SimpleCache: open with fewer seeks.

net/disk_cache/simple/simple_synchronous_entry.h

 // 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.
 
 #ifndef NET_DISK_CACHE_SIMPLE_SIMPLE_SYNCHRONOUS_ENTRY_H_
 #define NET_DISK_CACHE_SIMPLE_SIMPLE_SYNCHRONOUS_ENTRY_H_
 
 #include <stdint.h>
 
 #include <algorithm>
 #include <map>
 #include <memory>
 #include <string>
 #include <utility>
 #include <vector>
 
 #include "base/files/file.h"
 #include "base/files/file_path.h"
+#include "base/gtest_prod_util.h"
 #include "base/memory/ref_counted.h"
 #include "base/time/time.h"
 #include "net/base/cache_type.h"
 #include "net/base/net_export.h"
 #include "net/disk_cache/simple/simple_entry_format.h"
 
 namespace net {
 class GrowableIOBuffer;
 class IOBuffer;
 }
 
+FORWARD_DECLARE_TEST(DiskCacheBackendTest, SimpleCacheEnumerationLongKeys);
+
 namespace disk_cache {
 
 class SimpleSynchronousEntry;
 
 // This class handles the passing of data about the entry between
 // SimpleEntryImplementation and SimpleSynchronousEntry and the computation of
 // file offsets based on the data size for all streams.
 class NET_EXPORT_PRIVATE SimpleEntryStat {
  public:
   SimpleEntryStat(base::Time last_used,
                   base::Time last_modified,
                   const int32_t data_size[],
                   const int32_t sparse_data_size);
 
-  int GetOffsetInFile(const std::string& key,
-                      int offset,
-                      int stream_index) const;
-  int GetEOFOffsetInFile(const std::string& key, int stream_index) const;
-  int GetLastEOFOffsetInFile(const std::string& key, int file_index) const;
-  int64_t GetFileSize(const std::string& key, int file_index) const;
+  int GetOffsetInFile(size_t key_length, int offset, int stream_index) const;
+  int GetEOFOffsetInFile(size_t key_length, int stream_index) const;
+  int GetLastEOFOffsetInFile(size_t key_length, int file_index) const;
+  int64_t GetFileSize(size_t key_length, int file_index) const;
 
   base::Time last_used() const { return last_used_; }
   base::Time last_modified() const { return last_modified_; }
   void set_last_used(base::Time last_used) { last_used_ = last_used; }
   void set_last_modified(base::Time last_modified) {
     last_modified_ = last_modified;
   }
 
   int32_t data_size(int stream_index) const { return data_size_[stream_index]; }
   void set_data_size(int stream_index, int data_size) {
@@ skipping 47 matching lines @@
     EntryOperationData(int64_t sparse_offset_p, int buf_len_p);
 
     int index;
     int offset;
     int64_t sparse_offset;
     int buf_len;
     bool truncate;
     bool doomed;
   };
 
+  // Opens a disk cache entry on disk. The |key| parameter is optional, if empty
+  // the operation may be slower. The |entry_hash| parameter is required.
+  // |had_index| is provided only for histograms.
   static void OpenEntry(net::CacheType cache_type,
                         const base::FilePath& path,
+                        const std::string& key,
                         uint64_t entry_hash,
                         bool had_index,
                         SimpleEntryCreationResults* out_results);
 
   static void CreateEntry(net::CacheType cache_type,
                           const base::FilePath& path,
                           const std::string& key,
                           uint64_t entry_hash,
                           bool had_index,
                           SimpleEntryCreationResults* out_results);
@@ skipping 14 matching lines @@
   // |key_hashes|. Succeeds only when all entries are deleted. Returns a net
   // error code.
   static int DoomEntrySet(const std::vector<uint64_t>* key_hashes,
                           const base::FilePath& path);
 
   // N.B. ReadData(), WriteData(), CheckEOFRecord() and Close() may block on IO.
   void ReadData(const EntryOperationData& in_entry_op,
                 net::IOBuffer* out_buf,
                 uint32_t* out_crc32,
                 SimpleEntryStat* entry_stat,
-                int* out_result) const;
+                int* out_result);
   void WriteData(const EntryOperationData& in_entry_op,
                  net::IOBuffer* in_buf,
                  SimpleEntryStat* out_entry_stat,
                  int* out_result);
   void CheckEOFRecord(int index,
                       const SimpleEntryStat& entry_stat,
                       uint32_t expected_crc32,
                       int* out_result) const;
 
   void ReadSparseData(const EntryOperationData& in_entry_op,
@@ skipping 12 matching lines @@
   // Close all streams, and add write EOF records to streams indicated by the
   // CRCRecord entries in |crc32s_to_write|.
   void Close(const SimpleEntryStat& entry_stat,
              std::unique_ptr<std::vector<CRCRecord>> crc32s_to_write,
              net::GrowableIOBuffer* stream_0_data);
 
   const base::FilePath& path() const { return path_; }
   std::string key() const { return key_; }
 
  private:
+  FRIEND_TEST_ALL_PREFIXES(::DiskCacheBackendTest,
+                           SimpleCacheEnumerationLongKeys);
+
   enum CreateEntryResult {
     CREATE_ENTRY_SUCCESS = 0,
     CREATE_ENTRY_PLATFORM_FILE_ERROR = 1,
     CREATE_ENTRY_CANT_WRITE_HEADER = 2,
     CREATE_ENTRY_CANT_WRITE_KEY = 3,
     CREATE_ENTRY_MAX = 4,
   };
 
   enum FileRequired {
     FILE_NOT_REQUIRED,
     FILE_REQUIRED
   };
 
   struct SparseRange {
     int64_t offset;
     int64_t length;
     uint32_t data_crc32;
     int64_t file_offset;
 
     bool operator<(const SparseRange& other) const {
       return offset < other.offset;
     }
   };
 
