Fri Apr 1 14:33:54 2005 Jonathan Blandford <jrb@redhat.com>

        * shared-mime-info-spec.xml:
        * update-mime-database.c: Patch from Matthias Clasen
        <mclasen@redhat.com> to make the MIME Cache contain an mmappable
        binary format.

1 files changed, 127 insertions, 3 deletions

diff --git a/shared-mime-info-spec.xml b/shared-mime-info-spec.xml
index 537417fa..274c3c64 100644
--- a/shared-mime-info-spec.xml
+++ b/shared-mime-info-spec.xml
@@ -1,8 +1,8 @@
 <?xml version="1.0" standalone="no"?>
 <!DOCTYPE article PUBLIC "-//OASIS//DTD DocBook XML V4.1.2//EN"
 "/usr/share/sgml/docbook/dtd/xml/4.1.2/docbookx.dtd" [
-  <!ENTITY updated "15 Oct 2003">
-  <!ENTITY version "0.13">
+  <!ENTITY updated "1 April 2005">
+  <!ENTITY version "0.14">
 ]>
 <article id="index">
 
@@ -174,10 +174,15 @@ The files created by <command>update-mime-database</command> are:
 <filename>&lt;MIME&gt;/XMLnamespaces</filename> (contains a mapping from XML
 (namespaceURI, localName) pairs to MIME types)
 				</para></listitem>
-				<listitem><para>
+ 				<listitem><para>
 <filename>&lt;MIME&gt;/MEDIA/SUBTYPE.xml</filename> (one file for each MIME
 type, giving details about the type)
 				</para></listitem>
+				<listitem><para>
+<filename>&lt;MIME&gt;/mime.cache</filename> (contains the same information as the <filename>globs</filename>,
+<filename>magic</filename>, <filename>subclasses</filename>, <filename>aliases</filename> and 
+<filename>XMLnamespaces</filename> files, in a binary, mmappable format)
+				</para></listitem>
 			</itemizedlist>
 The format of these generated files and the source files in <filename>packages</filename>
 are explained in the following sections. This step serves several purposes. First, it allows
@@ -490,6 +495,122 @@ the namespaceURI.
 		</para>
 	</sect2>
 	<sect2>
+		<title>The mime.cache files</title>
+		<para>
+The <filename>mime.cache</filename> files contain the same information as the 
+<filename>globs</filename>, <filename>magic</filename>, <filename>subclasses</filename>, 
+<filename>aliases</filename> and <filename>XMLnamespaces</filename> files, in a binary, 
+mmappable format:
+</para>
+<programlisting>
+Header:
+2			CARD16		MAJOR_VERSION	1	
+2			CARD16		MINOR_VERSION	0	
+4			CARD32		ALIAS_LIST_OFFSET
+4			CARD32		PARENT_LIST_OFFSET
+4			CARD32		LITERAL_LIST_OFFSET
+4			CARD32		SUFFIX_LIST_OFFSET
+4			CARD32		GLOB_LIST_OFFSET
+4			CARD32		MAGIC_LIST_OFFSET
+4			CARD32		NAMESPACE_LIST_OFFSET
+
+AliasList:
+4			CARD32		N_ALIASES
+8*N_ALIASES		AliasListEntry
+
+AliasListEntry:
+4			CARD32		ALIAS_OFFSET
+4			CARD32		MIME_TYPE_OFFSET
+
+ParentList:
+4			CARD32		N_ENTRIES 
+8*N_ENTRIES		ParentListEntry
+
+ParentListEntry:
+4			CARD32		MIME_TYPE_OFFSET
+4			CARD32		PARENTS_OFFSET
+
+Parents:
+4			CARD32		N_PARENTS
+4*N_PARENTS		CARD32		MIME_TYPE_OFFSET
+
+LiteralList:
+4			CARD32		N_LITERALS
+8*N_LITERALS		LiteralEntry	
+
+LiteralEntry:
+4			CARD32		LITERAL_OFFSET
+4			CARD32		MIME_TYPE_OFFSET
+
+GlobList:
+4			CARD32		N_GLOBS
+8*N_GLOBS		GlobEntry	
+
+GlobEntry:
+4			CARD32		GLOB_OFFSET
+4			CARD32		MIME_TYPE_OFFSET
+
+SuffixTree:
+4			CARD32		N_ROOTS
+4	 		CARD32		FIRST_ROOT_OFFSET
+
+SuffixTreeNode:
+4			CARD32		CHARACTER
+4			CARD32		MIME_TYPE_OFFSET
+4			CARD32		N_CHILDREN			
+4			CARD32		FIRST_CHILD_OFFSET
+
+MagicList:
+4			CARD32		N_MATCHES
+4			CARD32		MAX_EXTENT
+4			CARD32		FIRST_MATCH_OFFSET
+
+Match:
+4			CARD32		PRIORITY
+4			CARD32		MIME_TYPE_OFFSET
+4			CARD32		N_MATCHLETS
+4			CARD32		FIRST_MATCHLET_OFFSET
+
+Matchlet:
+4			CARD32		RANGE_START
+4			CARD32		RANGE_LENGTH
+4			CARD32		WORD_SIZE
+4			CARD32		VALUE_LENGTH
+4			CARD32		VALUE
+4			CARD32		MASK
+4			CARD32		N_CHILDREN
+4			CARD32		FIRST_CHILD_OFFSET
+
+NamespaceList:
+4			CARD32		N_NAMESPACES
+12*N_NAMESPACES		NamespaceEntry	
+
+NamespaceEntry:
+4			CARD32		NAMESPACE_URI_OFFSET
+4			CARD32		LOCAL_NAME_OFFSET
+4			CARD32		MIME_TYPE_OFFSET
+</programlisting>
+<para>
+Lists in the file are sorted, to enable binary searching. The list of aliases is sorted by alias, 
+the list of literal globs is sorted by the literal. The SuffixTreeNode siblings are sorted by character. 
+The list of namespaces is sorted by namespace uri.
+</para>
+<para>
+All offsets are in bytes from the beginning of the file.
+</para>
+<para>
+Strings are zero-terminated.
+</para>
+<para>
+All numbers are in network (big-endian) order. This is necessary because the data will be stored in 
+arch-independent directories like <filename>/usr/share/mime</filename> or even in user's home directories.
+</para>
+<para>
+Cache files have to be written atomically - write to a temporary name, then move over the old file - so 
+that clients that have the old cache file open and mmap'ed won't get corrupt data.
+</para>
+	</sect2>
+	<sect2>
 		<title>Storing the MIME type using Extended Attributes</title>
 		<para>
 An implementation MAY also get a file's MIME type from the
@@ -658,6 +779,9 @@ Override.xml mentioned in <xref linkend="s2_layout"/>. Information such as
 		<member>
 			Christos Zoulas <email>christos at zoulas.com</email>
 		</member>
+		<member>
+			Matthias Clasen <email>mclasen at redhat.com</email>
+		</member>
 	</simplelist>
 </sect1>