[PATCH] Add support for brotli compression

[Jamie Magee]

* configure.ac (brotli): Register compression program.
* THANKS: Add Jamie Magee.
* doc/tar.1: Mention --brotli.
* doc/tar.texi: Document brotli support.
* src/buffer.c: Register brotli compression.
* src/suffix.c: Add suffixes br and tbr.
* src/tar.c: New compression option --brotli.
* tests/testsuite.at (Compression): Add brotli test.

Signed-off-by: Jamie Magee <jamie.magee@gmail.com>
---
 THANKS             |  1 +
 configure.ac       |  1 +
 doc/tar.1          |  5 +++++
 doc/tar.texi       | 13 ++++++++++++-
 src/buffer.c       |  4 ++++
 src/suffix.c       |  2 ++
 src/tar.c          | 10 ++++++++++
 tests/testsuite.at |  1 +
 8 files changed, 36 insertions(+), 1 deletion(-)

diff --git a/THANKS b/THANKS
index aee0a924..abde2dd0 100644
--- a/THANKS
+++ b/THANKS
@@ -228,6 +228,7 @@ James H Caldwell Jr caldwell@cs.fsu.edu
 James Stevens          James.Stevens@jrcs.co.uk
 James V. DI Toro III   karrde@gats.hampton.va.us
 James W. McKelvey      mckelvey@fafnir.com
+Jamie Magee            jamie.magee@gmail.com
 Jamie Zawinski         jwz@lucid.com
 Jan Carlson            janc@sni.ca
 Jan Djarv              jan.djarv@mbox200.swipnet.se
diff --git a/configure.ac b/configure.ac
index a376709a..fb0d8c64 100644
--- a/configure.ac
+++ b/configure.ac
@@ -275,6 +275,7 @@ fi
 
 TAR_COMPR_PROGRAM(compress)
 TAR_COMPR_PROGRAM(gzip)
+TAR_COMPR_PROGRAM(brotli)
 TAR_COMPR_PROGRAM(bzip2)
 TAR_COMPR_PROGRAM(lzip)
 TAR_COMPR_PROGRAM(lzma)
diff --git a/doc/tar.1 b/doc/tar.1
index 23ae7ac2..be6a362d 100644
--- a/doc/tar.1
+++ b/doc/tar.1
@@ -800,6 +800,10 @@ Filter data through \fICOMMAND\fR.  It must accept the 
\fB\-d\fR
 option, for decompression.  The argument can contain command line
 options.
 .TP
+\fB\-\-brotli\fR
+Filter the archive through
+.BR brotli (1).
+.TP
 \fB\-j\fR, \fB\-\-bzip2\fR
 Filter the archive through
 .BR bzip2 (1).
@@ -1296,6 +1300,7 @@ compressor program failed.  Another example is
 .B rmt
 failure during backup to a remote device.
 .SH "SEE ALSO"
+.BR brotli (1)
 .BR bzip2 (1),
 .BR compress (1),
 .BR gzip (1),
diff --git a/doc/tar.texi b/doc/tar.texi
index dac49f32..5449e65c 100644
--- a/doc/tar.texi
+++ b/doc/tar.texi
@@ -2545,6 +2545,9 @@ with the block number in the archive file.  
@xref{block-number}.
 Sets the blocking factor @command{tar} uses to @var{blocking} x 512 bytes per
 record.  @xref{Blocking Factor}.
 
+@item --brotli
+Use @command{brotli} for compressing or decompressing the archives.  
@xref{gzip}.
+
 @opsummary{bzip2}
 @item --bzip2
 @itemx -j
@@ -9694,6 +9697,7 @@ switch to @samp{posix}.
 @cindex Storing archives in compressed format
 
 @cindex gzip
+@cindex brotli
 @cindex bzip2
 @cindex lzip
 @cindex lzma
@@ -9702,7 +9706,7 @@ switch to @samp{posix}.
 @cindex zstd
 @GNUTAR{} is able to create and read compressed archives.  It supports
 a wide variety of compression programs, namely: @command{gzip},
-@command{bzip2}, @command{lzip}, @command{lzma}, @command{lzop},
+@command{brotli}, @command{bzip2}, @command{lzip}, @command{lzma}, 
@command{lzop},
 @command{zstd}, @command{xz} and traditional @command{compress}. The
 latter is supported mostly for backward compatibility, and we recommend
 against using it, because it is by far less effective than the other
@@ -9716,6 +9720,7 @@ table below:
 @multitable @columnfractions 0.4 0.2 0.4
 @headitem Long            @tab Short       @tab Archive format
 @item @option{--gzip}     @tab @option{-z} @tab @command{gzip}
+@item @option{--brotli}   @tab             @tab @command{brotli}
 @item @option{--bzip2}    @tab @option{-j} @tab @command{bzip2}
 @item @option{--xz}       @tab @option{-J} @tab @command{xz}
 @item @option{--lzip}     @tab             @tab @command{lzip}
@@ -9829,6 +9834,10 @@ Filter the archive through @command{gzip}.
 @itemx --xz
 Filter the archive through @code{xz}.
 
