net/disk_cache/blockfile/sparse_control_v3.cc

   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/sparse_control.h"
   6
   7 #include "base/bind.h"
   8 #include "base/format_macros.h"
   9 #include "base/logging.h"
  10 #include "base/message_loop/message_loop.h"
  11 #include "base/strings/string_util.h"
  12 #include "base/strings/stringprintf.h"
  13 #include "base/time/time.h"
  14 #include "net/base/io_buffer.h"
  15 #include "net/base/net_errors.h"
  16 #include "net/disk_cache/blockfile/backend_impl.h"
  17 #include "net/disk_cache/blockfile/entry_impl.h"
  18 #include "net/disk_cache/blockfile/file.h"
  19 #include "net/disk_cache/net_log_parameters.h"
  20
  21 using base::Time;
  22
  23 namespace {
  24
  25 // Stream of the sparse data index.
  26 const int kSparseIndex = 2;
  27
  28 // Stream of the sparse data.
  29 const int kSparseData = 1;
  30
  31 // We can have up to 64k children.
  32 const int kMaxMapSize = 8 * 1024;
  33
  34 // The maximum number of bytes that a child can store.
  35 const int kMaxEntrySize = 0x100000;
  36
  37 // The size of each data block (tracked by the child allocation bitmap).
  38 const int kBlockSize = 1024;
  39
  40 // Returns the name of a child entry given the base_name and signature of the
  41 // parent and the child_id.
  42 // If the entry is called entry_name, child entries will be named something
  43 // like Range_entry_name:XXX:YYY where XXX is the entry signature and YYY is the
  44 // number of the particular child.
  45 std::string GenerateChildName(const std::string& base_name, int64 signature,
  46                               int64 child_id) {
  47   return base::StringPrintf("Range_%s:%" PRIx64 ":%" PRIx64, base_name.c_str(),
  48                             signature, child_id);
  49 }
  50
  51 // This class deletes the children of a sparse entry.
  52 class ChildrenDeleter
  53     : public base::RefCounted<ChildrenDeleter>,
  54       public disk_cache::FileIOCallback {
  55  public:
  56   ChildrenDeleter(disk_cache::BackendImpl* backend, const std::string& name)
  57       : backend_(backend->GetWeakPtr()), name_(name), signature_(0) {}
  58
  59   void OnFileIOComplete(int bytes_copied) override;
  60
  61   // Two ways of deleting the children: if we have the children map, use Start()
  62   // directly, otherwise pass the data address to ReadData().
  63   void Start(char* buffer, int len);
  64   void ReadData(disk_cache::Addr address, int len);
  65
  66  private:
  67   friend class base::RefCounted<ChildrenDeleter>;
  68   ~ChildrenDeleter() override {}
  69
  70   void DeleteChildren();
  71
  72   base::WeakPtr<disk_cache::BackendImpl> backend_;
  73   std::string name_;
  74   disk_cache::Bitmap children_map_;
  75   int64 signature_;
  76   scoped_ptr<char[]> buffer_;
  77   DISALLOW_COPY_AND_ASSIGN(ChildrenDeleter);
  78 };
  79
  80 // This is the callback of the file operation.
  81 void ChildrenDeleter::OnFileIOComplete(int bytes_copied) {
  82   char* buffer = buffer_.release();
  83   Start(buffer, bytes_copied);
  84 }
  85
  86 void ChildrenDeleter::Start(char* buffer, int len) {
  87   buffer_.reset(buffer);
  88   if (len < static_cast<int>(sizeof(disk_cache::SparseData)))
  89     return Release();
  90
  91   // Just copy the information from |buffer|, delete |buffer| and start deleting
  92   // the child entries.
  93   disk_cache::SparseData* data =
  94       reinterpret_cast<disk_cache::SparseData*>(buffer);
  95   signature_ = data->header.signature;
  96
  97   int num_bits = (len - sizeof(disk_cache::SparseHeader)) * 8;
  98   children_map_.Resize(num_bits, false);
  99   children_map_.SetMap(data->bitmap, num_bits / 32);
 100   buffer_.reset();
 101
 102   DeleteChildren();
 103 }
 104
 105 void ChildrenDeleter::ReadData(disk_cache::Addr address, int len) {
 106   DCHECK(address.is_block_file());
 107   if (!backend_)
 108     return Release();
 109
 110   disk_cache::File* file(backend_->File(address));
 111   if (!file)
 112     return Release();
 113
 114   size_t file_offset = address.start_block() * address.BlockSize() +
 115                        disk_cache::kBlockHeaderSize;
 116
 117   buffer_.reset(new char[len]);
 118   bool completed;
 119   if (!file->Read(buffer_.get(), len, file_offset, this, &completed))
 120     return Release();
 121
 122   if (completed)
 123     OnFileIOComplete(len);
 124
 125   // And wait until OnFileIOComplete gets called.
