1// Copyright (c) 2012 The Chromium Authors. All rights reserved.
2// Use of this source code is governed by a BSD-style license that can be
3// found in the LICENSE file.
4
5#include "net/disk_cache/blockfile/block_files.h"
6
7#include "base/atomicops.h"
8#include "base/files/file_path.h"
9#include "base/metrics/histogram.h"
10#include "base/strings/string_util.h"
11#include "base/strings/stringprintf.h"
12#include "base/threading/thread_checker.h"
13#include "base/time/time.h"
14#include "net/disk_cache/blockfile/file_lock.h"
15#include "net/disk_cache/blockfile/stress_support.h"
16#include "net/disk_cache/blockfile/trace.h"
17#include "net/disk_cache/cache_util.h"
18
19using base::TimeTicks;
20
21namespace {
22
23const char* kBlockName = "data_";
24
25// This array is used to perform a fast lookup of the nibble bit pattern to the
26// type of entry that can be stored there (number of consecutive blocks).
27const char s_types[16] = {4, 3, 2, 2, 1, 1, 1, 1, 0, 0, 0, 0, 0, 0, 0, 0};
28
29// Returns the type of block (number of consecutive blocks that can be stored)
30// for a given nibble of the bitmap.
31inline int GetMapBlockType(uint8 value) {
32  value &= 0xf;
33  return s_types[value];
34}
35
36}  // namespace
37
38namespace disk_cache {
39
40BlockHeader::BlockHeader() : header_(NULL) {
41}
42
43BlockHeader::BlockHeader(BlockFileHeader* header) : header_(header) {
44}
45
46BlockHeader::BlockHeader(MappedFile* file)
47    : header_(reinterpret_cast<BlockFileHeader*>(file->buffer())) {
48}
49
50BlockHeader::BlockHeader(const BlockHeader& other) : header_(other.header_) {
51}
52
53BlockHeader::~BlockHeader() {
54}
55
56bool BlockHeader::CreateMapBlock(int size, int* index) {
57  DCHECK(size > 0 && size <= kMaxNumBlocks);
58  int target = 0;
59  for (int i = size; i <= kMaxNumBlocks; i++) {
60    if (header_->empty[i - 1]) {
61      target = i;
62      break;
63    }
64  }
65
66  if (!target) {
67    STRESS_NOTREACHED();
68    return false;
69  }
70
71  TimeTicks start = TimeTicks::Now();
72  // We are going to process the map on 32-block chunks (32 bits), and on every
73  // chunk, iterate through the 8 nibbles where the new block can be located.
74  int current = header_->hints[target - 1];
75  for (int i = 0; i < header_->max_entries / 32; i++, current++) {
76    if (current == header_->max_entries / 32)
77      current = 0;
78    uint32 map_block = header_->allocation_map[current];
79
80    for (int j = 0; j < 8; j++, map_block >>= 4) {
81      if (GetMapBlockType(map_block) != target)
82        continue;
83
84      disk_cache::FileLock lock(header_);
85      int index_offset = j * 4 + 4 - target;
86      *index = current * 32 + index_offset;
87      STRESS_DCHECK(*index / 4 == (*index + size - 1) / 4);
88      uint32 to_add = ((1 << size) - 1) << index_offset;
89      header_->num_entries++;
90
91      // Note that there is no race in the normal sense here, but if we enforce
92      // the order of memory accesses between num_entries and allocation_map, we
93      // can assert that even if we crash here, num_entries will never be less
94      // than the actual number of used blocks.
95      base::subtle::MemoryBarrier();
96      header_->allocation_map[current] |= to_add;
97
98      header_->hints[target - 1] = current;
99      header_->empty[target - 1]--;
100      STRESS_DCHECK(header_->empty[target - 1] >= 0);
101      if (target != size) {
102        header_->empty[target - size - 1]++;
103      }
104      LOCAL_HISTOGRAM_TIMES("DiskCache.CreateBlock", TimeTicks::Now() - start);
105      return true;
106    }
107  }
108
109  // It is possible to have an undetected corruption (for example when the OS
110  // crashes), fix it here.
