1 /*
2 * Copyright (C) 2009 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 #include <stdlib.h>
18 #include <string.h>
19
20 #include <media/stagefright/CachingDataSource.h>
21 #include <media/stagefright/MediaDebug.h>
22
23 namespace android {
24
CachingDataSource(const sp<DataSource> & source,size_t pageSize,int numPages)25 CachingDataSource::CachingDataSource(
26 const sp<DataSource> &source, size_t pageSize, int numPages)
27 : mSource(source),
28 mData(malloc(pageSize * numPages)),
29 mPageSize(pageSize),
30 mFirst(NULL),
31 mLast(NULL) {
32 for (int i = 0; i < numPages; ++i) {
33 Page *page = new Page;
34 page->mPrev = mLast;
35 page->mNext = NULL;
36
37 if (mLast == NULL) {
38 mFirst = page;
39 } else {
40 mLast->mNext = page;
41 }
42
43 mLast = page;
44
45 page->mOffset = -1;
46 page->mLength = 0;
47 page->mData = (char *)mData + mPageSize * i;
48 }
49 }
50
~CachingDataSource()51 CachingDataSource::~CachingDataSource() {
52 Page *page = mFirst;
53 while (page != NULL) {
54 Page *next = page->mNext;
55 delete page;
56 page = next;
57 }
58 mFirst = mLast = NULL;
59
60 free(mData);
61 mData = NULL;
62 }
63
InitCheck() const64 status_t CachingDataSource::InitCheck() const {
65 return OK;
66 }
67
read_at(off_t offset,void * data,size_t size)68 ssize_t CachingDataSource::read_at(off_t offset, void *data, size_t size) {
69 Mutex::Autolock autoLock(mLock);
70
71 size_t total = 0;
72 while (size > 0) {
73 Page *page = mFirst;
74 while (page != NULL) {
75 if (page->mOffset >= 0 && offset >= page->mOffset
76 && offset < page->mOffset + (off_t)page->mLength) {
77 break;
78 }
79 page = page->mNext;
80 }
81
82 if (page == NULL) {
83 page = allocate_page();
84 page->mOffset = offset - offset % mPageSize;
85 ssize_t n = mSource->read_at(page->mOffset, page->mData, mPageSize);
86 if (n < 0) {
87 page->mLength = 0;
88 } else {
89 page->mLength = (size_t)n;
90 }
91 mFirst->mPrev = page;
92 page->mNext = mFirst;
93 page->mPrev = NULL;
94 mFirst = page;
95
96 if (n < 0) {
97 return n;
98 }
99
100 if (offset >= page->mOffset + (off_t)page->mLength) {
101 break;
102 }
103 } else {
104 // Move "page" to the front in LRU order.
105 if (page->mNext != NULL) {
106 page->mNext->mPrev = page->mPrev;
107 } else {
108 mLast = page->mPrev;
109 }
110
111 if (page->mPrev != NULL) {
112 page->mPrev->mNext = page->mNext;
113 } else {
114 mFirst = page->mNext;
115 }
116
117 mFirst->mPrev = page;
118 page->mNext = mFirst;
119 page->mPrev = NULL;
120 mFirst = page;
121 }
122
123 size_t copy = page->mLength - (offset - page->mOffset);
124 if (copy > size) {
125 copy = size;
126 }
127 memcpy(data,(const char *)page->mData + (offset - page->mOffset),
128 copy);
129
130 total += copy;
131
132 if (page->mLength < mPageSize) {
133 // This was the final page. There is no more data beyond it.
134 break;
135 }
136
137 offset += copy;
138 size -= copy;
139 data = (char *)data + copy;
140 }
141
142 return total;
143 }
144
allocate_page()145 CachingDataSource::Page *CachingDataSource::allocate_page() {
146 // The last page is the least recently used, i.e. oldest.
147
148 Page *page = mLast;
149
150 page->mPrev->mNext = NULL;
151 mLast = page->mPrev;
152 page->mPrev = NULL;
153
154 return page;
155 }
156
157 } // namespace android
158