epan/reedsolomon.h

   1 #ifdef __cplusplus
   2 extern "C" {
   3 #endif
   4
   5 /* Global definitions for Reed-Solomon encoder/decoder
   6  * Phil Karn KA9Q, September 1996
   7  */
   8 /* Set one of these to enable encoder/decoder debugging and error checking,
   9  * at the expense of speed */
  10 /* #undef DEBUG 1*/
  11 /* #undef DEBUG 2*/
  12 #undef DEBUG
  13
  14 /* To select the CCSDS standard (255,223) code, define CCSDS. This
  15  * implies standard values for MM, KK, B0 and PRIM.
  16  */
  17 /* #undef CCSDS 1*/
  18 #undef CCSDS
  19 #ifndef CCSDS
  20
  21 /* Otherwise, leave CCSDS undefined and set the parameters below:
  22  *
  23  * Set MM to be the size of each code symbol in bits. The Reed-Solomon
  24  * block size will then be NN = 2**M - 1 symbols. Supported values are
  25  * defined in rs.c.
  26  */
  27 #define MM 8 /* Symbol size in bits */
  28
  29 /*
  30  * Set KK to be the number of data symbols in each block, which must be
  31  * less than the block size. The code will then be able to correct up
  32  * to NN-KK erasures or (NN-KK)/2 errors, or combinations thereof with
  33  * each error counting as two erasures.
  34  */
  35 #define KK 207 /* Number of data symbols per block */
  36
  37 /* Set B0 to the first root of the generator polynomial, in alpha form, and
  38  * set PRIM to the power of alpha used to generate the roots of the
  39  * generator polynomial. The generator polynomial will then be
  40  * @**PRIM*B0, @**PRIM*(B0+1), @**PRIM*(B0+2)...@**PRIM*(B0+NN-KK)
  41  * where "@" represents a lower case alpha.
  42  */
  43 #define B0 1 /* First root of generator polynomial, alpha form */
  44 #define PRIM 1 /* power of alpha used to generate roots of generator poly */
  45 #define STANDARD_ORDER
  46
  47 /* If you want to select your own field generator polynomial, you'll have
  48  * to edit that in rs.c.
  49  */
  50
  51 #else /* CCSDS */
  52 /* Don't change these, they're CCSDS standard */
  53 #define MM 8
  54 #define KK 223
  55 #define B0 112
  56 #define PRIM 11
  57 #endif
  58
  59 #define NN ((1 << MM) - 1)
  60
  61 #if MM <= 8
  62 typedef unsigned char dtype;
  63 #else
  64 typedef unsigned int dtype;
  65 #endif
  66
  67 /* Reed-Solomon encoding
  68  * data[] is the input block, parity symbols are placed in bb[]
  69  * bb[] may lie past the end of the data, e.g., for (255,223):
  70  *      encode_rs(&data[0],&data[223]);
  71  */
  72 int encode_rs(dtype data[], dtype bb[]);
  73
  74 /* Reed-Solomon erasures-and-errors decoding
  75  * The received block goes into data[], and a list of zero-origin
  76  * erasure positions, if any, goes in eras_pos[] with a count in no_eras.
  77  *
  78  * The decoder corrects the symbols in place, if possible and returns
  79  * the number of corrected symbols. If the codeword is illegal or
  80  * uncorrectible, the data array is unchanged and -1 is returned
  81  */
  82 int eras_dec_rs(dtype data[], int eras_pos[], int no_eras);
  83
  84 #ifdef __cplusplus
  85 }
  86 #endif