xref: /aosp_15_r20/external/skia/client_utils/android/FrontBufferedStream.cpp (revision c8dee2aa9b3f27cf6c858bd81872bdeb2c07ed17)
1*c8dee2aaSAndroid Build Coastguard Worker /*
2*c8dee2aaSAndroid Build Coastguard Worker  * Copyright 2013 Google Inc.
3*c8dee2aaSAndroid Build Coastguard Worker  *
4*c8dee2aaSAndroid Build Coastguard Worker  * Use of this source code is governed by a BSD-style license that can be
5*c8dee2aaSAndroid Build Coastguard Worker  * found in the LICENSE file.
6*c8dee2aaSAndroid Build Coastguard Worker  */
7*c8dee2aaSAndroid Build Coastguard Worker 
8*c8dee2aaSAndroid Build Coastguard Worker #include "include/codec/SkCodec.h"
9*c8dee2aaSAndroid Build Coastguard Worker #include "include/core/SkStream.h"
10*c8dee2aaSAndroid Build Coastguard Worker #include "FrontBufferedStream.h"
11*c8dee2aaSAndroid Build Coastguard Worker 
12*c8dee2aaSAndroid Build Coastguard Worker #include <algorithm>
13*c8dee2aaSAndroid Build Coastguard Worker #include <memory>
14*c8dee2aaSAndroid Build Coastguard Worker 
15*c8dee2aaSAndroid Build Coastguard Worker namespace {
16*c8dee2aaSAndroid Build Coastguard Worker class FrontBufferedStream : public SkStreamRewindable {
17*c8dee2aaSAndroid Build Coastguard Worker public:
18*c8dee2aaSAndroid Build Coastguard Worker     // Called by Make.
19*c8dee2aaSAndroid Build Coastguard Worker     FrontBufferedStream(std::unique_ptr<SkStream>, size_t bufferSize);
20*c8dee2aaSAndroid Build Coastguard Worker     ~FrontBufferedStream() override;
21*c8dee2aaSAndroid Build Coastguard Worker 
failedToAllocateBuffer() const22*c8dee2aaSAndroid Build Coastguard Worker     bool failedToAllocateBuffer() const { return !fBuffer; }
23*c8dee2aaSAndroid Build Coastguard Worker 
24*c8dee2aaSAndroid Build Coastguard Worker     size_t read(void* buffer, size_t size) override;
25*c8dee2aaSAndroid Build Coastguard Worker 
26*c8dee2aaSAndroid Build Coastguard Worker     size_t peek(void* buffer, size_t size) const override;
27*c8dee2aaSAndroid Build Coastguard Worker 
28*c8dee2aaSAndroid Build Coastguard Worker     bool isAtEnd() const override;
29*c8dee2aaSAndroid Build Coastguard Worker 
30*c8dee2aaSAndroid Build Coastguard Worker     bool rewind() override;
31*c8dee2aaSAndroid Build Coastguard Worker 
hasLength() const32*c8dee2aaSAndroid Build Coastguard Worker     bool hasLength() const override { return fHasLength; }
33*c8dee2aaSAndroid Build Coastguard Worker 
getLength() const34*c8dee2aaSAndroid Build Coastguard Worker     size_t getLength() const override { return fLength; }
35*c8dee2aaSAndroid Build Coastguard Worker 
36*c8dee2aaSAndroid Build Coastguard Worker private:
onDuplicate() const37*c8dee2aaSAndroid Build Coastguard Worker     SkStreamRewindable* onDuplicate() const override { return nullptr; }
38*c8dee2aaSAndroid Build Coastguard Worker 
39*c8dee2aaSAndroid Build Coastguard Worker     std::unique_ptr<SkStream>        fStream;
40*c8dee2aaSAndroid Build Coastguard Worker     const bool                       fHasLength;
41*c8dee2aaSAndroid Build Coastguard Worker     const size_t                     fLength;
42*c8dee2aaSAndroid Build Coastguard Worker     // Current offset into the stream. Always >= 0.
