<title>APT Cache File Format</title>
<author>Jason Gunthorpe <email>jgg@debian.org</email></author>
-<version>$Id: cache.sgml,v 1.1 1998/07/02 02:58:12 jgg Exp $</version>
+<version>$Id: cache.sgml,v 1.2 1998/07/05 05:43:09 jgg Exp $</version>
<abstract>
This document describes the complete implementation and format of the APT
</abstract>
<copyright>
-Copyright © Jason Gunthorpe, 1997.
+Copyright © Jason Gunthorpe, 1997-1998.
<p>
APT and this document are free software; you can redistribute them and/or
modify them under the terms of the GNU General Public License as published
Every item in every structure is stored as the index to that structure.
What this means is that once the files is mmaped every data access has to
go through a fixup stage to get a real memory pointer. This is done
-by taking the tndex, multiplying it by the type size and then adding
+by taking the index, multiplying it by the type size and then adding
it to the start address of the memory block. This sounds complex, but
in C it is a single array dereference. Because all items are aligned to
their size and indexs are stored as multiples of the size of the structure
unsigned short VersionSz;
unsigned short DependencySz;
unsigned short ProvidesSz;
-
+ unsigned short VerFileSz;
+
// Structure counts
unsigned long PackageCount;
unsigned long VersionCount;
unsigned long FileList; // PackageFile
unsigned long StringList; // StringItem
- // Pool structures
- unsigned long PoolStart[6];
- unsigned long PoolSize[6];
- unsigned long PoolAln[6];
-
+ // Allocation pools
+ struct
+ {
+ unsigned long ItemSize;
+ unsigned long Start;
+ unsigned long Count;
+ } Pools[7];
+
// Package name lookup
unsigned long HashTable[512]; // Package
};
<tag>PackageFileSz
<tag>VersionSz
<tag>DependencySz
+<tag>VerFileSz
<tag>ProvidesSz<item>
*Sz contains the sizeof() that particular structure. It is used as an
extra consistancy check on the structure of the file.
the cache. The parser reads this list into memory so it can match strings
against it.
-<tag>PoolStart
-<tag>PoolSize
-<tag>PoolAln<item>
+<tag>Pools<item>
The Pool structures manage the allocation pools that the generator uses.
-Start indicates the first byte of the pool, Size is the number of bytes
-remaining in the pool and Aln (alignment) is the structure size of the pool.
-An Aln of 0 indicates the slot is empty. There should be the same number of
-slots as there are structure types. The generator stores this information
-so future additions can make use of any unused pool blocks.
+Start indicates the first byte of the pool, Count is the number of objects
+remaining in the pool and ItemSize is the structure size (alignment factor)
+of the pool. An ItemSize of 0 indicates the pool is empty. There should be
+the same number of pools as there are structure types. The generator
+stores this information so future additions can make use of any unused pool
+blocks.
<tag>HashTable<item>
HashTable is a hash table that provides indexing for all of the packages.
// Unique ID for this pkg
unsigned short ID;
- unsigned short Flags;
+ unsigned long Flags;
};
</example>
// Linked list
unsigned long NextFile; // PackageFile
unsigned short ID;
- unsigned short Flags;
+ unsigned long Flags;
time_t mtime; // Modification time
};
</example>
struct Version
{
unsigned long VerStr; // Stringtable
- unsigned long File; // PackageFile
unsigned long Section; // StringTable (StringItem)
// Lists
+ unsigned long FileList; // VerFile
unsigned long NextVer; // Version
unsigned long DependsList; // Dependency
unsigned long ParentPkg; // Package
unsigned long ProvidesList; // Provides
-
- unsigned long Offset;
+
unsigned long Size;
unsigned long InstalledSize;
unsigned short ID;
<tag>VerStr<item>
This is the complete version string.
-<tag>File<item>
-References the PackageFile that this version came out of. File can be used
-to determine what distribution the Version applies to. If File is 0 then
-this is a blank version. The structure should also have a 0 in all other
-fields excluding VerStr and Possibly NextVer.
+<tag>FileList<item>
+References the all the PackageFile's that this version came out of. FileList
+can be used to determine what distribution(s) the Version applies to. If
+FileList is 0 then this is a blank version. The structure should also have
+a 0 in all other fields excluding VerStr and Possibly NextVer.
<tag>Section<item>
This string indicates which section it is part of. The string should be
<tag>ProvidesList<item>
Head of the linked list of Provides::NextPkgProv, forward provides.
-<tag>Offset<item>
-The byte offset of the first line of this item in the specified
-PackageFile
-
<tag>Size
<tag>InstalledSize<item>
The archive size for this version. For debian this is the size of the .deb
<tag>NextPkgProv<item>
Next link in the singly linked list of provides for 'Version'.
+</taglist>
+
+ <!-- }}} -->
+<!-- VerFile {{{ -->
+<!-- ===================================================================== -->
+<sect>VerFile
+<p>
+VerFile associates a version with a PackageFile, this allows a full
+description of all Versions in all files (and hence all sources) under
+consideration.
+
+<example>
+ struct pkgCache::VerFile
+ {
+ unsigned long File; // PackageFile
+ unsigned long NextFile; // PkgVerFile
+ unsigned long Offset;
+ unsigned short Size;
+ }
+</example>
+<taglist>
+<tag>File<item>
+The index of the package file that this version was found in.
+
+<tag>NextFile<item>
+The next step in the linked list.
+
+<tag>Offset
+<tag>Size<item>
+These describe the exact position in the package file for the section from
+this version.
</taglist>
<!-- }}} -->
projects / apt.git / commitdiff
