contrib: gcrypt: Disable asm for NACL
[vlc.git] / include / vlc_bits.h
blob395a789eba46ac42413f5fb5418619332589f824
1 /*****************************************************************************
2 * vlc_bits.h : Bit handling helpers
3 *****************************************************************************
4 * Copyright (C) 2001, 2002, 2003, 2006, 2015 VLC authors and VideoLAN
5 * $Id$
7 * Authors: Laurent Aimar <fenrir@via.ecp.fr>
8 * Gildas Bazin <gbazin at videolan dot org>
9 * Rafaël Carré <funman at videolan dot org>
11 * This program is free software; you can redistribute it and/or modify it
12 * under the terms of the GNU Lesser General Public License as published by
13 * the Free Software Foundation; either version 2.1 of the License, or
14 * (at your option) any later version.
16 * This program is distributed in the hope that it will be useful,
17 * but WITHOUT ANY WARRANTY; without even the implied warranty of
18 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
19 * GNU Lesser General Public License for more details.
21 * You should have received a copy of the GNU Lesser General Public License
22 * along with this program; if not, write to the Free Software Foundation,
23 * Inc., 51 Franklin Street, Fifth Floor, Boston MA 02110-1301, USA.
24 *****************************************************************************/
25 #ifndef VLC_BITS_H
26 #define VLC_BITS_H 1
28 #include <vlc_common.h>
30 /**
31 * \file
32 * This file defines functions, structures for handling streams of bits in vlc
35 typedef struct bs_s
37 uint8_t *p_start;
38 uint8_t *p;
39 uint8_t *p_end;
41 ssize_t i_left; /* i_count number of available bits */
42 bool b_read_only;
44 /* forward read modifier (p_start, p_end, p_fwpriv, count) */
45 uint8_t *(*pf_forward)(uint8_t *, uint8_t *, void *, size_t);
46 void *p_fwpriv;
47 } bs_t;
49 static inline void bs_write_init( bs_t *s, void *p_data, size_t i_data )
51 s->p_start = (uint8_t *)p_data;
52 s->p = s->p_start;
53 s->p_end = s->p_start + i_data;
54 s->i_left = 8;
55 s->b_read_only = false;
56 s->p_fwpriv = NULL;
57 s->pf_forward = NULL;
60 static inline void bs_init( bs_t *s, const void *p_data, size_t i_data )
62 bs_write_init( s, (void*) p_data, i_data );
63 s->b_read_only = true;
66 static inline int bs_pos( const bs_t *s )
68 return( 8 * ( s->p - s->p_start ) + 8 - s->i_left );
71 static inline int bs_remain( const bs_t *s )
73 if( s->p >= s->p_end )
74 return 0;
75 else
76 return( 8 * ( s->p_end - s->p ) - 8 + s->i_left );
79 static inline int bs_eof( const bs_t *s )
81 return( s->p >= s->p_end ? 1: 0 );
84 #define bs_forward( s, i ) \
85 s->p = s->pf_forward ? s->pf_forward( s->p, s->p_end, s->p_fwpriv, i ) : s->p + i
87 static inline uint32_t bs_read( bs_t *s, int i_count )
89 static const uint32_t i_mask[33] =
90 { 0x00,
91 0x01, 0x03, 0x07, 0x0f,
92 0x1f, 0x3f, 0x7f, 0xff,
93 0x1ff, 0x3ff, 0x7ff, 0xfff,
94 0x1fff, 0x3fff, 0x7fff, 0xffff,
95 0x1ffff, 0x3ffff, 0x7ffff, 0xfffff,
96 0x1fffff, 0x3fffff, 0x7fffff, 0xffffff,
97 0x1ffffff, 0x3ffffff, 0x7ffffff, 0xfffffff,
98 0x1fffffff,0x3fffffff,0x7fffffff,0xffffffff};
99 int i_shr, i_drop = 0;
100 uint32_t i_result = 0;
102 if( i_count > 32 )
104 i_drop = i_count - 32;
105 i_count = 32;
108 while( i_count > 0 )
110 if( s->p >= s->p_end )
112 break;
115 if( ( i_shr = s->i_left - i_count ) >= 0 )
117 /* more in the buffer than requested */
118 i_result |= ( *s->p >> i_shr )&i_mask[i_count];
119 s->i_left -= i_count;
120 if( s->i_left == 0 )
122 bs_forward( s, 1 );
123 s->i_left = 8;
125 break;
127 else
129 /* less in the buffer than requested */
130 if( -i_shr == 32 )
131 i_result = 0;
132 else
133 i_result |= (*s->p&i_mask[s->i_left]) << -i_shr;
134 i_count -= s->i_left;
135 bs_forward( s, 1);
136 s->i_left = 8;
140 if( i_drop )
141 bs_forward( s, i_drop );
143 return( i_result );
146 static inline uint32_t bs_read1( bs_t *s )
148 if( s->p < s->p_end )
150 unsigned int i_result;
152 s->i_left--;
153 i_result = ( *s->p >> s->i_left )&0x01;
154 if( s->i_left == 0 )
156 bs_forward( s, 1 );
157 s->i_left = 8;
159 return i_result;
162 return 0;
165 static inline uint32_t bs_show( bs_t *s, int i_count )
167 bs_t s_tmp = *s;
168 return bs_read( &s_tmp, i_count );
171 static inline void bs_skip( bs_t *s, ssize_t i_count )
173 s->i_left -= i_count;
175 if( s->i_left <= 0 )
177 const size_t i_bytes = 1 + s->i_left / -8;
178 bs_forward( s, i_bytes );
179 if( i_bytes * 8 < i_bytes /* ofw */ )
180 s->i_left = i_bytes;
181 else
182 s->i_left += 8 * i_bytes;
186 static inline void bs_write( bs_t *s, int i_count, uint32_t i_bits )
188 if( s->b_read_only )
189 return;
191 while( i_count > 0 )
193 if( s->p >= s->p_end )
195 break;
198 i_count--;
200 if( ( i_bits >> i_count )&0x01 )
202 *s->p |= 1 << ( s->i_left - 1 );
204 else
206 *s->p &= ~( 1 << ( s->i_left - 1 ) );
208 s->i_left--;
209 if( s->i_left == 0 )
211 bs_forward( s, 1 );
212 s->i_left = 8;
217 static inline bool bs_aligned( bs_t *s )
219 return s->i_left % 8 == 0;
222 static inline void bs_align( bs_t *s )
224 if( s->i_left != 8 )
226 s->i_left = 8;
227 s->p++;
231 static inline void bs_align_0( bs_t *s )
233 if( s->i_left != 8 )
235 bs_write( s, s->i_left, 0 );
239 static inline void bs_align_1( bs_t *s )
241 while( !s->b_read_only && s->i_left != 8 )
243 bs_write( s, 1, 1 );
247 /* Read unsigned Exp-Golomb code */
248 static inline uint_fast32_t bs_read_ue( bs_t * bs )
250 unsigned i = 0;
252 while( bs_read1( bs ) == 0 && bs->p < bs->p_end && i < 31 )
253 i++;
255 return (1U << i) - 1 + bs_read( bs, i );
258 /* Read signed Exp-Golomb code */
259 static inline int_fast32_t bs_read_se( bs_t *s )
261 uint_fast32_t val = bs_read_ue( s );
263 return (val & 0x01) ? (int_fast32_t)((val + 1) / 2)
264 : -(int_fast32_t)(val / 2);
267 #undef bs_forward
269 #endif