g2cindex.c(3)

πŸ“¦
version 2.3.0 Β· 2 versions
, in ubuntu resolute, ubuntu stonking

πŸ’– g2cindex.c β€” Library Functions Manual πŸ’–

okay bestie, gather round, because we're about to get deep into g2cindex.c, and this one is lowkey a whole saga (it's giving "two-parter", so buckle up). It's a Library Functions Manual situation, and it's so much. Let's go. πŸ¦‹


✨ NAME ✨

g2cindex.c β€” write summary output to an index file, exactly like the utility grb2index does. no cap. πŸ’…


🌸 SYNOPSIS 🌸

#include 'grib2_int.h'
#include <libgen.h>
#include <stdarg.h>
#include <time.h>

πŸŽ€ Macros

  • #define G2C_INDEX_BASENAME_LEN 40 β€” length of the basename in header record 2. 🫢
  • #define G2C_INDEX_BITMAP_BYTES 6 β€” length of the bitmap section included in the index record.
  • #define G2C_INDEX_DATE_STR_LEN 10 β€” length of the date string in the index record. πŸ“…
  • #define G2C_INDEX_FIXED_LEN 44 β€” length of the beginning of the index record.
  • #define G2C_INDEX_FIXED_LEN_2 48 β€” length of the beginning of the index record, but for the large files version. big girl energy. πŸ‘‘
  • #define G2C_INDEX_HEADER_LEN 81 β€” length of the two header lines at the top of the index file.
  • #define G2C_INDEX_STR1_LEN 7 β€” length of the str1 string in the index record.
  • #define G2C_INDEX_TIME_STR_LEN 8 β€” length of the time string in the index record. ⏰

πŸ’œ Functions

  • EXTERN_MUTEX (m) β€” use an externally-defined mutex for thread-safety. (mutexes are the moment, fr fr πŸ”’)
  • int g2c_get_prod_sections (G2C_MESSAGE_INFO_T *msg, int fieldnum, G2C_SECTION_INFO_T **sec3, G2C_SECTION_INFO_T **sec4, G2C_SECTION_INFO_T **sec5, G2C_SECTION_INFO_T **sec6, G2C_SECTION_INFO_T **sec7) β€” hand it a pointer to a message plus a field number, and it hands you back pointers to all the relevant section structs for that product. ✨
  • int g2c_open_index (const char *data_file, const char *index_file, int mode, int *g2cid) β€” open a GRIB2 file with the help of an index file.
  • int g2c_open_index1 (const char *index_file) β€” open a GRIB1 index file and read the contents.
  • int g2c_start_index1_record (FILE *f, int rw_flag, unsigned int *b2_msg, unsigned int *b2_pds, unsigned int *b2_gds, unsigned int *b2_bms, unsigned int *b2_bds, unsigned int *msglen, unsigned char *version, unsigned char *pds_val, unsigned char *gds_val, unsigned char *bms_val, unsigned char *bds_val, unsigned char *pds_val2, unsigned char *pds_val3, unsigned char *gds_val2) β€” read or write the start of a version 1 index record. 😌
  • int g2c_start_index_record (FILE *f, int rw_flag, int *reclen, int *msg, int *local, int *gds, int *pds, int *drs, int *bms, int *data, size_t *msglen, unsigned char *version, unsigned char *discipline, short *fieldnum) β€” read or write the start of a version 2 index record.
  • int g2c_start_index_record_lf (FILE *f, int rw_flag, int *reclen, size_t *msg, size_t *local, size_t *gds, size_t *pds, size_t *drs, size_t *bms, size_t *data, size_t *msglen, unsigned char *version, unsigned char *discipline, short *fieldnum) β€” read or write the start of a version 2 index record. (yes, again β€” this one's the "lf" twin 🧚)
  • int g2c_write_index (int g2cid, int mode, const char *index_file) β€” create an index file from a GRIB2 file, just like the ones the grb2index utility makes. ate. πŸ’…
  • static int read_hdr_rec1 (FILE *f, int *ip, int *jp, int *kp, char *date_str, char *time_str) β€” read the header record that is apparently named after Steve Lord. πŸ™ˆ iconic origin story tbh.
  • static int read_hdr_rec2 (FILE *f, int *skipp, int *total_lenp, int *num_recp, char *basename, int *index_version) β€” read the second header record of an index file.

