Replace the existing SpdyHeaderBlock typedef with a class.

net/tools/quic/spdy_balsa_utils.cc

Index: net/tools/quic/spdy_balsa_utils.cc
diff --git a/net/tools/quic/spdy_balsa_utils.cc b/net/tools/quic/spdy_balsa_utils.cc
index 3f0bbc60322d259d1585bf0a2d949a177113571d..fd72a06230a4df6397b2728175bb7d6e3a55009b 100644
--- a/net/tools/quic/spdy_balsa_utils.cc
+++ b/net/tools/quic/spdy_balsa_utils.cc
@@ -10,6 +10,7 @@
 #include "base/strings/string_number_conversions.h"
 #include "base/strings/string_piece.h"
 #include "base/strings/string_util.h"
+#include "net/base/linked_hash_map.h"
 #include "net/quic/quic_flags.h"
 #include "net/quic/spdy_utils.h"
 #include "net/spdy/spdy_frame_builder.h"
@@ -39,6 +40,11 @@ const char kV3Version[] = ":version";
 void PopulateSpdyHeaderBlock(const BalsaHeaders& headers,
                              SpdyHeaderBlock* block,
                              bool allow_empty_values) {
+  using HeaderValuesMap =
+      linked_hash_map<StringPiece, std::vector<StringPiece>>;
+  std::deque<string> names;
+  HeaderValuesMap header_values_map;
+  // First, gather references to all values for each name.
   for (BalsaHeaders::const_header_lines_iterator hi =
            headers.header_lines_begin();
        hi != headers.header_lines_end(); ++hi) {
@@ -47,17 +53,25 @@ void PopulateSpdyHeaderBlock(const BalsaHeaders& headers,
                << " from headers";
       continue;
     }
-
-    // This unfortunately involves loads of copying, but its the simplest way
-    // to sort the headers and leverage the framer.
-    string name = base::ToLowerASCII(hi->first.as_string());
-    SpdyHeaderBlock::iterator it = block->find(name);
-    if (it != block->end()) {
-      it->second.reserve(it->second.size() + 1 + hi->second.size());
-      it->second.append("\0", 1);
-      it->second.append(hi->second.data(), hi->second.size());
+    const string name = base::ToLowerASCII(hi->first.as_string());
+    names.push_back(name);
+    header_values_map[name].push_back(hi->second);
+  }
+  // Then, write joined representations to the header block.
+  for (const auto& header : header_values_map) {
+    if (header.second.size() == 1) {
+      // Avoid string allocation for the single value case.
+      block->ReplaceOrAppendHeader(header.first, header.second[0]);
     } else {
-      block->insert(make_pair(name, hi->second.as_string()));
+      StringPiece separator("\0", 1);
+      auto it = header.second.begin();
+      string value = it->as_string();
+      ++it;
+      for (; it != header.second.end(); ++it) {
+        separator.AppendToString(&value);
+        value.append(it->data(), it->size());
+      }
+      block->ReplaceOrAppendHeader(header.first, value);
     }
   }
 }
@@ -71,7 +85,7 @@ void PopulateSpdy3RequestHeaderBlock(const BalsaHeaders& headers,
   StringPiece host_header = headers.GetHeader("Host");
   if (!host_header.empty()) {
     DCHECK(host_and_port.empty() || host_header == host_and_port);
-    block->insert(make_pair(kV3Host, host_header.as_string()));
+    block->insert(make_pair(kV3Host, host_header));
   } else {
     block->insert(make_pair(kV3Host, host_and_port));
   }
@@ -79,11 +93,11 @@ void PopulateSpdy3RequestHeaderBlock(const BalsaHeaders& headers,
   block->insert(make_pair(kV3Scheme, scheme));
 
   if (!headers.request_method().empty()) {
-    block->insert(make_pair(kV3Method, headers.request_method().as_string()));
+    block->insert(make_pair(kV3Method, headers.request_method()));
   }
 
   if (!headers.request_version().empty()) {
-    (*block)[kV3Version] = headers.request_version().as_string();
+    (*block)[kV3Version] = headers.request_version();
   }
 }
 
@@ -96,7 +110,7 @@ void PopulateSpdy4RequestHeaderBlock(const BalsaHeaders& headers,
   StringPiece host_header = headers.GetHeader("Host");
   if (!host_header.empty()) {
     DCHECK(host_and_port.empty() || host_header == host_and_port);
-    block->insert(make_pair(kV4Host, host_header.as_string()));
+    block->insert(make_pair(kV4Host, host_header));
     // PopulateSpdyHeaderBlock already added the "host" header,
     // which is invalid for SPDY4.
     block->erase("host");
@@ -107,7 +121,7 @@ void PopulateSpdy4RequestHeaderBlock(const BalsaHeaders& headers,
   block->insert(make_pair(kV3Scheme, scheme));
 
   if (!headers.request_method().empty()) {
-    block->insert(make_pair(kV3Method, headers.request_method().as_string()));
+    block->insert(make_pair(kV3Method, headers.request_method()));
   }
 }
 
@@ -119,9 +133,9 @@ void PopulateSpdyResponseHeaderBlock(SpdyMajorVersion version,
     status.append(" ");
     status.append(headers.response_reason_phrase().as_string());
     (*block)[kV3Status] = status;
-    (*block)[kV3Version] = headers.response_version().as_string();
+    (*block)[kV3Version] = headers.response_version();
   } else {
-    (*block)[kV3Status] = headers.response_code().as_string();
+    (*block)[kV3Status] = headers.response_code();
   }
 
   PopulateSpdyHeaderBlock(headers, block, true);
@@ -129,11 +143,8 @@ void PopulateSpdyResponseHeaderBlock(SpdyMajorVersion version,
 
 bool IsSpecialSpdyHeader(SpdyHeaderBlock::const_iterator header,
                          BalsaHeaders* headers) {
-  if (header->first.empty() || header->second.empty()) {
-    return true;
-  }
-  const string& header_name = header->first;
-  return header_name.c_str()[0] == ':';
+  return header->first.empty() || header->second.empty() ||
+         header->first[0] == ':';
 }
 
 // The reason phrase should match regexp [\d\d\d [^\r\n]+].  If not, we will
@@ -224,13 +235,13 @@ void SpdyHeadersToRequestHeaders(const SpdyHeaderBlock& header_block,
   if (method_it == end_it) {
     method = "GET";
   } else {
-    method = method_it->second;
+    method = method_it->second.as_string();
   }
   string uri;
   if (path_it == end_it) {
     uri = "/";
   } else {
-    uri = path_it->second;
+    uri = path_it->second.as_string();
   }
   request_headers->SetRequestFirstlineFromStringPieces(
       method, uri, net::kHttp2VersionString);