grid and are just a consecutive
array of data points corresponding to each value of
’1’ in gfld->bmap.
gfld->ibmap = Bitmap indicator ( see Code Table 6.0 )
0 = bitmap applies and is included in Section 6.
1-253 = Predefined bitmap applies
254 = Previously defined bitmap applies to this field
255 = Bit map does not apply to this product.
gfld->bmap = integer array containing decoded bitmap,
if gfld->ibmap=0 or gfld->ibap=254. Otherwise
nullified
This element is a pointer to an array
that holds the data.
gfld->fld = Array of gfld->ndpts unpacked data points.
This element is a pointer to an array
that holds the data.
Returns
|
• |
0 no error | ||
|
• |
1 Beginning characters ’GRIB’ not found. | ||
|
• |
2 GRIB message is not Edition 2. | ||
|
• |
3 The data field request number was not positive. | ||
|
• |
4 End string ’7777’ found, but not where expected. | ||
|
• |
6 GRIB message did not contain the requested number of data fields. | ||
|
• |
7 End string ’7777’ not found at end of message. | ||
|
• |
8 Unrecognized Section encountered. | ||
|
• |
9 Data Representation Template 5.NN not yet implemented. | ||
|
• |
15 Error unpacking Section 1. | ||
|
• |
16 Error unpacking Section 2. | ||
|
• |
10 Error unpacking Section 3. | ||
|
• |
11 Error unpacking Section 4. | ||
|
• |
12 Error unpacking Section 5. | ||
|
• |
13 Error unpacking Section 6. | ||
|
• |
14 Error unpacking Section 7. | ||
|
• |
17 Previous bitmap specified, yet none exists. |
Note
Struct gribfield is allocated by this routine and it also contains pointers to many arrays of data that were allocated during decoding. Users are encouraged to free up this memory, when it is no longer needed, by an explicit call to routine g2_free.
EXAMPLE:
#include
"grib2.h"
gribfield *gfld;
ret=g2_getfld(cgrib,1,1,1,&gfld);
...
g2_free(gfld);
Routine g2_info can be used to first determine how many data fields exist in a given GRIB message.
Note
It may not always be possible to expand a bit-mapped data field. If a pre-defined bit-map is used and not included in the GRIB2 message itself, this routine would not have the necessary information to expand the data. In this case, gfld->expanded would would be set to 0 (false), regardless of the value of input argument expand.
Author
Stephen Gilbert
Date
2002-10-28
Definition at line 237 of file g2_getfld.c.
References g2_unpack1(), g2_unpack2(), g2_unpack3(), g2_unpack4(), g2_unpack5(), g2_unpack6(), g2_unpack7(), and gbit().
g2int
g2_gribend (unsigned char * cgrib)
This routine finalizes a GRIB2 message after all grids and
fields have been added. It adds the End Section
(’7777’) to the end of the GRIB message and
calculates the length and stores it in the appropriate place
in Section 0. This routine is used with routines
g2_create(), g2_addlocal(),
g2_addgrid(), and g2_addfield() to create a
complete GRIB2 message. g2_create() must be called
first to initialize a new GRIB2 message.
Parameters
cgrib Char array containing all the data sections added be previous calls to g2_create, g2_addlocal, g2_addgrid, and g2_addfield. After function is called, contains the finalized GRIB2 message.
Returns
|
• |
> 0 = Length of the final GRIB2 message in bytes. | ||
|
• |
-1 = GRIB message was not initialized. Need to call routine g2_create first. | ||
|
• |
-2 = GRIB message already complete. | ||
|
• |
-3 = Sum of Section byte counts doesn’t add to total byte count | ||
|
• |
-4 = Previous Section was not 7. |
Note
This routine is intended for use with routines g2_create(), g2_addlocal(), g2_addgrid(), and g2_addfield() to create a complete GRIB2 message.
Author
Stephen Gilbert
Date
2002-10-31
Definition at line 36 of file g2_gribend.c.
References gbit(), and sbit().
g2int
g2_info (unsigned char * cgrib, g2int * listsec0, g2int *
listsec1, g2int * numfields, g2int * numlocal)
This subroutine searches through a GRIB2 message and returns
the number of gridded fields found in the message and the
number (and maximum size) of Local Use Sections. Also
various checks are performed to see if the message is a
valid GRIB2 message.
