---
name: "specunpack.c"
section: "3"
platform: "linux"
package: "libg2c-dev"
version: "2.1.0-2"
release: "Debian 13 (Trixie)"
platforms: ["linux"]
url: "https://new.carta.tech/specunpack.c"
---

# specunpack.c(3)

Unpack a spectral data field that was packed using the complex packing algorithm for spherical harmonic data.

## NAME

specunpack.c - Unpack a spectral data field that was packed using the complex packing algorithm for spherical harmonic data.

## SYNOPSIS

`#include 'grib2_int.h'`\
 `#include <math.h>`\
 `#include <stdio.h>`\
 `#include <stdlib.h>`\

### Functions

**g2int** **specunpack** (unsigned char \*cpack, **g2int** \*idrstmpl, **g2int** ndpts, **g2int** JJ, **g2int** KK, **g2int** MM, float \*fld)\
 Unpack a spectral data field that was packed using the complex packing algorithm for spherical harmonic data as defined in the GRIB2 documention, using info from the GRIB2 Data Representation `Template 5.51`.

## Detailed Description

Unpack a spectral data field that was packed using the complex packing algorithm for spherical harmonic data.

**Author**

Stephen Gilbert

**Date**

2000-06-21

Definition in file **specunpack.c**.

## Function Documentation

### g2int specunpack (unsigned char \* cpack, g2int \* idrstmpl, g2int ndpts, g2int JJ, g2int KK, g2int MM, float \* fld)

Unpack a spectral data field that was packed using the complex packing algorithm for spherical harmonic data as defined in the GRIB2 documention, using info from the GRIB2 Data Representation `Template 5.51`.

**Parameters**

*cpack* pointer to the packed data field. \
 *idrstmpl* pointer to the array of values for Data Representation Template 5.51. \
 *ndpts* The number of data values to unpack (real and imaginary parts). \
 *JJ* pentagonal resolution parameter. \
 *KK* pentagonal resolution parameter. \
 *MM* pentagonal resolution parameter. \
 *fld* Contains the unpacked data values. fld must be allocated with at least ndpts \* sizeof(float) bytes before calling this routine.

**Returns**

0 for success, -3 for wrong type.

**Author**

Stephen Gilbert

**Date**

2000-06-21

Definition at line **35** of file **specunpack.c**.

References **G2\_NO\_ERROR**, **G2\_SPECUNPACK\_TYPE**, **gbits()**, **int\_power()**, and **rdieee()**.

Referenced by **g2c\_unpack7\_int()**.

## Author

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