111  LOG(ERROR) << "Failing CreateMapBlock";
112  FixAllocationCounters();
113  return false;
114}
115
116void BlockHeader::DeleteMapBlock(int index, int size) {
117  if (size < 0 || size > kMaxNumBlocks) {
118    NOTREACHED();
119    return;
120  }
121  TimeTicks start = TimeTicks::Now();
122  int byte_index = index / 8;
123  uint8* byte_map = reinterpret_cast<uint8*>(header_->allocation_map);
124  uint8 map_block = byte_map[byte_index];
125
126  if (index % 8 >= 4)
127    map_block >>= 4;
128
129  // See what type of block will be available after we delete this one.
130  int bits_at_end = 4 - size - index % 4;
131  uint8 end_mask = (0xf << (4 - bits_at_end)) & 0xf;
132  bool update_counters = (map_block & end_mask) == 0;
133  uint8 new_value = map_block & ~(((1 << size) - 1) << (index % 4));
134  int new_type = GetMapBlockType(new_value);
135
136  disk_cache::FileLock lock(header_);
137  STRESS_DCHECK((((1 << size) - 1) << (index % 8)) < 0x100);
138  uint8  to_clear = ((1 << size) - 1) << (index % 8);
139  STRESS_DCHECK((byte_map[byte_index] & to_clear) == to_clear);
140  byte_map[byte_index] &= ~to_clear;
141
142  if (update_counters) {
143    if (bits_at_end)
144      header_->empty[bits_at_end - 1]--;
145    header_->empty[new_type - 1]++;
146    STRESS_DCHECK(header_->empty[bits_at_end - 1] >= 0);
147  }
148  base::subtle::MemoryBarrier();
149  header_->num_entries--;
150  STRESS_DCHECK(header_->num_entries >= 0);
151  LOCAL_HISTOGRAM_TIMES("DiskCache.DeleteBlock", TimeTicks::Now() - start);
152}
153
154// Note that this is a simplified version of DeleteMapBlock().
155bool BlockHeader::UsedMapBlock(int index, int size) {
156  if (size < 0 || size > kMaxNumBlocks)
157    return false;
158
159  int byte_index = index / 8;
160  uint8* byte_map = reinterpret_cast<uint8*>(header_->allocation_map);
161  uint8 map_block = byte_map[byte_index];
162
163  if (index % 8 >= 4)
164    map_block >>= 4;
165
166  STRESS_DCHECK((((1 << size) - 1) << (index % 8)) < 0x100);
167  uint8  to_clear = ((1 << size) - 1) << (index % 8);
168  return ((byte_map[byte_index] & to_clear) == to_clear);
169}
170
171void BlockHeader::FixAllocationCounters() {
172  for (int i = 0; i < kMaxNumBlocks; i++) {
173    header_->hints[i] = 0;
174    header_->empty[i] = 0;
175  }
176
177  for (int i = 0; i < header_->max_entries / 32; i++) {
178    uint32 map_block = header_->allocation_map[i];
179
180    for (int j = 0; j < 8; j++, map_block >>= 4) {
181      int type = GetMapBlockType(map_block);
182      if (type)
183        header_->empty[type -1]++;
184    }
185  }
186}
187
188bool BlockHeader::NeedToGrowBlockFile(int block_count) const {
189  bool have_space = false;
190  int empty_blocks = 0;
191  for (int i = 0; i < kMaxNumBlocks; i++) {
192    empty_blocks += header_->empty[i] * (i + 1);
193    if (i >= block_count - 1 && header_->empty[i])
194      have_space = true;
195  }
196
197  if (header_->next_file && (empty_blocks < kMaxBlocks / 10)) {
198    // This file is almost full but we already created another one, don't use
199    // this file yet so that it is easier to find empty blocks when we start
200    // using this file again.
