[net/dns] Collect histogram on HOSTS file size.

net/dns/dns_hosts.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.
 
 #include "net/dns/dns_hosts.h"
 
 #include "base/file_util.h"
 #include "base/logging.h"
+#include "base/metrics/histogram.h"
 #include "base/string_tokenizer.h"
 #include "base/string_util.h"
 
 namespace net {
 
 void ParseHosts(const std::string& contents, DnsHosts* dns_hosts) {
   CHECK(dns_hosts);
   DnsHosts& hosts = *dns_hosts;
   // Split into lines. Accept CR for Windows.
   StringTokenizer contents_lines(contents, "\n\r");
@@ skipping 21 matching lines @@
           IPAddressNumber& mapped_ip = hosts[key];
           if (mapped_ip.empty())
             mapped_ip = ip;
           // else ignore this entry (first hit counts)
         }
       }
     }
   }
 }
 
-// Reads the contents of the file at |path| into |str| if the total length is
-// less than |max_size|.
-static bool ReadFile(const FilePath& path, int64 max_size, std::string* str) {

[szym, 2012/09/12 16:42:35]

I removed this function because it doesn't seem to be that helpful.

-  int64 size;
-  if (!file_util::GetFileSize(path, &size) || size > max_size)
-    return false;
-  return file_util::ReadFileToString(path, str);
-}
-
 bool ParseHostsFile(const FilePath& path, DnsHosts* dns_hosts) {
   dns_hosts->clear();
   // Missing file indicates empty HOSTS.
   if (!file_util::PathExists(path))
     return true;
 
+  int64 size;
+  if (!file_util::GetFileSize(path, &size))
+    return false;
+
+  UMA_HISTOGRAM_COUNTS("AsyncDNS.HostsSize", size);
+
+  // Reject HOSTS files larger than |kMaxHostsSize|.
+  const int64 kMaxHostsSize = 1 << 16;
+  if (size > kMaxHostsSize)
+    return false;
+
   std::string contents;
-  const int64 kMaxHostsSize = 1 << 16;
-  if (!ReadFile(path, kMaxHostsSize, &contents))
+  if (!file_util::ReadFileToString(path, &contents))
     return false;
 
   ParseHosts(contents, dns_hosts);
   return true;
 }
 
 }  // namespace net