https://bugs.gentoo.org/269742

From bfae00d02b5fb3a2ce34c09d2dbf0ca2f96b154f Mon Sep 17 00:00:00 2001
From: Karl Berry <karl@gnu.org>
Date: Sat, 14 Mar 2009 17:57:41 +0000
Subject: [PATCH] support xz compression, http://tukaani.org/xz

---
 ChangeLog                   |    6 ++++++
 NEWS                        |    4 ++++
 doc/info-stnd.texi          |   34 +++++++++++++++++-----------------
 info/filesys.c              |    1 +
 install-info/install-info.c |   29 +++++++++++++++++++++++++----
 5 files changed, 53 insertions(+), 21 deletions(-)

2009-03-14  Karl Berry  <karl@gnu.org>

	* info/filesys.c (compress_suffixes): add .xz/unxz.

	* info/filesys.h (DEFAULT_INFOPATH): include PATH by default.

diff --git a/doc/info-stnd.texi b/doc/info-stnd.texi
index 2bd67f3..c730cff 100644
--- a/doc/info-stnd.texi
+++ b/doc/info-stnd.texi
@@ -202,21 +202,21 @@ directory.
 @cindex Info files, compressed
 In every directory Info tries, if @var{filename} is not found, Info
 looks for it with a number of known extensions of Info files@footnote{
-@file{.info}, @file{-info}, @file{/index}, and @file{.inf}.}.  For every
-known extension, Info looks for a compressed file, if a regular file
-isn't found.  Info supports files compressed with @code{gzip},
-@code{bzip2}, @code{compress} and @code{yabba} programs; it calls
-@code{gunzip}, @code{bunzip2}, @code{uncompress} and @code{unyabba},
-accordingly, to decompress such files.  Compressed Info files are
-assumed to have @file{.z}, @file{.gz}, @file{.bz2}, @file{.Z}, or
-@file{.Y} extensions, possibly in addition to one of the known Info
-files extensions@footnote{The MS-DOS version allows for the Info
-extension, such as @code{.inf}, and the short compressed file
-extensions, such as @file{.z} and @file{.gz}, to be merged into a single
-extension, since DOS doesn't allow more than a single dot in the
-basename of a file.  Thus, on MS-DOS, if Info looks for @file{bison},
-file names like @file{bison.igz} and @file{bison.inz} will be found and
-decompressed by @code{gunzip}.}.
+@file{.info}, @file{-info}, @file{/index}, and @file{.inf}.}.  For
+every known extension, Info looks for a compressed file, if a regular
+file isn't found.  Info supports files compressed with @code{gzip},
+@code{xz}, @code{bzip2}, @code{lzma}, @code{compress} and @code{yabba}
+programs, assumed to have @file{.z}, @file{.gz}, @file{.xz},
+@file{.bz2}, @file{.lzma}, @file{.Z}, or @file{.Y} extensions,
+possibly after one of the known Info files extensions.
+
+On MS-DOS, Info allows for the Info extension, such as @code{.inf},
+and the short compressed file extensions, such as @file{.z} and
+@file{.gz}, to be merged into a single extension, since DOS doesn't
+allow more than a single dot in the basename of a file.  Thus, on
+MS-DOS, if Info looks for @file{bison}, file names like
+@file{bison.igz} and @file{bison.inz} will be found and decompressed
+by @code{gunzip}.
 
 @item --help
 @itemx -h
diff --git a/info/filesys.c b/info/filesys.c
index fdd18a8..5e795bc 100644
--- a/info/filesys.c
+++ b/info/filesys.c
@@ -55,6 +55,7 @@ static char *info_suffixes[] = {
 
 static COMPRESSION_ALIST compress_suffixes[] = {
   { ".gz", "gunzip" },
+  { ".xz", "unxz" },
   { ".bz2", "bunzip2" },
   { ".z", "gunzip" },
   { ".lzma", "unlzma" },
diff --git a/install-info/install-info.c b/install-info/install-info.c
index 24669b3..0f18ca4 100644
--- a/install-info/install-info.c
+++ b/install-info/install-info.c
@@ -400,6 +400,11 @@ strip_info_suffix (char *fname)
       len -= 3;
       ret[len] = 0;
     }
+  else if (len > 3 && FILENAME_CMP (ret + len - 3, ".xz") == 0)
+    {
+      len -= 3;
+      ret[len] = 0;
+    }
   else if (len > 4 && FILENAME_CMP (ret + len - 4, ".bz2") == 0)
     {
       len -= 4;
@@ -659,6 +664,12 @@ open_possibly_compressed_file (char *filename,
     {
       *opened_filename = concat (filename, ".gz", "");
       f = fopen (*opened_filename, FOPEN_RBIN);
+    }
+  if (!f)
+    {
+      *opened_filename = concat (filename, ".xz", "");
+      f = fopen (*opened_filename, FOPEN_RBIN);
+    }
   if (!f)
     {
       free (*opened_filename);
@@ -702,7 +712,6 @@ open_possibly_compressed_file (char *filename,
           else
             pfatal_with_name (filename);
         }
-    }
 
   /* Read first few bytes of file rather than relying on the filename.
      If the file is shorter than this it can't be usable anyway.  */
@@ -727,6 +736,15 @@ open_possibly_compressed_file (char *filename,
 #else
     *compression_program = "gzip";
 #endif
+
+  else if (data[0] == '\xFD' && data[1] == '7' && data[2] == 'z'
+           && data[3] == 'X' && data[4] == 'Z' && data[5] == 0)
+#ifndef STRIP_DOT_EXE
+    *compression_program = "xz.exe";
+#else
+    *compression_program = "xz";
+#endif
+
   else if (data[0] == 'B' && data[1] == 'Z' && data[2] == 'h')
 #ifndef STRIP_DOT_EXE
     *compression_program = "bzip2.exe";
-- 
1.7.4.rc2