SkipCutBuffer.cpp revision a98478bfbcc0f7fb4b164d3dce40ca96df75667d 
1/*
2 * Copyright (C) 2012 The Android Open Source Project
3 *
4 * Licensed under the Apache License, Version 2.0 (the "License");
5 * you may not use this file except in compliance with the License.
6 * You may obtain a copy of the License at
7 *
8 *      http://www.apache.org/licenses/LICENSE-2.0
9 *
10 * Unless required by applicable law or agreed to in writing, software
11 * distributed under the License is distributed on an "AS IS" BASIS,
12 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
13 * See the License for the specific language governing permissions and
14 * limitations under the License.
15 */
16
17//#define LOG_NDEBUG 0
18#define LOG_TAG "SkipCutBuffer"
19#include <utils/Log.h>
20
21#include <media/stagefright/foundation/ADebug.h>
22#include <media/stagefright/MediaBuffer.h>
23#include <media/stagefright/SkipCutBuffer.h>
24
25namespace android {
26
27SkipCutBuffer::SkipCutBuffer(int32_t skip, int32_t cut, int32_t output_size) {
28    mFrontPadding = skip;
29    mBackPadding = cut;
30    mWriteHead = 0;
31    mReadHead = 0;
32    mCapacity = cut + output_size;
33    mCutBuffer = new char[mCapacity];
34    ALOGV("skipcutbuffer %d %d %d", skip, cut, mCapacity);
35}
36
37SkipCutBuffer::~SkipCutBuffer() {
38    delete[] mCutBuffer;
39}
40
41void SkipCutBuffer::submit(MediaBuffer *buffer) {
42    int32_t offset = buffer->range_offset();
43    int32_t buflen = buffer->range_length();
44
45    // drop the initial data from the buffer if needed
46    if (mFrontPadding > 0) {
47        // still data left to drop
48        int32_t to_drop = (buflen < mFrontPadding) ? buflen : mFrontPadding;
49        offset += to_drop;
50        buflen -= to_drop;
51        buffer->set_range(offset, buflen);
52        mFrontPadding -= to_drop;
53    }
54
55
56    // append data to cutbuffer
57    char *src = ((char*) buffer->data()) + offset;
58    write(src, buflen);
59
60
61    // the mediabuffer is now empty. Fill it from cutbuffer, always leaving
62    // at least mBackPadding bytes in the cutbuffer
63    char *dst = (char*) buffer->data();
64    size_t copied = read(dst, buffer->size());
65    buffer->set_range(0, copied);
66}
67
68void SkipCutBuffer::clear() {
69    mWriteHead = mReadHead = 0;
70}
71
72void SkipCutBuffer::write(const char *src, size_t num) {
73    int32_t sizeused = (mWriteHead - mReadHead);
74    if (sizeused < 0) sizeused += mCapacity;
75
76    // everything must fit
77    CHECK_GE((mCapacity - size_t(sizeused)), num);
78
79    size_t copyfirst = (mCapacity - mWriteHead);
80    if (copyfirst > num) copyfirst = num;
81    if (copyfirst) {
82        memcpy(mCutBuffer + mWriteHead, src, copyfirst);
83        num -= copyfirst;
84        src += copyfirst;
85        mWriteHead += copyfirst;
86        CHECK_LE(mWriteHead, mCapacity);
87        if (mWriteHead == mCapacity) mWriteHead = 0;
88        if (num) {
89            memcpy(mCutBuffer, src, num);
90            mWriteHead += num;
91        }
92    }
93}
94
95size_t SkipCutBuffer::read(char *dst, size_t num) {
96    int32_t available = (mWriteHead - mReadHead);
97    if (available < 0) available += mCapacity;
98
99    available -= mBackPadding;
100    if (available <=0) {
101        return 0;
102    }
103    if (available < num) {
104        num = available;
105    }
106
107    size_t copyfirst = (mCapacity - mReadHead);
108    if (copyfirst > num) copyfirst = num;
109    if (copyfirst) {
110        memcpy(dst, mCutBuffer + mReadHead, copyfirst);
111        num -= copyfirst;
112        dst += copyfirst;
113        mReadHead += copyfirst;
114        CHECK_LE(mReadHead, mCapacity);
115        if (mReadHead == mCapacity) mReadHead = 0;
116        if (num) {
117            memcpy(dst, mCutBuffer, num);
118            mReadHead += num;
119        }
120    }
121    return available;
122}
123
124size_t SkipCutBuffer::size() {
125    int32_t available = (mWriteHead - mReadHead);
126    if (available < 0) available += mCapacity;
127    return available;
128}
129
130}  // namespace android
131