Add new simple disk cache backend.

net/disk_cache/simple/simple_synchronous_entry.cc

+// Copyright (c) 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_synchronous_entry.h"
+
+#include <algorithm>
+#include <cstring>
+
+#include "base/basictypes.h"
+#include "base/file_util.h"
+#include "base/hash.h"
+#include "base/location.h"
+#include "base/message_loop_proxy.h"
+#include "base/sha1.h"
+#include "base/stringprintf.h"
+#include "base/task_runner.h"
+#include "net/base/io_buffer.h"
+#include "net/base/net_errors.h"
+#include "net/disk_cache/simple/simple_disk_format.h"
+
+using base::ClosePlatformFile;
+using base::GetPlatformFileInfo;
+using base::PlatformFileError;
+using base::PlatformFileInfo;
+using base::PLATFORM_FILE_CREATE_ALWAYS;
+using base::PLATFORM_FILE_OK;
+using base::PLATFORM_FILE_OPEN;
+using base::PLATFORM_FILE_READ;
+using base::PLATFORM_FILE_WRITE;
+using base::ReadPlatformFile;
+using base::TaskRunner;
+using base::Time;
+using base::TruncatePlatformFile;
+using base::WritePlatformFile;
+
+namespace {
+
+std::string GetFilenameForKeyAndIndex(const std::string& key, int index) {
+  const std::string sha_hash = base::SHA1HashString(key);
+  return StringPrintf("%02x%02x%02x%02x%02x_%1d",
+                      implicit_cast<unsigned char>(sha_hash[0]),
+                      implicit_cast<unsigned char>(sha_hash[1]),
+                      implicit_cast<unsigned char>(sha_hash[2]),
+                      implicit_cast<unsigned char>(sha_hash[3]),
+                      implicit_cast<unsigned char>(sha_hash[4]), index);
+}
+
+int32 DataSizeFromKeyAndFileSize(size_t key_size, int64 file_size) {
+  return file_size - key_size - sizeof(disk_cache::SimpleFileHeader);
+}
+
+int64 FileOffsetFromDataOffset(size_t key_size, int offset) {
+  const int64 headers_size = sizeof(disk_cache::SimpleFileHeader) +
+                             key_size;
+  return headers_size + offset;
+}
+
+}  // namespace
+
+namespace disk_cache {
+
+// static
+void SimpleSynchronousEntry::OpenEntry(
+    const FilePath& path,
+    const std::string& key,
+    const scoped_refptr<TaskRunner>& callback_runner,
+    const SynchronousEntryCallback& callback) {
+  SimpleSynchronousEntry* sync_entry =
+      new SimpleSynchronousEntry(callback_runner, path, key);
+
+  if (!sync_entry->InitializeForOpen()) {
+    delete sync_entry;
+    sync_entry = NULL;
+  }
+  callback_runner->PostTask(FROM_HERE,
+                            base::Bind(callback, sync_entry,
+                                       sync_entry ? net::OK : net::ERR_FAILED));
+}
+
+// static
+void SimpleSynchronousEntry::CreateEntry(
+    const FilePath& path,
+    const std::string& key,
+    const scoped_refptr<TaskRunner>& callback_runner,
+    const SynchronousEntryCallback& callback) {
+  SimpleSynchronousEntry* sync_entry =
+      new SimpleSynchronousEntry(callback_runner, path, key);
+
+  if (!sync_entry->InitializeForCreate()) {
+    delete sync_entry;
+    sync_entry = NULL;
+  }
+  callback_runner->PostTask(FROM_HERE,
+                            base::Bind(callback, sync_entry,
+                                       sync_entry ? net::OK : net::ERR_FAILED));
+}
+
+// static
+void SimpleSynchronousEntry::DoomEntry(
+    const FilePath& path,
+    const std::string& key,
+    scoped_refptr<TaskRunner> callback_runner,
+    const net::CompletionCallback& callback) {
+  for (int i = 0; i < kIndexCount; ++i) {
+    bool delete_result =
+        file_util::Delete(path.AppendASCII(GetFilenameForKeyAndIndex(key, i)),
+                          false);
+    DCHECK(delete_result);
+  }
+  if (!callback.is_null())
+    callback_runner->PostTask(FROM_HERE, base::Bind(callback, net::OK));
+}
+
+void SimpleSynchronousEntry::DoomAndClose() {
+  scoped_refptr<TaskRunner> callback_runner = callback_runner_;
+  FilePath path = path_;
+  std::string key = key_;
+
+  Close();
+  // |this| is now deleted.
+
+  DoomEntry(path, key, callback_runner, net::CompletionCallback());
+}
+
+void SimpleSynchronousEntry::Close() {
+  for (int i = 0; i < kIndexCount; ++i) {
+    bool result = ClosePlatformFile(files_[i]);
+    DCHECK(result);
+  }
+  delete this;
+}
+
+void SimpleSynchronousEntry::ReadData(
+    int index,
+    int offset,
+    net::IOBuffer* buf,
+    int buf_len,
+    const SynchronousEntryCallback& callback) {
+  DCHECK(initialized_);
+  if (status_[index].mode != EntryStatus::ENTRY_READER)
+    status_[index].data_offset = 0;
+  DCHECK_EQ(status_[index].data_offset, offset);
+  status_[index].mode = EntryStatus::ENTRY_READER;
+
+  int64 file_offset = FileOffsetFromDataOffset(key_.size(), offset);
+  int bytes_read = ReadPlatformFile(files_[index], file_offset,
+                                    buf->data(), buf_len);
+  if (bytes_read > 0) {
+    last_used_ = Time::Now();
+    status_[index].data_offset += bytes_read;
+  }
+  int result = (bytes_read >= 0) ? bytes_read : net::ERR_FAILED;
+  callback_runner_->PostTask(FROM_HERE, base::Bind(callback, this, result));
+}
+
+void SimpleSynchronousEntry::WriteData(
+    int index,
+    int offset,
+    net::IOBuffer* buf,
+    int buf_len,
+    const SynchronousEntryCallback& callback,
+    bool truncate) {
+  DCHECK(initialized_);
+  if (status_[index].mode != EntryStatus::ENTRY_WRITER)
+    status_[index].data_offset = 0;
+  DCHECK_EQ(status_[index].data_offset, offset);
+  status_[index].mode = EntryStatus::ENTRY_WRITER;
+
+  int64 file_offset = FileOffsetFromDataOffset(key_.size(), offset);
+  if (buf_len > 0) {
+    if (WritePlatformFile(files_[index], file_offset, buf->data(), buf_len) !=
+        buf_len) {
+      callback_runner_->PostTask(FROM_HERE,
+                                 base::Bind(callback, this, net::ERR_FAILED));

