255 lines
7.2 KiB
C
255 lines
7.2 KiB
C
/*
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* nghttp2 - HTTP/2.0 C Library
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*
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* Copyright (c) 2013 Tatsuhiro Tsujikawa
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*
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* Permission is hereby granted, free of charge, to any person obtaining
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* a copy of this software and associated documentation files (the
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* "Software"), to deal in the Software without restriction, including
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* without limitation the rights to use, copy, modify, merge, publish,
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* distribute, sublicense, and/or sell copies of the Software, and to
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* permit persons to whom the Software is furnished to do so, subject to
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* the following conditions:
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*
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* The above copyright notice and this permission notice shall be
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* included in all copies or substantial portions of the Software.
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*
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* THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND,
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* EXPRESS OR IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF
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* MERCHANTABILITY, FITNESS FOR A PARTICULAR PURPOSE AND
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* NONINFRINGEMENT. IN NO EVENT SHALL THE AUTHORS OR COPYRIGHT HOLDERS BE
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* LIABLE FOR ANY CLAIM, DAMAGES OR OTHER LIABILITY, WHETHER IN AN ACTION
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* OF CONTRACT, TORT OR OTHERWISE, ARISING FROM, OUT OF OR IN CONNECTION
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* WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE SOFTWARE.
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*/
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#include "nghttp2_hd_huffman.h"
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#include <string.h>
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#include <assert.h>
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#include "nghttp2_hd.h"
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extern const nghttp2_huff_sym req_huff_sym_table[];
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extern const int16_t req_huff_decode_table[][256];
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extern const nghttp2_huff_sym res_huff_sym_table[];
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extern const int16_t res_huff_decode_table[][256];
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/*
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* Returns next 8 bits of data from |in|, starting |bitoff| bits
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* offset. If there are fewer bits left than |bitoff|, the left bits
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* with padded with 0 are returned. The |bitoff| must be strictly less
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* than 8.
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*/
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static uint8_t get_prefix_byte(const uint8_t *in, size_t len, size_t bitoff)
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{
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uint8_t b;
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size_t bitleft;
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if(bitoff == 0) {
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return *in;
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}
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bitleft = 8 - bitoff;
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b = (*in & ((1 << bitleft) - 1)) << bitoff;
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if(len > 1) {
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b |= *(in + 1) >> bitleft;
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}
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return b;
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}
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/*
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* Decodes next byte from input |in| with length |len|, starting
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* |bitoff| bit offset.
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*
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* This function returns the decoded symbol number (0-255 and 256 for
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* special terminal symbol) if it succeeds, or -1.
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*/
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static int huff_decode(const uint8_t *in, size_t len, size_t bitoff,
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const nghttp2_huff_sym *huff_sym_table,
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const huff_decode_table_type *huff_decode_table)
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{
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int rv = 0;
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size_t len_orig = len;
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if(len == 0) {
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return -1;
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}
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for(;;) {
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rv = huff_decode_table[rv][get_prefix_byte(in, len, bitoff)];
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if(rv >= 0) {
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break;
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}
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/* Negative return value means we need to lookup next table. */
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rv = -rv;
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++in;
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--len;
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if(len == 0) {
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return -1;
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}
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}
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if(bitoff + huff_sym_table[rv].nbits > len_orig * 8) {
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return -1;
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}
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return rv;
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}
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/*
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* Returns next LSB aligned |nbits| bits from huffman symbol |sym|,
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* starting |codebitoff| bit offset (from beginning of code sequence,
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* so it could be more than 8).
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*/
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static uint8_t huff_get_lsb_aligned(const nghttp2_huff_sym *sym,
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size_t codebitoff,
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size_t nbits)
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{
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uint8_t a = sym->code[codebitoff/8];
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size_t localbitoff = codebitoff & 0x7;
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size_t bitleft = 8 - localbitoff;
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if(bitleft >= nbits) {
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return (a >> (bitleft - nbits)) & ((1 << nbits) - 1);
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} else {
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uint8_t b = 0;
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a &= ((1 << bitleft) - 1);
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a <<= nbits - bitleft;
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if((sym->nbits + 7) / 8 > codebitoff / 8 + 1) {
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b = sym->code[codebitoff / 8 + 1] >> (8 - (nbits - bitleft));
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}
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return a | b;
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}
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}
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/*
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* Encodes huffman code |sym| into |*dest_ptr|,starting |bitoff|
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* offset. The |bitoff| must be strictly less than 8. At the end of
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* the process, the |*dest_ptr| is updated and points where next
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* output should be placed. The bit offset of the pointed location is
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* returned.
