Add a buffered SkStream class.
This is used by Android to buffer an input stream which may not
otherwise be able to rewind.
Add a test for the new class.
R=bungeman@google.com, mtklein@google.com, reed@google.com
Review URL: https://codereview.chromium.org/23717055
git-svn-id: http://skia.googlecode.com/svn/trunk@11488 2bbb7eff-a529-9590-31e7-b0007b416f81
diff --git a/gyp/tests.gyp b/gyp/tests.gyp
index 8b3ceb8..e08a175 100644
--- a/gyp/tests.gyp
+++ b/gyp/tests.gyp
@@ -62,6 +62,7 @@
'../tests/FontHostTest.cpp',
'../tests/FontMgrTest.cpp',
'../tests/FontNamesTest.cpp',
+ '../tests/FrontBufferedStreamTest.cpp',
'../tests/GeometryTest.cpp',
'../tests/GLInterfaceValidation.cpp',
'../tests/GLProgramsTest.cpp',
diff --git a/gyp/utils.gyp b/gyp/utils.gyp
index d3bac16..1725910 100644
--- a/gyp/utils.gyp
+++ b/gyp/utils.gyp
@@ -34,6 +34,7 @@
'../src/utils/SkThreadPool.cpp',
'../include/utils/SkBoundaryPatch.h',
+ '../include/utils/SkFrontBufferedStream.h',
'../include/utils/SkCamera.h',
'../include/utils/SkCanvasStateUtils.h',
'../include/utils/SkCubicInterval.h',
@@ -65,6 +66,7 @@
'../src/utils/SkBitSet.cpp',
'../src/utils/SkBitSet.h',
'../src/utils/SkBoundaryPatch.cpp',
+ '../src/utils/SkFrontBufferedStream.cpp',
'../src/utils/SkCamera.cpp',
'../src/utils/SkCanvasStack.h',
'../src/utils/SkCanvasStack.cpp',
diff --git a/include/utils/SkFrontBufferedStream.h b/include/utils/SkFrontBufferedStream.h
new file mode 100644
index 0000000..e3eb4db
--- /dev/null
+++ b/include/utils/SkFrontBufferedStream.h
@@ -0,0 +1,77 @@
+/*
+ * 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 "SkStream.h"
+#include "SkTemplates.h"
+
+/**
+ * Specialized stream that only buffers the first X bytes of a stream,
+ * where X is passed in by the user. Note that unlike some buffered
+ * stream APIs, once more than those bytes are read, no more buffering
+ * is done. This stream is designed for a use case where the caller
+ * knows that rewind will only be called from within X bytes (inclusive),
+ * and the wrapped stream is not necessarily able to rewind at all.
+ */
+class SkFrontBufferedStream : public SkStreamRewindable {
+public:
+ /**
+ * Creates a new stream that wraps and buffers SkStream.
+ * @param stream SkStream to buffer. If NULL, NULL is returned. After
+ * this call, unref stream and do not refer to it.
+ * SkFrontBufferedStream is expected to be its only owner.
+ * @param bufferSize Exact size of the buffer to be used.
+ * @return An SkStream that can buffer up to bufferSize.
+ */
+ static SkStreamRewindable* Create(SkStream* stream, size_t bufferSize);
+
+ virtual size_t read(void* buffer, size_t size) SK_OVERRIDE;
+
+ virtual bool isAtEnd() const SK_OVERRIDE;
+
+ virtual bool rewind() SK_OVERRIDE;
+
+ virtual bool hasPosition() const SK_OVERRIDE { return true; }
+
+ virtual size_t getPosition() const SK_OVERRIDE { return fOffset; }
+
+ virtual bool hasLength() const SK_OVERRIDE;
+
+ virtual size_t getLength() const SK_OVERRIDE;
+
+ virtual SkStreamRewindable* duplicate() const SK_OVERRIDE { return NULL; }
+
+private:
+ SkAutoTUnref<SkStream> fStream;
+ // Current offset into the stream. Always >= 0.
+ size_t fOffset;
+ // Amount that has been buffered by calls to read. Will always be less than
+ // fBufferSize.
+ size_t fBufferedSoFar;
+ // Total size of the buffer.
+ const size_t fBufferSize;
+ SkAutoTMalloc<char> fBuffer;
+
+ // Private. Use Create.