🌈 Variables

  • G2C_FILE_INFO_T g2c_file [G2C_MAX_FILES+1] β€” global file information. the whole vibe, stored globally. πŸ’Ύ

🫢 Detailed Description 🫢

Write summary output to an index file, as is done by utility grb2index. that's the whole assignment bestie. ✨

Author

Ed Hartnett

Date

10/12/22

Definition in file g2cindex.c.


πŸŽ€ Macro Definition Documentation πŸŽ€

#define G2C_INDEX_BASENAME_LEN 40

Length of the basename in header record 2.

Definition at line 20 of file g2cindex.c.

Referenced by g2c_open_index(), g2c_open_index1(), g2c_write_index(), and read_hdr_rec2().


#define G2C_INDEX_BITMAP_BYTES 6

Length of bitmap section included in the index record.

Definition at line 23 of file g2cindex.c.

Referenced by g2c_write_index().


#define G2C_INDEX_DATE_STR_LEN 10

Length of date string in index record.

Definition at line 32 of file g2cindex.c.

Referenced by g2c_open_index(), g2c_open_index1(), and read_hdr_rec1().


#define G2C_INDEX_FIXED_LEN 44

Length of beginning of index record.

Definition at line 26 of file g2cindex.c.

Referenced by g2c_write_index().


#define G2C_INDEX_FIXED_LEN_2 48

Length of beginning of index record for large files.

Definition at line 29 of file g2cindex.c.

Referenced by g2c_write_index().


#define G2C_INDEX_HEADER_LEN 81

Length of the two header lines at the top of the index file.

Definition at line 17 of file g2cindex.c.

Referenced by g2c_open_index(), g2c_open_index1(), g2c_write_index(), read_hdr_rec1(), and read_hdr_rec2().


#define G2C_INDEX_STR1_LEN 7

Length of str1 string in index record.

Definition at line 38 of file g2cindex.c.

Referenced by g2c_open_index(), and read_hdr_rec1().


#define G2C_INDEX_TIME_STR_LEN 8

Length of time string in index record.

Definition at line 35 of file g2cindex.c.

Referenced by g2c_open_index(), g2c_open_index1(), and read_hdr_rec1().


πŸ’œ Function Documentation πŸ’œ

πŸ¦‹ EXTERN_MUTEX (m )

Use externally-defined mutex for thread-safety. periodt. πŸ”’


🌸 int g2c_get_prod_sections (G2C_MESSAGE_INFO_T * msg, int fieldnum, G2C_SECTION_INFO_T ** sec3, G2C_SECTION_INFO_T ** sec4, G2C_SECTION_INFO_T ** sec5, G2C_SECTION_INFO_T ** sec6, G2C_SECTION_INFO_T ** sec7)

Given a pointer to a message, and a field number, return pointers to all relevant section structs for that product. Every product is defined in a section 4, and it has an associated section 3, 5, 6, and 7. it's giving "found family" but make it GRIB2 sections. πŸ₯Ή

Parameters

  • msg β€” pointer to a G2C_MESSAGE_INFO_T with information about the message.
  • fieldnum β€” the field number (first field in message is 0).
  • sec3 β€” pointer that gets a pointer to the G2C_SECTION_INFO_T struct for the section 3 associated with this product.
  • sec4 β€” pointer that gets a pointer to the G2C_SECTION_INFO_T struct for the section 4 associated with this product.
  • sec5 β€” pointer that gets a pointer to the G2C_SECTION_INFO_T struct for the section 5 associated with this product.
  • sec6 β€” pointer that gets a pointer to the G2C_SECTION_INFO_T struct for the section 6 associated with this product. NULL is returned if there is no section 6.
  • sec7 β€” pointer that gets a pointer to the G2C_SECTION_INFO_T struct for the section 7 associated with this product.

Note

This is an internal function and should not be called by users. bestie do NOT touch. πŸ™…β€β™€οΈ

Returns

  • G2C_NOERROR β€” no error.
  • G2C_EINVAL β€” invalid input.
  • G2C_ENOSECTION β€” section not found.