201    return true;
202  }
203  return !have_space;
204}
205
206bool BlockHeader::CanAllocate(int block_count) const {
207  DCHECK_GT(block_count, 0);
208  for (int i = block_count - 1; i < kMaxNumBlocks; i++) {
209    if (header_->empty[i])
210      return true;
211  }
212
213  return false;
214}
215
216int BlockHeader::EmptyBlocks() const {
217  int empty_blocks = 0;
218  for (int i = 0; i < kMaxNumBlocks; i++) {
219    empty_blocks += header_->empty[i] * (i + 1);
220    if (header_->empty[i] < 0)
221      return 0;
222  }
223  return empty_blocks;
224}
225
226int BlockHeader::MinimumAllocations() const {
227  return header_->empty[kMaxNumBlocks - 1];
228}
229
230int BlockHeader::Capacity() const {
231  return header_->max_entries;
232}
233
234bool BlockHeader::ValidateCounters() const {
235  if (header_->max_entries < 0 || header_->max_entries > kMaxBlocks ||
236      header_->num_entries < 0)
237    return false;
238
239  int empty_blocks = EmptyBlocks();
240  if (empty_blocks + header_->num_entries > header_->max_entries)
241    return false;
242
243  return true;
244}
245
246int BlockHeader::FileId() const {
247  return header_->this_file;
248}
249
250int BlockHeader::NextFileId() const {
251  return header_->next_file;
252}
253
254int BlockHeader::Size() const {
255  return static_cast<int>(sizeof(*header_));
256}
257
258BlockFileHeader* BlockHeader::Header() {
259  return header_;
260}
261
262// ------------------------------------------------------------------------
263
264BlockFiles::BlockFiles(const base::FilePath& path)
265    : init_(false), zero_buffer_(NULL), path_(path) {
266}
267
268BlockFiles::~BlockFiles() {
269  if (zero_buffer_)
270    delete[] zero_buffer_;
271  CloseFiles();
272}
273
274bool BlockFiles::Init(bool create_files) {
275  DCHECK(!init_);
276  if (init_)
277    return false;
278
279  thread_checker_.reset(new base::ThreadChecker);
280
281  block_files_.resize(kFirstAdditionalBlockFile);
282  for (int i = 0; i < kFirstAdditionalBlockFile; i++) {
283    if (create_files)
284      if (!CreateBlockFile(i, static_cast<FileType>(i + 1), true))
285        return false;
286
287    if (!OpenBlockFile(i))
288      return false;
289
290    // Walk this chain of files removing empty ones.
291    if (!RemoveEmptyFile(static_cast<FileType>(i + 1)))
292      return false;
293  }
294
295  init_ = true;
296  return true;
297}
298
299MappedFile* BlockFiles::GetFile(Addr address) {
300  DCHECK(thread_checker_->CalledOnValidThread());
301  DCHECK_GE(block_files_.size(),
302            static_cast<size_t>(kFirstAdditionalBlockFile));
303  DCHECK(address.is_block_file() || !address.is_initialized());
304  if (!address.is_initialized())
305    return NULL;
306
307  int file_index = address.FileNumber();
308  if (static_cast<unsigned int>(file_index) >= block_files_.size() ||
309      !block_files_[file_index]) {
310    // We need to open the file
311    if (!OpenBlockFile(file_index))
312      return NULL;
313  }
314  DCHECK_GE(block_files_.size(), static_cast<unsigned int>(file_index));
315  return block_files_[file_index];
316}
317
318bool BlockFiles::CreateBlock(FileType block_type, int block_count,
319                             Addr* block_address) {
320  DCHECK(thread_checker_->CalledOnValidThread());
321  DCHECK_NE(block_type, EXTERNAL);
322  DCHECK_NE(block_type, BLOCK_FILES);
323  DCHECK_NE(block_type, BLOCK_ENTRIES);
324  DCHECK_NE(block_type, BLOCK_EVICTED);
325  if (block_count < 1 || block_count > kMaxNumBlocks)
