| Index: net/disk_cache/blockfile/disk_format_v3.h
|
| diff --git a/net/disk_cache/blockfile/disk_format_v3.h b/net/disk_cache/blockfile/disk_format_v3.h
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| deleted file mode 100644
|
| index f16648b5bf1a456d86a6cc2c66acc75d0e98bd30..0000000000000000000000000000000000000000
|
| --- a/net/disk_cache/blockfile/disk_format_v3.h
|
| +++ /dev/null
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| @@ -1,246 +0,0 @@
|
| -// 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.
|
| -
|
| -// The cache is stored on disk as a collection of block-files, plus an index
|
| -// plus a collection of external files.
|
| -//
|
| -// Any data blob bigger than kMaxBlockSize (disk_cache/addr.h) will be stored in
|
| -// a separate file named f_xxx where x is a hexadecimal number. Shorter data
|
| -// will be stored as a series of blocks on a block-file. In any case, CacheAddr
|
| -// represents the address of the data inside the cache.
|
| -//
|
| -// The index is actually a collection of four files that store a hash table with
|
| -// allocation bitmaps and backup data. Hash collisions are handled directly by
|
| -// the table, which from some point of view behaves like a 4-way associative
|
| -// cache with overflow buckets (so not really open addressing).
|
| -//
|
| -// Basically the hash table is a collection of buckets. The first part of the
|
| -// table has a fixed number of buckets and it is directly addressed by the hash,
|
| -// while the second part of the table (stored on a second file) has a variable
|
| -// number of buckets. Each bucket stores up to four cells (each cell represents
|
| -// a possibl entry). The index bitmap tracks the state of individual cells.
|
| -//
|
| -// The last element of the cache is the block-file. A block file is a file
|
| -// designed to store blocks of data of a given size. For more details see
|
| -// disk_cache/disk_format_base.h
|
| -//
|
| -// A new cache is initialized with a set of block files (named data_0 through
|
| -// data_6), each one dedicated to store blocks of a given size or function. The
|
| -// number at the end of the file name is the block file number (in decimal).
|
| -//
|
| -// There are three "special" types of blocks: normal entries, evicted entries
|
| -// and control data for external files.
|
| -//
|
| -// The files that store internal information for the cache (blocks and index)
|
| -// are memory mapped. They have a location that is signaled every time the
|
| -// internal structures are modified, so it is possible to detect (most of the
|
| -// time) when the process dies in the middle of an update. There are dedicated
|
| -// backup files for cache bitmaps, used to detect entries out of date.
|
| -//
|
| -// Although cache files are to be consumed on the same machine that creates
|
| -// them, if files are to be moved accross machines, little endian storage is
|
| -// assumed.
|
| -
|
| -#ifndef NET_DISK_CACHE_BLOCKFILE_DISK_FORMAT_V3_H_
|
| -#define NET_DISK_CACHE_BLOCKFILE_DISK_FORMAT_V3_H_
|
| -
|
| -#include "base/basictypes.h"
|
| -#include "net/disk_cache/blockfile/disk_format_base.h"
|
| -
|
| -namespace disk_cache {
|
| -
|
| -const int kBaseTableLen = 0x400;
|
| -const uint32 kIndexMagicV3 = 0xC103CAC3;
|
| -const uint32 kVersion3 = 0x30000; // Version 3.0.
|
| -
|
| -// Flags for a given cache.
|
| -enum CacheFlags {
|
| - SMALL_CACHE = 1 << 0, // See IndexCell.
|
| - CACHE_EVICTION_2 = 1 << 1, // Keep multiple lists for eviction.
|
| - CACHE_EVICTED = 1 << 2 // Already evicted at least one entry.
|
| -};
|
| -
|
| -// Header for the master index file.
|
| -struct IndexHeaderV3 {
|
| - uint32 magic;
|
| - uint32 version;
|
| - int32 num_entries; // Number of entries currently stored.
|
| - int32 num_bytes; // Total size of the stored data.
|
| - int32 last_file; // Last external file created.
|
| - int32 reserved1;
|
| - CacheAddr stats; // Storage for usage data.