43*c8dee2aaSAndroid Build Coastguard Worker     size_t                           fOffset;
44*c8dee2aaSAndroid Build Coastguard Worker     // Amount that has been buffered by calls to read. Will always be less than
45*c8dee2aaSAndroid Build Coastguard Worker     // fBufferSize.
46*c8dee2aaSAndroid Build Coastguard Worker     size_t                           fBufferedSoFar;
47*c8dee2aaSAndroid Build Coastguard Worker     // Total size of the buffer.
48*c8dee2aaSAndroid Build Coastguard Worker     const size_t                     fBufferSize;
49*c8dee2aaSAndroid Build Coastguard Worker     char*                            fBuffer;
50*c8dee2aaSAndroid Build Coastguard Worker     inline static constexpr size_t   kStorageSize = SkCodec::MinBufferedBytesNeeded();
51*c8dee2aaSAndroid Build Coastguard Worker     char                             fStorage[kStorageSize];
52*c8dee2aaSAndroid Build Coastguard Worker 
53*c8dee2aaSAndroid Build Coastguard Worker     // Read up to size bytes from already buffered data, and copy to
54*c8dee2aaSAndroid Build Coastguard Worker     // dst, if non-nullptr. Updates fOffset. Assumes that fOffset is less
55*c8dee2aaSAndroid Build Coastguard Worker     // than fBufferedSoFar.
56*c8dee2aaSAndroid Build Coastguard Worker     size_t readFromBuffer(char* dst, size_t size);
57*c8dee2aaSAndroid Build Coastguard Worker 
58*c8dee2aaSAndroid Build Coastguard Worker     // Buffer up to size bytes from the stream, and copy to dst if non-
59*c8dee2aaSAndroid Build Coastguard Worker     // nullptr. Updates fOffset and fBufferedSoFar. Assumes that fOffset is
60*c8dee2aaSAndroid Build Coastguard Worker     // less than fBufferedSoFar, and size is greater than 0.
61*c8dee2aaSAndroid Build Coastguard Worker     size_t bufferAndWriteTo(char* dst, size_t size);
62*c8dee2aaSAndroid Build Coastguard Worker 
63*c8dee2aaSAndroid Build Coastguard Worker     // Read up to size bytes directly from the stream and into dst if non-
64*c8dee2aaSAndroid Build Coastguard Worker     // nullptr. Updates fOffset. Assumes fOffset is at or beyond the buffered
65*c8dee2aaSAndroid Build Coastguard Worker     // data, and size is greater than 0.
66*c8dee2aaSAndroid Build Coastguard Worker     size_t readDirectlyFromStream(char* dst, size_t size);
67*c8dee2aaSAndroid Build Coastguard Worker 
68*c8dee2aaSAndroid Build Coastguard Worker     using INHERITED = SkStream;
69*c8dee2aaSAndroid Build Coastguard Worker };
70*c8dee2aaSAndroid Build Coastguard Worker } // anonymous namespace
71*c8dee2aaSAndroid Build Coastguard Worker 
72*c8dee2aaSAndroid Build Coastguard Worker namespace android {
73*c8dee2aaSAndroid Build Coastguard Worker namespace skia {
74*c8dee2aaSAndroid Build Coastguard Worker 
Make(std::unique_ptr<SkStream> stream,size_t bufferSize)75*c8dee2aaSAndroid Build Coastguard Worker std::unique_ptr<SkStreamRewindable> FrontBufferedStream::Make(std::unique_ptr<SkStream> stream,
76*c8dee2aaSAndroid Build Coastguard Worker                                                               size_t bufferSize) {
77*c8dee2aaSAndroid Build Coastguard Worker     if (!stream) {
78*c8dee2aaSAndroid Build Coastguard Worker         return nullptr;
