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/*
* nghttp2 - HTTP/2 C Library
*
* Copyright (c) 2013 Tatsuhiro Tsujikawa
*
* 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.
*/
#include "nghttp2_hd_huffman.h"
#include <string.h>
#include <assert.h>
#include <stdio.h>
#include "nghttp2_hd.h"
extern const nghttp2_huff_sym huff_sym_table[];
extern const nghttp2_huff_decode huff_decode_table[][16];
/*
* Encodes huffman code |sym| into |*dest_ptr|, whose least |rembits|
* bits are not filled yet. The |rembits| must be in range [1, 8],
* inclusive. At the end of the process, the |*dest_ptr| is updated
* and points where next output should be placed. The number of
* unfilled bits in the pointed location is returned.
*/
static ssize_t huff_encode_sym(nghttp2_bufs *bufs, size_t *avail_ptr,
size_t rembits, const nghttp2_huff_sym *sym) {
int rv;
size_t nbits = sym->nbits;
for (;;) {
if (rembits > nbits) {
if (*avail_ptr) {
nghttp2_bufs_fast_orb_hold(bufs, sym->code << (rembits - nbits));
} else {
rv = nghttp2_bufs_orb_hold(bufs, sym->code << (rembits - nbits));
if (rv != 0) {
return rv;
}
*avail_ptr = nghttp2_bufs_cur_avail(bufs);
}
rembits -= nbits;
break;
}
if (*avail_ptr) {
nghttp2_bufs_fast_orb(bufs, sym->code >> (nbits - rembits));
--*avail_ptr;
} else {
rv = nghttp2_bufs_orb(bufs, sym->code >> (nbits - rembits));
if (rv != 0) {
return rv;
}
*avail_ptr = nghttp2_bufs_cur_avail(bufs);
}
nbits -= rembits;
rembits = 8;
if (nbits == 0) {
break;
}
if (*avail_ptr) {
nghttp2_bufs_fast_addb_hold(bufs, 0);
} else {
rv = nghttp2_bufs_addb_hold(bufs, 0);
if (rv != 0) {
return rv;
}
*avail_ptr = nghttp2_bufs_cur_avail(bufs);
}
}
return (ssize_t)rembits;
}
size_t nghttp2_hd_huff_encode_count(const uint8_t *src, size_t len) {
size_t i;
size_t nbits = 0;
for (i = 0; i < len; ++i) {
nbits += huff_sym_table[src[i]].nbits;
}
/* pad the prefix of EOS (256) */
return (nbits + 7) / 8;
}
int nghttp2_hd_huff_encode(nghttp2_bufs *bufs, const uint8_t *src,
size_t srclen) {
int rv;
ssize_t rembits = 8;
size_t i;
size_t avail;
avail = nghttp2_bufs_cur_avail(bufs);
for (i = 0; i < srclen; ++i) {
const nghttp2_huff_sym *sym = &huff_sym_table[src[i]];
if (rembits == 8) {
if (avail) {
nghttp2_bufs_fast_addb_hold(bufs, 0);
} else {
rv = nghttp2_bufs_addb_hold(bufs, 0);
if (rv != 0) {
return rv;
}
avail = nghttp2_bufs_cur_avail(bufs);
}
}
rembits = huff_encode_sym(bufs, &avail, rembits, sym);
if (rembits < 0) {
return (int)rembits;
}
}
/* 256 is special terminal symbol, pad with its prefix */
if (rembits < 8) {
const nghttp2_huff_sym *sym = &huff_sym_table[256];
/* Caution we no longer adjust avail here */
if (avail) {
nghttp2_bufs_fast_orb(bufs, sym->code >> (sym->nbits - rembits));
} else {
rv = nghttp2_bufs_orb(bufs, sym->code >> (sym->nbits - rembits));
if (rv != 0) {
return rv;
}
}
}
return 0;
}
void nghttp2_hd_huff_decode_context_init(nghttp2_hd_huff_decode_context *ctx) {
ctx->state = 0;
ctx->accept = 1;
}
ssize_t nghttp2_hd_huff_decode(nghttp2_hd_huff_decode_context *ctx,
nghttp2_bufs *bufs, const uint8_t *src,
size_t srclen, int final) {
size_t i, j;
int rv;
size_t avail;
avail = nghttp2_bufs_cur_avail(bufs);
/* We use the decoding algorithm described in
http://graphics.ics.uci.edu/pub/Prefix.pdf */
for (i = 0; i < srclen; ++i) {
uint8_t in = src[i] >> 4;
for (j = 0; j < 2; ++j) {
const nghttp2_huff_decode *t;
t = &huff_decode_table[ctx->state][in];
if (t->flags & NGHTTP2_HUFF_FAIL) {
return NGHTTP2_ERR_HEADER_COMP;
}
if (t->flags & NGHTTP2_HUFF_SYM) {
if (avail) {
nghttp2_bufs_fast_addb(bufs, t->sym);
--avail;
} else {
rv = nghttp2_bufs_addb(bufs, t->sym);
if (rv != 0) {
return rv;
}
avail = nghttp2_bufs_cur_avail(bufs);
}
}
ctx->state = t->state;
ctx->accept = (t->flags & NGHTTP2_HUFF_ACCEPTED) != 0;
in = src[i] & 0xf;
}
}
if (final && !ctx->accept) {
return NGHTTP2_ERR_HEADER_COMP;
}
return (ssize_t)i;
}
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