 126 }
 127
 128 void ChildrenDeleter::DeleteChildren() {
 129   int child_id = 0;
 130   if (!children_map_.FindNextSetBit(&child_id) || !backend_) {
 131     // We are done. Just delete this object.
 132     return Release();
 133   }
 134   std::string child_name = GenerateChildName(name_, signature_, child_id);
 135   backend_->SyncDoomEntry(child_name);
 136   children_map_.Set(child_id, false);
 137
 138   // Post a task to delete the next child.
 139   base::MessageLoop::current()->PostTask(
 140       FROM_HERE, base::Bind(&ChildrenDeleter::DeleteChildren, this));
 141 }
 142
 143 // -----------------------------------------------------------------------
 144
 145 // Returns the NetLog event type corresponding to a SparseOperation.
 146 net::NetLog::EventType GetSparseEventType(
 147     disk_cache::SparseControl::SparseOperation operation) {
 148   switch (operation) {
 149     case disk_cache::SparseControl::kReadOperation:
 150       return net::NetLog::TYPE_SPARSE_READ;
 151     case disk_cache::SparseControl::kWriteOperation:
 152       return net::NetLog::TYPE_SPARSE_WRITE;
 153     case disk_cache::SparseControl::kGetRangeOperation:
 154       return net::NetLog::TYPE_SPARSE_GET_RANGE;
 155     default:
 156       NOTREACHED();
 157       return net::NetLog::TYPE_CANCELLED;
 158   }
 159 }
 160
 161 // Logs the end event for |operation| on a child entry.  Range operations log
 162 // no events for each child they search through.
 163 void LogChildOperationEnd(const net::BoundNetLog& net_log,
 164                           disk_cache::SparseControl::SparseOperation operation,
 165                           int result) {
 166   if (net_log.IsCapturing()) {
 167     net::NetLog::EventType event_type;
 168     switch (operation) {
 169       case disk_cache::SparseControl::kReadOperation:
 170         event_type = net::NetLog::TYPE_SPARSE_READ_CHILD_DATA;
 171         break;
 172       case disk_cache::SparseControl::kWriteOperation:
 173         event_type = net::NetLog::TYPE_SPARSE_WRITE_CHILD_DATA;
 174         break;
 175       case disk_cache::SparseControl::kGetRangeOperation:
 176         return;
 177       default:
 178         NOTREACHED();
 179         return;
 180     }
 181     net_log.EndEventWithNetErrorCode(event_type, result);
 182   }
 183 }
 184
 185 }  // namespace.
 186
 187 namespace disk_cache {
 188
 189 SparseControl::SparseControl(EntryImpl* entry)
 190     : entry_(entry),
 191       child_(NULL),
 192       operation_(kNoOperation),
 193       pending_(false),
 194       finished_(false),
 195       init_(false),
 196       range_found_(false),
 197       abort_(false),
 198       child_map_(child_data_.bitmap, kNumSparseBits, kNumSparseBits / 32),
 199       offset_(0),
 200       buf_len_(0),
 201       child_offset_(0),
 202       child_len_(0),
 203       result_(0) {
 204   memset(&sparse_header_, 0, sizeof(sparse_header_));
 205   memset(&child_data_, 0, sizeof(child_data_));
 206 }
 207
 208 SparseControl::~SparseControl() {
 209   if (child_)
 210     CloseChild();
 211   if (init_)
 212     WriteSparseData();
 213 }
 214
 215 bool SparseControl::CouldBeSparse() const {
 216   DCHECK(!init_);
 217
 218   if (entry_->GetDataSize(kSparseData))
 219     return false;
 220
 221   // We don't verify the data, just see if it could be there.