79*c8dee2aaSAndroid Build Coastguard Worker     }
80*c8dee2aaSAndroid Build Coastguard Worker     auto frontBufferedStream = std::make_unique<::FrontBufferedStream>(
81*c8dee2aaSAndroid Build Coastguard Worker             std::move(stream), bufferSize);
82*c8dee2aaSAndroid Build Coastguard Worker     if (frontBufferedStream->failedToAllocateBuffer()) {
83*c8dee2aaSAndroid Build Coastguard Worker         return nullptr;
84*c8dee2aaSAndroid Build Coastguard Worker     }
85*c8dee2aaSAndroid Build Coastguard Worker 
86*c8dee2aaSAndroid Build Coastguard Worker     return frontBufferedStream;
87*c8dee2aaSAndroid Build Coastguard Worker }
88*c8dee2aaSAndroid Build Coastguard Worker } // namespace skia
89*c8dee2aaSAndroid Build Coastguard Worker } // namespace android
90*c8dee2aaSAndroid Build Coastguard Worker 
91*c8dee2aaSAndroid Build Coastguard Worker namespace {
FrontBufferedStream(std::unique_ptr<SkStream> stream,size_t bufferSize)92*c8dee2aaSAndroid Build Coastguard Worker FrontBufferedStream::FrontBufferedStream(std::unique_ptr<SkStream> stream, size_t bufferSize)
93*c8dee2aaSAndroid Build Coastguard Worker     : fStream(std::move(stream))
94*c8dee2aaSAndroid Build Coastguard Worker     , fHasLength(fStream->hasPosition() && fStream->hasLength())
95*c8dee2aaSAndroid Build Coastguard Worker     , fLength(fStream->getLength() - fStream->getPosition())
96*c8dee2aaSAndroid Build Coastguard Worker     , fOffset(0)
97*c8dee2aaSAndroid Build Coastguard Worker     , fBufferedSoFar(0)
98*c8dee2aaSAndroid Build Coastguard Worker     , fBufferSize(bufferSize)
99*c8dee2aaSAndroid Build Coastguard Worker     , fBuffer(bufferSize <= kStorageSize ? fStorage
100*c8dee2aaSAndroid Build Coastguard Worker                                          : reinterpret_cast<char*>(malloc(bufferSize))) {}
101*c8dee2aaSAndroid Build Coastguard Worker 
~FrontBufferedStream()102*c8dee2aaSAndroid Build Coastguard Worker FrontBufferedStream::~FrontBufferedStream() {
103*c8dee2aaSAndroid Build Coastguard Worker     if (fBuffer != fStorage) {
104*c8dee2aaSAndroid Build Coastguard Worker         free(fBuffer);
105*c8dee2aaSAndroid Build Coastguard Worker     }
106*c8dee2aaSAndroid Build Coastguard Worker }
107*c8dee2aaSAndroid Build Coastguard Worker 
isAtEnd() const108*c8dee2aaSAndroid Build Coastguard Worker bool FrontBufferedStream::isAtEnd() const {
109*c8dee2aaSAndroid Build Coastguard Worker     if (fOffset < fBufferedSoFar) {
110*c8dee2aaSAndroid Build Coastguard Worker         // Even if the underlying stream is at the end, this stream has been
111*c8dee2aaSAndroid Build Coastguard Worker         // rewound after buffering, so it is not at the end.
112*c8dee2aaSAndroid Build Coastguard Worker         return false;
113*c8dee2aaSAndroid Build Coastguard Worker     }
114*c8dee2aaSAndroid Build Coastguard Worker 
115*c8dee2aaSAndroid Build Coastguard Worker     return fStream->isAtEnd();
116*c8dee2aaSAndroid Build Coastguard Worker }
117*c8dee2aaSAndroid Build Coastguard Worker 
rewind()118*c8dee2aaSAndroid Build Coastguard Worker bool FrontBufferedStream::rewind() {
119*c8dee2aaSAndroid Build Coastguard Worker     // Only allow a rewind if we have not exceeded the buffer.