326    return false;
327
328  if (!init_)
329    return false;
330
331  MappedFile* file = FileForNewBlock(block_type, block_count);
332  if (!file)
333    return false;
334
335  ScopedFlush flush(file);
336  BlockHeader file_header(file);
337
338  int index;
339  if (!file_header.CreateMapBlock(block_count, &index))
340    return false;
341
342  Addr address(block_type, block_count, file_header.FileId(), index);
343  block_address->set_value(address.value());
344  Trace("CreateBlock 0x%x", address.value());
345  return true;
346}
347
348void BlockFiles::DeleteBlock(Addr address, bool deep) {
349  DCHECK(thread_checker_->CalledOnValidThread());
350  if (!address.is_initialized() || address.is_separate_file())
351    return;
352
353  if (!zero_buffer_) {
354    zero_buffer_ = new char[Addr::BlockSizeForFileType(BLOCK_4K) * 4];
355    memset(zero_buffer_, 0, Addr::BlockSizeForFileType(BLOCK_4K) * 4);
356  }
357  MappedFile* file = GetFile(address);
358  if (!file)
359    return;
360
361  Trace("DeleteBlock 0x%x", address.value());
362
363  size_t size = address.BlockSize() * address.num_blocks();
364  size_t offset = address.start_block() * address.BlockSize() +
365                  kBlockHeaderSize;
366  if (deep)
367    file->Write(zero_buffer_, size, offset);
368
369  BlockHeader file_header(file);
370  file_header.DeleteMapBlock(address.start_block(), address.num_blocks());
371  file->Flush();
372
373  if (!file_header.Header()->num_entries) {
374    // This file is now empty. Let's try to delete it.
375    FileType type = Addr::RequiredFileType(file_header.Header()->entry_size);
376    if (Addr::BlockSizeForFileType(RANKINGS) ==
377        file_header.Header()->entry_size) {
378      type = RANKINGS;
379    }
380    RemoveEmptyFile(type);  // Ignore failures.
381  }
382}
383
384void BlockFiles::CloseFiles() {
385  if (init_) {
386    DCHECK(thread_checker_->CalledOnValidThread());
387  }
388  init_ = false;
389  for (unsigned int i = 0; i < block_files_.size(); i++) {
390    if (block_files_[i]) {
391      block_files_[i]->Release();
392      block_files_[i] = NULL;
393    }
394  }
395  block_files_.clear();
396}
397
398void BlockFiles::ReportStats() {
399  DCHECK(thread_checker_->CalledOnValidThread());
400  int used_blocks[kFirstAdditionalBlockFile];
401  int load[kFirstAdditionalBlockFile];
402  for (int i = 0; i < kFirstAdditionalBlockFile; i++) {
403    GetFileStats(i, &used_blocks[i], &load[i]);
404  }
405  UMA_HISTOGRAM_COUNTS("DiskCache.Blocks_0", used_blocks[0]);
406  UMA_HISTOGRAM_COUNTS("DiskCache.Blocks_1", used_blocks[1]);
407  UMA_HISTOGRAM_COUNTS("DiskCache.Blocks_2", used_blocks[2]);
408  UMA_HISTOGRAM_COUNTS("DiskCache.Blocks_3", used_blocks[3]);
409
410  UMA_HISTOGRAM_ENUMERATION("DiskCache.BlockLoad_0", load[0], 101);
411  UMA_HISTOGRAM_ENUMERATION("DiskCache.BlockLoad_1", load[1], 101);
412  UMA_HISTOGRAM_ENUMERATION("DiskCache.BlockLoad_2", load[2], 101);
413  UMA_HISTOGRAM_ENUMERATION("DiskCache.BlockLoad_3", load[3], 101);
414}
415
416bool BlockFiles::IsValid(Addr address) {
417#ifdef NDEBUG
418  return true;
419#else
420  if (!address.is_initialized() || address.is_separate_file())
421    return false;
422
423  MappedFile* file = GetFile(address);
424  if (!file)
425    return false;
426
427  BlockHeader header(file);
428  bool rv = header.UsedMapBlock(address.start_block(), address.num_blocks());
429  DCHECK(rv);
430
431  static bool read_contents = false;