|
| - int32 table_len; // Actual size of the table.
|
| - int32 crash; // Signals a previous crash.
|
| - int32 experiment; // Id of an ongoing test.
|
| - int32 max_bytes; // Total maximum size of the stored data.
|
| - uint32 flags;
|
| - int32 used_cells;
|
| - int32 max_bucket;
|
| - uint64 create_time; // Creation time for this set of files.
|
| - uint64 base_time; // Current base for timestamps.
|
| - uint64 old_time; // Previous time used for timestamps.
|
| - int32 max_block_file;
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| - int32 num_no_use_entries;
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| - int32 num_low_use_entries;
|
| - int32 num_high_use_entries;
|
| - int32 reserved;
|
| - int32 num_evicted_entries;
|
| - int32 pad[6];
|
| -};
|
| -
|
| -const int kBaseBitmapBytes = 3968;
|
| -// The IndexBitmap is directly saved to a file named index. The file grows in
|
| -// page increments (4096 bytes), but all bits don't have to be in use at any
|
| -// given time. The required file size can be computed from header.table_len.
|
| -struct IndexBitmap {
|
| - IndexHeaderV3 header;
|
| - uint32 bitmap[kBaseBitmapBytes / 4]; // First page of the bitmap.
|
| -};
|
| -static_assert(sizeof(IndexBitmap) == 4096, "bad IndexHeader");
|
| -
|
| -// Possible states for a given entry.
|
| -enum EntryState {
|
| - ENTRY_FREE = 0, // Available slot.
|
| - ENTRY_NEW, // The entry is being created.
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| - ENTRY_OPEN, // The entry is being accessed.
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| - ENTRY_MODIFIED, // The entry is being modified.
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| - ENTRY_DELETED, // The entry is being deleted.
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| - ENTRY_FIXING, // Inconsistent state. The entry is being verified.
|
| - ENTRY_USED // The slot is in use (entry is present).
|
| -};
|
| -static_assert(ENTRY_USED <= 7, "state uses 3 bits");
|
| -
|
| -enum EntryGroup {
|
| - ENTRY_NO_USE = 0, // The entry has not been reused.
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| - ENTRY_LOW_USE, // The entry has low reuse.
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| - ENTRY_HIGH_USE, // The entry has high reuse.
|
| - ENTRY_RESERVED, // Reserved for future use.
|
| - ENTRY_EVICTED // The entry was deleted.
|
| -};
|
| -static_assert(ENTRY_USED <= 7, "group uses 3 bits");
|
| -
|
| -#pragma pack(push, 1)
|
| -struct IndexCell {
|
| - void Clear() { memset(this, 0, sizeof(*this)); }
|
| -
|
| - // A cell is a 9 byte bit-field that stores 7 values:
|
| - // location : 22 bits
|
| - // id : 18 bits
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| - // timestamp : 20 bits
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| - // reuse : 4 bits
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| - // state : 3 bits
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| - // group : 3 bits
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| - // sum : 2 bits
|
| - // The id is derived from the full hash of the entry.
|
| - //
|
| - // The actual layout is as follows:
|
| - //
|
| - // first_part (low order 32 bits):
|
| - // 0000 0000 0011 1111 1111 1111 1111 1111 : location
|
| - // 1111 1111 1100 0000 0000 0000 0000 0000 : id
|
| - //
|
| - // first_part (high order 32 bits):
|
| - // 0000 0000 0000 0000 0000 0000 1111 1111 : id
|
| - // 0000 1111 1111 1111 1111 1111 0000 0000 : timestamp
|
| - // 1111 0000 0000 0000 0000 0000 0000 0000 : reuse
|
| - //
|
| - // last_part:
|
| - // 0000 0111 : state
|
| - // 0011 1000 : group
|
| - // 1100 0000 : sum
|
| - //
|
| - // The small-cache version of the format moves some bits from the location to
|
| - // the id fileds, like so:
|
| - // location : 16 bits
|
| - // id : 24 bits
|
| - //
|
| - // first_part (low order 32 bits):
|
| - // 0000 0000 0000 0000 1111 1111 1111 1111 : location
|
| - // 1111 1111 1111 1111 0000 0000 0000 0000 : id
|
| - //
|
| - // The actual bit distribution between location and id is determined by the
|
| - // table size (IndexHeaderV3.table_len). Tables smaller than 65536 entries
|
| - // use the small-cache version; after that size, caches should have the
|
| - // SMALL_CACHE flag cleared.
