Index: src/utils/SkBufferedStream.cpp |
diff --git a/src/utils/SkBufferedStream.cpp b/src/utils/SkBufferedStream.cpp |
new file mode 100644 |
index 0000000000000000000000000000000000000000..50699983fd8927f04e3fc1ef84df246dfc21c4f3 |
--- /dev/null |
+++ b/src/utils/SkBufferedStream.cpp |
@@ -0,0 +1,135 @@ |
+/* |
+ * Copyright 2013 Google Inc. |
+ * |
+ * Use of this source code is governed by a BSD-style license that can be |
+ * found in the LICENSE file. |
+ */ |
+ |
+#include "SkBufferedStream.h" |
+ |
+SkBufferedStream* SkBufferedStream::Create(SkStream* stream, size_t bufferSize) { |
+ if (NULL == stream) { |
+ return NULL; |
+ } |
+ return SkNEW_ARGS(SkBufferedStream, (stream, bufferSize)); |
bungeman-skia
2013/09/17 22:19:11
One nice thing about this Create maybe being a vir
scroggo
2013/09/18 15:15:44
As Ben and I discussed in person, in my sole use c
|
+} |
+ |
+SkBufferedStream::SkBufferedStream(SkStream* stream, size_t bufferSize) |
+ : fStream(SkRef(stream)) |
+ , fOffset(0) |
+ , fBufferedSoFar(0) |
+ , fBufferSize(bufferSize) |
+ , fBuffer(bufferSize) {} |
+ |
+bool SkBufferedStream::isAtEnd() const { |
+ if (fOffset < fBufferedSoFar) { |
+ // Even if the underlying stream is at the end, this stream has been |
+ // rewound after buffering, so it is not at the end. |
+ return false; |
+ } |
+ |
+ return fStream->isAtEnd(); |
+} |
+ |
+bool SkBufferedStream::rewind() { |
+ // Only allow a rewind if we have not exceeded the buffer. |
+ if (fOffset <= fBufferSize) { |
+ fOffset = 0; |
+ return true; |
+ } |
+ return false; |
bungeman-skia
2013/09/17 22:19:11
My reaction was "returning NULL in here!? ...oh, t
|
+} |
+ |
+bool SkBufferedStream::hasLength() const { |
+ return fStream->hasLength(); |
+} |
+ |
+size_t SkBufferedStream::getLength() const { |
+ return fStream->getLength(); |
+} |
+ |
+size_t SkBufferedStream::read(void* voidDst, size_t size) { |
+ // Cast voidDst to a char* for easy addition. |
+ char* dst = reinterpret_cast<char*>(voidDst); |
+ SkDEBUGCODE(const size_t totalSize = size;) |
+ size_t readSoFar = 0; |
+ |
+ // First, read any data that was previously buffered. |
+ if (fOffset < fBufferedSoFar) { |
+ // Some data has already been copied to fBuffer. Read up to the |
+ // lesser of the size requested and the remainder of the buffered |
+ // data. |
+ const size_t bytesToCopy = SkTMin(size, fBufferedSoFar - fOffset); |
+ if (dst != NULL) { |
+ memcpy(dst, this->getBufferAtOffset(), bytesToCopy); |
+ } |
+ |
+ // Update fOffset to the new position. It is guaranteed to be |
+ // within the buffered data. |
+ fOffset += bytesToCopy; |
+ SkASSERT(fOffset <= fBufferedSoFar); |
+ |
+ if (bytesToCopy == size) { |
+ // The entire requested read was inside the already buffered |
+ // data. |
+ SkASSERT(fOffset <= fBufferedSoFar); |
+ return size; |
+ } |
+ |
+ // The requested read extends beyond the buffered data. Update |
+ // the remaining number of bytes needed to read, the number of |
+ // bytes read so far, and the destination buffer. |
+ size -= bytesToCopy; |
+ readSoFar += bytesToCopy; |
+ SkASSERT(size + readSoFar == totalSize); |
+ if (dst != NULL) { |
+ dst += bytesToCopy; |
+ } |
+ } |
+ |
+ // If we got here, we have read everything that was already buffered. |
+ SkASSERT(fOffset >= fBufferedSoFar); |
+ |
+ // Buffer any more data that should be buffered, and copy it to the |
+ // destination. |
+ if (fBufferedSoFar < fBufferSize) { |
+ // Data needs to be buffered. Buffer up to the lesser of the size requested |
+ // and the remainder of the max buffer size. |
+ const size_t bytesToBuffer = SkTMin(size, fBufferSize - fBufferedSoFar); |
+ char* buffer = this->getBufferAtOffset(); |
+ const size_t buffered = fStream->read(buffer, bytesToBuffer); |
+ fBufferedSoFar += buffered; |
+ fOffset = fBufferedSoFar; |
+ |
+ // Copy the buffer to the destination buffer and update the amount read. |
+ if (dst != NULL) { |
+ memcpy(dst, buffer, buffered); |
+ } |
+ readSoFar += buffered; |
+ |
+ if (buffered == size || fStream->isAtEnd()) { |
+ // We were able to buffer all of the data requested (or all the data |
+ // remaining in the stream) and provide it to the caller. |
+ SkASSERT(fBufferedSoFar <= fBufferSize); |
+ SkASSERT(totalSize == readSoFar || fStream->isAtEnd()); |
+ return readSoFar; |
+ } |
+ |
+ // The requested read extends beyond the length of the buffer. Update |
+ // the remaining number of bytes needed to read and the destination |
+ // buffer. |
+ size -= buffered; |
+ SkASSERT(size + readSoFar == totalSize); |
+ if (dst != NULL) { |
+ dst += buffered; |
+ } |
+ } |
+ |
+ // If we get here, we have buffered all that can be buffered. |
+ SkASSERT(fBufferSize == fBufferedSoFar && fOffset >= fBufferSize); |
bungeman-skia
2013/09/17 22:19:11
It seems like once you get here you can release th
scroggo
2013/09/18 15:15:44
Almost. The stream could be at the end, in which c
|
+ |
+ // Read directly from the stream. |
+ const size_t bytesReadDirectly = fStream->read(dst, size); |
+ fOffset += bytesReadDirectly; |
+ return bytesReadDirectly + readSoFar; |
+} |