Author

Ed Hartnett

Date

10/27/22

Definition at line 317 of file g2cindex.c.

References G2C_EINVAL, G2C_ENOSECTION, G2C_NOERROR, g2c_section_info::next, g2c_section_info::prev, g2c_message_info::sec, g2c_section_info::sec_info, and g2c_section_info::sec_num.

Referenced by g2c_write_index().


πŸ’– int g2c_open_index (const char * data_file, const char * index_file, int mode, int * g2cid)

Open a GRIB2 file with the help of an index file. The index file β€” generated by the grb2index utility, or by the g2c_write_index() function β€” contains the byte offsets for the sections of each message in the GRIB2 file. When a GRIB2 file is opened with an index file, the library does not have to scan the file to locate all metadata. it's giving shortcut, it's giving efficiency, it's giving main character. ⚑

Parameters

  • data_file β€” the name of the data file to which the index applies.
  • index_file β€” the name that will be given to the index file. An existing file will be overwritten. 😱
  • mode β€” open mode flags.
  • g2cid β€” pointer that gets the g2cid for this file. Ignored if NULL.

Returns

  • G2C_NOERROR β€” no error.

Author

Ed Hartnett

Date

10/12/22

Definition at line 914 of file g2cindex.c.

References add_msg(), add_section(), g2c_message_info::bytes_to_bms, g2c_message_info::bytes_to_data, g2c_message_info::bytes_to_local, g2c_message_info::bytes_to_msg, g2c_message_info::discipline, g2c_add_file(), G2C_EBADSECTION, G2C_EFILE, G2C_EINVAL, G2C_ENAMETOOLONG, g2c_file, g2c_file_io_ubyte(), g2c_file_io_uint(), G2C_FILE_READ, G2C_INDEX_BASENAME_LEN, G2C_INDEX_DATE_STR_LEN, G2C_INDEX_HEADER_LEN, G2C_INDEX_STR1_LEN, G2C_INDEX_TIME_STR_LEN, g2c_log_section1(), G2C_MAX_NAME, G2C_NOERROR, g2c_rw_section1_metadata(), g2c_start_index_record(), g2c_start_index_record_lf(), LOG, g2c_message_info::master_version, MUTEX_LOCK, and MUTEX_UNLOCK.

Referenced by main().


🌈 int g2c_open_index1 (const char * index_file)

Open a GRIB1 index file and read the contents. This function opens the GRIB2 index file and reads its metadata, and opens the accompanying GRIB2 file. (yes it says GRIB1 in the name and then talks about GRIB2, we don't make the rules πŸ’€)

GRIB2 messages in the file are assigned a message ID, starting with 0 for the first message in the file.

Each product within a message is assigned a product ID, starting with 0 for the first product in the message.

Files opened with this function should be closed with a call g2c_close() to release resources. don't leave them hanging bestie, that's rude. 🫢

Parameters

  • index_file β€” the name that will be given to the index file. An existing file will be overwritten. 😭

Returns

  • G2C_NOERROR β€” no error.

Author

Ed Hartnett

Date

10/12/22

Definition at line 812 of file g2cindex.c.

References G2C_EFILE, G2C_EINVAL, G2C_FILE_READ, G2C_INDEX1_BDS_VAL_LEN, G2C_INDEX1_BMS_VAL_LEN, G2C_INDEX1_GDS_VAL_LEN, G2C_INDEX1_PDS_VAL_LEN, G2C_INDEX_BASENAME_LEN, G2C_INDEX_DATE_STR_LEN, G2C_INDEX_HEADER_LEN, G2C_INDEX_TIME_STR_LEN, G2C_NOERROR, g2c_start_index1_record(), LOG, MUTEX_LOCK, MUTEX_UNLOCK, read_hdr_rec1(), and read_hdr_rec2().