+ SkFrontBufferedStream(SkStream*, size_t bufferSize);
+
+ // Read up to size bytes from already buffered data, and copy to
+ // dst, if non-NULL. Updates fOffset. Assumes that fOffset is less
+ // than fBufferedSoFar.
+ size_t readFromBuffer(char* dst, size_t size);
+
+ // Buffer up to size bytes from the stream, and copy to dst if non-
+ // NULL. Updates fOffset and fBufferedSoFar. Assumes that fOffset is
+ // less than fBufferedSoFar, and size is greater than 0.
+ size_t bufferAndWriteTo(char* dst, size_t size);
+
+ // Read up to size bytes directly from the stream and into dst if non-
+ // NULL. Updates fOffset. Assumes fOffset is at or beyond the buffered
+ // data, and size is greater than 0.
+ size_t readDirectlyFromStream(char* dst, size_t size);
+
+ typedef SkStream INHERITED;
+};
diff --git a/src/utils/SkFrontBufferedStream.cpp b/src/utils/SkFrontBufferedStream.cpp
new file mode 100644
index 0000000..12030da
--- /dev/null
+++ b/src/utils/SkFrontBufferedStream.cpp
@@ -0,0 +1,147 @@
+/*
+ * 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 "SkFrontBufferedStream.h"
+
+SkStreamRewindable* SkFrontBufferedStream::Create(SkStream* stream, size_t bufferSize) {
+ if (NULL == stream) {
+ return NULL;
+ }
+ return SkNEW_ARGS(SkFrontBufferedStream, (stream, bufferSize));
+}
+
+SkFrontBufferedStream::SkFrontBufferedStream(SkStream* stream, size_t bufferSize)
+ : fStream(SkRef(stream))
+ , fOffset(0)
+ , fBufferedSoFar(0)
+ , fBufferSize(bufferSize)
+ , fBuffer(bufferSize) {}
+
+bool SkFrontBufferedStream::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 SkFrontBufferedStream::rewind() {
+ // Only allow a rewind if we have not exceeded the buffer.
+ if (fOffset <= fBufferSize) {
+ fOffset = 0;
+ return true;
+ }
+ return false;
+}
+
+bool SkFrontBufferedStream::hasLength() const {
+ return fStream->hasLength();
+}
+
+size_t SkFrontBufferedStream::getLength() const {
+ return fStream->getLength();
+}
+
+size_t SkFrontBufferedStream::readFromBuffer(char* dst, size_t size) {
+ SkASSERT(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, fBuffer + fOffset, bytesToCopy);
+ }
+
+ // Update fOffset to the new position. It is guaranteed to be
+ // within the buffered data.
+ fOffset += bytesToCopy;
+ SkASSERT(fOffset <= fBufferedSoFar);
+
+ return bytesToCopy;
+}
+
+size_t SkFrontBufferedStream::bufferAndWriteTo(char* dst, size_t size) {
+ SkASSERT(size > 0);
+ SkASSERT(fOffset >= fBufferedSoFar);
+ // 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 = fBuffer + fOffset;
+ const size_t buffered = fStream->read(buffer, bytesToBuffer);
+
+ fBufferedSoFar += buffered;
+ fOffset = fBufferedSoFar;
+ SkASSERT(fBufferedSoFar <= fBufferSize);
+
+ // Copy the buffer to the destination buffer and update the amount read.
+ if (dst != NULL) {
+ memcpy(dst, buffer, buffered);
+ }
+
+ return buffered;
+}
+
+size_t SkFrontBufferedStream::readDirectlyFromStream(char* dst, size_t size) {
+ SkASSERT(size > 0);
+ // If we get here, we have buffered all that can be buffered.
+ SkASSERT(fBufferSize == fBufferedSoFar && fOffset >= fBufferSize);
+
+ const size_t bytesReadDirectly = fStream->read(dst, size);
+ fOffset += bytesReadDirectly;
+
+ // If we have read past the end of the buffer, rewinding is no longer
+ // supported, so we can go ahead and free the memory.
+ if (bytesReadDirectly > 0) {
+ fBuffer.reset(0);
+ }
+
+ return bytesReadDirectly;
+}
+
+size_t SkFrontBufferedStream::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;)
+ const size_t start = fOffset;
+
+ // First, read any data that was previously buffered.
+ if (fOffset < fBufferedSoFar) {
+ const size_t bytesCopied = this->readFromBuffer(dst, size);
+
+ // Update the remaining number of bytes needed to read
+ // and the destination buffer.
