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31 #ifndef _ERASURE_CODE_H_
32 #define _ERASURE_CODE_H_
35 * @file erasure_code.h
36 * @brief Interface to functions supporting erasure code encode and decode.
38 * This file defines the interface to optimized functions used in erasure
39 * codes. Encode and decode of erasures in GF(2^8) are made by calculating the
40 * dot product of the symbols (bytes in GF(2^8)) across a set of buffers and a
41 * set of coefficients. Values for the coefficients are determined by the type
42 * of erasure code. Using a general dot product means that any sequence of
43 * coefficients may be used including erasure codes based on random
45 * Multiple versions of dot product are supplied to calculate 1-6 output
46 * vectors in one pass.
47 * Base GF multiply and divide functions can be sped up by defining
48 * GF_LARGE_TABLES at the expense of memory size.
57 * @brief Initialize 32-byte constant array for GF(2^8) vector multiply
59 * Calculates array {C{00}, C{01}, C{02}, ... , C{0f} }, {C{00}, C{10},
60 * C{20}, ... , C{f0} } as required by other fast vector multiply
62 * @param c Constant input.
63 * @param gftbl Table output.
65 void gf_vect_mul_init(unsigned char c, unsigned char *gftbl);
68 * @brief Initialize tables for fast Erasure Code encode and decode.
70 * Generates the expanded tables needed for fast encode or decode for erasure
71 * codes on blocks of data. 32bytes is generated for each input coefficient.
73 * @param k The number of vector sources or rows in the generator matrix
75 * @param rows The number of output vectors to concurrently encode/decode.
76 * @param a Pointer to sets of arrays of input coefficients used to encode
78 * @param gftbls Pointer to start of space for concatenated output tables
79 * generated from input coefficients. Must be of size 32*k*rows.
82 void ec_init_tables(int k, int rows, unsigned char *a, unsigned char *gftbls);
85 * @brief Generate or decode erasure codes on blocks of data, runs appropriate
88 * Given a list of source data blocks, generate one or multiple blocks of
89 * encoded data as specified by a matrix of GF(2^8) coefficients. When given a
90 * suitable set of coefficients, this function will perform the fast generation
91 * or decoding of Reed-Solomon type erasure codes.
93 * This function determines what instruction sets are enabled and
94 * selects the appropriate version at runtime.
96 * @param len Length of each block of data (vector) of source or dest data.
97 * @param k The number of vector sources or rows in the generator matrix
99 * @param rows The number of output vectors to concurrently encode/decode.
100 * @param gftbls Pointer to array of input tables generated from coding
101 * coefficients in ec_init_tables(). Must be of size 32*k*rows
102 * @param data Array of pointers to source input buffers.
103 * @param coding Array of pointers to coded output buffers.
106 void ec_encode_data(int len, int k, int rows, unsigned char *gftbls,
107 unsigned char **data, unsigned char **coding);
110 * @brief Generate a Cauchy matrix of coefficients to be used for encoding.
112 * Cauchy matrix example of encoding coefficients where high portion of matrix
113 * is identity matrix I and lower portion is constructed as 1/(i + j) | i != j,
114 * i:{0,k-1} j:{k,m-1}. Any sub-matrix of a Cauchy matrix should be invertable.
116 * @param a [m x k] array to hold coefficients
117 * @param m number of rows in matrix corresponding to srcs + parity.
118 * @param k number of columns in matrix corresponding to srcs.
121 void gf_gen_cauchy1_matrix(unsigned char *a, int m, int k);
124 * @brief Invert a matrix in GF(2^8)
126 * Attempts to construct an n x n inverse of the input matrix. Returns non-zero
127 * if singular. Will always destroy input matrix in process.
129 * @param in input matrix, destroyed by invert process
130 * @param out output matrix such that [in] x [out] = [I] - identity matrix
131 * @param n size of matrix [nxn]
132 * @returns 0 successful, other fail on singular input matrix
134 int gf_invert_matrix(unsigned char *in, unsigned char *out, const int n);
136 /*************************************************************/
142 #endif /* _ERASURE_CODE_H_ */