Adds media::AudioPullFifo class to Chrome.

media/base/audio_pull_fifo_unittest.cc

Index: media/base/audio_pull_fifo_unittest.cc
diff --git a/media/base/audio_pull_fifo_unittest.cc b/media/base/audio_pull_fifo_unittest.cc
new file mode 100644
index 0000000000000000000000000000000000000000..7a385ff9eb4293bb3c60f48d6edda2e951529635
--- /dev/null
+++ b/media/base/audio_pull_fifo_unittest.cc
@@ -0,0 +1,100 @@
+// Copyright (c) 2012 The Chromium Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style license that can be
+// found in the LICENSE file.
+
+#include "base/bind.h"
+#include "base/bind_helpers.h"
+#include "media/base/audio_pull_fifo.h"
+#include "testing/gtest/include/gtest/gtest.h"
+
+namespace media {
+
+// Block diagram of a possible real-world usage:
+//
+//       | Provider | ----> | AudioPullFifo | ----> | Consumer |
+//                    push                    pull
+//          2048      ---->       (4096)      ---->     ~441     [#frames]

[DaleCurtis, 2012/09/07 13:48:38]

As noted in my other comments, it's possible the Provider could ask for a 1024
buffer size and the hardware wants a 2048 buffer.

+
+// Number of channels in each audio bus.
+static int kChannels = 2;
+
+// Max number of audio framed the FIFO can contain.
+static const int kMaxFramesInFifo = 4096;
+
+// The provider will be asked to provide audio frames of this size by the
+// consumer.
+static const int kReadFramesFromProvider = 2048;
+
+// Max number of frames the consumer can ask for.
+static const int kMaxFramesToConsume = 496;
+
+// List of |frames_to_consume| which will be used as input parameter to
+// AudioPullFifo::Consume() when the consumer asks for data.
+// Sum(kConsumeFrames)=5733 and Mean(kConsumeFrames)=441, hence the provider
+// will be called three times in this example and provide in total 6144 audio
+// frames.
+static const int kConsumeFrames[] =
+    {440, 441, 442, 440, 440, 441, 442, 440, 441, 442, 441, 441, 442};

[DaleCurtis, 2012/09/07 13:48:38]

SincResampler will actually look something like 544, 512, 512, 512, 512. So I'd
increase the spread on these test values some more.

+
+class AudioPullFifoTest : public testing::Test {
+ public:
+  AudioPullFifoTest()
+      : audio_bus_(AudioBus::Create(kChannels, kMaxFramesToConsume)),
+        fill_value_(0) {}
+  ~AudioPullFifoTest() {}
+
+  void VerifyValue(const float data[], int size, float start_value) {
+    float value = start_value;
+    for (int i = 0; i < size; ++i) {
+      ASSERT_FLOAT_EQ(value++, data[i]) << "i=" << i;
+    }
+  }
+
+  // AudioPullFifo::ReadCB implementation where we increase a value for each
+  // audio frame that we provide. Note that all channels are given the same
+  // value to simplify the verification.
+  virtual void ProvideInput(AudioBus* audio_bus) {
+    EXPECT_EQ(audio_bus->channels(), audio_bus_->channels());
+    EXPECT_EQ(audio_bus->frames(), kReadFramesFromProvider);
+    for (int i = 0; i < audio_bus->frames(); ++i) {
+      for (int j = 0; j < audio_bus->channels(); ++j) {
+        // Store same value in all channels.
+        audio_bus->channel(j)[i] = fill_value_;
+      }
+      fill_value_++;
+    }
+  }
+
+ protected:
+  scoped_ptr<AudioBus> audio_bus_;
+  int fill_value_;
+
+  DISALLOW_COPY_AND_ASSIGN(AudioPullFifoTest);
+};
+
+// Emulate a scenario where the consumer ask for data using the sizes in
+// kConsumeFrames at each call. The provider is asked to provide input when
+// the FIFO can't fulfill the request and kReadFramesFromProvider will be
+// provided in each callback. The provider updates and stores a data value for
+// each audio frame it provides which makes it possible to verify that the
+// consumer reads out correct values.
+TEST_F(AudioPullFifoTest, Consume) {
+  AudioPullFifo pull_fifo(kChannels, kMaxFramesInFifo, base::Bind(
+      &AudioPullFifoTest::ProvideInput, base::Unretained(this)),
+      kReadFramesFromProvider);
+
+  // Consume data using different sizes, acquire audio frames from the FIFO
+  // and verify that the retrieved values matches the values written by the
+  // provider.
+  int start_value = 0;
+  for (int i = 0; i < sizeof(kConsumeFrames) / sizeof(kConsumeFrames[0]); ++i) {

[DaleCurtis, 2012/09/07 13:48:38]

use the arraysize() macro from basictypes.h

+    int frames_to_consume = kConsumeFrames[i];
+    EXPECT_TRUE(pull_fifo.Consume(audio_bus_.get(), frames_to_consume));
+    for (int j = 0; j < kChannels; ++j) {
+      VerifyValue(audio_bus_->channel(j), frames_to_consume, start_value);
+    }
+    start_value += frames_to_consume;
+  }
+}
+
+}  // namespace media