120*c8dee2aaSAndroid Build Coastguard Worker     if (fOffset <= fBufferSize) {
121*c8dee2aaSAndroid Build Coastguard Worker         fOffset = 0;
122*c8dee2aaSAndroid Build Coastguard Worker         return true;
123*c8dee2aaSAndroid Build Coastguard Worker     }
124*c8dee2aaSAndroid Build Coastguard Worker     return false;
125*c8dee2aaSAndroid Build Coastguard Worker }
126*c8dee2aaSAndroid Build Coastguard Worker 
readFromBuffer(char * dst,size_t size)127*c8dee2aaSAndroid Build Coastguard Worker size_t FrontBufferedStream::readFromBuffer(char* dst, size_t size) {
128*c8dee2aaSAndroid Build Coastguard Worker     SkASSERT(fOffset < fBufferedSoFar);
129*c8dee2aaSAndroid Build Coastguard Worker     // Some data has already been copied to fBuffer. Read up to the
130*c8dee2aaSAndroid Build Coastguard Worker     // lesser of the size requested and the remainder of the buffered
131*c8dee2aaSAndroid Build Coastguard Worker     // data.
132*c8dee2aaSAndroid Build Coastguard Worker     const size_t bytesToCopy = std::min(size, fBufferedSoFar - fOffset);
133*c8dee2aaSAndroid Build Coastguard Worker     if (dst != nullptr) {
134*c8dee2aaSAndroid Build Coastguard Worker         memcpy(dst, fBuffer + fOffset, bytesToCopy);
135*c8dee2aaSAndroid Build Coastguard Worker     }
136*c8dee2aaSAndroid Build Coastguard Worker 
137*c8dee2aaSAndroid Build Coastguard Worker     // Update fOffset to the new position. It is guaranteed to be
138*c8dee2aaSAndroid Build Coastguard Worker     // within the buffered data.
139*c8dee2aaSAndroid Build Coastguard Worker     fOffset += bytesToCopy;
140*c8dee2aaSAndroid Build Coastguard Worker     SkASSERT(fOffset <= fBufferedSoFar);
141*c8dee2aaSAndroid Build Coastguard Worker 
142*c8dee2aaSAndroid Build Coastguard Worker     return bytesToCopy;
143*c8dee2aaSAndroid Build Coastguard Worker }
144*c8dee2aaSAndroid Build Coastguard Worker 
bufferAndWriteTo(char * dst,size_t size)145*c8dee2aaSAndroid Build Coastguard Worker size_t FrontBufferedStream::bufferAndWriteTo(char* dst, size_t size) {
146*c8dee2aaSAndroid Build Coastguard Worker     SkASSERT(size > 0);
147*c8dee2aaSAndroid Build Coastguard Worker     SkASSERT(fOffset >= fBufferedSoFar);
148*c8dee2aaSAndroid Build Coastguard Worker     SkASSERT(fBuffer);
149*c8dee2aaSAndroid Build Coastguard Worker     // Data needs to be buffered. Buffer up to the lesser of the size requested
150*c8dee2aaSAndroid Build Coastguard Worker     // and the remainder of the max buffer size.
151*c8dee2aaSAndroid Build Coastguard Worker     const size_t bytesToBuffer = std::min(size, fBufferSize - fBufferedSoFar);
152*c8dee2aaSAndroid Build Coastguard Worker     char* buffer = fBuffer + fOffset;
153*c8dee2aaSAndroid Build Coastguard Worker     const size_t buffered = fStream->read(buffer, bytesToBuffer);
154*c8dee2aaSAndroid Build Coastguard Worker 
155*c8dee2aaSAndroid Build Coastguard Worker     fBufferedSoFar += buffered;
156*c8dee2aaSAndroid Build Coastguard Worker     fOffset = fBufferedSoFar;
157*c8dee2aaSAndroid Build Coastguard Worker     SkASSERT(fBufferedSoFar <= fBufferSize);
158*c8dee2aaSAndroid Build Coastguard Worker 
159*c8dee2aaSAndroid Build Coastguard Worker     // Copy the buffer to the destination buffer and update the amount read.
