GIF: Avoid copying/storing data when possible
If the input SkStream has a length and position, do not copy and store
LZW blocks or ColorMaps. Instead, mark the position and size, and read
from the stream when necessary.
This will save memory in Chromium's use case, which has already
buffered all of its data.
In the case where we *do* need to copy, store it on the SkStreamBuffer.
This allows SkGifImageReader to have simpler code.
Add tests.
Change-Id: Ic65fa766328ae2e5974b2084bc2099e19aced731
Reviewed-on: https://skia-review.googlesource.com/6157
Reviewed-by: Matt Sarett <msarett@google.com>
Commit-Queue: Leon Scroggins <scroggo@google.com>
diff --git a/tests/StreamBufferTest.cpp b/tests/StreamBufferTest.cpp
new file mode 100644
index 0000000..96bca35
--- /dev/null
+++ b/tests/StreamBufferTest.cpp
@@ -0,0 +1,135 @@
+/*
+ * Copyright 2016 Google Inc.
+ *
+ * Use of this source code is governed by a BSD-style license that can be
+ * found in the LICENSE file.
+ */
+
+#include "SkData.h"
+#include "SkOSPath.h"
+#include "SkStream.h"
+#include "SkStreamBuffer.h"
+
+#include "FakeStreams.h"
+#include "Test.h"
+
+static const char* gText = "Four score and seven years ago";
+
+static void test_get_data_at_position(skiatest::Reporter* r, SkStreamBuffer* buffer, size_t position,
+ size_t length) {
+ sk_sp<SkData> data = buffer->getDataAtPosition(position, length);
+ REPORTER_ASSERT(r, data);
+ if (data) {
+ REPORTER_ASSERT(r, !memcmp(data->data(), gText + position, length));
+ }
+}
+
+// Test buffering from the beginning, by different amounts.
+static void test_buffer_from_beginning(skiatest::Reporter* r, SkStream* stream, size_t length) {
+ SkStreamBuffer buffer(stream);
+
+ // Buffer an arbitrary amount:
+ size_t buffered = length / 2;
+ REPORTER_ASSERT(r, buffer.buffer(buffered));
+ REPORTER_ASSERT(r, !memcmp(buffer.get(), gText, buffered));
+
+ // Buffering less is free:
+ REPORTER_ASSERT(r, buffer.buffer(buffered / 2));
+
+ // Buffer more should succeed:
+ REPORTER_ASSERT(r, buffer.buffer(length));
+ REPORTER_ASSERT(r, !memcmp(buffer.get(), gText, length));
+}
+
+// Test flushing the stream as we read.
+static void test_flushing(skiatest::Reporter* r, SkStream* stream, size_t length,
+ bool getDataAtPosition) {
+ SkStreamBuffer buffer(stream);
+ const size_t step = 5;
+ for (size_t position = 0; position + step <= length; position += step) {
+ REPORTER_ASSERT(r, buffer.buffer(step));
+ REPORTER_ASSERT(r, buffer.markPosition() == position);
+
+ if (!getDataAtPosition) {
+ REPORTER_ASSERT(r, !memcmp(buffer.get(), gText + position, step));
+ }
+ buffer.flush();
+ }
+
+ REPORTER_ASSERT(r, !buffer.buffer(step));
+
+ if (getDataAtPosition) {
+ for (size_t position = 0; position + step <= length; position += step) {
+ test_get_data_at_position(r, &buffer, position, step);
+ }
+ }
+}
+
+DEF_TEST(StreamBuffer, r) {
+ const size_t size = strlen(gText);
+ sk_sp<SkData> data(SkData::MakeWithoutCopy(gText, size));
+
+ SkString tmpDir = skiatest::GetTmpDir();
+ const char* subdir = "streamBuffer.txt";
+ SkString path;
+
+ if (!tmpDir.isEmpty()) {
+ path = SkOSPath::Join(tmpDir.c_str(), subdir);
+ SkFILEWStream writer(path.c_str());
+ writer.write(gText, size);
+ }
+
+ struct {
+ std::function<SkStream*()> createStream;
+ bool skipIfNoTmpDir;
+ } factories[] = {
+ { [&data]() { return new SkMemoryStream(data); }, false },
+ { [&data]() { return new NotAssetMemStream(data); }, false },
+ { [&path]() { return new SkFILEStream(path.c_str()); }, true },
+ };
+
+ for (auto f : factories) {
+ if (tmpDir.isEmpty() && f.skipIfNoTmpDir) {
+ continue;
+ }
+ test_buffer_from_beginning(r, f.createStream(), size);
+ test_flushing(r, f.createStream(), size, false);
+ test_flushing(r, f.createStream(), size, true);
+ }
+
+ // Stream that will receive more data. Will be owned by the SkStreamBuffer.
+ HaltingStream* stream = new HaltingStream(data, 6);
+ SkStreamBuffer buffer(stream);
+
+ // Can only buffer less than what's available (6).
+ REPORTER_ASSERT(r, !buffer.buffer(7));
+ REPORTER_ASSERT(r, buffer.buffer(5));
+ REPORTER_ASSERT(r, !memcmp(buffer.get(), gText, 5));
+
+ // Add some more data. We can buffer and read all of it.
+ stream->addNewData(8);
+ REPORTER_ASSERT(r, buffer.buffer(14));
+ REPORTER_ASSERT(r, !memcmp(buffer.get(), gText, 14));
+
+ // Flush the buffer, which moves the position.
+ buffer.flush();
+
+ // Add some data, and try to read more. Can only read what is
+ // available.
+ stream->addNewData(9);
+ REPORTER_ASSERT(r, !buffer.buffer(13));
+ stream->addNewData(4);
+ REPORTER_ASSERT(r, buffer.buffer(13));
+
+ // Do not call get on this data. We'll come back to this data after adding
+ // more.
+ buffer.flush();
+ const size_t remaining = size - 27;
+ REPORTER_ASSERT(r, remaining > 0);
+ stream->addNewData(remaining);
+ REPORTER_ASSERT(r, buffer.buffer(remaining));
+ REPORTER_ASSERT(r, !memcmp(buffer.get(), gText + 27, remaining));
+
+ // Now go back to the data we skipped.
+ test_get_data_at_position(r, &buffer, 14, 13);
+}