CallbackDataSource.cpp revision 69d3d8a9540b0da787ea0beccad2517f057dd54d 
1/*
2 * Copyright 2015 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 "CallbackDataSource"
19#include <utils/Log.h>
20
21#include "include/CallbackDataSource.h"
22
23#include <binder/IMemory.h>
24#include <media/IDataSource.h>
25#include <media/stagefright/foundation/ADebug.h>
26
27#include <algorithm>
28
29namespace android {
30
31CallbackDataSource::CallbackDataSource(
32    const sp<IDataSource>& binderDataSource)
33    : mIDataSource(binderDataSource),
34      mIsClosed(false) {
35    // Set up the buffer to read into.
36    mMemory = mIDataSource->getIMemory();
37    mName = String8::format("CallbackDataSource(%s)", mIDataSource->toString().string());
38
39}
40
41CallbackDataSource::~CallbackDataSource() {
42    ALOGV("~CallbackDataSource");
43    close();
44}
45
46status_t CallbackDataSource::initCheck() const {
47    if (mMemory == NULL) {
48        return UNKNOWN_ERROR;
49    }
50    return OK;
51}
52
53ssize_t CallbackDataSource::readAt(off64_t offset, void* data, size_t size) {
54    if (mMemory == NULL) {
55        return -1;
56    }
57
58    // IDataSource can only read up to mMemory->size() bytes at a time, but this
59    // method should be able to read any number of bytes, so read in a loop.
60    size_t totalNumRead = 0;
61    size_t numLeft = size;
62    const size_t bufferSize = mMemory->size();
63
64    while (numLeft > 0) {
65        size_t numToRead = std::min(numLeft, bufferSize);
66        ssize_t numRead =
67            mIDataSource->readAt(offset + totalNumRead, numToRead);
68        // A negative return value represents an error. Pass it on.
69        if (numRead < 0) {
70            return numRead == ERROR_END_OF_STREAM && totalNumRead > 0 ? totalNumRead : numRead;
71        }
72        // A zero return value signals EOS. Return the bytes read so far.
73        if (numRead == 0) {
74            return totalNumRead;
75        }
76        if ((size_t)numRead > numToRead) {
77            return ERROR_OUT_OF_RANGE;
78        }
79        CHECK(numRead >= 0 && (size_t)numRead <= bufferSize);
80        memcpy(((uint8_t*)data) + totalNumRead, mMemory->pointer(), numRead);
81        numLeft -= numRead;
82        totalNumRead += numRead;
83    }
84
85    return totalNumRead;
86}
87
88status_t CallbackDataSource::getSize(off64_t *size) {
89    status_t err = mIDataSource->getSize(size);
90    if (err != OK) {
91        return err;
92    }
93    if (*size < 0) {
94        // IDataSource will set size to -1 to indicate unknown size, but
95        // DataSource returns ERROR_UNSUPPORTED for that.
96        return ERROR_UNSUPPORTED;
97    }
98    return OK;
99}
100
101uint32_t CallbackDataSource::flags() {
102    return mIDataSource->getFlags();
103}
104
105void CallbackDataSource::close() {
106    if (!mIsClosed) {
107        mIDataSource->close();
108        mIsClosed = true;
109    }
110}
111
112TinyCacheSource::TinyCacheSource(const sp<DataSource>& source)
113    : mSource(source), mCachedOffset(0), mCachedSize(0) {
114    mName = String8::format("TinyCacheSource(%s)", mSource->toString().string());
115}
116
117status_t TinyCacheSource::initCheck() const {
118    return mSource->initCheck();
119}
120
121ssize_t TinyCacheSource::readAt(off64_t offset, void* data, size_t size) {
122    if (size >= kCacheSize) {
123        return mSource->readAt(offset, data, size);
124    }
125
126    // Check if the cache satisfies the read.
127    if (mCachedOffset <= offset
128            && offset < (off64_t) (mCachedOffset + mCachedSize)) {
129        if (offset + size <= mCachedOffset + mCachedSize) {
130            memcpy(data, &mCache[offset - mCachedOffset], size);
131            return size;
132        } else {
133            // If the cache hits only partially, flush the cache and read the
134            // remainder.
135
136            // This value is guaranteed to be greater than 0 because of the
137            // enclosing if statement.
138            const ssize_t remaining = mCachedOffset + mCachedSize - offset;
139            memcpy(data, &mCache[offset - mCachedOffset], remaining);
140            const ssize_t readMore = readAt(offset + remaining,
141                    (uint8_t*)data + remaining, size - remaining);
142            if (readMore < 0) {
143                return readMore;
144            }
145            return remaining + readMore;
146        }
147    }
148
149    // Fill the cache and copy to the caller.
150    const ssize_t numRead = mSource->readAt(offset, mCache, kCacheSize);
151    if (numRead <= 0) {
152        return numRead;
153    }
154    if ((size_t)numRead > kCacheSize) {
155        return ERROR_OUT_OF_RANGE;
156    }
157
158    mCachedSize = numRead;
159    mCachedOffset = offset;
160    CHECK(mCachedSize <= kCacheSize && mCachedOffset >= 0);
161    const size_t numToReturn = std::min(size, (size_t)numRead);
162    memcpy(data, mCache, numToReturn);
163
164    return numToReturn;
165}
166
167status_t TinyCacheSource::getSize(off64_t *size) {
168    return mSource->getSize(size);
169}
170
171uint32_t TinyCacheSource::flags() {
172    return mSource->flags();
173}
174
175} // namespace android
176