 222   return (entry_->GetDataSize(kSparseIndex) != 0);
 223 }
 224
 225 int SparseControl::StartIO(SparseOperation op, int64 offset, net::IOBuffer* buf,
 226                            int buf_len, const CompletionCallback& callback) {
 227   DCHECK(init_);
 228   // We don't support simultaneous IO for sparse data.
 229   if (operation_ != kNoOperation)
 230     return net::ERR_CACHE_OPERATION_NOT_SUPPORTED;
 231
 232   if (offset < 0 || buf_len < 0)
 233     return net::ERR_INVALID_ARGUMENT;
 234
 235   // We only support up to 64 GB.
 236   if (offset + buf_len >= 0x1000000000LL || offset + buf_len < 0)
 237     return net::ERR_CACHE_OPERATION_NOT_SUPPORTED;
 238
 239   DCHECK(!user_buf_);
 240   DCHECK(user_callback_.is_null());
 241
 242   if (!buf && (op == kReadOperation || op == kWriteOperation))
 243     return 0;
 244
 245   // Copy the operation parameters.
 246   operation_ = op;
 247   offset_ = offset;
 248   user_buf_ = buf ? new net::DrainableIOBuffer(buf, buf_len) : NULL;
 249   buf_len_ = buf_len;
 250   user_callback_ = callback;
 251
 252   result_ = 0;
 253   pending_ = false;
 254   finished_ = false;
 255   abort_ = false;
 256
 257   if (entry_->net_log().IsCapturing()) {
 258     entry_->net_log().BeginEvent(
 259         GetSparseEventType(operation_),
 260         CreateNetLogSparseOperationCallback(offset_, buf_len_));
 261   }
 262   DoChildrenIO();
 263
 264   if (!pending_) {
 265     // Everything was done synchronously.
 266     operation_ = kNoOperation;
 267     user_buf_ = NULL;
 268     user_callback_.Reset();
 269     return result_;
 270   }
 271
 272   return net::ERR_IO_PENDING;
 273 }
 274
 275 int SparseControl::GetAvailableRange(int64 offset, int len, int64* start) {
 276   DCHECK(init_);
 277   // We don't support simultaneous IO for sparse data.
 278   if (operation_ != kNoOperation)
 279     return net::ERR_CACHE_OPERATION_NOT_SUPPORTED;
 280
 281   DCHECK(start);
 282
 283   range_found_ = false;
 284   int result = StartIO(
 285       kGetRangeOperation, offset, NULL, len, CompletionCallback());
 286   if (range_found_) {
 287     *start = offset_;
 288     return result;
 289   }
 290
 291   // This is a failure. We want to return a valid start value in any case.
 292   *start = offset;
 293   return result < 0 ? result : 0;  // Don't mask error codes to the caller.
 294 }
 295
 296 void SparseControl::CancelIO() {
 297   if (operation_ == kNoOperation)
 298     return;
 299   abort_ = true;
 300 }
 301
 302 int SparseControl::ReadyToUse(const CompletionCallback& callback) {
 303   if (!abort_)
 304     return net::OK;
 305
 306   // We'll grab another reference to keep this object alive because we just have
 307   // one extra reference due to the pending IO operation itself, but we'll
 308   // release that one before invoking user_callback_.
 309   entry_->AddRef();  // Balanced in DoAbortCallbacks.
 310   abort_callbacks_.push_back(callback);
 311   return net::ERR_IO_PENDING;
 312 }
 313
 314 // Static
 315 void SparseControl::DeleteChildren(EntryImpl* entry) {
 316   DCHECK(entry->GetEntryFlags() & PARENT_ENTRY);
 317   int data_len = entry->GetDataSize(kSparseIndex);
 318   if (data_len < static_cast<int>(sizeof(SparseData)) ||
 319       entry->GetDataSize(kSparseData))
 320     return;
 321
 322   int map_len = data_len - sizeof(SparseHeader);
 323   if (map_len > kMaxMapSize || map_len % 4)
 324     return;
 325
 326   char* buffer;
 327   Addr address;
 328   entry->GetData(kSparseIndex, &buffer, &address);
 329   if (!buffer && !address.is_initialized())
 330     return;
 331
 332   entry->net_log().AddEvent(net::NetLog::TYPE_SPARSE_DELETE_CHILDREN);
 333
 334   DCHECK(entry->backend_);
 335   ChildrenDeleter* deleter = new ChildrenDeleter(entry->backend_.get(),
 336                                                  entry->GetKey());
 337   // The object will self destruct when finished.
