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Unified Diff: net/disk_cache/blockfile/disk_format_v3.h

Issue 992733002: Remove //net (except for Android test stuff) and sdch (Closed) Base URL: git@github.com:domokit/mojo.git@master
Patch Set: Created 5 years, 9 months ago
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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
deleted file mode 100644
index f16648b5bf1a456d86a6cc2c66acc75d0e98bd30..0000000000000000000000000000000000000000
--- a/net/disk_cache/blockfile/disk_format_v3.h
+++ /dev/null
@@ -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;
- int32 num_no_use_entries;
- 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.
- ENTRY_OPEN, // The entry is being accessed.
- ENTRY_MODIFIED, // The entry is being modified.
- ENTRY_DELETED, // The entry is being deleted.
- 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.
- ENTRY_LOW_USE, // The entry has low reuse.
- 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
- // timestamp : 20 bits
- // reuse : 4 bits
- // state : 3 bits
- // group : 3 bits
- // 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_
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