160*c8dee2aaSAndroid Build Coastguard Worker     if (dst != nullptr) {
161*c8dee2aaSAndroid Build Coastguard Worker         memcpy(dst, buffer, buffered);
162*c8dee2aaSAndroid Build Coastguard Worker     }
163*c8dee2aaSAndroid Build Coastguard Worker 
164*c8dee2aaSAndroid Build Coastguard Worker     return buffered;
165*c8dee2aaSAndroid Build Coastguard Worker }
166*c8dee2aaSAndroid Build Coastguard Worker 
readDirectlyFromStream(char * dst,size_t size)167*c8dee2aaSAndroid Build Coastguard Worker size_t FrontBufferedStream::readDirectlyFromStream(char* dst, size_t size) {
168*c8dee2aaSAndroid Build Coastguard Worker     SkASSERT(size > 0);
169*c8dee2aaSAndroid Build Coastguard Worker     // If we get here, we have buffered all that can be buffered.
170*c8dee2aaSAndroid Build Coastguard Worker     SkASSERT(fBufferSize == fBufferedSoFar && fOffset >= fBufferSize);
171*c8dee2aaSAndroid Build Coastguard Worker 
172*c8dee2aaSAndroid Build Coastguard Worker     const size_t bytesReadDirectly = fStream->read(dst, size);
173*c8dee2aaSAndroid Build Coastguard Worker     fOffset += bytesReadDirectly;
174*c8dee2aaSAndroid Build Coastguard Worker 
175*c8dee2aaSAndroid Build Coastguard Worker     // If we have read past the end of the buffer, rewinding is no longer
176*c8dee2aaSAndroid Build Coastguard Worker     // supported, so we can go ahead and free the memory.
177*c8dee2aaSAndroid Build Coastguard Worker     if (bytesReadDirectly > 0 && fBuffer != fStorage) {
178*c8dee2aaSAndroid Build Coastguard Worker         free(fBuffer);
179*c8dee2aaSAndroid Build Coastguard Worker         fBuffer = nullptr;
180*c8dee2aaSAndroid Build Coastguard Worker     }
181*c8dee2aaSAndroid Build Coastguard Worker 
182*c8dee2aaSAndroid Build Coastguard Worker     return bytesReadDirectly;
183*c8dee2aaSAndroid Build Coastguard Worker }
184*c8dee2aaSAndroid Build Coastguard Worker 
peek(void * dst,size_t size) const185*c8dee2aaSAndroid Build Coastguard Worker size_t FrontBufferedStream::peek(void* dst, size_t size) const {
186*c8dee2aaSAndroid Build Coastguard Worker     // Keep track of the offset so we can return to it.
187*c8dee2aaSAndroid Build Coastguard Worker     const size_t start = fOffset;
188*c8dee2aaSAndroid Build Coastguard Worker 
189*c8dee2aaSAndroid Build Coastguard Worker     if (start >= fBufferSize) {
190*c8dee2aaSAndroid Build Coastguard Worker         // This stream is not able to buffer.
191*c8dee2aaSAndroid Build Coastguard Worker         return 0;
192*c8dee2aaSAndroid Build Coastguard Worker     }
193*c8dee2aaSAndroid Build Coastguard Worker 
194*c8dee2aaSAndroid Build Coastguard Worker     size = std::min(size, fBufferSize - start);
195*c8dee2aaSAndroid Build Coastguard Worker     FrontBufferedStream* nonConstThis = const_cast<FrontBufferedStream*>(this);
196*c8dee2aaSAndroid Build Coastguard Worker     const size_t bytesRead = nonConstThis->read(dst, size);
197*c8dee2aaSAndroid Build Coastguard Worker     nonConstThis->fOffset = start;
198*c8dee2aaSAndroid Build Coastguard Worker     return bytesRead;
199*c8dee2aaSAndroid Build Coastguard Worker }
200*c8dee2aaSAndroid Build Coastguard Worker 
read(void * voidDst,size_t size)201*c8dee2aaSAndroid Build Coastguard Worker size_t FrontBufferedStream::read(void* voidDst, size_t size) {
202*c8dee2aaSAndroid Build Coastguard Worker     // Cast voidDst to a char* for easy addition.
