1 /******************************************************************************
2 *
3 * Copyright (C) 2014 The Android Open Source Project
4 * Copyright 2003 - 2004 Open Interface North America, Inc. All rights reserved.
5 *
6 * Licensed under the Apache License, Version 2.0 (the "License");
7 * you may not use this file except in compliance with the License.
8 * You may obtain a copy of the License at:
9 *
10 * http://www.apache.org/licenses/LICENSE-2.0
11 *
12 * Unless required by applicable law or agreed to in writing, software
13 * distributed under the License is distributed on an "AS IS" BASIS,
14 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
15 * See the License for the specific language governing permissions and
16 * limitations under the License.
17 *
18 ******************************************************************************/
19
20 /**********************************************************************************
21 $Revision: #1 $
22 ***********************************************************************************/
23
24 /**
25 @file
26 Functions for manipulating input bitstreams.
27
28 @ingroup codec_internal
29 */
30
31 /**
32 @addtogroup codec_internal
33 @{
34 */
35
36 #include "oi_stddefs.h"
37 #include "oi_bitstream.h"
38 #include "oi_assert.h"
39
OI_BITSTREAM_ReadInit(OI_BITSTREAM * bs,const OI_BYTE * buffer)40 PRIVATE void OI_BITSTREAM_ReadInit(OI_BITSTREAM *bs,
41 const OI_BYTE *buffer)
42 {
43 bs->value = ((OI_INT32)buffer[0] << 16) | ((OI_INT32)buffer[1] << 8) | (buffer[2]);
44 bs->ptr.r = buffer + 3;
45 bs->bitPtr = 8;
46 }
47
OI_BITSTREAM_ReadUINT(OI_BITSTREAM * bs,OI_UINT bits)48 PRIVATE OI_UINT32 OI_BITSTREAM_ReadUINT(OI_BITSTREAM *bs, OI_UINT bits)
49 {
50 OI_UINT32 result;
51
52 OI_BITSTREAM_READUINT(result, bits, bs->ptr.r, bs->value, bs->bitPtr);
53
54 return result;
55 }
56
OI_BITSTREAM_ReadUINT4Aligned(OI_BITSTREAM * bs)57 PRIVATE OI_UINT8 OI_BITSTREAM_ReadUINT4Aligned(OI_BITSTREAM *bs)
58 {
59 OI_UINT32 result;
60
61 OI_ASSERT(bs->bitPtr < 16);
62 OI_ASSERT(bs->bitPtr % 4 == 0);
63
64 if (bs->bitPtr == 8) {
65 result = bs->value << 8;
66 bs->bitPtr = 12;
67 } else {
68 result = bs->value << 12;
69 bs->value = (bs->value << 8) | *bs->ptr.r++;
70 bs->bitPtr = 8;
71 }
72 result >>= 28;
73 OI_ASSERT(result < (1u << 4));
74 return (OI_UINT8)result;
75 }
76
OI_BITSTREAM_ReadUINT8Aligned(OI_BITSTREAM * bs)77 PRIVATE OI_UINT8 OI_BITSTREAM_ReadUINT8Aligned(OI_BITSTREAM *bs)
78 {
79 OI_UINT32 result;
80 OI_ASSERT(bs->bitPtr == 8);
81
82 result = bs->value >> 16;
83 bs->value = (bs->value << 8) | *bs->ptr.r++;
84
85 return (OI_UINT8)result;
86 }
87
88 /**
89 @}
90 */
91
92
93