From 1dafc7583808f609ba9891d57e6af32e5b011fc7 Mon Sep 17 00:00:00 2001
From: "yutak@chromium.org"
 <yutak@chromium.org@0039d316-1c4b-4281-b951-d872f2087c98>
Date: Tue, 21 Aug 2012 06:41:31 +0000
Subject: Add a function that calculates the size of WebSocket frame header.

This function will be used to determine the size of buffer needed for
writing WebSocket frame header.

BUG=116624
R=mmenke@chromium.org


Review URL: https://chromiumcodereview.appspot.com/10825444

git-svn-id: svn://svn.chromium.org/chrome/trunk/src@152518 0039d316-1c4b-4281-b951-d872f2087c98
---
 net/websockets/websocket_frame.cc | 33 ++++++++++++++++++++-------------
 net/websockets/websocket_frame.h  | 14 ++++++++++----
 2 files changed, 30 insertions(+), 17 deletions(-)

diff --git a/net/websockets/websocket_frame.cc b/net/websockets/websocket_frame.cc
index da65cba..2194f60 100644
--- a/net/websockets/websocket_frame.cc
+++ b/net/websockets/websocket_frame.cc
@@ -42,6 +42,20 @@ WebSocketFrameChunk::WebSocketFrameChunk() : final_chunk(false) {
 WebSocketFrameChunk::~WebSocketFrameChunk() {
 }
 
+int GetWebSocketFrameHeaderSize(const WebSocketFrameHeader& header) {
+  int extended_length_size = 0;
+  if (header.payload_length > kMaxPayloadLengthWithoutExtendedLengthField &&
+      header.payload_length <= kuint16max) {
+    extended_length_size = 2;
+  } else if (header.payload_length > kuint16max) {
+    extended_length_size = 8;
+  }
+
+  return (WebSocketFrameHeader::kBaseHeaderSize +
+          extended_length_size +
+          (header.masked ? WebSocketFrameHeader::kMaskingKeyLength : 0));
+}
+
 int WriteWebSocketFrameHeader(const WebSocketFrameHeader& header,
                               const WebSocketMaskingKey* masking_key,
                               char* buffer,
@@ -63,17 +77,7 @@ int WriteWebSocketFrameHeader(const WebSocketFrameHeader& header,
   // This function constructs frame header (the first three in the list
   // above).
 
-  size_t extended_length_size = 0;
-  if (header.payload_length > kMaxPayloadLengthWithoutExtendedLengthField &&
-      header.payload_length <= kuint16max) {
-    extended_length_size = 2;
-  } else if (header.payload_length > kuint16max) {
-    extended_length_size = 8;
-  }
-  int header_size =
-      WebSocketFrameHeader::kBaseHeaderSize +
-      extended_length_size +
-      (header.masked ? WebSocketFrameHeader::kMaskingKeyLength : 0);
+  int header_size = GetWebSocketFrameHeaderSize(header);
   if (header_size > buffer_size)
     return ERR_INVALID_ARGUMENT;
 
@@ -87,6 +91,7 @@ int WriteWebSocketFrameHeader(const WebSocketFrameHeader& header,
   first_byte |= header.opcode & kOpCodeMask;
   buffer[buffer_index++] = first_byte;
 
+  int extended_length_size = 0;
   uint8 second_byte = 0u;
   second_byte |= header.masked ? kMaskBit : 0u;
   if (header.payload_length <=
@@ -94,17 +99,19 @@ int WriteWebSocketFrameHeader(const WebSocketFrameHeader& header,
     second_byte |= header.payload_length;
   } else if (header.payload_length <= kuint16max) {
     second_byte |= kPayloadLengthWithTwoByteExtendedLengthField;
+    extended_length_size = 2;
   } else {
     second_byte |= kPayloadLengthWithEightByteExtendedLengthField;
+    extended_length_size = 8;
   }
   buffer[buffer_index++] = second_byte;
 
   // Writes "extended payload length" field.
-  if (extended_length_size == 2u) {
+  if (extended_length_size == 2) {
     uint16 payload_length_16 = static_cast<uint16>(header.payload_length);
     WriteBigEndian(buffer + buffer_index, payload_length_16);
     buffer_index += sizeof(uint16);
-  } else if (extended_length_size == 8u) {
+  } else if (extended_length_size == 8) {
     WriteBigEndian(buffer + buffer_index, header.payload_length);
     buffer_index += sizeof(uint64);
   }
diff --git a/net/websockets/websocket_frame.h b/net/websockets/websocket_frame.h
index 9f7c7fd..94f4ede 100644
--- a/net/websockets/websocket_frame.h
+++ b/net/websockets/websocket_frame.h
@@ -86,6 +86,12 @@ struct WebSocketMaskingKey {
   char key[WebSocketFrameHeader::kMaskingKeyLength];
 };
 
+// Returns the size of WebSocket frame header. The size of WebSocket frame
+// header varies from 2 bytes to 14 bytes depending on the payload length
+// and maskedness.
+NET_EXPORT_PRIVATE int GetWebSocketFrameHeaderSize(
+    const WebSocketFrameHeader& header);
+
 // Writes wire format of a WebSocket frame header into |output|, and returns
 // the number of bytes written.
 //
@@ -98,10 +104,10 @@ struct WebSocketMaskingKey {
 // (possibly generated by GenerateWebSocketMaskingKey() function below).
 // Otherwise, |masking_key| must be NULL.
 //
-// |buffer| should have enough size to contain the frame header. Size of a
-// frame header varies from 2 bytes to 14 bytes depending on the payload length
-// and maskedness. If the size of |buffer| is insufficient, this function
-// returns ERR_INVALID_ARGUMENT and does not write any data to |buffer|.
+// |buffer| should have enough size to contain the frame header.
+// GetWebSocketFrameHeaderSize() can be used to know the size of header
+// beforehand. If the size of |buffer| is insufficient, this function returns
+// ERR_INVALID_ARGUMENT and does not write any data to |buffer|.
 NET_EXPORT_PRIVATE int WriteWebSocketFrameHeader(
     const WebSocketFrameHeader& header,
     const WebSocketMaskingKey* masking_key,
-- 
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