 338   deleter->AddRef();
 339
 340   if (buffer) {
 341     base::MessageLoop::current()->PostTask(
 342         FROM_HERE,
 343         base::Bind(&ChildrenDeleter::Start, deleter, buffer, data_len));
 344   } else {
 345     base::MessageLoop::current()->PostTask(
 346         FROM_HERE,
 347         base::Bind(&ChildrenDeleter::ReadData, deleter, address, data_len));
 348   }
 349 }
 350
 351 // -----------------------------------------------------------------------
 352
 353 int SparseControl::Init() {
 354   DCHECK(!init_);
 355
 356   // We should not have sparse data for the exposed entry.
 357   if (entry_->GetDataSize(kSparseData))
 358     return net::ERR_CACHE_OPERATION_NOT_SUPPORTED;
 359
 360   // Now see if there is something where we store our data.
 361   int rv = net::OK;
 362   int data_len = entry_->GetDataSize(kSparseIndex);
 363   if (!data_len) {
 364     rv = CreateSparseEntry();
 365   } else {
 366     rv = OpenSparseEntry(data_len);
 367   }
 368
 369   if (rv == net::OK)
 370     init_ = true;
 371   return rv;
 372 }
 373
 374 // We are going to start using this entry to store sparse data, so we have to
 375 // initialize our control info.
 376 int SparseControl::CreateSparseEntry() {
 377   if (CHILD_ENTRY & entry_->GetEntryFlags())
 378     return net::ERR_CACHE_OPERATION_NOT_SUPPORTED;
 379
 380   memset(&sparse_header_, 0, sizeof(sparse_header_));
 381   sparse_header_.signature = Time::Now().ToInternalValue();
 382   sparse_header_.magic = kIndexMagic;
 383   sparse_header_.parent_key_len = entry_->GetKey().size();
 384   children_map_.Resize(kNumSparseBits, true);
 385
 386   // Save the header. The bitmap is saved in the destructor.
 387   scoped_refptr<net::IOBuffer> buf(
 388       new net::WrappedIOBuffer(reinterpret_cast<char*>(&sparse_header_)));
 389
 390   int rv = entry_->WriteData(kSparseIndex, 0, buf.get(), sizeof(sparse_header_),
 391                              CompletionCallback(), false);
 392   if (rv != sizeof(sparse_header_)) {
 393     DLOG(ERROR) << "Unable to save sparse_header_";
 394     return net::ERR_CACHE_OPERATION_NOT_SUPPORTED;
 395   }
 396
 397   entry_->SetEntryFlags(PARENT_ENTRY);
 398   return net::OK;
 399 }
 400
 401 // We are opening an entry from disk. Make sure that our control data is there.
 402 int SparseControl::OpenSparseEntry(int data_len) {
 403   if (data_len < static_cast<int>(sizeof(SparseData)))
 404     return net::ERR_CACHE_OPERATION_NOT_SUPPORTED;
 405
 406   if (entry_->GetDataSize(kSparseData))
 407     return net::ERR_CACHE_OPERATION_NOT_SUPPORTED;
 408
 409   if (!(PARENT_ENTRY & entry_->GetEntryFlags()))
 410     return net::ERR_CACHE_OPERATION_NOT_SUPPORTED;
 411
 412   // Dont't go over board with the bitmap. 8 KB gives us offsets up to 64 GB.
 413   int map_len = data_len - sizeof(sparse_header_);
 414   if (map_len > kMaxMapSize || map_len % 4)
 415     return net::ERR_CACHE_OPERATION_NOT_SUPPORTED;
 416
 417   scoped_refptr<net::IOBuffer> buf(
 418       new net::WrappedIOBuffer(reinterpret_cast<char*>(&sparse_header_)));
 419
 420   // Read header.
 421   int rv = entry_->ReadData(kSparseIndex, 0, buf.get(), sizeof(sparse_header_),
 422                             CompletionCallback());
 423   if (rv != static_cast<int>(sizeof(sparse_header_)))
 424     return net::ERR_CACHE_READ_FAILURE;
 425
 426   // The real validation should be performed by the caller. This is just to
 427   // double check.