Parameters
cgrib Character pointer
to the GRIB2 message.
listsec0 pointer to an array containing information
decoded from GRIB Indicator Section 0. Must be allocated
with >= 3 elements.
|
• |
listsec0[0] Discipline-GRIB Master Table Number (see Code Table 0.0). | ||
|
• |
listsec0[1] GRIB Edition Number (currently 2). | ||
|
• |
listsec0[2] Length of GRIB message. |
listsec1 Pointer to an array containing information read from GRIB Identification Section 1. Must be allocated with >= 13 elements.
|
• |
listsec1[0] Id of orginating centre (Common Code Table C-1) | ||
|
• |
listsec1[1] Id of orginating sub-centre (local table) | ||
|
• |
listsec1[2] GRIB Master Tables Version Number (Code Table 1.0) | ||
|
• |
listsec1[3] GRIB Local Tables Version Number | ||
|
• |
listsec1[4] Significance of Reference Time (Code Table 1.1) | ||
|
• |
listsec1[5] Reference Time - Year (4 digits) | ||
|
• |
listsec1[6] Reference Time - Month | ||
|
• |
listsec1[7] Reference Time - Day | ||
|
• |
listsec1[8] Reference Time - Hour | ||
|
• |
listsec1[9] Reference Time - Minute | ||
|
• |
listsec1[10] Reference Time - Second | ||
|
• |
listsec1[11] Production status of data (Code Table 1.2) | ||
|
• |
listsec1[12] Type of processed data (Code Table 1.3) |
numfields
The number of gridded fields found in the GRIB message. That
is, the number of occurences of Sections 4 - 7.
numlocal The number of Local Use Sections ( Section 2 )
found in the GRIB message.
Returns
0 foe success, otherwise:
|
• |
1 Beginning characters ’GRIB’ not found. |
|||
|
• |
2 GRIB message is not Edition 2. |
|||
|
• |
3 Could not find Section 1, where expected. |
|||
|
• |
4 End string ’7777’ found, but not where expected. |
|||
|
• |
5 End string ’7777’ not found at end of message. |
|||
|
• |
6 Invalid section number found. |
Author
Stephen Gilbeert
Date
2002-10-28
Definition at line 59 of file g2_info.c.
References gbit().
g2int
g2_unpack1 (unsigned char * cgrib, g2int * iofst, g2int **
ids, g2int * idslen)
This subroutine unpacks Section 1 (Identification Section)
as defined in GRIB Edition 2.
Parameters
cgrib char array
containing Section 1 of the GRIB2 message.
iofst Bit offset for the beginning of Section 1 in
cgrib.
ids address of pointer to integer array containing
information read from Section 1, the Identification
section.
|
• |
ids[0] Identification of originating Centre (see Common Code Table C-1). | ||
|
• |
ids[1] Identification of originating Sub-centre. | ||
|
• |
ids[2] GRIB Master Tables Version Number (see Code Table 1.0). | ||
|
• |
ids[3] GRIB Local Tables Version Number (see Code Table 1.1). | ||
|
• |
ids[4] Significance of Reference Time (Code Table 1.2) | ||
|
• |
ids[5] Year ( 4 digits ) | ||
|
• |
ids[6] Month | ||
|
• |
ids[7] Day | ||
|
• |
ids[8] Hour | ||
|
• |
ids[9] Minute | ||
|
• |
ids[10] Second | ||
|
• |
ids[11] Production status of processed data (see Code Table 1.3). | ||
|
• |
ids[12] Type of processed data (see Code Table 1.4). |
idslen Number of elements in ids.
Returns
|
• |
0 no error |
|||
|
• |
2 Array passed is not section 1 |
|||
|
• |
6 memory allocation error |
Author
Stephen Gilbert
Date
2002-10-29
Definition at line 44 of file g2_unpack1.c.
g2int
g2_unpack3 (unsigned char * cgrib, g2int * iofst, g2int **
igds, g2int ** igdstmpl, g2int * mapgridlen, g2int **
ideflist, g2int * idefnum)
This routine unpacks Section 3 (Grid Definition Section) as
defined in GRIB Edition 2. PROGRAM HISTORY LOG:
|
• |
2002-10-31 Gilbert | ||
|
• |
2009-01-14 Vuong Changed structure name template to gtemplate |
Parameters
cgrib Char array
ontaining Section 3 of the GRIB2 message.
iofst Bit offset for the beginning of Section 3 in
cgrib.
igds Contains information read from the appropriate GRIB
Grid Definition Section 3 for the field being returned.
|
• |
igds[0] Source of grid definition (see Code Table 3.0) | ||
|
• |
igds[1] Number of grid points in the defined grid. | ||
|
• |
igds[2] Number of octets needed for each additional grid points definition. Used to define number of points in each row (or column) for non-regular grids. = 0, if using regular grid. | ||
|
• |
igds[3] Interpretation of list for optional points definition. (Code Table 3.11) | ||
|
• |
igds[4] Grid Definition Template Number (Code Table 3.1). |
igdstmpl
- Pointer to integer array containing the data values for
the specified Grid Definition Template (NN=igds[4]). Each
element of this integer array contains an entry (in the
order specified) of Grid Defintion Template 3.NN
mapgridlen- Number of elements in igdstmpl[]. i.e.
number of entries in Grid Defintion Template 3.NN
(NN=igds[4]).
ideflist (Used if igds[2] .ne. 0) Pointer to integer
array containing the number of grid points contained in each
row ( or column ). (part of Section 3).
idefnum (Used if igds[2] .ne. 0) The number of entries
in array ideflist. i.e. number of rows (or columns) for
which optional grid points are defined.