432  if (read_contents) {
433    scoped_ptr<char[]> buffer;
434    buffer.reset(new char[Addr::BlockSizeForFileType(BLOCK_4K) * 4]);
435    size_t size = address.BlockSize() * address.num_blocks();
436    size_t offset = address.start_block() * address.BlockSize() +
437                    kBlockHeaderSize;
438    bool ok = file->Read(buffer.get(), size, offset);
439    DCHECK(ok);
440  }
441
442  return rv;
443#endif
444}
445
446bool BlockFiles::CreateBlockFile(int index, FileType file_type, bool force) {
447  base::FilePath name = Name(index);
448  int flags = force ? base::File::FLAG_CREATE_ALWAYS : base::File::FLAG_CREATE;
449  flags |= base::File::FLAG_WRITE | base::File::FLAG_EXCLUSIVE_WRITE;
450
451  scoped_refptr<File> file(new File(base::File(name, flags)));
452  if (!file->IsValid())
453    return false;
454
455  BlockFileHeader header;
456  memset(&header, 0, sizeof(header));
457  header.magic = kBlockMagic;
458  header.version = kBlockVersion2;
459  header.entry_size = Addr::BlockSizeForFileType(file_type);
460  header.this_file = static_cast<int16>(index);
461  DCHECK(index <= kint16max && index >= 0);
462
463  return file->Write(&header, sizeof(header), 0);
464}
465
466bool BlockFiles::OpenBlockFile(int index) {
467  if (block_files_.size() - 1 < static_cast<unsigned int>(index)) {
468    DCHECK(index > 0);
469    int to_add = index - static_cast<int>(block_files_.size()) + 1;
470    block_files_.resize(block_files_.size() + to_add);
471  }
472
473  base::FilePath name = Name(index);
474  scoped_refptr<MappedFile> file(new MappedFile());
475
476  if (!file->Init(name, kBlockHeaderSize)) {
477    LOG(ERROR) << "Failed to open " << name.value();
478    return false;
479  }
480
481  size_t file_len = file->GetLength();
482  if (file_len < static_cast<size_t>(kBlockHeaderSize)) {
483    LOG(ERROR) << "File too small " << name.value();
484    return false;
485  }
486
487  BlockHeader file_header(file.get());
488  BlockFileHeader* header = file_header.Header();
489  if (kBlockMagic != header->magic || kBlockVersion2 != header->version) {
490    LOG(ERROR) << "Invalid file version or magic " << name.value();
491    return false;
492  }
493
494  if (header->updating || !file_header.ValidateCounters()) {
495    // Last instance was not properly shutdown, or counters are out of sync.
496    if (!FixBlockFileHeader(file.get())) {
497      LOG(ERROR) << "Unable to fix block file " << name.value();
498      return false;
499    }
500  }
501
502  if (static_cast<int>(file_len) <
503      header->max_entries * header->entry_size + kBlockHeaderSize) {
504    LOG(ERROR) << "File too small " << name.value();
505    return false;
506  }
507
508  if (index == 0) {
509    // Load the links file into memory.
510    if (!file->Preload())
511      return false;
512  }
513
514  ScopedFlush flush(file.get());
515  DCHECK(!block_files_[index]);
516  file.swap(&block_files_[index]);
517  return true;
518}
519
520bool BlockFiles::GrowBlockFile(MappedFile* file, BlockFileHeader* header) {
521  if (kMaxBlocks == header->max_entries)
522    return false;
523
524  ScopedFlush flush(file);
525  DCHECK(!header->empty[3]);
526  int new_size = header->max_entries + 1024;
527  if (new_size > kMaxBlocks)
528    new_size = kMaxBlocks;
529
530  int new_size_bytes = new_size * header->entry_size + sizeof(*header);
531
532  if (!file->SetLength(new_size_bytes)) {
533    // Most likely we are trying to truncate the file, so the header is wrong.