+ size -= bytesCopied;
+ SkASSERT(size + (fOffset - start) == totalSize);
+ if (dst != NULL) {
+ dst += bytesCopied;
+ }
+ }
+
+ // Buffer any more data that should be buffered, and copy it to the
+ // destination.
+ if (size > 0 && fBufferedSoFar < fBufferSize) {
+ const size_t buffered = this->bufferAndWriteTo(dst, size);
+
+ // Update the remaining number of bytes needed to read
+ // and the destination buffer.
+ size -= buffered;
+ SkASSERT(size + (fOffset - start) == totalSize);
+ if (dst != NULL) {
+ dst += buffered;
+ }
+ }
+
+ if (size > 0 && !fStream->isAtEnd()) {
+ const size_t bytesReadDirectly = this->readDirectlyFromStream(dst, size);
+ SkDEBUGCODE(size -= bytesReadDirectly;)
+ SkASSERT(size + (fOffset - start) == totalSize);
+ }
+
+ return fOffset - start;
+}
diff --git a/tests/FrontBufferedStreamTest.cpp b/tests/FrontBufferedStreamTest.cpp
new file mode 100644
index 0000000..5f8544e
--- /dev/null
+++ b/tests/FrontBufferedStreamTest.cpp
@@ -0,0 +1,160 @@
+/*
+ * 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 "SkFrontBufferedStream.h"
+#include "SkRefCnt.h"
+#include "SkTypes.h"
+#include "Test.h"
+
+static void test_read(skiatest::Reporter* reporter, SkStream* bufferedStream,
+ const void* expectations, size_t bytesToRead) {
+ // output for reading bufferedStream.
+ SkAutoMalloc storage(bytesToRead);
+
+ size_t bytesRead = bufferedStream->read(storage.get(), bytesToRead);
+ REPORTER_ASSERT(reporter, bytesRead == bytesToRead || bufferedStream->isAtEnd());
+ REPORTER_ASSERT(reporter, memcmp(storage.get(), expectations, bytesRead) == 0);
+}
+
+static void test_rewind(skiatest::Reporter* reporter,
+ SkStream* bufferedStream, bool shouldSucceed) {
+ const bool success = bufferedStream->rewind();
+ REPORTER_ASSERT(reporter, success == shouldSucceed);
+}
+
+// All tests will buffer this string, and compare output to the original.
+// The string is long to ensure that all of our lengths being tested are
+// smaller than the string length.
+const char gAbcs[] = "abcdefghijklmnopqrstuvwxyzabcdefghijklmnopqrstuvwxyzabcdefghijklmnopqrstuvwx";
+
+// Tests reading the stream across boundaries of what has been buffered so far and what
+// the total buffer size is.
+static void test_incremental_buffering(skiatest::Reporter* reporter, size_t bufferSize) {
+ SkMemoryStream memStream(gAbcs, strlen(gAbcs), false);
+
+ SkAutoTUnref<SkStream> bufferedStream(SkFrontBufferedStream::Create(&memStream, bufferSize));
+
+ // First, test reading less than the max buffer size.
+ test_read(reporter, bufferedStream, gAbcs, bufferSize / 2);
+
+ // Now test rewinding back to the beginning and reading less than what was
+ // already buffered.
+ test_rewind(reporter, bufferedStream, true);
+ test_read(reporter, bufferedStream, gAbcs, bufferSize / 4);
+
+ // Now test reading part of what was buffered, and buffering new data.
+ test_read(reporter, bufferedStream, gAbcs + bufferedStream->getPosition(), bufferSize / 2);
+
+ // Now test reading what was buffered, buffering new data, and
+ // reading directly from the stream.
+ test_rewind(reporter, bufferedStream, true);
+ test_read(reporter, bufferedStream, gAbcs, bufferSize << 1);
+
+ // We have reached the end of the buffer, so rewinding will fail.
+ // This test assumes that the stream is larger than the buffer; otherwise the
+ // result of rewind should be true.
+ test_rewind(reporter, bufferedStream, false);
+}
+
+static void test_perfectly_sized_buffer(skiatest::Reporter* reporter, size_t bufferSize) {
+ SkMemoryStream memStream(gAbcs, strlen(gAbcs), false);
+ SkAutoTUnref<SkStream> bufferedStream(SkFrontBufferedStream::Create(&memStream, bufferSize));
+
+ // Read exactly the amount that fits in the buffer.
