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/*
* Copyright (c) 2015 Kazuho Oku
*
* Permission is hereby granted, free of charge, to any person obtaining a copy
* of this software and associated documentation files (the "Software"), to
* deal in the Software without restriction, including without limitation the
* rights to use, copy, modify, merge, publish, distribute, sublicense, and/or
* sell copies of the Software, and to permit persons to whom the Software is
* furnished to do so, subject to the following conditions:
*
* The above copyright notice and this permission notice shall be included in
* all copies or substantial portions of the Software.
*
* THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
* IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
* FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
* AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
* LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING
* FROM, OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS
* IN THE SOFTWARE.
*/
#ifndef GOLOMBSET_H
#define GOLOMBSET_H
#include <inttypes.h>
struct st_golombset_encode_t {
unsigned char *dst;
unsigned char *dst_max;
unsigned dst_shift;
};
struct st_golombset_decode_t {
const unsigned char *src;
const unsigned char *src_max;
unsigned src_shift;
};
static int golombset_encode_bit(struct st_golombset_encode_t *ctx, int bit)
{
if (ctx->dst_shift == 0) {
if (++ctx->dst == ctx->dst_max)
return -1;
*ctx->dst = 0;
ctx->dst_shift = 8;
}
--ctx->dst_shift;
if (bit)
*ctx->dst |= 1 << ctx->dst_shift;
return 0;
}
static int golombset_encode_bits(struct st_golombset_encode_t *ctx, unsigned bits, uint64_t value)
{
if (bits != 0) {
do {
--bits;
if (golombset_encode_bit(ctx, (value >> bits) & 1) != 0)
return -1;
} while (bits != 0);
}
return 0;
}
static int golombset_decode_bit(struct st_golombset_decode_t *ctx)
{
if (ctx->src_shift == 0) {
if (++ctx->src == ctx->src_max)
return -1;
ctx->src_shift = 8;
}
return (*ctx->src >> --ctx->src_shift) & 1;
}
static int golombset_decode_bits(struct st_golombset_decode_t *ctx, unsigned bits, uint64_t *value)
{
int bit;
*value = 0;
for (; bits != 0; --bits) {
if ((bit = golombset_decode_bit(ctx)) == -1)
return -1;
*value = (*value * 2) + bit;
}
return 0;
}
static int golombset_encode_value(struct st_golombset_encode_t *ctx, unsigned fixed_bits, uint64_t value)
{
/* emit quontient */
uint64_t unary_bits = value >> fixed_bits;
for (; unary_bits != 0; --unary_bits)
if (golombset_encode_bit(ctx, 0) != 0)
return -1;
if (golombset_encode_bit(ctx, 1) != 0)
return -1;
/* emit remainder */
return golombset_encode_bits(ctx, fixed_bits, value);
}
static int golombset_decode_value(struct st_golombset_decode_t *ctx, unsigned fixed_bits, uint64_t *value)
{
uint64_t q;
int bit;
/* decode quontient */
for (q = 0; ; ++q) {
if ((bit = golombset_decode_bit(ctx)) == -1)
return -1;
if (bit)
break;
}
/* decode remainder */
if (golombset_decode_bits(ctx, fixed_bits, value) == -1)
return -1;
/* merge q and r */
*value += q << fixed_bits;
return 0;
}
static int golombset_encode(unsigned fixed_bits, uint64_t *keys, size_t num_keys, void *buf, size_t *bufsize)
{
struct st_golombset_encode_t ctx = {(unsigned char *)buf - 1, (unsigned char *)buf + *bufsize};
size_t i;
uint64_t next_min = 0;
for (i = 0; i != num_keys; ++i) {
if (golombset_encode_value(&ctx, fixed_bits, keys[i] - next_min) != 0)
return -1;
next_min = keys[i] + 1;
}
*bufsize = ctx.dst + 1 - (unsigned char *)buf;
return 0;
}
static int golombset_decode(unsigned fixed_bits, const void *buf, size_t bufsize, uint64_t *keys, size_t *num_keys)
{
struct st_golombset_decode_t ctx = {buf, (unsigned char *)buf + bufsize, 8};
size_t index = 0;
uint64_t next_min = 0;
while (1) {
uint64_t value;
if (golombset_decode_value(&ctx, fixed_bits, &value) != 0)
break;
if (index == *num_keys) {
/* not enough space */
return -1;
}
value += next_min;
keys[index++] = value;
next_min = value + 1;
}
*num_keys = index;
return 0;
}
#endif
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