 428   if (sparse_header_.magic != kIndexMagic ||
 429       sparse_header_.parent_key_len !=
 430           static_cast<int>(entry_->GetKey().size()))
 431     return net::ERR_CACHE_OPERATION_NOT_SUPPORTED;
 432
 433   // Read the actual bitmap.
 434   buf = new net::IOBuffer(map_len);
 435   rv = entry_->ReadData(kSparseIndex, sizeof(sparse_header_), buf.get(),
 436                         map_len, CompletionCallback());
 437   if (rv != map_len)
 438     return net::ERR_CACHE_READ_FAILURE;
 439
 440   // Grow the bitmap to the current size and copy the bits.
 441   children_map_.Resize(map_len * 8, false);
 442   children_map_.SetMap(reinterpret_cast<uint32*>(buf->data()), map_len);
 443   return net::OK;
 444 }
 445
 446 bool SparseControl::OpenChild() {
 447   DCHECK_GE(result_, 0);
 448
 449   std::string key = GenerateChildKey();
 450   if (child_) {
 451     // Keep using the same child or open another one?.
 452     if (key == child_->GetKey())
 453       return true;
 454     CloseChild();
 455   }
 456
 457   // See if we are tracking this child.
 458   if (!ChildPresent())
 459     return ContinueWithoutChild(key);
 460
 461   if (!entry_->backend_)
 462     return false;
 463
 464   child_ = entry_->backend_->OpenEntryImpl(key);
 465   if (!child_)
 466     return ContinueWithoutChild(key);
 467
 468   EntryImpl* child = static_cast<EntryImpl*>(child_);
 469   if (!(CHILD_ENTRY & child->GetEntryFlags()) ||
 470       child->GetDataSize(kSparseIndex) <
 471           static_cast<int>(sizeof(child_data_)))
 472     return KillChildAndContinue(key, false);
 473
 474   scoped_refptr<net::WrappedIOBuffer> buf(
 475       new net::WrappedIOBuffer(reinterpret_cast<char*>(&child_data_)));
 476
 477   // Read signature.
 478   int rv = child_->ReadData(kSparseIndex, 0, buf.get(), sizeof(child_data_),
 479                             CompletionCallback());
 480   if (rv != sizeof(child_data_))
 481     return KillChildAndContinue(key, true);  // This is a fatal failure.
 482
 483   if (child_data_.header.signature != sparse_header_.signature ||
 484       child_data_.header.magic != kIndexMagic)
 485     return KillChildAndContinue(key, false);
 486
 487   if (child_data_.header.last_block_len < 0 ||
 488       child_data_.header.last_block_len > kBlockSize) {
 489     // Make sure these values are always within range.
 490     child_data_.header.last_block_len = 0;
 491     child_data_.header.last_block = -1;
 492   }
 493
 494   return true;
 495 }
 496
 497 void SparseControl::CloseChild() {
 498   scoped_refptr<net::WrappedIOBuffer> buf(
 499       new net::WrappedIOBuffer(reinterpret_cast<char*>(&child_data_)));
 500
 501   // Save the allocation bitmap before closing the child entry.
 502   int rv = child_->WriteData(kSparseIndex, 0, buf.get(), sizeof(child_data_),
 503                              CompletionCallback(),
 504       false);
 505   if (rv != sizeof(child_data_))
 506     DLOG(ERROR) << "Failed to save child data";
 507   child_->Release();
 508   child_ = NULL;
 509 }
 510
 511 // We were not able to open this child; see what we can do.
 512 bool SparseControl::ContinueWithoutChild(const std::string& key) {
 513   if (kReadOperation == operation_)
 514     return false;
 515   if (kGetRangeOperation == operation_)
 516     return true;
 517
 518   if (!entry_->backend_)
 519     return false;
 520
 521   child_ = entry_->backend_->CreateEntryImpl(key);
 522   if (!child_) {
 523     child_ = NULL;
 524     result_ = net::ERR_CACHE_READ_FAILURE;
 525     return false;
 526   }
 527   // Write signature.