|
| - //
|
| - // To locate a given entry after recovering the location from the cell, the
|
| - // file type and file number are appended (see disk_cache/addr.h). For a large
|
| - // table only the file type is implied; for a small table, the file number
|
| - // is also implied, and it should be the first file for that type of entry,
|
| - // as determined by the EntryGroup (two files in total, one for active entries
|
| - // and another one for evicted entries).
|
| - //
|
| - // For example, a small table may store something like 0x1234 as the location
|
| - // field. That means it stores the entry number 0x1234. If that record belongs
|
| - // to a deleted entry, the regular cache address may look something like
|
| - // BLOCK_EVICTED + 1 block + file number 6 + entry number 0x1234
|
| - // so Addr = 0xf0061234
|
| - //
|
| - // If that same Addr is stored on a large table, the location field would be
|
| - // 0x61234
|
| -
|
| - uint64 first_part;
|
| - uint8 last_part;
|
| -};
|
| -static_assert(sizeof(IndexCell) == 9, "bad IndexCell");
|
| -
|
| -const int kCellsPerBucket = 4;
|
| -struct IndexBucket {
|
| - IndexCell cells[kCellsPerBucket];
|
| - int32 next;
|
| - uint32 hash; // The high order byte is reserved (should be zero).
|
| -};
|
| -static_assert(sizeof(IndexBucket) == 44, "bad IndexBucket");
|
| -const int kBytesPerCell = 44 / kCellsPerBucket;
|
| -
|
| -// The main cache index. Backed by a file named index_tb1.
|
| -// The extra table (index_tb2) has a similar format, but different size.
|
| -struct Index {
|
| - // Default size. Actual size controlled by header.table_len.
|
| - IndexBucket table[kBaseTableLen / kCellsPerBucket];
|
| -};
|
| -#pragma pack(pop)
|
| -
|
| -// Flags that can be applied to an entry.
|
| -enum EntryFlags {
|
| - PARENT_ENTRY = 1, // This entry has children (sparse) entries.
|
| - CHILD_ENTRY = 1 << 1 // Child entry that stores sparse data.
|
| -};
|
| -
|
| -struct EntryRecord {
|
| - uint32 hash;
|
| - uint32 pad1;
|
| - uint8 reuse_count;
|
| - uint8 refetch_count;
|
| - int8 state; // Current EntryState.
|
| - uint8 flags; // Any combination of EntryFlags.
|
| - int32 key_len;
|
| - int32 data_size[4]; // We can store up to 4 data streams for each
|
| - CacheAddr data_addr[4]; // entry.
|
| - uint32 data_hash[4];
|
| - uint64 creation_time;
|
| - uint64 last_modified_time;
|
| - uint64 last_access_time;
|
| - int32 pad[3];
|
| - uint32 self_hash;
|
| -};
|
| -static_assert(sizeof(EntryRecord) == 104, "bad EntryRecord");
|
| -
|
| -struct ShortEntryRecord {
|
| - uint32 hash;
|
| - uint32 pad1;
|
| - uint8 reuse_count;
|
| - uint8 refetch_count;
|
| - int8 state; // Current EntryState.
|
| - uint8 flags;
|
| - int32 key_len;
|
| - uint64 last_access_time;
|
| - uint32 long_hash[5];
|
| - uint32 self_hash;
|
| -};
|
| -static_assert(sizeof(ShortEntryRecord) == 48, "bad ShortEntryRecord");
|
| -
|
| -} // namespace disk_cache
|
| -
|
| -#endif // NET_DISK_CACHE_BLOCKFILE_DISK_FORMAT_V3_H_
|
|
|