<?xml version="1.0" encoding="utf-8"?>

 <!DOCTYPE book PUBLIC "-//OASIS//DTD DocBook XML V4.1.2//EN" "http://www.oasis-open.org/docbook/xml/4.1.2/docbookx.dtd">

 <chapter id="file-format">

   <title>Package Set File Format</title>

   <sect2 id="file-header">

     <title>File header</title>

     <para>

       The rzdb file starts with a header, containing some number of

       sections, terminated by a section with type 0:

     </para>

     <programlisting><![CDATA[

 struct razor_set_header {

 	uint32_t magic;

 	uint32_t version;

 	struct razor_set_section sections[0];

 };

 struct razor_set_section {

 	uint32_t type;

 	uint32_t offset;

 	uint32_t size;

 };

 ]]></programlisting>

     <para>

       razor_set_open() mmaps the rzdb file, and creates a struct razor_set:

     </para>

     <programlisting><![CDATA[

 struct razor_set {

 	struct array string_pool;

  	struct array packages;

  	struct array properties;

  	struct array files;

 	struct array package_pool;

  	struct array property_pool;

  	struct array file_pool;

 	struct razor_set_header *header;

 };

 ]]></programlisting>

     <para>

       by finding the sections with those IDs and creating struct

       array's pointing to the right places in the mmapped data. (This

       is the only processing needed when reading in the file;

       everything else is used exactly as-is.)

     </para>

   </sect2>

   <sect2 id="sections">

     <title>The sections</title>

     <itemizedlist>

       <listitem>

         <para>

           <emphasis>RAZOR_STRING_POOL</emphasis> Stores one copy of

 	  each string that appears in the rzdb file. (At the moment,

 	  this is: package names, package versions, property names,

 	  property versions, and (basenames of) filenames.) The

 	  strings are arbitrarily-sized, 0-terminated, and not in any

 	  particular order (although the empty string always ends up

 	  being at offset 0).

 	</para>

       </listitem>

       <listitem>

         <para>

           <emphasis>RAZOR_PACKAGES</emphasis> Array of struct

 	  razor_package; one for each package in the set, sorted by

 	  name.

 	</para>

       </listitem>

       <listitem>

         <para>

           <emphasis>RAZOR_PROPERTIES</emphasis> Array of struct

 	  razor_property; one for each unique property in the set,

 	  sorted by type, then name, then relation type (eg, "<" or

 	  ">="), then version. (Properties with no version have

 	  relation type RAZOR_VERSION_EQUAL, and version "".)

 	</para>

       </listitem>

       <listitem>

         <para>

           <emphasis>RAZOR_FILES</emphasis> Array of struct

 	  razor_entry; one for each file owned by any package in the

 	  set. The current sort order (which is subject to change)

 	  is breadth-first, sorted by basename. So eg: /, /bin,

 	  /dev, /etc, /bin/false, /bin/true, /dev/null, /etc/passwd.

 	</para>

       </listitem>

       <listitem>

         <para>

           <emphasis>RAZOR_PACKAGE_POOL</emphasis> Array of struct

 	  list, with each list item containing the index of a struct

 	  razor_package in the packages section. See the discussion

 	  of lists below.

 	</para>

       </listitem>

       <listitem>

         <para>

           <emphasis>RAZOR_PROPERTY_POOL</emphasis> Array of struct

 	  list, with each list item containing the index of a struct

 	  razor_property in the properties section. See the

 	  discussion of lists below.

 	</para>

       </listitem>

       <listitem>

         <para>

           <emphasis>RAZOR_FILE_POOL</emphasis> Array of struct list,

 	  with each list item containing the index of a struct

 	  razor_entry in the files section. See the discussion of

 	  lists below.

 	</para>

       </listitem>

     </itemizedlist>

   </sect2>

   <sect2 id="data-types">

     <title>Data types</title>

     <para>

       Note that the exact layout of bits involves some historical

       accidents.  (Particularly the fact that the "name" field in most

       structs loses its high bits to a flags field.)

     </para>

     <programlisting><![CDATA[

 struct list_head

 	uint list_ptr : 24;

 	uint flags    : 8;

 struct list

 	uint data  : 24;

 	uint flags : 8;

 ]]></programlisting>

     <para>

       Used to store lists of package, property, or file IDs. "struct

       list_head" stores the head of the list, which points to one or

       more "struct list"s in the appropriate "pool" section.  ("struct

       list" should probably be called "struct list_item".)

     </para>

     <para>

       "list_first(&head, &pool)" returns a "struct list *"

       pointing to the first element of the list (or NULL for an empty

       list), and "list_next(list)" will return successive elements,

       until NULL is returned. Each "list->data" contains the index of

       a package, property, or file in the corresponding section of the

       set.

     </para>

     <para>

       Peeking underneath the abstraction, a list_head's "flags" is

       0xff if the list is empty, 0x80 if it contains a single element,

       or 0x00 if it contains more than one element. In the

       single-element case, that element is actually stored in the

       list_head directly rather than being stored in a pool (and so

       list_first() just casts the list_head* to a list* and returns

       it). For multi-element lists, list_ptr is the index in the pool

       of the first element of this list; the list continues through

       successive elements of the pool until one with non-zero flags is

       reached, indicating the end of the list.

     </para>

     <programlisting><![CDATA[

 struct razor_package

 	uint name    : 24;

 	uint flags   : 8;

 	uint version : 32;

 	struct list_head properties;

 	struct list_head files;

 ]]></programlisting>

     <para>

       name and version are indexes into string_pool. properties is a

       list of all of the package's properties, and files is a list of

       its files. flags is currently only used during razor_set

       merging, to keep track of which set a package came from.

     </para>

     <programlisting><![CDATA[

 struct razor_property

 	uint name     : 24;

 	uint flags    : 6;

 	uint type     : 2;

 	uint relation : 32;

 	uint version  : 32;

 	struct list_head packages;

 ]]></programlisting>

     <para>

       name and version are indexes into string_pool. type is an enum

       razor_property_type (eg, RAZOR_PROPERTY_REQUIRES), and relation

       is an enum razor_version_relation (eg,

       RAZOR_VERSION_GREATER_OR_EQUAL). packages is a list of the

       packages that have this property. flags is currently unused.

     </para>

     <programlisting><![CDATA[

 struct razor_entry

 	uint name  : 24;

 	uint flags : 8;

 	uint start : 32;

 	struct list_head packages;

 ]]></programlisting>

     <para>

       name is an index into string_pool, giving the basename of the

       file. start is either 0, or an index pointing to another

       razor_entry that is the first child of this entry (for a

       non-empty directory). (Entry 0 is always the root of the tree,

       so no entry could have entry 0 as a child.) flags is 0x80

       (RAZOR_ENTRY_LAST) if an entry is the last entry in its

       directory. Otherwise it is 0.

     </para>

     <para>

       Note that given a pointer to a struct_razor_entry (eg, from a

       package's "files" list), there is no way to reconstruct its full

       name without walking the entire files array up to that

       point. Because of this and other problems (fix_file_map()), it

       seems like razor_entry should be modified to include a pointer

       to its parent. (Storing full paths instead of just basenames

       would also fix this problem, but that would use much more

       memory.)

     </para>

   </sect2>

 </chapter>