πŸ’… int g2c_start_index1_record (FILE * f, int rw_flag, unsigned int * b2_msg, unsigned int * b2_pds, unsigned int * b2_gds, unsigned int * b2_bms, unsigned int * b2_bds, unsigned int * msglen, unsigned char * version, unsigned char * pds_val, unsigned char * gds_val, unsigned char * bms_val, unsigned char * bds_val, unsigned char * pds_val2, unsigned char * pds_val3, unsigned char * gds_val2)

Read or write the start of a version 1 index record. For more detail on version 1 of the index format, see the grbindex documentation in the NCEPLIBS-grib_util. πŸ“š


✨ okay bestie, that's the end of part 1 ✨ β€” there's more coming, so don't go anywhere. πŸ’–

okay so the params for this one are literally the blueprint, bestie β€” read them like your life depends on it (it doesn't, but still):

  • f β€” FILE * to open index file.
  • rw_flag β€” True if function should write, false if it should read.
  • b2_msg β€” Pointer that gets the bytes to skip in file before msg.
  • b2_pds β€” Pointer that gets bytes to skip in message before pds.
  • b2_gds β€” Pointer that gets bytes to skip in message before gds (0 if no gds).
  • b2_bms β€” Pointer that gets bytes to skip in message before bms (0 if no bms).
  • b2_bds β€” Pointer that gets bytes to skip in message before bds.
  • msglen β€” Pointer that gets bytes total in the message.
  • version β€” Pointer that gets grib version number (always 1 for this function).
  • pds_val β€” Pointer that gets an array of 27 bytes of the product definition section (pds).
  • gds_val β€” Pointer that gets an array of 41 bytes of the gds.
  • bms_val β€” Pointer that gets an array of 5 bytes of the bms.
  • bds_val β€” Pointer that gets an array of 10 bytes, bytes 41-100 of the bds.
  • pds_val2 β€” Pointer that gets an array of 59 bytes 41-100 of the pds. Ignored if null.
  • pds_val3 β€” Pointer that gets an array of 11 bytes 29-40 of the pds. Ignored if null.
  • gds_val2 β€” Pointer that gets an array of 135 bytes 43-178 of the gds. Ignored if null.

Returns β€” the vibe check results, no cap:

  • G2C_NOERROR β€” No error.
  • G2C_EINVAL β€” Invalid input.
  • G2C_EFILE β€” File I/O error.

Author β€” Ed Hartnett 9/11/23

Definition at line 238 of file g2cindex.c.

References β€” G2C_EFILE, G2C_EINVAL, g2c_file_io_ubyte(), g2c_file_io_uint(), G2C_INDEX1_BDS_VAL_LEN, G2C_INDEX1_BMS_VAL_LEN, G2C_INDEX1_GDS_VAL_LEN, G2C_INDEX1_PDS_VAL_LEN, and G2C_NOERROR.

Referenced by g2c_open_index1().


πŸ¦‹ g2c_start_index_record πŸ¦‹

int g2c_start_index_record (FILE * f, int rw_flag, int * reclen, int * msg,
    int * local, int * gds, int * pds, int * drs, int * bms, int * data,
    size_t * msglen, unsigned char * version, unsigned char * discipline,
    short * fieldnum)

Read or write the start of a version 2 index record. It's giving "index record opening ceremony" and honestly? Slay.

Parameters

  • f β€” FILE * to open index file.
  • rw_flag β€” True if function should write, false if it should read.
  • reclen β€” Pointer to reclen.
  • msg β€” Pointer to msg.
  • local β€” Pointer to local.
  • gds β€” Pointer to gds.
  • pds β€” Pointer to pds.
  • drs β€” Pointer to drs.
  • bms β€” Pointer to bms.
  • data β€” Pointer to data.
  • msglen β€” Pointer to msglen.
  • version β€” Pointer to version.
  • discipline β€” Pointer to discipline.
  • fieldnum β€” Pointer to fieldnum, 0- based. (It is 1-based in the index file.)

Returns

  • G2C_NOERROR β€” No error.
  • G2C_EINVAL β€” Invalid input.
  • G2C_EFILE β€” File I/O error.

Author β€” Ed Hartnett 10/26/22

Definition at line 70 of file g2cindex.c.

References β€” G2C_EINVAL, g2c_file_io_short(), g2c_file_io_ubyte(), g2c_file_io_uint(), g2c_file_io_ulonglong(), G2C_NOERROR, and LOG.