534    if (header->updating < 10 && !FixBlockFileHeader(file)) {
535      // If we can't fix the file increase the lock guard so we'll pick it on
536      // the next start and replace it.
537      header->updating = 100;
538      return false;
539    }
540    return (header->max_entries >= new_size);
541  }
542
543  FileLock lock(header);
544  header->empty[3] = (new_size - header->max_entries) / 4;  // 4 blocks entries
545  header->max_entries = new_size;
546
547  return true;
548}
549
550MappedFile* BlockFiles::FileForNewBlock(FileType block_type, int block_count) {
551  COMPILE_ASSERT(RANKINGS == 1, invalid_file_type);
552  MappedFile* file = block_files_[block_type - 1];
553  BlockHeader file_header(file);
554
555  TimeTicks start = TimeTicks::Now();
556  while (file_header.NeedToGrowBlockFile(block_count)) {
557    if (kMaxBlocks == file_header.Header()->max_entries) {
558      file = NextFile(file);
559      if (!file)
560        return NULL;
561      file_header = BlockHeader(file);
562      continue;
563    }
564
565    if (!GrowBlockFile(file, file_header.Header()))
566      return NULL;
567    break;
568  }
569  LOCAL_HISTOGRAM_TIMES("DiskCache.GetFileForNewBlock",
570                        TimeTicks::Now() - start);
571  return file;
572}
573
574MappedFile* BlockFiles::NextFile(MappedFile* file) {
575  ScopedFlush flush(file);
576  BlockFileHeader* header = reinterpret_cast<BlockFileHeader*>(file->buffer());
577  int new_file = header->next_file;
578  if (!new_file) {
579    // RANKINGS is not reported as a type for small entries, but we may be
580    // extending the rankings block file.
581    FileType type = Addr::RequiredFileType(header->entry_size);
582    if (header->entry_size == Addr::BlockSizeForFileType(RANKINGS))
583      type = RANKINGS;
584
585    new_file = CreateNextBlockFile(type);
586    if (!new_file)
587      return NULL;
588
589    FileLock lock(header);
590    header->next_file = new_file;
591  }
592
593  // Only the block_file argument is relevant for what we want.
594  Addr address(BLOCK_256, 1, new_file, 0);
595  return GetFile(address);
596}
597
598int BlockFiles::CreateNextBlockFile(FileType block_type) {
599  for (int i = kFirstAdditionalBlockFile; i <= kMaxBlockFile; i++) {
600    if (CreateBlockFile(i, block_type, false))
601      return i;
602  }
603  return 0;
604}
605
606// We walk the list of files for this particular block type, deleting the ones
607// that are empty.
608bool BlockFiles::RemoveEmptyFile(FileType block_type) {
609  MappedFile* file = block_files_[block_type - 1];
610  BlockFileHeader* header = reinterpret_cast<BlockFileHeader*>(file->buffer());
611
612  while (header->next_file) {
613    // Only the block_file argument is relevant for what we want.
614    Addr address(BLOCK_256, 1, header->next_file, 0);
615    MappedFile* next_file = GetFile(address);
616    if (!next_file)
617      return false;
618
619    BlockFileHeader* next_header =
620        reinterpret_cast<BlockFileHeader*>(next_file->buffer());
621    if (!next_header->num_entries) {
622      DCHECK_EQ(next_header->entry_size, header->entry_size);
623      // Delete next_file and remove it from the chain.
