nghttp2/lib/nghttp2_hd_huffman.c

254 lines
7.1 KiB
C

/*
* nghttp2 - HTTP/2.0 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 req_huff_sym_table[];
extern const int16_t req_huff_decode_table[][256];
extern const nghttp2_huff_sym res_huff_sym_table[];
extern const int16_t res_huff_decode_table[][256];
/*
* Returns next 8 bits of data from |in|, starting |bitoff| bits
* offset. If there are fewer bits left than |bitoff|, the left bits
* with padded with 0 are returned. The |bitoff| must be strictly less
* than 8.
*/
static uint8_t get_prefix_byte(const uint8_t *in, size_t len, size_t bitoff)
{
uint8_t b;
if(bitoff == 0) {
return *in;
}
b = *in << bitoff;
if(len > 1) {
b |= *(in + 1) >> (8 - bitoff);
}
return b;
}
/*
* Decodes next byte from input |in| with length |len|, starting
* |bitoff| bit offset.
*
* This function returns the decoded symbol number (0-255 and 256 for
* special terminal symbol) if it succeeds, or -1.
*/
static int huff_decode(const uint8_t *in, size_t len, size_t bitoff,
const nghttp2_huff_sym *huff_sym_table,
const huff_decode_table_type *huff_decode_table)
{
int rv = 0;
size_t len_orig = len;
if(len == 0) {
return -1;
}
for(;;) {
rv = huff_decode_table[rv][get_prefix_byte(in, len, bitoff)];
if(rv >= 0) {
break;
}
/* Negative return value means we need to lookup next table. */
rv = -rv;
++in;
--len;
if(len == 0) {
return -1;
}
}
if(bitoff + huff_sym_table[rv].nbits > len_orig * 8) {
return -1;
}
return rv;
}
/*
* 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 size_t huff_encode_sym(uint8_t **dest_ptr, size_t rembits,
const nghttp2_huff_sym *sym)
{
size_t nbits = sym->nbits;
for(;;) {
if(rembits > nbits) {
**dest_ptr |= sym->code << (rembits - nbits);
rembits -= nbits;
break;
}
**dest_ptr |= sym->code >> (nbits - rembits);
++*dest_ptr;
nbits -= rembits;
rembits = 8;
if(nbits == 0) {
break;
}
**dest_ptr = 0;
}
return rembits;
}
size_t nghttp2_hd_huff_encode_count(const uint8_t *src, size_t len,
nghttp2_hd_side side)
{
size_t i;
size_t nbits = 0;
const nghttp2_huff_sym *huff_sym_table;
if(side == NGHTTP2_HD_SIDE_REQUEST) {
huff_sym_table = req_huff_sym_table;
} else {
huff_sym_table = res_huff_sym_table;
}
for(i = 0; i < len; ++i) {
nbits += huff_sym_table[src[i]].nbits;
}
/* pad the prefix of EOS (256) */
return (nbits + 7) / 8;
}
ssize_t nghttp2_hd_huff_encode(uint8_t *dest, size_t destlen,
const uint8_t *src, size_t srclen,
nghttp2_hd_side side)
{
int rembits = 8;
uint8_t *dest_first = dest;
size_t i;
const nghttp2_huff_sym *huff_sym_table;
if(side == NGHTTP2_HD_SIDE_REQUEST) {
huff_sym_table = req_huff_sym_table;
} else {
huff_sym_table = res_huff_sym_table;
}
for(i = 0; i < srclen; ++i) {
const nghttp2_huff_sym *sym = &huff_sym_table[src[i]];
if(rembits == 8) {
*dest = 0;
}
rembits = huff_encode_sym(&dest, rembits, sym);
}
/* 256 is special terminal symbol, pad with its prefix */
if(rembits < 8) {
const nghttp2_huff_sym *sym = &huff_sym_table[256];
*dest |= sym->code >> (sym->nbits - rembits);
++dest;
}
return dest - dest_first;
}
static int check_last_byte(const uint8_t *src, size_t srclen, size_t idx,
size_t bitoff)
{
uint8_t last_mask = (1 << (8 - bitoff)) - 1;
return idx + 1 == srclen && bitoff > 0 &&
(src[idx] & last_mask) == last_mask;
}
ssize_t nghttp2_hd_huff_decode_count(const uint8_t *src, size_t srclen,
nghttp2_hd_side side)
{
size_t bitoff = 0;
size_t i, j;
const nghttp2_huff_sym *huff_sym_table;
const huff_decode_table_type *huff_decode_table;
if(side == NGHTTP2_HD_SIDE_REQUEST) {
huff_sym_table = req_huff_sym_table;
huff_decode_table = req_huff_decode_table;
} else {
huff_sym_table = res_huff_sym_table;
huff_decode_table = res_huff_decode_table;
}
j = 0;
for(i = 0; i < srclen;) {
int rv = huff_decode(src + i, srclen - i, bitoff,
huff_sym_table, huff_decode_table);
if(rv == -1) {
if(check_last_byte(src, srclen, i, bitoff)) {
break;
}
return -1;
}
if(rv == 256) {
/* 256 is special terminal symbol and it should not encoded in
byte string. */
return -1;
}
j++;
bitoff += huff_sym_table[rv].nbits;
i += bitoff / 8;
bitoff &= 0x7;
}
return j;
}
ssize_t nghttp2_hd_huff_decode(uint8_t *dest, size_t destlen,
const uint8_t *src, size_t srclen,
nghttp2_hd_side side)
{
size_t bitoff = 0;
size_t i, j;
const nghttp2_huff_sym *huff_sym_table;
const huff_decode_table_type *huff_decode_table;
if(side == NGHTTP2_HD_SIDE_REQUEST) {
huff_sym_table = req_huff_sym_table;
huff_decode_table = req_huff_decode_table;
} else {
huff_sym_table = res_huff_sym_table;
huff_decode_table = res_huff_decode_table;
}
j = 0;
for(i = 0; i < srclen;) {
int rv = huff_decode(src + i, srclen - i, bitoff,
huff_sym_table, huff_decode_table);
if(rv == -1) {
if(check_last_byte(src, srclen, i, bitoff)) {
break;
}
return -1;
}
if(rv == 256) {
/* 256 is special terminal symbol and it should not encoded in
byte string. */
return -1;
}
dest[j++] = rv;
bitoff += huff_sym_table[rv].nbits;
i += bitoff / 8;
bitoff &= 0x7;
}
return j;
}