ui-snapshot: add support for zstd compression

This patch adds support for zstd [0] compressed snapshots (*.tar.zst).
We enable multiple working threads (-T0), but keep default compression
level. The latter can be influenced by environment variable.

[0] https://www.zstd.net/

Signed-off-by: Christian Hesse <mail@eworm.de>

4 files changed, 56 insertions, 4 deletions

@@ -407,9 +407,12 @@ side-by-side-diffs::
 snapshots::
         Text which specifies the default set of snapshot formats that cgit
         generates links for. The value is a space-separated list of zero or
-        more of the values "tar", "tar.gz", "tar.bz2", "tar.xz", "tar.lz" and
-        "zip". The special value "all" enables all snapshot formats.
-        Default value: none.
+        more of the values "tar", "tar.gz", "tar.bz2", "tar.lz", "tar.xz",
+        "tar.zst" and "zip". The special value "all" enables all snapshot
+        formats. Default value: none.
+        All compressors use default settings. Some settings can be influenced
+        with environment variables, for example set ZSTD_CLEVEL=10 in web
+        server environment for higher (but slower) zstd compression.
 
 source-filter::
         Specifies a command which will be invoked to format plaintext blobs
@@ -104,7 +104,7 @@ virtual-root=/
 cache-root=$PWD/cache
 
 cache-size=1021
-snapshots=tar.gz tar.bz tar.lz tar.xz zip
+snapshots=tar.gz tar.bz tar.lz tar.xz tar.zst zip
 enable-log-filecount=1
 enable-log-linecount=1
 summary-log=5
@@ -122,6 +122,48 @@ test_expect_success XZ 'verify untarred file-5' '
         test_line_count = 1 master/file-5
 '
 
+if test -n "$(which zstd 2>/dev/null)"; then
+        test_set_prereq ZSTD
+else
+        say 'Skipping ZSTD validation tests: zstd not found'
+fi
+
+test_expect_success ZSTD 'get foo/snapshot/master.tar.zst' '
+        cgit_url "foo/snapshot/master.tar.zst" >tmp
+'
+
+test_expect_success ZSTD 'check html headers' '
+        head -n 1 tmp |
+        grep "Content-Type: application/x-zstd" &&
+
+        head -n 2 tmp |
+        grep "Content-Disposition: inline; filename=.master.tar.zst."
+'
+
+test_expect_success ZSTD 'strip off the header lines' '
+        strip_headers <tmp >master.tar.zst
+'
+
+test_expect_success ZSTD 'verify zstd format' '
+        zstd --test master.tar.zst &&
+        cp master.tar.zst /tmp/.
+'
+
+test_expect_success ZSTD 'untar' '
+        rm -rf master &&
+        tar --zstd -xf master.tar.zst
+'
+
+test_expect_success ZSTD 'count files' '
+        ls master/ >output &&
+        test_line_count = 5 output
+'
+
+test_expect_success ZSTD 'verify untarred file-5' '
+        grep "^5$" master/file-5 &&
+        test_line_count = 1 master/file-5
+'
+
 test_expect_success 'get foo/snapshot/master.zip' '
         cgit_url "foo/snapshot/master.zip" >tmp
 '
@@ -91,6 +91,12 @@ static int write_tar_xz_archive(const char *hex, const char *prefix)
         return write_compressed_tar_archive(hex, prefix, argv);
 }
 
+static int write_tar_zstd_archive(const char *hex, const char *prefix)
+{
+        char *argv[] = { "zstd", "-T0", NULL };
+        return write_compressed_tar_archive(hex, prefix, argv);
+}
+
 const struct cgit_snapshot_format cgit_snapshot_formats[] = {
         /* .tar must remain the 0 index */
         { ".tar",       "application/x-tar",    write_tar_archive       },
@@ -98,6 +104,7 @@ const struct cgit_snapshot_format cgit_snapshot_formats[] = {
         { ".tar.bz2",   "application/x-bzip2",  write_tar_bzip2_archive },
         { ".tar.lz",    "application/x-lzip",   write_tar_lzip_archive  },
         { ".tar.xz",    "application/x-xz",     write_tar_xz_archive    },
+        { ".tar.zst",   "application/x-zstd",   write_tar_zstd_archive  },
         { ".zip",       "application/x-zip",    write_zip_archive       },
         { NULL }
 };