 528   InitChildData();
 529   return true;
 530 }
 531
 532 void SparseControl::WriteSparseData() {
 533   scoped_refptr<net::IOBuffer> buf(new net::WrappedIOBuffer(
 534       reinterpret_cast<const char*>(children_map_.GetMap())));
 535
 536   int len = children_map_.ArraySize() * 4;
 537   int rv = entry_->WriteData(kSparseIndex, sizeof(sparse_header_), buf.get(),
 538                              len, CompletionCallback(), false);
 539   if (rv != len) {
 540     DLOG(ERROR) << "Unable to save sparse map";
 541   }
 542 }
 543
 544 bool SparseControl::DoChildIO() {
 545   finished_ = true;
 546   if (!buf_len_ || result_ < 0)
 547     return false;
 548
 549   if (!OpenChild())
 550     return false;
 551
 552   if (!VerifyRange())
 553     return false;
 554
 555   // We have more work to do. Let's not trigger a callback to the caller.
 556   finished_ = false;
 557   CompletionCallback callback;
 558   if (!user_callback_.is_null()) {
 559     callback =
 560         base::Bind(&SparseControl::OnChildIOCompleted, base::Unretained(this));
 561   }
 562
 563   int rv = 0;
 564   switch (operation_) {
 565     case kReadOperation:
 566       if (entry_->net_log().IsCapturing()) {
 567         entry_->net_log().BeginEvent(
 568             net::NetLog::TYPE_SPARSE_READ_CHILD_DATA,
 569             CreateNetLogSparseReadWriteCallback(child_->net_log().source(),
 570                                                 child_len_));
 571       }
 572       rv = child_->ReadDataImpl(kSparseData, child_offset_, user_buf_.get(),
 573                                 child_len_, callback);
 574       break;
 575     case kWriteOperation:
 576       if (entry_->net_log().IsCapturing()) {
 577         entry_->net_log().BeginEvent(
 578             net::NetLog::TYPE_SPARSE_WRITE_CHILD_DATA,
 579             CreateNetLogSparseReadWriteCallback(child_->net_log().source(),
 580                                                 child_len_));
 581       }
 582       rv = child_->WriteDataImpl(kSparseData, child_offset_, user_buf_.get(),
 583                                  child_len_, callback, false);
 584       break;
 585     case kGetRangeOperation:
 586       rv = DoGetAvailableRange();
 587       break;
 588     default:
 589       NOTREACHED();
 590   }
 591
 592   if (rv == net::ERR_IO_PENDING) {
 593     if (!pending_) {
 594       pending_ = true;
 595       // The child will protect himself against closing the entry while IO is in
 596       // progress. However, this entry can still be closed, and that would not
 597       // be a good thing for us, so we increase the refcount until we're
 598       // finished doing sparse stuff.
 599       entry_->AddRef();  // Balanced in DoUserCallback.
 600     }
 601     return false;
 602   }
 603   if (!rv)
 604     return false;
 605
 606   DoChildIOCompleted(rv);
 607   return true;
 608 }
 609
 610 void SparseControl::DoChildIOCompleted(int result) {
 611   LogChildOperationEnd(entry_->net_log(), operation_, result);
 612   if (result < 0) {
 613     // We fail the whole operation if we encounter an error.
 614     result_ = result;
 615     return;
 616   }
 617
 618   UpdateRange(result);
 619
 620   result_ += result;
 621   offset_ += result;
 622   buf_len_ -= result;
 623
 624   // We'll be reusing the user provided buffer for the next chunk.
 625   if (buf_len_ && user_buf_)
 626     user_buf_->DidConsume(result);
 627 }
 628
 629 std::string SparseControl::GenerateChildKey() {
 630   return GenerateChildName(entry_->GetKey(), sparse_header_.signature,
 631                            offset_ >> 20);
 632 }
 633
 634 // We are deleting the child because something went wrong.
 635 bool SparseControl::KillChildAndContinue(const std::string& key, bool fatal) {
 636   SetChildBit(false);
 637   child_->DoomImpl();
 638   child_->Release();
 639   child_ = NULL;
 640   if (fatal) {
 641     result_ = net::ERR_CACHE_READ_FAILURE;
 642     return false;
 643   }
 644   return ContinueWithoutChild(key);
 645 }
 646
 647 bool SparseControl::ChildPresent() {
 648   int child_bit = static_cast<int>(offset_ >> 20);
 649   if (children_map_.Size() <= child_bit)
 650     return false;
 651
 652   return children_map_.Get(child_bit);
 653 }
 654
 655 void SparseControl::SetChildBit(bool value) {
 656   int child_bit = static_cast<int>(offset_ >> 20);
 657
 658   // We may have to increase the bitmap of child entries.