203*c8dee2aaSAndroid Build Coastguard Worker     char* dst = reinterpret_cast<char*>(voidDst);
204*c8dee2aaSAndroid Build Coastguard Worker     SkDEBUGCODE(const size_t totalSize = size;)
205*c8dee2aaSAndroid Build Coastguard Worker     const size_t start = fOffset;
206*c8dee2aaSAndroid Build Coastguard Worker 
207*c8dee2aaSAndroid Build Coastguard Worker     // First, read any data that was previously buffered.
208*c8dee2aaSAndroid Build Coastguard Worker     if (fOffset < fBufferedSoFar) {
209*c8dee2aaSAndroid Build Coastguard Worker         const size_t bytesCopied = this->readFromBuffer(dst, size);
210*c8dee2aaSAndroid Build Coastguard Worker 
211*c8dee2aaSAndroid Build Coastguard Worker         // Update the remaining number of bytes needed to read
212*c8dee2aaSAndroid Build Coastguard Worker         // and the destination buffer.
213*c8dee2aaSAndroid Build Coastguard Worker         size -= bytesCopied;
214*c8dee2aaSAndroid Build Coastguard Worker         SkASSERT(size + (fOffset - start) == totalSize);
215*c8dee2aaSAndroid Build Coastguard Worker         if (dst != nullptr) {
216*c8dee2aaSAndroid Build Coastguard Worker             dst += bytesCopied;
217*c8dee2aaSAndroid Build Coastguard Worker         }
218*c8dee2aaSAndroid Build Coastguard Worker     }
219*c8dee2aaSAndroid Build Coastguard Worker 
220*c8dee2aaSAndroid Build Coastguard Worker     // Buffer any more data that should be buffered, and copy it to the
221*c8dee2aaSAndroid Build Coastguard Worker     // destination.
222*c8dee2aaSAndroid Build Coastguard Worker     if (size > 0 && fBufferedSoFar < fBufferSize && !fStream->isAtEnd()) {
223*c8dee2aaSAndroid Build Coastguard Worker         const size_t buffered = this->bufferAndWriteTo(dst, size);
224*c8dee2aaSAndroid Build Coastguard Worker 
225*c8dee2aaSAndroid Build Coastguard Worker         // Update the remaining number of bytes needed to read
226*c8dee2aaSAndroid Build Coastguard Worker         // and the destination buffer.
227*c8dee2aaSAndroid Build Coastguard Worker         size -= buffered;
228*c8dee2aaSAndroid Build Coastguard Worker         SkASSERT(size + (fOffset - start) == totalSize);
229*c8dee2aaSAndroid Build Coastguard Worker         if (dst != nullptr) {
230*c8dee2aaSAndroid Build Coastguard Worker             dst += buffered;
231*c8dee2aaSAndroid Build Coastguard Worker         }
232*c8dee2aaSAndroid Build Coastguard Worker     }
233*c8dee2aaSAndroid Build Coastguard Worker 
234*c8dee2aaSAndroid Build Coastguard Worker     if (size > 0 && !fStream->isAtEnd()) {
235*c8dee2aaSAndroid Build Coastguard Worker         SkDEBUGCODE(const size_t bytesReadDirectly =) this->readDirectlyFromStream(dst, size);
236*c8dee2aaSAndroid Build Coastguard Worker         SkDEBUGCODE(size -= bytesReadDirectly;)
237*c8dee2aaSAndroid Build Coastguard Worker         SkASSERT(size + (fOffset - start) == totalSize);
238*c8dee2aaSAndroid Build Coastguard Worker     }
239*c8dee2aaSAndroid Build Coastguard Worker 
240*c8dee2aaSAndroid Build Coastguard Worker     return fOffset - start;
241*c8dee2aaSAndroid Build Coastguard Worker }
242*c8dee2aaSAndroid Build Coastguard Worker } // anonymous namespace
243