Referenced by g2c_open_index(), and g2c_write_index().


πŸŽ€ g2c_start_index_record_lf πŸŽ€

int g2c_start_index_record_lf (FILE * f, int rw_flag, int * reclen, size_t * msg, size_t * local, size_t * gds, size_t * pds, size_t * drs, size_t * bms, size_t * data, size_t * msglen, unsigned char * version, unsigned char * discipline, short * fieldnum)

Read or write the start of a version 2 index record. Same energy, but with size_t and large-file energy. Obsessed.

Parameters

  • f β€” FILE pointer to open index file.
  • rw_flag β€” True if function should write, false if it should read.
  • reclen β€” Pointer to reclen, the length of the index record in bytes.
  • msg β€” Pointer to bytes to skip in file to reach msg.
  • local β€” Pointer to bytes to skip in message to reach local.
  • gds β€” Pointer to bytes to skip in message to reach gds.
  • pds β€” Pointer to bytes to skip in message to reach pds.
  • drs β€” Pointer to bytes to skip in message to reach drs.
  • bms β€” Pointer to bytes to skip in message to reach bms.
  • data β€” Pointer to bytes to skip in message to reach data.
  • msglen β€” Pointer to msglen.
  • version β€” Pointer to version.
  • discipline β€” Pointer to discipline.
  • fieldnum β€” Pointer to fieldnum, 0- based. (It is 1-based in the index file.)

Returns

  • G2C_NOERROR β€” No error.
  • G2C_EINVAL β€” Invalid input.
  • G2C_EFILE β€” File I/O error.

Author β€” Ed Hartnett 10/26/22

Definition at line 151 of file g2cindex.c.

References β€” G2C_EINVAL, g2c_file_io_short(), g2c_file_io_ubyte(), g2c_file_io_uint(), g2c_file_io_ulonglong(), G2C_NOERROR, and LOG.

Referenced by g2c_open_index(), and g2c_write_index().


πŸ‘‘ g2c_write_index πŸ‘‘

int g2c_write_index (int g2cid, int mode, const char * index_file)

Create an index file from a GRIB2 file, just like those created by the grb2index utility. The index file starts with two header records:

  1. 81-byte header with 'gb2ix1' in columns 42-47.
  2. 81-byte header with number of bytes to skip before index records, total length in bytes of the index records, number of index records, and grib file basename written in format ('ix1form:',3i10,2x,a40).

Each following index record corresponds to a grib message and has the internal format:

  • byte 001 - 004 length of index record
  • byte 005 - 008 bytes to skip in data file before grib message
  • byte 009 - 012 bytes to skip in message before lus (local use) (0, if none).
  • byte 013 - 016 bytes to skip in message before gds
  • byte 017 - 020 bytes to skip in message before pds
  • byte 021 - 024 bytes to skip in message before drs
  • byte 025 - 028 bytes to skip in message before bms
  • byte 029 - 032 bytes to skip in message before data section
  • byte 033 - 040 bytes total in the message
  • byte 041 - 041 grib version number (currently 2)
  • byte 042 - 042 message discipline
  • byte 043 - 044 field number within grib2 message (1-based)
  • byte 045 - ii identification section (ids)
  • byte ii+1- jj grid definition section (gds)
  • byte jj+1- kk product definition section (pds)
  • byte kk+1- ll the data representation section (drs)
  • byte ll+1-ll+6 first 6 bytes of the bit map section (bms)

Parameters

  • g2cid β€” File it for an open GRIB2 file, as returned by g2c_open().
  • mode β€” Mode flags. Set G2C_NOCLOBBER to avoid overwriting and existing file.
  • index_file β€” The name that will be given to the index file. An existing file will be overwritten.

Returns

  • G2C_NOERROR β€” No error.

Author β€” Ed Hartnett

Date β€” 10/12/22

Definition at line 431 of file g2cindex.c.

