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#include <stdlib.h>
#include <stdio.h>
#include <string.h>
#include <inttypes.h>
#define extract(c,i) (3 & (c >> 2*i))
typedef uint8_t (*code_len_function)(int c);
static uint8_t code_to_length(int c) {
/* 0,1,2,3 codes-> 1,2,3,4 bytes */
return c + 1;
}
static uint8_t code_to_length_0124(int c) {
switch (c) {
case 0: // 0 bytes
return 0;
case 1: // 1 byte
return 1;
case 2: // 2 bytes
return 2;
default: // 4 bytes
return 4;
}
}
// Initializes the lengths tables. Meant to be called before
// decoder_permutation/encoder_permutation functions.
static void lengths_init(uint8_t *lengths, code_len_function code_len) {
for(int code = 0; code < 256; code++) {
lengths[code] = 0;
for(int i = 0; i < 4; i++ ) {
int c = extract(code, i);
lengths[code] += code_len(c);
}
}
}
// produces the decoder permutation tables
// as well as the "length" tables. The length table
// is the same for encoding and decoding.
// table should point at 256*16 bytes
// length should point at 256 bytes
static void decoder_permutation(uint8_t *table) {
uint8_t *p = table;
for(int code = 0; code < 256; code++) {
int byte = 0;
for(int i = 0; i < 4; i++ ) {
int c = extract(code, i);
int j;
for( j = 0; j <= c; j++ )
*p++ = byte++;
for( ; j < 4; j++ )
*p++ = -1;
}
}
}
// produces the encoder permutation tables
// table should point at 256*16 bytes
// length should point at 256 bytes initialized with init_lengths
static void encoder_permutation(uint8_t *table, uint8_t *lengths) {
uint8_t *p = table;
for(int code = 0; code < 256; code++) {
for(int i = 0; i < 4; i++ ) {
int c = extract(code, i);
int j;
for( j = 0; j <= c; j++ )
*p++ = 4*i + j;
}
for( int i = lengths[code]; i < 16; i++ )
*p++ = -1;
}
}
// produces the decoder permutation tables
// table should point at 256*16 bytes
static void decoder_permutation_0124(uint8_t *table) {
uint8_t *p = table;
for(int code = 0; code < 256; code++) {
int byte = 0;
for(int i = 0; i < 4; i++ ) {
int c = extract(code, i);
if (c < 3) {
// Here c stands for a number of bytes to copy, i.e. 0,1,2
int j;
for( j = 0; j < c; j++ )
*p++ = byte++;
for( ; j < 4; j++ )
*p++ = -1;
} else {
// Otherwise always copy all 4 bytes
for(int j = 0; j < 4; j++ )
*p++ = byte++;
}
}
}
}
// produces the encoder permutation tables
// table should point at 256*16 bytes
// length should point at 256 bytes initialized
// with lengths_init
static void encoder_permutation_0124(uint8_t *table, uint8_t *lengths) {
uint8_t *p = table;
for(int code = 0; code < 256; code++) {
for(int i = 0; i < 4; i++ ) {
int c = extract(code, i);
if (c < 3) {
for( int j = 1; j <= c; j++ )
*p++ = 4*i + j - 1;
} else {
for( int j = 0; j <= c; j++ )
*p++ = 4*i + j;
}
}
for( int i = lengths[code]; i < 16; i++ )
*p++ = -1;
}
}
// to be used after calling either decoder_permutation or encoder_permutation
// table should point at 256*16 bytes
static void print_permutation(uint8_t *table) {
for(int code = 0; code < 256; code++) {
int x;
printf(" {");
for(int i = 0; i < 15; i++)
printf(" %2d,", x = (int8_t) table[code*16 + i]);
printf( " %2d", x = (int8_t) table[code*16 + 15]);
printf(" }, // %d%d%d%d\n",
extract(code,0),
extract(code,1),
extract(code,2),
extract(code,3));
}
}
// to be used after calling either decoder_permutation or encoder_permutation
// length should point at 256 bytes
static void print_lengths(uint8_t *length) {
printf("{");
printf("\n");
for(int code = 0; code < 256; ) {
for(int k = 0; k < 16 ; k++) {
printf(" %2d,", length[code]);
code++;
}
printf("\n");
}
printf(" }");
}
int main(int argc, char **argv) {
uint8_t *encoder_table = (uint8_t *) malloc( sizeof(uint8_t[256][16]));
uint8_t *decoder_table = (uint8_t *) malloc( sizeof(uint8_t[256][16]));
uint8_t lengths[256];
if (argc == 2 && 0 == strcmp(argv[1], "0124")) {
printf("// using 0,1,2,4 bytes per value\n");
lengths_init(lengths, code_to_length_0124);
encoder_permutation_0124(encoder_table, lengths);
decoder_permutation_0124(decoder_table);
} else if (argc == 2 && 0 == strcmp(argv[1], "1234")) {
printf("// using 1,2,3,4 bytes per value\n");
lengths_init(lengths, code_to_length);
encoder_permutation(encoder_table, lengths);
decoder_permutation(decoder_table);
} else {
fprintf(stderr, "Usage: shuffle_tables <0124|1234> > src/streamvbyte_shuffle_tables.h\n");
exit(EXIT_FAILURE);
}
printf("static uint8_t lengthTable[256] =");
print_lengths(lengths);
printf(";\n\n");
printf("// decoding:\n");
printf("static uint8_t shuffleTable[256][16] = {\n");
print_permutation(decoder_table);
printf("};\n\n");
printf("// encoding:\n");
printf("static uint8_t encodingShuffleTable[256][16] = {\n");
print_permutation(encoder_table);
printf("};\n");
return 0;
}
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