SimpleCache: open with fewer seeks.

net/disk_cache/simple/simple_test_util.cc

 // Copyright 2013 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/disk_cache/simple/simple_test_util.h"
 
 #include "base/files/file.h"
 #include "base/files/file_path.h"
+#include "net/base/hash_value.h"
+#include "net/disk_cache/simple/simple_entry_format.h"
 #include "net/disk_cache/simple/simple_util.h"
 
 namespace disk_cache {
 namespace simple_util {
 
+using base::File;
+using base::FilePath;
+
 bool CreateCorruptFileForTests(const std::string& key,
-                               const base::FilePath& cache_path) {
-  base::FilePath entry_file_path = cache_path.AppendASCII(
+                               const FilePath& cache_path) {
+  FilePath entry_file_path = cache_path.AppendASCII(
       disk_cache::simple_util::GetFilenameFromKeyAndFileIndex(key, 0));
-  int flags = base::File::FLAG_CREATE_ALWAYS | base::File::FLAG_WRITE;
-  base::File entry_file(entry_file_path, flags);
+  int flags = File::FLAG_CREATE_ALWAYS | File::FLAG_WRITE;
+  File entry_file(entry_file_path, flags);
 
   if (!entry_file.IsValid())
     return false;
 
   return entry_file.Write(0, "dummy", 1) == 1;
 }
 
+bool RemoveKeySHA256FromEntry(const std::string& key,
+                              const FilePath& cache_path) {
+  FilePath entry_file_path = cache_path.AppendASCII(
+      disk_cache::simple_util::GetFilenameFromKeyAndFileIndex(key, 0));
+  int flags = File::FLAG_OPEN | File::FLAG_READ | File::FLAG_WRITE;
+  File entry_file(entry_file_path, flags);
+  if (!entry_file.IsValid())
+    return false;
+  int file_length = entry_file.GetLength();
+  SimpleFileEOF eof_record;
+  if (entry_file.Read(file_length - sizeof(eof_record),
+                      reinterpret_cast<char*>(&eof_record),
+                      sizeof(eof_record)) != sizeof(eof_record)) {
+    return false;
+  }
+  if (eof_record.final_magic_number != disk_cache::kSimpleFinalMagicNumber ||
+      (eof_record.flags & SimpleFileEOF::FLAG_HAS_KEY_SHA256) !=
+          SimpleFileEOF::FLAG_HAS_KEY_SHA256) {
+    return false;
+  }
+  eof_record.flags &= ~SimpleFileEOF::FLAG_HAS_KEY_SHA256;
+  if (entry_file.Write(
+          file_length - sizeof(eof_record) - sizeof(net::SHA256HashValue),

[Randy Smith (Not in Mondays), 2016/05/19 19:38:50]

Comment calling out that record is being moved back by
sizeof(net::SHA256HashValue)?  It find it easy to miss things like that when
reading a wall of code.

[gavinp, 2016/05/20 01:42:32]

Done.

+          reinterpret_cast<char*>(&eof_record),
+          sizeof(eof_record)) != sizeof(eof_record)) {
+    return false;
+  }
+  if (!entry_file.SetLength(file_length - sizeof(net::SHA256HashValue))) {
+    return false;
+  }
+  return true;
+}
+
+bool CorruptKeySHA256FromEntry(const std::string& key,
+                               const base::FilePath& cache_path) {
+  FilePath entry_file_path = cache_path.AppendASCII(
+      disk_cache::simple_util::GetFilenameFromKeyAndFileIndex(key, 0));
+  int flags = File::FLAG_OPEN | File::FLAG_READ | File::FLAG_WRITE;
+  File entry_file(entry_file_path, flags);
+  if (!entry_file.IsValid())
+    return false;
+  int file_length = entry_file.GetLength();
+  SimpleFileEOF eof_record;
+  if (entry_file.Read(file_length - sizeof(eof_record),
+                      reinterpret_cast<char*>(&eof_record),
+                      sizeof(eof_record)) != sizeof(eof_record)) {
+    return false;
+  }
+  if (eof_record.final_magic_number != disk_cache::kSimpleFinalMagicNumber ||
+      (eof_record.flags & SimpleFileEOF::FLAG_HAS_KEY_SHA256) !=
+          SimpleFileEOF::FLAG_HAS_KEY_SHA256) {
+    return false;
+  }
+
+  const char corrupt_data[] = "corrupt data";
+  static_assert(sizeof(corrupt_data) <= sizeof(net::SHA256HashValue),
+                "corrupt data should not be larger than a SHA-256");
+  if (entry_file.Write(
+          file_length - sizeof(eof_record) - sizeof(net::SHA256HashValue),
+          corrupt_data, sizeof(corrupt_data)) != sizeof(corrupt_data)) {
+    return false;
+  }
+  return true;
+}
+
 }  // namespace simple_util
 }  // namespace disk_cache