[pasko-google - do not use, 2013/02/11 13:59:25]

I am wondering why some errors are logged and some others aren't. Should be
consistent or comment where we handle these errors above the stack.

[gavinp, 2013/02/11 17:55:50]

The rule is that there's logging in code that has required debugging work in the
past, and not where there isn't.

I like comments about where these errors are handled up the stack. I'll add some
of those on my next upload.

+      return;
+    }
+    data_size_[index] = std::max(data_size_[index], offset + buf_len);
+    status_[index].data_offset += buf_len;
+  }
+  if (truncate) {
+    data_size_[index] = offset + buf_len;
+    if (!TruncatePlatformFile(files_[index], file_offset + buf_len)) {
+      callback_runner_->PostTask(FROM_HERE,
+                                 base::Bind(callback, this, net::ERR_FAILED));
+      return;
+    }
+  }
+  last_modified_ = Time::Now();
+  callback_runner_->PostTask(FROM_HERE, base::Bind(callback, this, buf_len));
+}
+
+SimpleSynchronousEntry::EntryStatus::EntryStatus()
+    : mode(ENTRY_UNINITIALIZED),
+      data_offset(0) {
+}
+
+SimpleSynchronousEntry::SimpleSynchronousEntry(
+    const scoped_refptr<TaskRunner>& callback_runner,
+    const FilePath& path,
+    const std::string& key) : callback_runner_(callback_runner),
+                              path_(path),
+                              key_(key),
+                              initialized_(false) {
+}
+
+SimpleSynchronousEntry::~SimpleSynchronousEntry() {
+}
+
+bool SimpleSynchronousEntry::OpenOrCreateFiles(bool create) {
+  for (int i = 0; i < kIndexCount; ++i) {
+    FilePath filename = path_.AppendASCII(GetFilenameForKeyAndIndex(key_, i));
+    int flags = PLATFORM_FILE_READ | PLATFORM_FILE_WRITE;
+    if (create)
+      flags |= PLATFORM_FILE_CREATE_ALWAYS;
+    else
+      flags |= PLATFORM_FILE_OPEN;
+    PlatformFileError error;
+    files_[i] = CreatePlatformFile(filename, flags, NULL, &error);
+    if (error != PLATFORM_FILE_OK) {
+      while (--i >= 0) {
+        bool did_close = ClosePlatformFile(files_[i]);
+        DCHECK(did_close);
+      }
+      return false;
+    }
+  }
+
+  for (int i = 0; i < kIndexCount; ++i) {
+    PlatformFileInfo file_info;
+    CHECK(GetPlatformFileInfo(files_[i], &file_info));
+    last_used_ = std::max(last_used_, file_info.last_accessed);