Returns
|
• |
0 no error | ||
|
• |
2 Not Section 3 | ||
|
• |
5 ’GRIB’ message contains an undefined Grid Definition Template. | ||
|
• |
6 memory allocation error |
Author
Stephen Gilbert
Date
2002-10-31
Definition at line 53 of file g2_unpack3.c.
g2int
g2_unpack4 (unsigned char * cgrib, g2int * iofst, g2int *
ipdsnum, g2int ** ipdstmpl, g2int * mappdslen, g2float **
coordlist, g2int * numcoord)
This subroutine unpacks Section 4 (Product Definition
Section) as defined in GRIB Edition 2. PROGRAM HISTORY
LOG:
|
• |
2002-10-31 Gilbert | ||
|
• |
2009-01-14 Vuong Changed structure name template to gtemplate |
Parameters
cgrib Char array
containing Section 4 of the GRIB2 message.
iofst Bit offset of the beginning of Section 4 in cgrib.
Returned with updated bit offset.
ipdsnum Product Definition Template Number (see Code
Table 4.0).
ipdstmpl Pointer to integer array containing the data
values for the specified Product Definition Template
(N=ipdsnum). Each element of this integer array contains an
entry (in the order specified) of Product Defintion Template
4.N.
mappdslen Number of elements in ipdstmpl. i.e. number of
entries in Product Defintion Template 4.N (N=ipdsnum).
coordlist Pointer to real array containing floating
point values intended to document the vertical
discretisation associated to model data on hybrid coordinate
vertical levels. (part of Section 4).
numcoord number of values in array coordlist.
Returns
|
• |
0 no error | ||
|
• |
2 Not section 4 | ||
|
• |
5 ’GRIB’ message contains an undefined Product Definition Template. | ||
|
• |
6 memory allocation error |
Author
Stephen Gilbert
Date
2002-10-31
Definition at line 42 of file g2_unpack4.c.
g2int
g2_unpack5 (unsigned char * cgrib, g2int * iofst, g2int *
ndpts, g2int * idrsnum, g2int ** idrstmpl, g2int *
mapdrslen)
This subroutine unpacks Section 5 (Data Representation
Section) as defined in GRIB Edition 2. PROGRAM HISTORY
LOG:
|
• |
2002-10-31 Gilbert | ||
|
• |
2009-01-14 Vuong Changed structure name template to gtemplate |
Parameters
cgrib char array
containing Section 5 of the GRIB2 message.
iofst Bit offset for the beginning of Section 5 in
cgrib. Returned with bit offset at the end of Section 5.
ndpts Number of data points unpacked and returned.
idrsnum Data Representation Template Number (see Code
Table 5.0).
idrstmpl Pointer to an integer array containing the data
values for the specified Data Representation Template
(N=idrsnum). Each element of this integer array contains an
entry (in the order specified) of Data Representation
Template 5.N.
mapdrslen- Number of elements in idrstmpl. i.e. number
of entries in Data Representation Template 5.N
(N=idrsnum).
Returns
|
• |
0 no error | ||
|
• |
2 Not Section 5 | ||
|
• |
6 memory allocation error | ||
|
• |
7 ’GRIB’ message contains an undefined Data Representation Template. |
Author
Stephen Gilbert
Date
2002-10-31
Definition at line 40 of file g2_unpack5.c.
g2int
g2_unpack6 (unsigned char * cgrib, g2int * iofst, g2int
ngpts, g2int * ibmap, g2int ** bmap)
This subroutine unpacks Section 6 (Bit-Map Section) as
defined in GRIB Edition 2.
Parameters
cgrib char array
containing Section 6 of the GRIB2 message.
iofst Bit offset of the beginning of Section 6 in cgrib.
ngpts Number of grid points specified in the bit-map
ibmap Bitmap indicator (see Code Table 6.0)
|
• |
0 bitmap applies and is included in Section 6. |
|||
|
• |
1-253 Predefined bitmap applies |
|||
|
• |
254 Previously defined bitmap applies to this field |
|||
|
• |
255 Bit map does not apply to this product. |
bmap Pointer to an integer array containing decoded bitmap. (if ibmap=0)
Returns
|
• |
0 no error |
|||
|
• |
2 Not Section 6 |
|||
|
• |
4 Unrecognized pre-defined bit-map. |
|||
|
• |
6 memory allocation error |
Author
Stephen Gilbert
Date
2002-10-31
Definition at line 33 of file g2_unpack6.c.
