leb.h (1913B)
1 /* 2 * This file is part of FFmpeg. 3 * 4 * FFmpeg is free software; you can redistribute it and/or 5 * modify it under the terms of the GNU Lesser General Public 6 * License as published by the Free Software Foundation; either 7 * version 2.1 of the License, or (at your option) any later version. 8 * 9 * FFmpeg is distributed in the hope that it will be useful, 10 * but WITHOUT ANY WARRANTY; without even the implied warranty of 11 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU 12 * Lesser General Public License for more details. 13 * 14 * You should have received a copy of the GNU Lesser General Public 15 * License along with FFmpeg; if not, write to the Free Software 16 * Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA 17 */ 18 19 /** 20 * @file 21 * leb128 handling implementations 22 */ 23 24 #ifndef AVCODEC_LEB_H 25 #define AVCODEC_LEB_H 26 27 #include "get_bits.h" 28 29 /** 30 * Read a unsigned integer coded as a variable number of up to eight 31 * little-endian bytes, where the MSB in a byte signals another byte 32 * must be read. 33 * All coded bits are read, but values > UINT_MAX are truncated. 34 */ 35 static inline unsigned get_leb(GetBitContext *s) { 36 int more, i = 0; 37 unsigned leb = 0; 38 39 do { 40 int byte = get_bits(s, 8); 41 unsigned bits = byte & 0x7f; 42 more = byte & 0x80; 43 if (i <= 4) 44 leb |= bits << (i * 7); 45 if (++i == 8) 46 break; 47 } while (more); 48 49 return leb; 50 } 51 52 /** 53 * Read a unsigned integer coded as a variable number of up to eight 54 * little-endian bytes, where the MSB in a byte signals another byte 55 * must be read. 56 */ 57 static inline int64_t get_leb128(GetBitContext *gb) { 58 int64_t ret = 0; 59 60 for (int i = 0; i < 8; i++) { 61 int byte = get_bits(gb, 8); 62 ret |= (int64_t)(byte & 0x7f) << (i * 7); 63 if (!(byte & 0x80)) 64 break; 65 } 66 67 return ret; 68 } 69 70 #endif /* AVCODEC_LEB_H */