 659   if (children_map_.Size() <= child_bit)
 660     children_map_.Resize(Bitmap::RequiredArraySize(child_bit + 1) * 32, true);
 661
 662   children_map_.Set(child_bit, value);
 663 }
 664
 665 bool SparseControl::VerifyRange() {
 666   DCHECK_GE(result_, 0);
 667
 668   child_offset_ = static_cast<int>(offset_) & (kMaxEntrySize - 1);
 669   child_len_ = std::min(buf_len_, kMaxEntrySize - child_offset_);
 670
 671   // We can write to (or get info from) anywhere in this child.
 672   if (operation_ != kReadOperation)
 673     return true;
 674
 675   // Check that there are no holes in this range.
 676   int last_bit = (child_offset_ + child_len_ + 1023) >> 10;
 677   int start = child_offset_ >> 10;
 678   if (child_map_.FindNextBit(&start, last_bit, false)) {
 679     // Something is not here.
 680     DCHECK_GE(child_data_.header.last_block_len, 0);
 681     DCHECK_LT(child_data_.header.last_block_len, kMaxEntrySize);
 682     int partial_block_len = PartialBlockLength(start);
 683     if (start == child_offset_ >> 10) {
 684       // It looks like we don't have anything.
 685       if (partial_block_len <= (child_offset_ & (kBlockSize - 1)))
 686         return false;
 687     }
 688
 689     // We have the first part.
 690     child_len_ = (start << 10) - child_offset_;
 691     if (partial_block_len) {
 692       // We may have a few extra bytes.
 693       child_len_ = std::min(child_len_ + partial_block_len, buf_len_);
 694     }
 695     // There is no need to read more after this one.
 696     buf_len_ = child_len_;
 697   }
 698   return true;
 699 }
 700
 701 void SparseControl::UpdateRange(int result) {
 702   if (result <= 0 || operation_ != kWriteOperation)
 703     return;
 704
 705   DCHECK_GE(child_data_.header.last_block_len, 0);
 706   DCHECK_LT(child_data_.header.last_block_len, kMaxEntrySize);
 707
 708   // Write the bitmap.
 709   int first_bit = child_offset_ >> 10;
 710   int block_offset = child_offset_ & (kBlockSize - 1);
 711   if (block_offset && (child_data_.header.last_block != first_bit ||
 712                        child_data_.header.last_block_len < block_offset)) {
 713     // The first block is not completely filled; ignore it.
 714     first_bit++;
 715   }
 716
 717   int last_bit = (child_offset_ + result) >> 10;
 718   block_offset = (child_offset_ + result) & (kBlockSize - 1);
 719
 720   // This condition will hit with the following criteria:
 721   // 1. The first byte doesn't follow the last write.
 722   // 2. The first byte is in the middle of a block.
 723   // 3. The first byte and the last byte are in the same block.
 724   if (first_bit > last_bit)
 725     return;
 726
 727   if (block_offset && !child_map_.Get(last_bit)) {
 728     // The last block is not completely filled; save it for later.
 729     child_data_.header.last_block = last_bit;
 730     child_data_.header.last_block_len = block_offset;
 731   } else {
 732     child_data_.header.last_block = -1;
 733   }
 734
 735   child_map_.SetRange(first_bit, last_bit, true);
 736 }
 737
 738 int SparseControl::PartialBlockLength(int block_index) const {
 739   if (block_index == child_data_.header.last_block)
 740     return child_data_.header.last_block_len;
 741
 742   // This may be the last stored index.
 743   int entry_len = child_->GetDataSize(kSparseData);
 744   if (block_index == entry_len >> 10)
 745     return entry_len & (kBlockSize - 1);
 746
 747   // This is really empty.
 748   return 0;
 749 }
 750
 751 void SparseControl::InitChildData() {
 752   // We know the real type of child_.