g2int
g2_unpack7 (unsigned char * cgrib, g2int * iofst, g2int
igdsnum, g2int * igdstmpl, g2int idrsnum, g2int * idrstmpl,
g2int ndpts, g2float ** fld)
This subroutine unpacks Section 7 (Data Section) as defined
in GRIB Edition 2. PROGRAM HISTORY LOG:
|
• |
2002-10-31 Gilbert | ||
|
• |
2002-12-20 Gilbert - Added GDT info to arguments and added 5.51 processing. | ||
|
• |
2003-08-29 Gilbert - Added support for new templates using PNG and JPEG2000 algorithms/templates. | ||
|
• |
2004-11-29 Gilbert - JPEG2000 now allowed to use WMO Template no. 5.40 PNG now allowed to use WMO Template no. 5.41 | ||
|
• |
2004-12-16 Taylor - Added check on comunpack return code. | ||
|
• |
2008-12-23 Wesley - Initialize Number of data points unpacked |
Parameters
cgrib char array
containing Section 7 of the GRIB2 message
iofst Bit offset of the beginning of Section 7 in cgrib.
igdsnum Grid Definition Template Number (see Code Table
3.0) (Only used for DRS Template 5.51)
igdstmpl Pointer to an integer array containing the data
values for the specified Grid Definition Template
(N=igdsnum). Each element of this integer array contains an
entry (in the order specified) of Grid Definition Template
3.N. (Only used for DRS Template 5.51).
idrsnum Data Representation Template Number (see Code
Table 5.0)
idrstmpl Pointer to an integer array containing the data
values for the specified Data Representation Template
(N=idrsnum). Each element of this integer array contains an
entry (in the order specified) of Data Representation
Template 5.N
ndpts Number of data points unpacked and returned.
fld Pointer to a float array containing the unpacked
data field.
Returns
|
• |
0 no error | ||
|
• |
2 Not section 7 | ||
|
• |
4 Unrecognized Data Representation Template | ||
|
• |
5 need one of GDT 3.50 through 3.53 to decode DRT 5.51 | ||
|
• |
6 memory allocation error | ||
|
• |
7 corrupt section 7. |
Author
Stephen Gilbert
Date
2002-10-31
Definition at line 66 of file g2_unpack7.c.
void gbit
(unsigned char * in, g2int * iout, g2int iskip, g2int
nbyte)
Get bits - unpack bits: Extract arbitrary size values from a
packed bit string, right justifying each value in the
unpacked iout array.
Parameters
in pointer to character
array input.
iout pointer to unpacked array output.
iskip initial number of bits to skip.
nbyte number of bits to take.
Author
NOAA Programmer
Definition at line 20 of file gbits.c.
References gbits().
Referenced by comunpack(), g2_addfield(), g2_addgrid(), g2_addlocal(), g2_getfld(), g2_gribend(), g2_info(), g2_unpack1(), g2_unpack2(), g2_unpack3(), g2_unpack4(), g2_unpack5(), g2_unpack6(), g2_unpack7(), and seekgb().
void gbits
(unsigned char * in, g2int * iout, g2int iskip, g2int nbyte,
g2int nskip, g2int n)
Get bits - unpack bits: Extract arbitrary size values from a
packed bit string, right justifying each value in the
unpacked iout array.
Parameters
in pointer to character
array input.
iout pointer to unpacked array output.
iskip initial number of bits to skip.
nbyte number of bits to take.
nskip additional number of bits to skip on each
iteration.
n number of iterations.
Author
NOAA Programmer
Definition at line 57 of file gbits.c.
Referenced by comunpack(), g2_unpack3(), g2_unpack4(), g2_unpack6(), gbit(), pngunpack(), simunpack(), and specunpack().
gtemplate*
getdrstemplate (g2int number)
This subroutine returns DRS template information for a
specified Data Representation Template 5.NN. The number of
entries in the template is returned along with a map of the
number of octets occupied by each entry. Also, a flag is
returned to indicate whether the template would need to be
extended.
PROGRAM HISTORY LOG:
|
• |
2000-05-11 Gilbert | ||
|
• |
2009-01-14 Vuong Changed structure name template to gtemplate |
Parameters
number NN, indicating the number of the Data Representation Template 5.NN that is being requested.
Returns
Pointer to the returned template struct. Returns NULL pointer, if template not found.
Author
Stephen Gilbert
Date
2000-05-11
Definition at line 57 of file drstemplates.c.
References getdrsindex(), drstemplate::mapdrslen, drstemplate::needext, drstemplate::template_num, and templatesdrs.
Referenced by extdrstemplate(), g2_addfield(), and g2_unpack5().
gtemplate*
getgridtemplate (g2int number)
This subroutine returns grid template information for a
specified Grid Definition Template 3.NN. The number of
entries in the template is returned along with a map of the
number of octets occupied by each entry. Also, a flag is
returned to indicate whether the template would need to be
extended.