[pasko-google - do not use, 2013/02/11 13:59:25]

I am wondering how last_used is actually used. Here we probably want
file_info.last_accessed although it is unsurprisingly rather last_modified on
Linux and Android systems.

[gavinp, 2013/02/11 17:55:50]

Yeah. Tricky. Could force this issue with filesystem operations, or live with
this (bad) compromise while we wait for the index to be alive.

+    last_modified_ = std::max(last_modified_, file_info.last_modified);
+    data_size_[i] = DataSizeFromKeyAndFileSize(key_.size(), file_info.size);
+  }
+
+  return true;
+}
+
+bool SimpleSynchronousEntry::InitializeForOpen() {
+  DCHECK(!initialized_);
+  if (!OpenOrCreateFiles(false))
+    return false;
+
+  for (int i = 0; i < kIndexCount; ++i) {
+    SimpleFileHeader header;
+    if (ReadPlatformFile(files_[i], 0, reinterpret_cast<char*>(&header),
+                         sizeof(header)) != sizeof(header)) {
+      return false;
+    }
+    if (header.initial_magic_number != kSimpleInitialMagicNumber ||
+        header.version != kSimpleVersion) {
+      DVLOG(6) << "Error: No magic number.";

[pasko-google - do not use, 2013/02/11 13:59:25]

This is a pretty serious error, so sounds rather LOG(WARNING). Although probably
needs to be put once in the log to avoid severe pollution.

[gavinp, 2013/02/11 17:55:50]

I'll leave it LOG(WARNING) for now with a TODO. We're going to hit this a lot
during development as we change the format.

+      return false;
+    }
+
+    char key[1024];
+    DCHECK_LE(header.key_length, sizeof(key));
+    if (ReadPlatformFile(files_[i], sizeof(header), key, header.key_length) !=
+        implicit_cast<int>(header.key_length)) {
+      DVLOG(6) << "Error: No key.";
+      return false;
+    }
+    if (std::memcmp(static_cast<const void*>(key_.data()),
+                    static_cast<const void*>(key),
+                    key_.size()) != 0) {
+      DVLOG(6) << "Error: Bad key.";
+      return false;
+    }
+
+    if (base::Hash(key, header.key_length) == header.key_hash) {
+      DVLOG(6) << "Error: Bad key hash.";
+      return false;
+    }
+  }
+
+  initialized_ = true;
+  return true;
+}
+
+bool SimpleSynchronousEntry::InitializeForCreate() {
+  DCHECK(!initialized_);
+  if (!OpenOrCreateFiles(true))
+    return false;
+
+  for (int i = 0; i < kIndexCount; ++i) {
+    SimpleFileHeader header;
+    header.initial_magic_number = kSimpleInitialMagicNumber;
+    header.version = kSimpleVersion;
+
+    header.key_length = key_.size();
+    header.key_hash = base::Hash(key_);
+
+    if (WritePlatformFile(files_[i], 0, reinterpret_cast<char*>(&header),
+                          sizeof(header)) != sizeof(header)) {

[pasko-google - do not use, 2013/02/11 13:59:25]

would be helpful: LOG(WARNING) or explanation where we log about this

[gavinp, 2013/02/11 17:55:50]

Done.

+      return false;
+    }
+
+    if (WritePlatformFile(files_[i], sizeof(header), key_.data(),
+                          key_.size()) != implicit_cast<int>(key_.size())) {
+      return false;
+    }
+  }
+
+  initialized_ = true;
+  return true;
+}
+
+}  // namespace disk_cache