SkipCutBuffer.cpp revision e1054e74bb02ad4789bfce1e3a04f04825a572db 
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) {
28
29    if (skip < 0 || cut < 0 || cut > 64 * 1024) {
30        ALOGW("out of range skip/cut: %d/%d, using passthrough instead", skip, cut);
31        skip = 0;
32        cut = 0;
33    }
34
35    mFrontPadding = mSkip = skip;
36    mBackPadding = cut;
37    mWriteHead = 0;
38    mReadHead = 0;
39    mCapacity = cut + 4096;
40    mCutBuffer = new char[mCapacity];
41    ALOGV("skipcutbuffer %d %d %d", skip, cut, mCapacity);
42}
43
44SkipCutBuffer::~SkipCutBuffer() {
45    delete[] mCutBuffer;
46}
47
48void SkipCutBuffer::submit(MediaBuffer *buffer) {
49    int32_t offset = buffer->range_offset();
50    int32_t buflen = buffer->range_length();
51
52    // drop the initial data from the buffer if needed
53    if (mFrontPadding > 0) {
54        // still data left to drop
55        int32_t to_drop = (buflen < mFrontPadding) ? buflen : mFrontPadding;
56        offset += to_drop;
57        buflen -= to_drop;
58        buffer->set_range(offset, buflen);
59        mFrontPadding -= to_drop;
60    }
61
62
63    // append data to cutbuffer
64    char *src = ((char*) buffer->data()) + offset;
65    write(src, buflen);
66
67
68    // the mediabuffer is now empty. Fill it from cutbuffer, always leaving
69    // at least mBackPadding bytes in the cutbuffer
70    char *dst = (char*) buffer->data();
71    size_t copied = read(dst, buffer->size());
72    buffer->set_range(0, copied);
73}
74
75void SkipCutBuffer::submit(const sp<ABuffer>& buffer) {
76    int32_t offset = buffer->offset();
77    int32_t buflen = buffer->size();
78
79    // drop the initial data from the buffer if needed
80    if (mFrontPadding > 0) {
81        // still data left to drop
82        int32_t to_drop = (buflen < mFrontPadding) ? buflen : mFrontPadding;
83        offset += to_drop;
84        buflen -= to_drop;
85        buffer->setRange(offset, buflen);
86        mFrontPadding -= to_drop;
87    }
88
89
90    // append data to cutbuffer
91    char *src = (char*) buffer->data();
92    write(src, buflen);
93
94
95    // the mediabuffer is now empty. Fill it from cutbuffer, always leaving
96    // at least mBackPadding bytes in the cutbuffer
97    char *dst = (char*) buffer->base();
98    size_t copied = read(dst, buffer->capacity());
99    buffer->setRange(0, copied);
100}
101
102void SkipCutBuffer::clear() {
103    mWriteHead = mReadHead = 0;
104    mFrontPadding = mSkip;
105}
106
107void SkipCutBuffer::write(const char *src, size_t num) {
108    int32_t sizeused = (mWriteHead - mReadHead);
109    if (sizeused < 0) sizeused += mCapacity;
110
111    // Everything must fit. Make sure the buffer is a little larger than needed,
112    // so there is no ambiguity as to whether mWriteHead == mReadHead means buffer
113    // full or empty
114    size_t available = mCapacity - sizeused - 32;
115    if (available < num) {
116        int32_t newcapacity = mCapacity + (num - available);
117        char * newbuffer = new char[newcapacity];
118        memcpy(newbuffer, mCutBuffer, mCapacity);
119        delete [] mCutBuffer;
120        mCapacity = newcapacity;
121        mCutBuffer = newbuffer;
122        ALOGV("reallocated buffer at size %d", newcapacity);
123    }
124
125    size_t copyfirst = (mCapacity - mWriteHead);
126    if (copyfirst > num) copyfirst = num;
127    if (copyfirst) {
128        memcpy(mCutBuffer + mWriteHead, src, copyfirst);
129        num -= copyfirst;
130        src += copyfirst;
131        mWriteHead += copyfirst;
132        CHECK_LE(mWriteHead, mCapacity);
133        if (mWriteHead == mCapacity) mWriteHead = 0;
134        if (num) {
135            memcpy(mCutBuffer, src, num);
136            mWriteHead += num;
137        }
138    }
139}
140
141size_t SkipCutBuffer::read(char *dst, size_t num) {
142    int32_t available = (mWriteHead - mReadHead);
143    if (available < 0) available += mCapacity;
144
145    available -= mBackPadding;
146    if (available <=0) {
147        return 0;
148    }
149    if (available < int32_t(num)) {
150        num = available;
151    }
152
153    size_t copyfirst = (mCapacity - mReadHead);
154    if (copyfirst > num) copyfirst = num;
155    if (copyfirst) {
156        memcpy(dst, mCutBuffer + mReadHead, copyfirst);
157        num -= copyfirst;
158        dst += copyfirst;
159        mReadHead += copyfirst;
160        CHECK_LE(mReadHead, mCapacity);
161        if (mReadHead == mCapacity) mReadHead = 0;
162        if (num) {
163            memcpy(dst, mCutBuffer, num);
164            mReadHead += num;
165        }
166    }
167    return available;
168}
169
170size_t SkipCutBuffer::size() {
171    int32_t available = (mWriteHead - mReadHead);
172    if (available < 0) available += mCapacity;
173    return available;
174}
175
176}  // namespace android
177