PROGRAM HISTORY LOG:
|
• |
2000-05-09 Gilbert | ||
|
• |
2007-08-16 Vuong - Added GDT 3.204 Curvilinear Orthogonal Grid | ||
|
• |
2008-07-08 Vuong - Added GDT 3.32768 Rotate Lat/Lon E-grid (Arakawa) | ||
|
• |
2010-05-11 Vuong - Added GDT 3.32769 Rotate Lat/Lon Non-E Staggered grid (Arakawa) | ||
|
• |
2009-01-14 Vuong - Changed structure name template to gtemplate |
Parameters
number NN, indicating the number of the Grid Definition Template 3.NN that is being requested.
Returns
Pointer to the returned template struct. Returns NULL pointer, if template not found.
Author
Stephen Gilbert
Date
2000-05-09
Definition at line 68 of file gridtemplates.c.
References getgridindex(), and templatesgrid.
Referenced by extgridtemplate(), g2_addgrid(), and g2_unpack3().
gtemplate*
getpdstemplate (g2int number)
This subroutine returns PDS template information for a
specified Product Definition Template 4.NN. The number of
entries in the template is returned along with a map of the
number of octets occupied by each entry. Also, a flag is
returned to indicate whether the template would need to be
extended.
Parameters
number NN, indicating the number of the Product Definition Template 4.NN that is being requested.
Returns
Pointer to the returned template struct. Returns NULL pointer, if template not found.
Author
Stephen Gilbert
Date
2000-05-11
Definition at line 65 of file pdstemplates.c.
References getpdsindex(), and templatespds.
Referenced by extpdstemplate(), g2_addfield(), and g2_unpack4().
double
int_power (double x, g2int y)
Function similar to C pow() power function.
Parameters
x The base value whose
power is to be calculated.
y The power value.
Returns
x**y
Author
Wesley Ebisuzaki
Definition at line 17 of file int_power.c.
Referenced by compack(), comunpack(), jpcpack(), jpcunpack(), misspack(), mkieee(), pngpack(), pngunpack(), rdieee(), simpack(), simunpack(), specpack(), and specunpack().
void
misspack (g2float * fld, g2int ndpts, g2int idrsnum, g2int *
idrstmpl, unsigned char * cpack, g2int * lcpack)
This subroutine packs up a data field using a complex
packing algorithm as defined in the GRIB2 documention. It
supports GRIB2 complex packing templates with or without
spatial differences (i.e. DRTs 5.2 and 5.3). It also fills
in GRIB2 Data Representation Template 5.2 or 5.3 with the
appropriate values. This version assumes that Missing Value
Management is being used and that 1 or 2 missing values
appear in the data.
Parameters
fld Contains the data
values to pack
ndpts The number of data values in array fld
idrsnum Data Representation Template number 5.N Must
equal 2 or 3.
idrstmpl Contains the array of values for Data
Representation Template 5.2 or 5.3.
|
• |
0 Reference value - ignored on input, set by misspack routine. | ||
|
• |
1 Binary Scale Factor - used on input. | ||
|
• |
2 Decimal Scale Factor- used on input. | ||
|
• |
6 Missing value management. | ||
|
• |
7 Primary missing value. | ||
|
• |
8 Secondary missing value. | ||
|
• |
16 Order of Spatial Differencing (1 or 2). |
cpack
The packed data field (character*1 array).
lcpack length of packed field cpack.
Author
Stephen Gilbert
Date
2000-06-21
Definition at line 38 of file misspack.c.
References int_power(), mkieee(), pack_gp(), rdieee(), sbit(), and sbits().
Referenced by cmplxpack().
void mkieee
(g2float * a, g2int * rieee, g2int num)
This subroutine stores a list of real values in 32-bit IEEE
floating point format.
Parameters
a Input array of
floating point values.
num Number of floating point values to convert.
rieee Output array of data values in 32-bit IEEE format
stored in g2int integer array. rieee must be allocated with
at least 4*num bytes of memory before calling this
function.
Author
Stephen Gilbert
Date
2002-10-29
Definition at line 21 of file mkieee.c.
References int_power().
Referenced by compack(), g2_addfield(), jpcpack(), misspack(), pngpack(), simpack(), and specpack().
