Adds a modified copy of talk/base to webrtc/base. It is the first step in migrating talk/base to webrtc/base.

BUG=N/A
R=andrew@webrtc.org, wu@webrtc.org

Review URL: https://webrtc-codereview.appspot.com/12199004

git-svn-id: http://webrtc.googlecode.com/svn/trunk@6107 4adac7df-926f-26a2-2b94-8c16560cd09d
diff --git a/webrtc/base/buffer.h b/webrtc/base/buffer.h
new file mode 100644
index 0000000..dbe7b1a
--- /dev/null
+++ b/webrtc/base/buffer.h
@@ -0,0 +1,102 @@
+/*
+ *  Copyright 2004 The WebRTC Project Authors. All rights reserved.
+ *
+ *  Use of this source code is governed by a BSD-style license
+ *  that can be found in the LICENSE file in the root of the source
+ *  tree. An additional intellectual property rights grant can be found
+ *  in the file PATENTS.  All contributing project authors may
+ *  be found in the AUTHORS file in the root of the source tree.
+ */
+
+#ifndef WEBRTC_BASE_BUFFER_H_
+#define WEBRTC_BASE_BUFFER_H_
+
+#include <string.h>
+
+#include "webrtc/base/scoped_ptr.h"
+
+namespace rtc {
+
+// Basic buffer class, can be grown and shrunk dynamically.
+// Unlike std::string/vector, does not initialize data when expanding capacity.
+class Buffer {
+ public:
+  Buffer() {
+    Construct(NULL, 0, 0);
+  }
+  Buffer(const void* data, size_t length) {
+    Construct(data, length, length);
+  }
+  Buffer(const void* data, size_t length, size_t capacity) {
+    Construct(data, length, capacity);
+  }
+  Buffer(const Buffer& buf) {
+    Construct(buf.data(), buf.length(), buf.length());
+  }
+
+  const char* data() const { return data_.get(); }
+  char* data() { return data_.get(); }
+  // TODO: should this be size(), like STL?
+  size_t length() const { return length_; }
+  size_t capacity() const { return capacity_; }
+
+  Buffer& operator=(const Buffer& buf) {
+    if (&buf != this) {
+      Construct(buf.data(), buf.length(), buf.length());
+    }
+    return *this;
+  }
+  bool operator==(const Buffer& buf) const {
+    return (length_ == buf.length() &&
+            memcmp(data_.get(), buf.data(), length_) == 0);
+  }
+  bool operator!=(const Buffer& buf) const {
+    return !operator==(buf);
+  }
+
+  void SetData(const void* data, size_t length) {
+    ASSERT(data != NULL || length == 0);
+    SetLength(length);
+    memcpy(data_.get(), data, length);
+  }
+  void AppendData(const void* data, size_t length) {
+    ASSERT(data != NULL || length == 0);
+    size_t old_length = length_;
+    SetLength(length_ + length);
+    memcpy(data_.get() + old_length, data, length);
+  }
+  void SetLength(size_t length) {
+    SetCapacity(length);
+    length_ = length;
+  }
+  void SetCapacity(size_t capacity) {
+    if (capacity > capacity_) {
+      rtc::scoped_ptr<char[]> data(new char[capacity]);
+      memcpy(data.get(), data_.get(), length_);
+      data_.swap(data);
+      capacity_ = capacity;
+    }
+  }
+
+  void TransferTo(Buffer* buf) {
+    ASSERT(buf != NULL);
+    buf->data_.reset(data_.release());
+    buf->length_ = length_;
+    buf->capacity_ = capacity_;
+    Construct(NULL, 0, 0);
+  }
+
+ protected:
+  void Construct(const void* data, size_t length, size_t capacity) {
+    data_.reset(new char[capacity_ = capacity]);
+    SetData(data, length);
+  }
+
+  scoped_ptr<char[]> data_;
+  size_t length_;
+  size_t capacity_;
+};
+
+}  // namespace rtc
+
+#endif  // WEBRTC_BASE_BUFFER_H_