 753   EntryImpl* child = static_cast<EntryImpl*>(child_);
 754   child->SetEntryFlags(CHILD_ENTRY);
 755
 756   memset(&child_data_, 0, sizeof(child_data_));
 757   child_data_.header = sparse_header_;
 758
 759   scoped_refptr<net::WrappedIOBuffer> buf(
 760       new net::WrappedIOBuffer(reinterpret_cast<char*>(&child_data_)));
 761
 762   int rv = child_->WriteData(kSparseIndex, 0, buf.get(), sizeof(child_data_),
 763                              CompletionCallback(), false);
 764   if (rv != sizeof(child_data_))
 765     DLOG(ERROR) << "Failed to save child data";
 766   SetChildBit(true);
 767 }
 768
 769 int SparseControl::DoGetAvailableRange() {
 770   if (!child_)
 771     return child_len_;  // Move on to the next child.
 772
 773   // Check that there are no holes in this range.
 774   int last_bit = (child_offset_ + child_len_ + 1023) >> 10;
 775   int start = child_offset_ >> 10;
 776   int partial_start_bytes = PartialBlockLength(start);
 777   int found = start;
 778   int bits_found = child_map_.FindBits(&found, last_bit, true);
 779
 780   // We don't care if there is a partial block in the middle of the range.
 781   int block_offset = child_offset_ & (kBlockSize - 1);
 782   if (!bits_found && partial_start_bytes <= block_offset)
 783     return child_len_;
 784
 785   // We are done. Just break the loop and reset result_ to our real result.
 786   range_found_ = true;
 787
 788   // found now points to the first 1. Lets see if we have zeros before it.
 789   int empty_start = std::max((found << 10) - child_offset_, 0);
 790
 791   int bytes_found = bits_found << 10;
 792   bytes_found += PartialBlockLength(found + bits_found);
 793
 794   if (start == found)
 795     bytes_found -= block_offset;
 796
 797   // If the user is searching past the end of this child, bits_found is the
 798   // right result; otherwise, we have some empty space at the start of this
 799   // query that we have to subtract from the range that we searched.
 800   result_ = std::min(bytes_found, child_len_ - empty_start);
 801
 802   if (!bits_found) {
 803     result_ = std::min(partial_start_bytes - block_offset, child_len_);
 804     empty_start = 0;
 805   }
 806
 807   // Only update offset_ when this query found zeros at the start.
 808   if (empty_start)
 809     offset_ += empty_start;
 810
 811   // This will actually break the loop.
 812   buf_len_ = 0;
 813   return 0;
 814 }
 815
 816 void SparseControl::DoUserCallback() {
 817   DCHECK(!user_callback_.is_null());
 818   CompletionCallback cb = user_callback_;
 819   user_callback_.Reset();
 820   user_buf_ = NULL;
 821   pending_ = false;
 822   operation_ = kNoOperation;
 823   int rv = result_;
 824   entry_->Release();  // Don't touch object after this line.
 825   cb.Run(rv);
 826 }
 827
 828 void SparseControl::DoAbortCallbacks() {
 829   for (size_t i = 0; i < abort_callbacks_.size(); i++) {
 830     // Releasing all references to entry_ may result in the destruction of this
 831     // object so we should not be touching it after the last Release().
 832     CompletionCallback cb = abort_callbacks_[i];
 833     if (i == abort_callbacks_.size() - 1)
 834       abort_callbacks_.clear();
 835
 836     entry_->Release();  // Don't touch object after this line.
 837     cb.Run(net::OK);
 838   }
 839 }
 840
 841 void SparseControl::OnChildIOCompleted(int result) {
 842   DCHECK_NE(net::ERR_IO_PENDING, result);
 843   DoChildIOCompleted(result);
 844
 845   if (abort_) {
 846     // We'll return the current result of the operation, which may be less than
 847     // the bytes to read or write, but the user cancelled the operation.
 848     abort_ = false;
 849     if (entry_->net_log().IsCapturing()) {
 850       entry_->net_log().AddEvent(net::NetLog::TYPE_CANCELLED);
 851       entry_->net_log().EndEvent(GetSparseEventType(operation_));
 852     }
 853     // We have an indirect reference to this object for every callback so if
 854     // there is only one callback, we may delete this object before reaching
 855     // DoAbortCallbacks.
 856     bool has_abort_callbacks = !abort_callbacks_.empty();
 857     DoUserCallback();
 858     if (has_abort_callbacks)
 859       DoAbortCallbacks();
 860     return;
 861   }
 862
 863   // We are running a callback from the message loop. It's time to restart what
 864   // we were doing before.
 865   DoChildrenIO();
 866 }
 867
 868 }  // namespace disk_cache