int pack_gp
(integer * kfildo, integer * ic, integer * nxy, integer *
is523, integer * minpk, integer * inc, integer * missp,
integer * misss, integer * jmin, integer * jmax, integer *
lbit, integer * nov, integer * ndg, integer * lx, integer *
ibit, integer * jbit, integer * kbit, integer * novref,
integer * lbitref, integer * ier)
Determines groups of variable size, but at least of size
minpk, the associated max (jmax( )) and min (jmin( )), the
number of bits necessary to hold the values in each group
(lbit( )), the number of values in each group (nov( )), the
number of bits necessary to pack the jmin( ) values (ibit),
the number of bits necessary to pack the lbit( ) values
(jbit), and the number of bits necessary to pack the nov( )
values (kbit). The routine is designed to determine the
groups such that a small number of bits is necessary to pack
the data without excessive computations. If all values in
the group are zero, the number of bits to use in packing is
defined as zero when there can be no missing values; when
there can be missing values, the number of bits must be at
least 1 to have the capability to recognize the missing
value. However, if all values in a group are missing, the
number of bits needed is 0, and the unpacker recognizes
this. All variables are integer. Even though the groups are
initially of size minpk or larger, an adjustment between two
groups (the lookback procedure) may make a group smaller
than minpk. The control on group size is that the sum of the
sizes of the two consecutive groups, each of size minpk or
larger, is not decreased. When determining the number of
bits necessary for packing, the largest value that can be
accommodated in, say, mbits, is 2**mbits-1; this largest
value (and the next smallest value) is reserved for the
missing value indicator (only) when is523 ne 0. If the
dimension ndg is not large enough to hold all the groups,
the local value of minpk is increased by 50 percent. This is
repeated until ndg will suffice. A diagnostic is printed
whenever this happens, which should be very rarely. If it
happens often, ndg in subroutine pack should be increased
and a corresponding increase in subroutine unpack made.
Considerable code is provided so that no more checking for
missing values within loops is done than necessary; the
added efficiency of this is relatively minor, but does no
harm. For grib2, the reference value for the length of
groups in nov( ) and for the number of bits necessary to
pack group values are determined, and subtracted before jbit
and kbit are determined.
When 1 or more groups are large compared to the others, the width of all groups must be as large as the largest. A subroutine reduce breaks up large groups into 2 or more to reduce total bits required. If reduce should abort, pack_gp will be executed again without the call to reduce.
PROGRAM HISTORY LOG:
|
• |
February 1994 Glahn tdl mos-2000 | ||
|
• |
June 1995 Glahn modified for lmiss error. | ||
|
• |
July 1996 Glahn added misss | ||
|
• |
February 1997 Glahn removed 4 redundant tests for missp.eq.0; inserted a test to better handle a string of 9999’s | ||
|
• |
February 1997 Glahn added loops to eliminate test for misss when misss = 0 | ||
|
• |
March 1997 Glahn corrected for secondary missing value | ||
|
• |
March 1997 Glahn corrected for use of local value of minpk | ||
|
• |
March 1997 Glahn corrected for secondary missing value | ||
|
• |
March 1997 Glahn changed calculating number of bits through exponents to an array (improved overall packing performance by about 35 percent!). allowed 0 bits for packing jmin( ), lbit( ), and nov( ). | ||
|
• |
May 1997 Glahn a number of changes for efficiency. mod functions eliminated and one ifthen added. jount removed. recomputation of bits not made unless necessary after moving points from one group to another. nendb adjusted to eliminate possibility of very small group at the end. about 8 percent improvement in overall packing. iskipa removed; there is always a group b that can become group a. control on size of group b (statement below 150) added. added adda, and use of ge and le instead of gt and lt in loops between 150 and 160. ibitbs added to shorten trips through loop. | ||
|
• |
March 2000 Glahn modified for grib2; changed name from packgp | ||
|
• |
january 2001 Glahn comments; ier = 706 substituted for stops; added return1; removed statement number 110; added ier and * return | ||
|
• |
November 2001 Glahn changed some diagnostic formats to allow printing larger numbers | ||
|
• |
November 2001 Glahn added misslx( ) to put maximum value into jmin( ) when all values missing to agree with grib standard. | ||
|
• |
November 2001 Glahn changed two tests on missp and misss eq 0 to tests on is523. however, missp and misss cannot in general be = 0. | ||
|
• |
November 2001 Glahn added call to reduce; defined itest before loops to reduce computation; started large group when all same value | ||
|
• |
December 2001 Glahn modified and added a few comments | ||
|
• |
January 2002 Glahn removed loop before 150 to determine a group of all same value | ||
|
• |
January 2002 Glahn changed mallow from 9999999 to 2**30+1, and made it a parameter | ||
|
• |
March 2002 Glahn added non fatal ier = 716, 717; removed nendb=nxy above 150; added iersav=0; comments |
DATA SET USE
|
• |
kfildo - unit number for output (print) file. (output) |
Parameters
kfildo unit number for
output (print) file. (input)
ic array to hold data for packing. the values do not
have to be positive at this point, but must be in the range
-2**30 to +2**30 (the the value of mallow). these integer
values will be retained exactly through packing and
unpacking. (input)
nxy number of values in ic( ). also treated as its
dimension. (input)
is523 missing value management 0=data contains no
missing values 1=data contains primary missing values 2=data
contains primary and secondary missing values (input)
minpk the minimum size of each group, except possibly
the last one. (input)
inc the number of values to add to an already existing
group in determining whether or not to start a new group.
