[PPAPI] Implement an IOStreamResource for data transmission between plugin and renderer.

ppapi/shared_impl/circular_buffer.cc

Index: ppapi/shared_impl/circular_buffer.cc
diff --git a/ppapi/shared_impl/circular_buffer.cc b/ppapi/shared_impl/circular_buffer.cc
new file mode 100644
index 0000000000000000000000000000000000000000..8623a82ffad3635db3be6c0d3d71f7ab5f9bb5e4
--- /dev/null
+++ b/ppapi/shared_impl/circular_buffer.cc
@@ -0,0 +1,164 @@
+// Copyright (c) 2014 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 "ppapi/shared_impl/circular_buffer.h"
+
+#include <algorithm>
+
+#include "base/logging.h"
+#include "ppapi/c/pp_errors.h"
+
+namespace ppapi {
+
+CircularBuffer::CircularBuffer(void* buffer, uint32_t size)
+    : buffer_(static_cast<uint8_t*>(buffer)),
+      buffer_size_(size),
+      position_(0),
+      limit_(0),
+      remaining_(0),
+      locked_buffer_(NULL),
+      locked_buffer_size_(0) {
+}
+
+CircularBuffer::~CircularBuffer() {
+}
+
+void CircularBuffer::MovePosition(uint32_t offset) {
+  CHECK(offset);
+  CHECK(offset <= remaining_);
+
+  position_ += offset;
+  remaining_ -= offset;
+  if (position_ >= buffer_size_)
+    position_ -= buffer_size_;
+}
+
+void CircularBuffer::MoveLimit(uint32_t offset) {
+  CHECK(offset);
+  CHECK(offset <= (buffer_size_ - remaining_));
+
+  limit_ += offset;
+  remaining_ += offset;
+  if (limit_ >= buffer_size_)
+    limit_ -= buffer_size_;
+}
+
+int32_t CircularBuffer::Read(void* buffer, uint32_t size) {
+  // Buffer has been locked.
+  if (locked_buffer_)
+    return PP_ERROR_INPROGRESS;
+
+  size = std::min(size, remaining_);
+
+  if (!size)
+    return 0;
+
+  return ReadInternal(buffer, size);
+}
+
+int32_t CircularBuffer::ReadAll(void* buffer, uint32_t size) {
+  // Buffer has been locked.
+  if (locked_buffer_)
+    return PP_ERROR_INPROGRESS;
+
+  if (size > buffer_size_)
+    return PP_ERROR_BADARGUMENT;
+
+  if (size > remaining_)
+    return PP_ERROR_NOSPACE;
+
+  return ReadInternal(buffer, size);
+
+}
+
+int32_t CircularBuffer::ReadInternal(void* buffer, uint32_t size) {
+  uint32_t n = std::min(buffer_size_ - position_, size);
+  memcpy(buffer, buffer_ + position_,  n);
+  if (n != size) {
+    memcpy(static_cast<uint8_t*>(buffer) + n, buffer_,  size - n);
+  }
+  MovePosition(size);
+  return size;
+}
+
+int32_t CircularBuffer::Write(const void* buffer, uint32_t size) {
+  // Buffer has been locked.
+  if (locked_buffer_)
+    return PP_ERROR_INPROGRESS;
+
+  size = std::min(size, remaining_);
+  if (!size)
+    return 0;
+
+  return WriteInternal(buffer, size);
+}
+
+int32_t CircularBuffer::WriteAll(const void* buffer, uint32_t size) {
+  // Buffer has been locked.
+  if (locked_buffer_)
+    return PP_ERROR_INPROGRESS;
+
+  if (size > buffer_size_)
+    return PP_ERROR_BADARGUMENT;
+
+  if (size > remaining_)
+    return PP_ERROR_NOSPACE;
+
+  return WriteInternal(buffer, size);
+}
+
+int32_t CircularBuffer::WriteInternal(const void* buffer, uint32_t size) {
+  uint32_t n = std::min(buffer_size_ - position_, size);
+  memcpy(buffer_ + position_, buffer, n);
+  if (n != size) {
+    memcpy(buffer_, static_cast<const uint8_t*>(buffer) + n,  size - n);
+  }
+  MovePosition(size);
+  return size;
+}
+
+int32_t CircularBuffer::Lock(void** buffer, uint32_t size) {
+  CHECK(buffer);
+  CHECK(size);
+
+  if (locked_buffer_)
+    return PP_ERROR_INPROGRESS;
+
+  // Request memory is not continuous.
+  if (position_ + size > buffer_size_)
+    return PP_ERROR_FAILED;
+
+  // Do not have enough space for locking.
+  if (size > remaining_)
+    return PP_ERROR_NOSPACE;
+
+  locked_buffer_ = buffer_ + position_;
+  *buffer = locked_buffer_;
+  locked_buffer_size_ = size;
+  return PP_OK;
+}
+
+int32_t CircularBuffer::Relock(void* buffer, uint32_t size) {
+  if (locked_buffer_ != buffer)
+    return PP_ERROR_BADARGUMENT;
+  locked_buffer_size_ = size;
+  return PP_OK;
+}
+
+int32_t CircularBuffer::Unlock(const void* buffer) {
+  if (!buffer)
+    return PP_ERROR_BADARGUMENT;
+  if (locked_buffer_ != buffer)
+    return PP_ERROR_BADARGUMENT;
+
+  int32_t size = locked_buffer_size_;
+
+  locked_buffer_ = NULL;
+  locked_buffer_size_ = 0;
+
+  MovePosition(size);
+  return size;
+}
+
+}  // namespace ppapi