+  // When opening an entry without knowing the key, the header must be read
+  // without knowing the size of the key. This is how much to read initially, to
+  // make it likely the entire key is read.
+  static const size_t kInitialHeaderRead = 64 * 1024;
+
   SimpleSynchronousEntry(net::CacheType cache_type,
                          const base::FilePath& path,
                          const std::string& key,
-                         uint64_t entry_hash);
+                         uint64_t entry_hash,
+                         bool had_index);
 
   // Like Entry, the SimpleSynchronousEntry self releases when Close() is
   // called.
   ~SimpleSynchronousEntry();
 
   // Tries to open one of the cache entry files. Succeeds if the open succeeds
   // or if the file was not found and is allowed to be omitted if the
   // corresponding stream is empty.
   bool MaybeOpenFile(int file_index,
                      base::File::Error* out_error);
   // Creates one of the cache entry files if necessary. If the file is allowed
   // to be omitted if the corresponding stream is empty, and if |file_required|
   // is FILE_NOT_REQUIRED, then the file is not created; otherwise, it is.
   bool MaybeCreateFile(int file_index,
                        FileRequired file_required,
                        base::File::Error* out_error);
-  bool OpenFiles(bool had_index,
-                 SimpleEntryStat* out_entry_stat);
-  bool CreateFiles(bool had_index,
-                   SimpleEntryStat* out_entry_stat);
+  bool OpenFiles(SimpleEntryStat* out_entry_stat);
+  bool CreateFiles(SimpleEntryStat* out_entry_stat);
   void CloseFile(int index);
   void CloseFiles();
 
-  // Returns a net error, i.e. net::OK on success. |had_index| is passed
-  // from the main entry for metrics purposes, and is true if the index was
-  // initialized when the open operation began.
-  int InitializeForOpen(bool had_index,
-                        SimpleEntryStat* out_entry_stat,
+  // Read the header and key at the beginning of the file, and validate that
+  // they are correct. If this entry was opened with a key, the key is checked
+  // for a match. If not, then the |key_| member is set based on the value in
+  // this header. Records histograms if any check is failed.
+  bool CheckHeaderAndKeyForOpen(int file_index);
+
+  // Returns a net error, i.e. net::OK on success.
+  int InitializeForOpen(SimpleEntryStat* out_entry_stat,
                         scoped_refptr<net::GrowableIOBuffer>* stream_0_data,
                         uint32_t* out_stream_0_crc32);
 
   // Writes the header and key to a newly-created stream file. |index| is the
   // index of the stream. Returns true on success; returns false and sets
   // |*out_result| on failure.
   bool InitializeCreatedFile(int index, CreateEntryResult* out_result);
 
   // Returns a net error, including net::OK on success and net::FILE_EXISTS
-  // when the entry already exists. |had_index| is passed from the main entry
-  // for metrics purposes, and is true if the index was initialized when the
-  // create operation began.
-  int InitializeForCreate(bool had_index, SimpleEntryStat* out_entry_stat);
+  // when the entry already exists.
+  int InitializeForCreate(SimpleEntryStat* out_entry_stat);
 
   // Allocates and fills a buffer with stream 0 data in |stream_0_data|, then
   // checks its crc32.
   int ReadAndValidateStream0(
       int total_data_size,
       SimpleEntryStat* out_entry_stat,
       scoped_refptr<net::GrowableIOBuffer>* stream_0_data,
       uint32_t* out_stream_0_crc32) const;
 
   int GetEOFRecordData(int index,
@@ skipping 48 matching lines @@
 
   base::FilePath GetFilenameFromFileIndex(int file_index);
 
   bool sparse_file_open() const {
     return sparse_file_.IsValid();
   }
 
   const net::CacheType cache_type_;
   const base::FilePath path_;
   const uint64_t entry_hash_;
+  const bool had_index_;
   std::string key_;
 
   bool have_open_files_;
   bool initialized_;
 
+  // Normally false. This is set to true when an entry is opened without
+  // checking the file headers. Any subsequent read will perform the check
+  // before completing.
+  bool header_and_key_check_needed_;
+
   base::File files_[kSimpleEntryFileCount];
 
   // True if the corresponding stream is empty and therefore no on-disk file
   // was created to store it.
   bool empty_file_omitted_[kSimpleEntryFileCount];
 
   typedef std::map<int64_t, SparseRange> SparseRangeOffsetMap;
   typedef SparseRangeOffsetMap::iterator SparseRangeIterator;
   SparseRangeOffsetMap sparse_ranges_;
   base::File sparse_file_;
   // Offset of the end of the sparse file (where the next sparse range will be
   // written).
   int64_t sparse_tail_offset_;
 
   // True if the entry was created, or false if it was opened. Used to log
   // SimpleCache.*.EntryCreatedWithStream2Omitted only for created entries.
   bool files_created_;
 };
 
 }  // namespace disk_cache
 
 #endif  // NET_DISK_CACHE_SIMPLE_SIMPLE_SYNCHRONOUS_ENTRY_H_