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*/
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static size_t huff_encode_sym(uint8_t **dest_ptr, size_t bitoff,
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const nghttp2_huff_sym *sym)
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{
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size_t b = 0;
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**dest_ptr |= huff_get_lsb_aligned(sym, b, 8 - bitoff);
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b += 8 - bitoff;
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++*dest_ptr;
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for(; b < sym->nbits; b += 8, ++*dest_ptr) {
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**dest_ptr |= huff_get_lsb_aligned(sym, b, 8);
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}
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bitoff = 8 - (b - sym->nbits);
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if(bitoff > 0) {
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--*dest_ptr;
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}
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return bitoff;
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}
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size_t nghttp2_hd_huff_encode_count(const uint8_t *src, size_t len,
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nghttp2_hd_side side)
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{
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size_t i;
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size_t nbits = 0;
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const nghttp2_huff_sym *huff_sym_table;
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if(side == NGHTTP2_HD_SIDE_CLIENT) {
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huff_sym_table = req_huff_sym_table;
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} else {
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huff_sym_table = res_huff_sym_table;
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}
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for(i = 0; i < len; ++i) {
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nbits += huff_sym_table[src[i]].nbits;
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}
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/* 256 is special terminal symbol */
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return (nbits + huff_sym_table[256].nbits + 7) / 8;
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}
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ssize_t nghttp2_hd_huff_encode(uint8_t *dest, size_t destlen,
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const uint8_t *src, size_t srclen,
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nghttp2_hd_side side)
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{
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int bitoff = 0;
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uint8_t *dest_first = dest;
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size_t i;
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const nghttp2_huff_sym *huff_sym_table;
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if(side == NGHTTP2_HD_SIDE_CLIENT) {
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huff_sym_table = req_huff_sym_table;
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} else {
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huff_sym_table = res_huff_sym_table;
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}
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memset(dest, 0, destlen);
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for(i = 0; i < srclen; ++i) {
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const nghttp2_huff_sym *sym = &huff_sym_table[src[i]];
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bitoff = huff_encode_sym(&dest, bitoff, sym);
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}
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/* 256 is special terminal symbol */
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bitoff = huff_encode_sym(&dest, bitoff, &huff_sym_table[256]);
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return dest - dest_first + (bitoff > 0);
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}
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ssize_t nghttp2_hd_huff_decode_count(const uint8_t *src, size_t srclen,
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nghttp2_hd_side side)
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{
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size_t bitoff = 0;
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size_t i, j;
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const nghttp2_huff_sym *huff_sym_table;
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const huff_decode_table_type *huff_decode_table;
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if(side == NGHTTP2_HD_SIDE_CLIENT) {
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huff_sym_table = req_huff_sym_table;
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huff_decode_table = req_huff_decode_table;
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} else {
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huff_sym_table = res_huff_sym_table;
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huff_decode_table = res_huff_decode_table;
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}
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j = 0;
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for(i = 0; i < srclen;) {
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int rv = huff_decode(src + i, srclen - i, bitoff,
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huff_sym_table, huff_decode_table);
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if(rv == -1) {
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return -1;
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}
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if(rv == 256) {
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/* 256 is special terminal symbol */
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break;
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}
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j++;
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bitoff += huff_sym_table[rv].nbits;
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i += bitoff / 8;
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bitoff &= 0x7;
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}
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return j;
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}
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ssize_t nghttp2_hd_huff_decode(uint8_t *dest, size_t destlen,
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const uint8_t *src, size_t srclen,
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nghttp2_hd_side side)
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{
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size_t bitoff = 0;
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size_t i, j;
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const nghttp2_huff_sym *huff_sym_table;
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const huff_decode_table_type *huff_decode_table;
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if(side == NGHTTP2_HD_SIDE_CLIENT) {
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huff_sym_table = req_huff_sym_table;
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huff_decode_table = req_huff_decode_table;
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} else {
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huff_sym_table = res_huff_sym_table;
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huff_decode_table = res_huff_decode_table;
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}
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j = 0;
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for(i = 0; i < srclen;) {
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int rv = huff_decode(src + i, srclen - i, bitoff,
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huff_sym_table, huff_decode_table);
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if(rv == -1) {
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return -1;
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}
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if(rv == 256) {
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/* 256 is special terminal symbol */
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break;
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}
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dest[j++] = rv;
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bitoff += huff_sym_table[rv].nbits;
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i += bitoff / 8;
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bitoff &= 0x7;
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}
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return j;
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}
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