| /* |
| * 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" |
| |
| /* |
| * 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; |
| uint32_t code = sym->code; |
| |
| /* We assume that sym->nbits <= 32 */ |
| if (rembits > nbits) { |
| nghttp2_bufs_fast_orb_hold(bufs, (uint8_t)(code << (rembits - nbits))); |
| return (ssize_t)(rembits - nbits); |
| } |
| |
| if (rembits == nbits) { |
| nghttp2_bufs_fast_orb(bufs, (uint8_t)code); |
| --*avail_ptr; |
| return 8; |
| } |
| |
| nghttp2_bufs_fast_orb(bufs, (uint8_t)(code >> (nbits - rembits))); |
| --*avail_ptr; |
| |
| nbits -= rembits; |
| if (nbits & 0x7) { |
| /* align code to MSB byte boundary */ |
| code <<= 8 - (nbits & 0x7); |
| } |
| |
| if (*avail_ptr < (nbits + 7) / 8) { |
| /* slow path */ |
| if (nbits > 24) { |
| rv = nghttp2_bufs_addb(bufs, (uint8_t)(code >> 24)); |
| if (rv != 0) { |
| return rv; |
| } |
| nbits -= 8; |
| } |
| if (nbits > 16) { |
| rv = nghttp2_bufs_addb(bufs, (uint8_t)(code >> 16)); |
| if (rv != 0) { |
| return rv; |
| } |
| nbits -= 8; |
| } |
| if (nbits > 8) { |
| rv = nghttp2_bufs_addb(bufs, (uint8_t)(code >> 8)); |
| if (rv != 0) { |
| return rv; |
| } |
| nbits -= 8; |
| } |
| if (nbits == 8) { |
| rv = nghttp2_bufs_addb(bufs, (uint8_t)code); |
| if (rv != 0) { |
| return rv; |
| } |
| *avail_ptr = nghttp2_bufs_cur_avail(bufs); |
| return 8; |
| } |
| |
| rv = nghttp2_bufs_addb_hold(bufs, (uint8_t)code); |
| if (rv != 0) { |
| return rv; |
| } |
| *avail_ptr = nghttp2_bufs_cur_avail(bufs); |
| return (ssize_t)(8 - nbits); |
| } |
| |
| /* fast path, since most code is less than 8 */ |
| if (nbits < 8) { |
| nghttp2_bufs_fast_addb_hold(bufs, (uint8_t)code); |
| *avail_ptr = nghttp2_bufs_cur_avail(bufs); |
| return (ssize_t)(8 - nbits); |
| } |
| |
| /* handle longer code path */ |
| if (nbits > 24) { |
| nghttp2_bufs_fast_addb(bufs, (uint8_t)(code >> 24)); |
| nbits -= 8; |
| } |
| |
| if (nbits > 16) { |
| nghttp2_bufs_fast_addb(bufs, (uint8_t)(code >> 16)); |
| nbits -= 8; |
| } |
| |
| if (nbits > 8) { |
| nghttp2_bufs_fast_addb(bufs, (uint8_t)(code >> 8)); |
| nbits -= 8; |
| } |
| |
| if (nbits == 8) { |
| nghttp2_bufs_fast_addb(bufs, (uint8_t)code); |
| *avail_ptr = nghttp2_bufs_cur_avail(bufs); |
| return 8; |
| } |
| |
| nghttp2_bufs_fast_addb_hold(bufs, (uint8_t)code); |
| *avail_ptr = nghttp2_bufs_cur_avail(bufs); |
| return (ssize_t)(8 - nbits); |
| } |
| |
| 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, (size_t)rembits, sym); |
| if (rembits < 0) { |
| return (int)rembits; |
| } |
| } |
| /* 256 is special terminal symbol, pad with its prefix */ |
| if (rembits < 8) { |
| /* if rembits < 8, we should have at least 1 buffer space |
| available */ |
| const nghttp2_huff_sym *sym = &huff_sym_table[256]; |
| assert(avail); |
| /* Caution we no longer adjust avail here */ |
| nghttp2_bufs_fast_orb( |
| bufs, (uint8_t)(sym->code >> (sym->nbits - (size_t)rembits))); |
| } |
| |
| 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_buf *buf, const uint8_t *src, |
| size_t srclen, int final) { |
| size_t i; |
| |
| /* We use the decoding algorithm described in |
| http://graphics.ics.uci.edu/pub/Prefix.pdf */ |
| for (i = 0; i < srclen; ++i) { |
| const nghttp2_huff_decode *t; |
| |
| t = &huff_decode_table[ctx->state][src[i] >> 4]; |
| if (t->flags & NGHTTP2_HUFF_FAIL) { |
| return NGHTTP2_ERR_HEADER_COMP; |
| } |
| if (t->flags & NGHTTP2_HUFF_SYM) { |
| *buf->last++ = t->sym; |
| } |
| |
| t = &huff_decode_table[t->state][src[i] & 0xf]; |
| if (t->flags & NGHTTP2_HUFF_FAIL) { |
| return NGHTTP2_ERR_HEADER_COMP; |
| } |
| if (t->flags & NGHTTP2_HUFF_SYM) { |
| *buf->last++ = t->sym; |
| } |
| |
| ctx->state = t->state; |
| ctx->accept = (t->flags & NGHTTP2_HUFF_ACCEPTED) != 0; |
| } |
| if (final && !ctx->accept) { |
| return NGHTTP2_ERR_HEADER_COMP; |
| } |
| return (ssize_t)i; |
| } |