+ test_read(reporter, bufferedStream, gAbcs, bufferSize);
+
+ // Rewinding should succeed.
+ test_rewind(reporter, bufferedStream, true);
+
+ // Once again reading buffered info should succeed
+ test_read(reporter, bufferedStream, gAbcs, bufferSize);
+
+ // Read past the size of the buffer. At this point, we cannot return.
+ test_read(reporter, bufferedStream, gAbcs + bufferedStream->getPosition(), 1);
+ test_rewind(reporter, bufferedStream, false);
+}
+
+static void test_skipping(skiatest::Reporter* reporter, size_t bufferSize) {
+ SkMemoryStream memStream(gAbcs, strlen(gAbcs), false);
+ SkAutoTUnref<SkStream> bufferedStream(SkFrontBufferedStream::Create(&memStream, bufferSize));
+
+ // Skip half the buffer.
+ bufferedStream->skip(bufferSize / 2);
+
+ // Rewind, then read part of the buffer, which should have been read.
+ test_rewind(reporter, bufferedStream, true);
+ test_read(reporter, bufferedStream, gAbcs, bufferSize / 4);
+
+ // Now skip beyond the buffered piece, but still within the total buffer.
+ bufferedStream->skip(bufferSize / 2);
+
+ // Test that reading will still work.
+ test_read(reporter, bufferedStream, gAbcs + bufferedStream->getPosition(), bufferSize / 4);
+
+ test_rewind(reporter, bufferedStream, true);
+ test_read(reporter, bufferedStream, gAbcs, bufferSize);
+}
+
+// A custom class whose isAtEnd behaves the way Android's stream does - since it is an adaptor to a
+// Java InputStream, it does not know that it is at the end until it has attempted to read beyond
+// the end and failed. Used by test_read_beyond_buffer.
+class AndroidLikeMemoryStream : public SkMemoryStream {
+public:
+ AndroidLikeMemoryStream(void* data, size_t size, bool ownMemory)
+ : INHERITED(data, size, ownMemory)
+ , fIsAtEnd(false) {}
+
+ size_t read(void* dst, size_t requested) SK_OVERRIDE {
+ size_t bytesRead = this->INHERITED::read(dst, requested);
+ if (bytesRead < requested) {
+ fIsAtEnd = true;
+ }
+ return bytesRead;
+ }
+
+ bool isAtEnd() const SK_OVERRIDE {
+ return fIsAtEnd;
+ }
+
+private:
+ bool fIsAtEnd;
+ typedef SkMemoryStream INHERITED;
+};
+
+// This test ensures that buffering the exact length of the stream and attempting to read beyond it
+// does not invalidate the buffer.
+static void test_read_beyond_buffer(skiatest::Reporter* reporter, size_t bufferSize) {
+ // Use a stream that behaves like Android's stream.
+ AndroidLikeMemoryStream memStream((void*)gAbcs, bufferSize, false);
+
+ // Create a buffer that matches the length of the stream.
+ SkAutoTUnref<SkStream> bufferedStream(SkFrontBufferedStream::Create(&memStream, bufferSize));
+
+ // Attempt to read one more than the bufferSize
+ test_read(reporter, bufferedStream.get(), gAbcs, bufferSize + 1);
+ test_rewind(reporter, bufferedStream.get(), true);
+
+ // Ensure that the initial read did not invalidate the buffer.
+ test_read(reporter, bufferedStream, gAbcs, bufferSize);
+}
+
+static void test_buffers(skiatest::Reporter* reporter, size_t bufferSize) {
+ test_incremental_buffering(reporter, bufferSize);
+ test_perfectly_sized_buffer(reporter, bufferSize);
+ test_skipping(reporter, bufferSize);
+ test_read_beyond_buffer(reporter, bufferSize);
+}
+
+static void TestStreams(skiatest::Reporter* reporter) {
+ // Test 6 and 64, which are used by Android, as well as another arbitrary length.
+ test_buffers(reporter, 6);
+ test_buffers(reporter, 15);
+ test_buffers(reporter, 64);
+}
+
+#include "TestClassDef.h"
+DEFINE_TESTCLASS("FrontBufferedStream", FrontBufferedStreamTestClass, TestStreams)