624      int file_index = header->next_file;
625      header->next_file = next_header->next_file;
626      DCHECK(block_files_.size() >= static_cast<unsigned int>(file_index));
627      file->Flush();
628
629      // We get a new handle to the file and release the old one so that the
630      // file gets unmmaped... so we can delete it.
631      base::FilePath name = Name(file_index);
632      scoped_refptr<File> this_file(new File(false));
633      this_file->Init(name);
634      block_files_[file_index]->Release();
635      block_files_[file_index] = NULL;
636
637      int failure = DeleteCacheFile(name) ? 0 : 1;
638      UMA_HISTOGRAM_COUNTS("DiskCache.DeleteFailed2", failure);
639      if (failure)
640        LOG(ERROR) << "Failed to delete " << name.value() << " from the cache.";
641      continue;
642    }
643
644    header = next_header;
645    file = next_file;
646  }
647  return true;
648}
649
650// Note that we expect to be called outside of a FileLock... however, we cannot
651// DCHECK on header->updating because we may be fixing a crash.
652bool BlockFiles::FixBlockFileHeader(MappedFile* file) {
653  ScopedFlush flush(file);
654  BlockHeader file_header(file);
655  int file_size = static_cast<int>(file->GetLength());
656  if (file_size < file_header.Size())
657    return false;  // file_size > 2GB is also an error.
658
659  const int kMinBlockSize = 36;
660  const int kMaxBlockSize = 4096;
661  BlockFileHeader* header = file_header.Header();
662  if (header->entry_size < kMinBlockSize ||
663      header->entry_size > kMaxBlockSize || header->num_entries < 0)
664    return false;
665
666  // Make sure that we survive crashes.
667  header->updating = 1;
668  int expected = header->entry_size * header->max_entries + file_header.Size();
669  if (file_size != expected) {
670    int max_expected = header->entry_size * kMaxBlocks + file_header.Size();
671    if (file_size < expected || header->empty[3] || file_size > max_expected) {
672      NOTREACHED();
673      LOG(ERROR) << "Unexpected file size";
674      return false;
675    }
676    // We were in the middle of growing the file.
677    int num_entries = (file_size - file_header.Size()) / header->entry_size;
678    header->max_entries = num_entries;
679  }
680
681  file_header.FixAllocationCounters();
682  int empty_blocks = file_header.EmptyBlocks();
683  if (empty_blocks + header->num_entries > header->max_entries)
684    header->num_entries = header->max_entries - empty_blocks;
685
686  if (!file_header.ValidateCounters())
687    return false;
688
689  header->updating = 0;
690  return true;
691}
692
693// We are interested in the total number of blocks used by this file type, and
694// the max number of blocks that we can store (reported as the percentage of
695// used blocks). In order to find out the number of used blocks, we have to
696// substract the empty blocks from the total blocks for each file in the chain.
697void BlockFiles::GetFileStats(int index, int* used_count, int* load) {
698  int max_blocks = 0;
699  *used_count = 0;
700  *load = 0;
701  for (;;) {
702    if (!block_files_[index] && !OpenBlockFile(index))
703      return;
704
705    BlockFileHeader* header =
706        reinterpret_cast<BlockFileHeader*>(block_files_[index]->buffer());
707
708    max_blocks += header->max_entries;
709    int used = header->max_entries;
710    for (int i = 0; i < kMaxNumBlocks; i++) {
711      used -= header->empty[i] * (i + 1);
712      DCHECK_GE(used, 0);
713    }
714    *used_count += used;
715
716    if (!header->next_file)
717      break;
718    index = header->next_file;
719  }
720  if (max_blocks)
721    *load = *used_count * 100 / max_blocks;
722}
723
724base::FilePath BlockFiles::Name(int index) {
725  // The file format allows for 256 files.
726  DCHECK(index < 256 && index >= 0);
727  std::string tmp = base::StringPrintf("%s%d", kBlockName, index);
728  return path_.AppendASCII(tmp);
729}
730
731}  // namespace disk_cache
732