Fix random number generation in disk_cache_perftests.

net/disk_cache/disk_cache_perftest.cc

 // Copyright (c) 2011 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 <limits>
 #include <string>
 
 #include "base/bind.h"
 #include "base/bind_helpers.h"
 #include "base/files/file_enumerator.h"
 #include "base/files/file_path.h"
 #include "base/hash.h"
 #include "base/process/process_metrics.h"
+#include "base/rand_util.h"
 #include "base/run_loop.h"
 #include "base/strings/string_util.h"
 #include "base/test/perf_time_logger.h"
 #include "base/test/test_file_util.h"
 #include "base/threading/thread.h"
 #include "net/base/cache_type.h"
 #include "net/base/io_buffer.h"
 #include "net/base/net_errors.h"
 #include "net/base/test_completion_callback.h"
 #include "net/disk_cache/blockfile/backend_impl.h"
@@ skipping 83 matching lines @@
   int expected = 0;
 
   MessageLoopHelper helper;
   CallbackTest callback(&helper, true);
 
   base::PerfTimeLogger timer("Write disk cache entries");
 
   for (int i = 0; i < kNumEntries; i++) {
     TestEntry entry;
     entry.key = GenerateKey(true);
-    entry.data_len = rand() % kBodySize;
+    entry.data_len = base::RandInt(0, kBodySize);
     entries_.push_back(entry);
 
     disk_cache::Entry* cache_entry;
     net::TestCompletionCallback cb;
     int rv = cache_->CreateEntry(entry.key, &cache_entry, cb.callback());
     if (net::OK != cb.GetResult(rv))
       break;
     int ret = cache_entry->WriteData(
         0, 0, buffer1.get(), kHeadersSize,
         base::Bind(&CallbackTest::Run, base::Unretained(&callback)), false);
@@ skipping 61 matching lines @@
     cache_entry->Close();
   }
 
   helper.WaitUntilCacheIoFinished(expected);
   timer.Done();
 
   return (expected == helper.callbacks_called());
 }
 
 TEST_F(DiskCachePerfTest, BlockfileHashes) {
-  int seed = static_cast<int>(Time::Now().ToInternalValue());
-  srand(seed);
-
   base::PerfTimeLogger timer("Hash disk cache keys");
   for (int i = 0; i < 300000; i++) {
     std::string key = GenerateKey(true);
     base::Hash(key);
   }
   timer.Done();
 }
 
 void DiskCachePerfTest::ResetAndEvictSystemDiskCache() {
   base::RunLoop().RunUntilIdle();
@@ skipping 50 matching lines @@
 TEST_F(DiskCachePerfTest, CacheBackendPerformance) {
   CacheBackendPerformance();
 }
 
 TEST_F(DiskCachePerfTest, SimpleCacheBackendPerformance) {
   SetSimpleCacheMode();
   CacheBackendPerformance();
 }
 
 int BlockSize() {
   // We can use form 1 to 4 blocks.

[jkarlin, 2016/11/15 12:18:29]

While you're here..
s/form/from/

[gavinp, 2016/11/15 15:30:53]

Done. Also removed the function; documented the role with a variable instead.
And killed the comment rather than fixing it, since it was just recapitulating
code.

-  return (rand() & 0x3) + 1;
+  return base::RandInt(1, 4);
 }
 
 // Creating and deleting "entries" on a block-file is something quite frequent
 // (after all, almost everything is stored on block files). The operation is
 // almost free when the file is empty, but can be expensive if the file gets
 // fragmented, or if we have multiple files. This test measures that scenario,
 // by using multiple, highly fragmented files.
 TEST_F(DiskCachePerfTest, BlockFilesPerformance) {
   ASSERT_TRUE(CleanupCacheDir());
 
   disk_cache::BlockFiles files(cache_path_);
   ASSERT_TRUE(files.Init(true));
 
-  int seed = static_cast<int>(Time::Now().ToInternalValue());
-  srand(seed);
-
   const int kNumBlocks = 60000;
   disk_cache::Addr address[kNumBlocks];
 
   base::PerfTimeLogger timer1("Fill three block-files");
 
   // Fill up the 32-byte block file (use three files).
   for (int i = 0; i < kNumBlocks; i++) {
     EXPECT_TRUE(
         files.CreateBlock(disk_cache::RANKINGS, BlockSize(), &address[i]));
   }
 
   timer1.Done();
   base::PerfTimeLogger timer2("Create and delete blocks");
 
   for (int i = 0; i < 200000; i++) {
-    int entry = rand() * (kNumBlocks / RAND_MAX + 1);
+    int entry = base::RandInt(0, kNumBlocks);

[jkarlin, 2016/11/15 12:18:29]

base::RandInt(0, kNumBlocks-1) since it's inclusive and this value is used as an
index. Then you can drop the condition below.

[gavinp, 2016/11/15 15:30:54]

Done.

I can't believe these gymnastics. This is such a horrible test.

+
     if (entry >= kNumBlocks)

[jkarlin, 2016/11/15 12:18:29]

This condition should go.

[gavinp, 2016/11/15 15:30:54]

Done.

       entry = 0;
 
     files.DeleteBlock(address[entry], false);
     EXPECT_TRUE(
         files.CreateBlock(disk_cache::RANKINGS, BlockSize(), &address[entry]));
   }
 
   timer2.Done();
   base::RunLoop().RunUntilIdle();
 }
 
 }  // namespace