ideally, this would be 1, but each time inc values are
attempted, the max and min of the next minpk values must be
found. this is ’a loop within a loop,’ and a
slightly larger value may give about as good results with
slightly less computational time. if inc is le 0, 1 is used,
and a diagnostic is output. note: it is expected that inc
will equal 1. the code uses inc primarily in the loops
starting at statement 180. if inc were 1, there would not
need to be loops as such. however, kinc (the local value of
inc) is set ge 1 when near the end of the data to forestall
a very small group at the end. (input)
missp when missing points can be present in the data,
they will have the value missp or misss. missp is the
primary missing value and misss is the secondary missing
value . these must not be values that would occur with
subtracting the minimum (reference) value or scaling. for
example, missp = 0 would not be advisable. (input)
misss secondary missing value indicator (see missp).
(input)
jmin the minimum of each group (j=1,lx). (output)
jmax the maximum of each group (j=1,lx). this is not
really needed, but since the max of each group must be
found, saving it here is cheap in case the user wants it.
(output)
lbit the number of bits necessary to pack each group
(j=1,lx). it is assumed the minimum of each group will be
removed before packing, and the values to pack will,
therefore, all be positive. however, ic( ) does not
necessarily contain all positive values. if the overall
minimum has been removed (the usual case), then ic( ) will
contain only positive values. (output)
nov the number of values in each group (j=1,lx).
(output)
ndg the dimension of jmin, jmax, lbit, and nov. (input)
lx the number of groups determined. (output)
ibit the number of bits necessary to pack the jmin(j)
values, j=1,lx. (output)
jbit the number of bits necessary to pack the lbit(j)
values, j=1,lx. (output)
kbit the number of bits necessary to pack the nov(j)
values, j=1,lx. (output)
novref reference value for nov( ). (output)
lbitref reference value for lbit( ). (output)
ier Error code
|
• |
0 No error. |
|||
|
• |
706 value will not pack in 30 bits--fatal |
|||
|
• |
714 error in reduce--non-fatal |
|||
|
• |
715 ngp not large enough in reduce--non-fatal |
|||
|
• |
716 minpk inceased--non-fatal |
|||
|
• |
717 inc set |
|||
|
• |
1--non-fatal |
|||
|
• |
alternate return when ier ne 0 and fatal error. |
Returns
0 - check ier for error code.
INTERNAL VARIABLES
cfeed =
contains the character representation
of a printer form feed.
ifeed = contains the integer value of a printer
form feed.
kinc = working copy of inc. may be modified.
mina = minimum value in group a.
maxa = maximum value in group a.
nenda = the place in ic( ) where group a ends.
kstart = the place in ic( ) where group a starts.
ibita = number of bits needed to hold values in group a.
minb = minimum value in group b.
maxb = maximum value in group b.
nendb = the place in ic( ) where group b ends.
ibitb = number of bits needed to hold values in group b.
minc = minimum value in group c.
maxc = maximum value in group c.
ktotal = count of number of values in ic( ) processed.
nount = number of values added to group a.
lmiss = 0 when is523 = 0. when packing into a
specific number of bits, say mbits,
the maximum value that can be handled is
2**mbits-1. when is523 = 1, indicating
primary missing values, this maximum value
is reserved to hold the primary missing value
indicator and lmiss = 1. when is523 = 2,
the value just below the maximum (i.e.,
2**mbits-2) is reserved to hold the secondary
missing value indicator and lmiss = 2.
lminpk = local value of minpk. this will be adjusted
upward whenever ndg is not large enough to hold
all the groups.
mallow = the largest allowable value for packing.
mislla = set to 1 when all values in group a are missing.
this is used to distinguish between a real
minimum when all values are not missing
and a minimum that has been set to zero when
all values are missing. 0 otherwise.
note that this does not distinguish between
primary and secondary missings when secondary
missings are present. this means that
lbit( ) will not be zero with the resulting
compression efficiency when secondary missings
are present. also note that a check has been
made earlier to determine that secondary
missings are really there.
misllb = set to 1 when all values in group b are missing.
this is used to distinguish between a real
minimum when all values are not missing
and a minimum that has been set to zero when
all values are missing. 0 otherwise.
misllc = performs the same function for group c that
mislla and misllb do for groups b and c,
respectively.
ibxx2(j) = an array that when this routine is first entered
is set to 2**j, j=0,30. ibxx2(30) = 2**30, which
is the largest value packable, because 2**31
is larger than the integer word size.
ifirst = set by data statement to 0. changed to 1 on
first
entry when ibxx2( ) is filled.
minak = keeps track of the location in ic( ) where the
minimum value in group a is located.
maxak = does the same as minak, except for the maximum.
minbk = the same as minak for group b.
maxbk = the same as maxak for group b.
minck = the same as minak for group c.
maxck = the same as maxak for group c.
adda = keeps track whether or not an attempt to add
points to group a was made. if so, then adda
keeps from trying to put one back into b.
