Record UMA statistics for file_stream operations.

net/base/file_stream_metrics_win.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 "net/base/file_stream_metrics.h"
+
+#include <windows.h>
+
+#include "base/basictypes.h"
+
+namespace net {
+
+namespace {
+
+struct Range {
+  int low;
+  int high;
+};
+
+// The error range list is extracted from WinError.h.
+//
+// NOTE: The gaps between the ranges need to be recorded too.
+// They will have odd-numbered buckets.
+const Range kErrorRangeList[] = {
+  { 0, 321 },  // 2.
+  { 335, 371 },  // 4.
+  { 383, 387 },  // 6.
+  { 399, 404 },  // etc.
+  { 415, 418 },
+  { 431, 433 },
+  { 447, 868 },
+  { 994, 1471 },
+  { 1500, 1513 },
+  { 1536, 1553 },
+  { 1601, 1654 },
+  { 1700, 1834 },
+  { 1898, 1938 },
+  { 2000, 2024 },
+  { 2048, 2085 },
+  { 2108, 2110 },
+  { 2202, 2203 },
+  { 2250, 2251 },
+  { 2401, 2405 },
+  { 3000, 3021 },
+  { 3950, 3951 },
+  { 4000, 4007 },
+  { 4050, 4066 },
+  { 4096, 4116 },
+  { 4200, 4215 },
+  { 4300, 4353 },
+  { 4390, 4395 },
+  { 4500, 4501 },
+  { 4864, 4905 },
+  { 5001, 5090 },
+  { 5890, 5953 },
+  { 6000, 6023 },
+  { 6118, 6119 },
+  { 6200, 6201 },
+  { 6600, 6649 },
+  { 6700, 6732 },
+  { 6800, 6856 },
+  { 7001, 7071 },
+  { 8001, 8018 },
+  { 8192, 8263 },
+  { 8301, 8640 },
+  { 8704, 8705 },
+  { 8960, 9053 },
+  { 9216, 9218 },
+  { 9263, 9276 },
+  { 9472, 9506 },
+  { 9550, 9573 },
+  { 9600, 9622 },
+  { 9650, 9656 },
+  { 9688, 9723 },
+  { 9750, 9754 },
+  { 9800, 9802 },
+  { 9850, 9853 },
+  { 9900, 9907 },
+  { 10000, 10072 },
+  { 10091, 10113 },
+  { 11001, 11034 },
+  { 12288, 12335 },
+  { 12544, 12559 },
+  { 12595, 12597 },
+  { 12801, 12803 },
+  { 13000, 13026 },
+  { 13800, 13933 },
+  { 14000, 14111 },
+  { 15000, 15039 },
+  { 15080, 15086 },
+  { 15100, 15109 },
+  { 15200, 15208 },
+  { 15250, 15251 },
+  { 15299, 15302 },
+  { 16385, 16436 },
+  { 18432, 18454 },
+  { 20480, 20486 },
+  { 24577, 24607 },
+  { 28673, 28698 },
+  { 32790, 32816 },
+  { 33281, 33322 },
+  { 35005, 35024 },
+  { 36000, 36004 },
+  { 40010, 40011 },
+  { 40067, 40069 },
+  { 53248, 53293 },
+  { 53376, 53382 },
+  { 57344, 57360 },
+  { 57377, 57394 },
+  { 65535, 65536 }  // 2 * kNumErrorRanges.
+};
+const size_t kNumErrorRanges = ARRAYSIZE_UNSAFE(kErrorRangeList);
+
+}  // namespace
+
+// Windows has very many errors.  We're not interested in most of them, but we
+// don't know which ones are significant.
+// This function maps error ranges to specific buckets.
+// If we get hits on the buckets, we can add those values to the values we
+// record individually.
+// If we get values *between* the buckets, we record those as buckets too.
+int GetErrorBucket(int error) {
+  error = HRESULT_CODE(error);
+
+  // This is a linear search, but of a short fixed-size array.
+  // It also gets called infrequently, on errors.
+  for (size_t n = 0; n < kNumErrorRanges; ++n) {
+    if (error < kErrorRangeList[n].low)
+      return (2 * (n + 1)) - 1;  // In gap before the range.

[cbentzel, 2011/08/31 19:53:23]

This could be 2 * n and the "in-range" as 2*n+1 to not leave a hole at 0. Not a
huge deal. 

+    if (error <= kErrorRangeList[n].high)
+      return 2 * (n + 1);  // In the range.
+  }
+
+  // After the last bucket.
+  return 2 * kNumErrorRanges + 1;
+}
+
+int MaxBucket() {
+  return 2 * kNumErrorRanges + 2;
+}
+
+int MaxError() {
+  return kErrorRangeList[0].high + 1;
+}
+
+}  // namespace net