Mojo C bindings library pt1: MojomBuffer

mojo/public/c/bindings/buffer.h

Index: mojo/public/c/bindings/buffer.h
diff --git a/mojo/public/c/bindings/buffer.h b/mojo/public/c/bindings/buffer.h
new file mode 100644
index 0000000000000000000000000000000000000000..ca79f6369ade87d306252d6335203f489324cde3
--- /dev/null
+++ b/mojo/public/c/bindings/buffer.h
@@ -0,0 +1,31 @@
+// Copyright 2016 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.
+
+#ifndef MOJO_PUBLIC_C_BINDINGS_BUFFER_H_
+#define MOJO_PUBLIC_C_BINDINGS_BUFFER_H_
+
+#include <stddef.h>
+
+#include "mojo/public/c/system/macros.h"
+
+MOJO_BEGIN_EXTERN_C
+
+// |MojomBuffer| is an object that manages a buffer. It is used as a

[viettrungluu, 2016/06/15 15:00:57]

nit: "object" and "manages" are both stretches. Probably just say that it's used
to track buffer state during mojom serialization.

[vardhan, 2016/06/15 15:48:00]

Done.

+// linear allocator for mojom serialization. The user must initialize this
+// struct themselves. See the fields for details.
+struct MojomBuffer {
+  char* buf;
+  // The number of bytes described by |buf|.
+  size_t buf_size;
+  // Must be initialized to 0. MojomBuffer_Allocate() will update it as it
+  // consumes |buf|.
+  size_t num_bytes_used;
+};
+
+// Allocates |num_bytes| (aligned to 8 bytes) from |buf|.

[viettrungluu, 2016/06/15 15:00:57]

nit: "aligned" -> "rounded up to a multiple of", since there's no requirement
that |buf->buf| be aligned.

You should also say that it returns null on failure (and maybe clarify that this
occurs if there's not enough space).

[vardhan, 2016/06/15 15:48:00]

Done.

+void* MojomBuffer_Allocate(struct MojomBuffer* buf, size_t num_bytes);
+
+MOJO_END_EXTERN_C
+
+#endif  // MOJO_PUBLIC_C_BINDINGS_BUFFER_H_