(logical)
ibitbs = keeps current value if ibitb so that loop
ending at 166 doesn’t have to start at
ibitb = 0 every time.
misslx(j) = mallow except when a group is all one value (and
lbit(j) = 0) and that value is missing. in
that case, misslx(j) is missp or misss. this
gets inserted into jmin(j) later as the
missing indicator; it can’t be put in until
the end, because jmin( ) is used to calculate
the maximum number of bits (ibits) needed to
pack jmin( ).
Definition at line 256 of file pack_gp.c.
References FALSE_, reduce(), and TRUE_.
Referenced by compack(), and misspack().
void rdieee
(g2int * rieee, g2float * a, g2int num)
This subroutine reads a list of real values in 32-bit IEEE
floating point format.
Parameters
rieee g2int array of
floating point values in 32-bit IEEE format.
num Number of floating point values to convert.
a float array of real values. a must be allocated with
at least 4*num bytes of memory before calling this
function.
Author
Stephen Gilbert
Date
2002-10-25
Definition at line 20 of file rdieee.c.
References int_power().
Referenced by comunpack(), g2_miss(), g2_unpack4(), g2_unpack7(), jpcunpack(), misspack(), pngunpack(), simunpack(), and specunpack().
void sbit
(unsigned char * out, g2int * in, g2int iskip, g2int
nbyte)
Store bits - put arbitrary size values into a packed bit
string, taking the low order bits from each value in the
unpacked array.
Parameters
out pointer to packed
array output. Must be allocated large enough to hold output.
in pointer to unpacked array input.
iskip initial number of bits to skip.
nbyte number of bits to pack.
Author
NOAA Programmer
Definition at line 38 of file gbits.c.
References sbits().
Referenced by compack(), g2_addfield(), g2_addgrid(), g2_addlocal(), g2_create(), g2_gribend(), misspack(), and simpack().
void sbits
(unsigned char * out, g2int * in, g2int iskip, g2int nbyte,
g2int nskip, g2int n)
Store bits - put arbitrary size values into a packed bit
string, taking the low order bits from each value in the
unpacked array.
Parameters
out pointer to packed
array output. Must be allocated large enough to hold output.
in pointer to unpacked array input.
iskip initial number of bits to skip.
nbyte number of bits to pack.
nskip additional number of bits to skip on each
iteration.
n number of iterations.
Author
NOAA Programmer
Definition at line 110 of file gbits.c.
Referenced by compack(), g2_addfield(), g2_addgrid(), jpcpack(), misspack(), pngpack(), sbit(), and simpack().
void seekgb
(FILE * lugb, g2int iseek, g2int mseek, g2int * lskip, g2int
* lgrib)
This subprogram searches a file for the next GRIB Message.
The search is done starting at byte offset iseek of the file
referenced by lugb for mseek bytes at a time. If found, the
starting position and length of the message are returned in
lskip and lgrib, respectively. The search is terminated when
an EOF or I/O error is encountered.
PROGRAM HISTORY LOG:
|
• |
2002-10-28 GILBERT Modified from Iredell’s skgb subroutine | ||
|
• |
2009-01-16 VUONG Changed lskip to 4 instead of sizof(g2int) |
Parameters
lugb FILE pointer for
the file to search. File must be opened before this routine
is called.
iseek number of bytes in the file to skip before search.
mseek number of bytes to search at a time.
lskip number of bytes to skip from the beggining of the
file to where the GRIB message starts.
lgrib number of bytes in message (set to 0, if no
message found).
Author
Stephen Gilbert
Date
2002-10-28
Definition at line 32 of file seekgb.c.
References gbit().
void simpack
(g2float * fld, g2int ndpts, g2int * idrstmpl, unsigned char
* cpack, g2int * lcpack)
This subroutine packs up a data field using the simple
packing algorithm as defined in the GRIB2 documention. It
also fills in GRIB2 Data Representation Template 5.0 with
the appropriate values.
Parameters
fld Contains the data
values to pack.
ndpts The number of data values in array fld.
idrstmpl Contains the array of values for Data
Representation Template 5.0.
|
• |
0 Reference value - ignored on input - set by simpack routine. | ||
|
• |
1 Binary Scale Factor - unchanged from input. | ||
|
• |
2 Decimal Scale Factor - unchanged from input. | ||
|
• |
3 Number of bits used to pack data, if value is > 0 and <= 31. If this input value is 0 or outside above range then the num of bits is calculated based on given data and scale factors. | ||
|
• |
4 Original field type - currently ignored on input. Data values assumed to be reals. Set to 0 by simpack routine. |
cpack
The packed data field
lcpack length of packed field starting at cpack.
Author
Stephen Gilbert
Date
2002-11-06
Definition at line 32 of file simpack.c.
Author
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