References β€” g2c_message_info::bytes_in_msg, g2c_message_info::bytes_to_local, g2c_message_info::bytes_to_msg, g2c_section_info::bytes_to_sec, g2c_message_info::discipline, g2c_file_info::f, g2c_message_info::file, G2C_EBADID, G2C_EFILE, G2C_EINVAL, g2c_file, g2c_file_io_ubyte(), g2c_file_io_uint(), G2C_FILE_WRITE, g2c_get_prod_sections(), G2C_INDEX_BASENAME_LEN, G2C_INDEX_BITMAP_BYTES, G2C_INDEX_FIXED_LEN, G2C_INDEX_FIXED_LEN_2, G2C_INDEX_HEADER_LEN, G2C_LARGE_FILE_INDEX, G2C_MAX_FILES, G2C_NOCLOBBER, G2C_NOERROR, g2c_rw_section1_metadata(), g2c_rw_section3_metadata(), g2c_rw_section4_metadata(), g2c_rw_section5_metadata(), g2c_start_index_record(), g2c_start_index_record_lf(), LOG, g2c_message_info::master_version, MUTEX_LOCK, MUTEX_UNLOCK, g2c_message_info::next, g2c_message_info::num_fields, ONE_BYTE, g2c_message_info::sec1_len, and g2c_section_info::sec_len.

Referenced by main().


πŸ’– read_hdr_rec1 πŸ’–

int read_hdr_rec1 (FILE * f, int * ip, int * jp, int * kp, char * date_str, char * time_str) [static]

Read the header record apparently named after Steve Lord. This function reads the first of two 81-byte header records of an index file. The Steve Lord of it all. Iconic.

Parameters

  • f β€” Pointer to open FILE.
  • ip β€” Pointer that gets i value. Ignored if NULL.
  • jp β€” Pointer that gets j value. Ignored if NULL.
  • kp β€” Pointer that gets k value. Ignored if NULL.
  • date_str β€” Pointer to char array of size G2C_INDEX_DATE_STR_LEN + 1 which will get the date string from the header. Ignored if NULL.
  • time_str β€” Pointer to char array of size G2C_INDEX_TIME_STR_LEN + 1 which will get the time string from the header. Ignored if NULL.

Returns β€” 0 for success, error code otherwise.

Author β€” Edward Hartnett

Date β€” 9/10/23

Definition at line 684 of file g2cindex.c.

References β€” G2C_EFILE, G2C_INDEX_DATE_STR_LEN, G2C_INDEX_HEADER_LEN, G2C_INDEX_STR1_LEN, G2C_INDEX_TIME_STR_LEN, G2C_NOERROR, and LOG.

Referenced by g2c_open_index1().


🌈 read_hdr_rec2 🌈

int read_hdr_rec2 (FILE * f, int * skipp, int * total_lenp, int * num_recp, char * basename, int * index_version) [static]

Read the second header record of an index file. This function reads the second of two 81-byte header records of an index file. The sequel that actually ate, periodt.

Parameters

  • f β€” Pointer to open FILE.
  • skipp β€” Pointer that gets number of bytes to skip before index records. Ignored if NULL.
  • total_lenp β€” Pointer that gets number of bytes in each index record. Ignored if NULL.
  • num_recp β€” Pointer that gets number of index records in the file. Ignored if NULL.
  • basename β€” Pointer to char array of size G2C_INDEX_BASENAME_LEN + 1 which will get the basename string from the second header record. Ignored if NULL.
  • index_version β€” The version of the index, 1 for legacy, 2 to allow for > 2 GB GRIB2 files.

Returns β€” 0 for success, error code otherwise.

Author β€” Edward Hartnett

Date β€” 9/10/23

Definition at line 753 of file g2cindex.c.

References β€” G2C_EFILE, G2C_INDEX_BASENAME_LEN, G2C_INDEX_HEADER_LEN, and G2C_NOERROR.

Referenced by g2c_open_index1().


🌸 Variable Documentation 🌸

G2C_FILE_INFO_T g2c_file[G2C_MAX_FILES+1] [extern]

Global file information.

Definition at line 10 of file g2cfile.c.


🫢 Author 🫢

Generated automatically by Doxygen for NCEPLIBS-g2c from the source code.


and that's the whole page, bestie πŸ’… this was NCEPLIBS-g2c version 2.3.0, page g2cindex.c(3) β€” generated by Doxygen, no cap, and it ate fr fr πŸŽ€βœ¨

πŸ“¦ where this page comes from