Use net's response header parser for parsing multipart headers.

net/http/http_util.cc

 // 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.
 
 // The rules for parsing content-types were borrowed from Firefox:
 // http://lxr.mozilla.org/mozilla/source/netwerk/base/src/nsURLHelper.cpp#834
 
 #include "net/http/http_util.h"
 
 #include <algorithm>
@@ skipping 524 matching lines @@
   if (buf_len >= http_len) {
     int i_max = std::min(buf_len - http_len, slop);
     for (int i = 0; i <= i_max; ++i) {
       if (LowerCaseEqualsASCII(buf + i, buf + i + http_len, "http"))
         return i;
     }
   }
   return -1;  // Not found
 }
 
-int HttpUtil::LocateEndOfHeaders(const char* buf, int buf_len, int i) {
+static int LocateEndOfHeadersHelper(const char* buf,
+                                    int buf_len,
+                                    int i,
+                                    bool accept_empty_header_list) {
+  char last_c = '\0';
   bool was_lf = false;
-  char last_c = '\0';
+  if (accept_empty_header_list) {
+    // Normally two line breaks signal the end of a header list. An empty header
+    // list ends with a single line break at the start of the buffer.
+    last_c = '\n';
+    was_lf = true;
+  }
+
   for (; i < buf_len; ++i) {
     char c = buf[i];
     if (c == '\n') {
       if (was_lf)
         return i + 1;
       was_lf = true;
     } else if (c != '\r' || last_c != '\n') {
       was_lf = false;
     }
     last_c = c;
   }
   return -1;
 }
 
+int HttpUtil::LocateEndOfAdditionalHeaders(const char* buf,
+                                           int buf_len,
+                                           int i) {
+  return LocateEndOfHeadersHelper(buf, buf_len, i, true);
+}
+
+int HttpUtil::LocateEndOfHeaders(const char* buf, int buf_len, int i) {
+  return LocateEndOfHeadersHelper(buf, buf_len, i, false);
+}
+
 // In order for a line to be continuable, it must specify a
 // non-blank header-name. Line continuations are specifically for
 // header values -- do not allow headers names to span lines.
 static bool IsLineSegmentContinuable(const char* begin, const char* end) {
   if (begin == end)
     return false;
 
   const char* colon = std::find(begin, end, ':');
   if (colon == end)
     return false;
@@ skipping 362 matching lines @@
       value_is_quoted_ = true;
       // Do not store iterators into this. See declaration of unquoted_value_.
       unquoted_value_ = HttpUtil::Unquote(value_begin_, value_end_);
     }
   }
 
   return true;
 }
 
 }  // namespace net