+@opindex brotli
+@item --brotli
+Filter the archive through @command{brotli}.
+
 @item -j
 @itemx --bzip2
 Filter the archive through @code{bzip2}.
@@ -9912,6 +9921,8 @@ suffix.  The following suffixes are recognized:
 @item @samp{.taz} @tab @command{gzip}
 @item @samp{.Z} @tab @command{compress}
 @item @samp{.taZ} @tab @command{compress}
+@item @samp{.br} @tab @command{brotli}
+@item @samp{.tbr} @tab @command{brotli}
 @item @samp{.bz2} @tab @command{bzip2}
 @item @samp{.tz2} @tab @command{bzip2}
 @item @samp{.tbz2} @tab @command{bzip2}
diff --git a/src/buffer.c b/src/buffer.c
index a929138f..f1af7850 100644
--- a/src/buffer.c
+++ b/src/buffer.c
@@ -276,6 +276,7 @@ enum compress_type {
   ct_tar,              /* Plain tar file */
   ct_compress,
   ct_gzip,
+  ct_brotli,
   ct_bzip2,
   ct_lzip,
   ct_lzma,
@@ -305,6 +306,8 @@ static struct zip_magic const magic[] = {
   { ct_tar,      0, 0 },
   { ct_compress, 2, "\037\235" },
   { ct_gzip,     2, "\037\213" },
+  { ct_brotli,   4, "\x91\x19\x62\x66" },
+  { ct_brotli,   4, "\xCE\xB2\xCF\x81" },
   { ct_bzip2,    3, "BZh" },
   { ct_lzip,     4, "LZIP" },
   { ct_lzma,     6, "\xFFLZMA" },
@@ -320,6 +323,7 @@ static struct zip_program zip_program[] = {
   { ct_compress, COMPRESS_PROGRAM, "-Z" },
   { ct_compress, GZIP_PROGRAM,     "-z" },
   { ct_gzip,     GZIP_PROGRAM,     "-z" },
+  { ct_brotli,   BROTLI_PROGRAM,   "--brotli" },
   { ct_bzip2,    BZIP2_PROGRAM,    "-j" },
   { ct_bzip2,    "lbzip2",         "-j" },
   { ct_lzip,     LZIP_PROGRAM,     "--lzip" },
diff --git a/src/suffix.c b/src/suffix.c
index f03a3960..b0d0531e 100644
--- a/src/suffix.c
+++ b/src/suffix.c
@@ -35,6 +35,8 @@ static struct compression_suffix compression_suffixes[] = {
   { S(taz,  GZIP) },
   { S(Z,    COMPRESS) },
   { S(taZ,  COMPRESS) },
+  { S(br,   BROTLI) },
+  { S(tbr,  BROTLI) },
   { S(bz2,  BZIP2) },
   { S(tbz,  BZIP2) },
   { S(tbz2, BZIP2) },
diff --git a/src/tar.c b/src/tar.c
index d65fc806..f48b5625 100644
--- a/src/tar.c
+++ b/src/tar.c
@@ -273,6 +273,7 @@ enum
   ACLS_OPTION = CHAR_MAX + 1,
   ATIME_PRESERVE_OPTION,
   BACKUP_OPTION,
+  BROTLI_OPTION,
   CHECK_DEVICE_OPTION,
   CHECKPOINT_OPTION,
   CHECKPOINT_ACTION_OPTION,
@@ -720,6 +721,7 @@ static struct argp_option options[] = {
   {"use-compress-program", 'I', N_("PROG"), 0,
    N_("filter through PROG (must accept -d)"), GRID_COMPRESS },
   /* Note: docstrings for the options below are generated by tar_help_filter */
+  {"brotli", BROTLI_OPTION, 0, 0, NULL, GRID_COMPRESS },
   {"bzip2", 'j', 0, 0, NULL, GRID_COMPRESS },
   {"gzip", 'z', 0, 0, NULL, GRID_COMPRESS },
   {"gunzip", 0, 0, OPTION_ALIAS, NULL, GRID_COMPRESS },
@@ -1146,6 +1148,10 @@ tar_help_filter (int key, const char *text, void *input)
       s = (char*) text;
       break;
 
+    case BROTLI_OPTION:
+      s = easprintf (_("filter the archive through %s"), BROTLI_PROGRAM);
+      break;
+
     case 'j':
       s = easprintf (_("filter the archive through %s"), BZIP2_PROGRAM);
       break;
@@ -1417,6 +1423,10 @@ parse_opt (int key, char *arg, struct argp_state *state)
       read_full_records_option = true;
       break;
 
+    case BROTLI_OPTION:
+      set_use_compress_program_option (BROTLI_PROGRAM, args->loc);
+      break;
+
     case 'c':
       set_subcommand_option (CREATE_SUBCOMMAND);
       break;
diff --git a/tests/testsuite.at b/tests/testsuite.at
index 9ee9dd9a..6c3643a7 100644
--- a/tests/testsuite.at
+++ b/tests/testsuite.at
@@ -240,6 +240,7 @@ m4_popdef([CPT_CHECK])
 AT_BANNER([Compression])
 m4_include([compress.m4])
 TAR_CHECK_COMPRESS(gzip, gz, tgz)
+TAR_CHECK_COMPRESS(brotli, br, tbr)
 TAR_CHECK_COMPRESS(bzip2, bz2, tbz2)
 TAR_CHECK_COMPRESS(xz, xz, txz)
 dnl: omit lzma, because it would fail due to magic number mismatch
-- 
2.40.1