compression: add build-time option to select default

Compression and decompression are controlled by the same build flag,
so if one wants to use, say, LZ4 to compress, ZSTD has to be disabled,
which means one loses the ability to read zstd-compressed journals.

Add a default-compression meson option, that allows to select any of
the available compression algorithms as the default.

1 files changed, 24 insertions, 0 deletions

diff --git a/meson.build b/meson.build
index d60be1b050..723bc8dac1 100644
--- a/meson.build
+++ b/meson.build
@@ -1452,6 +1452,30 @@ conf.set10('HAVE_ZSTD', have_zstd)
 
 conf.set10('HAVE_COMPRESSION', have_xz or have_lz4 or have_zstd)
 
+compression = get_option('default-compression')
+if compression == 'auto'
+        if have_zstd
+                compression = 'zstd'
+        elif have_lz4
+                compression = 'lz4'
+        elif have_xz
+                compression = 'xz'
+        else
+                compression = 'none'
+        endif
+elif compression == 'zstd' and not have_zstd
+        error('default-compression=zstd requires zstd')
+elif compression == 'lz4' and not have_lz4
+        error('default-compression=lz4 requires lz4')
+elif compression == 'xz' and not have_xz
+        error('default-compression=xz requires xz')
+endif
+conf.set('OBJECT_COMPRESSED_NONE', 0)
+conf.set('OBJECT_COMPRESSED_XZ', 1)
+conf.set('OBJECT_COMPRESSED_LZ4', 2)
+conf.set('OBJECT_COMPRESSED_ZSTD', 4)
+conf.set('DEFAULT_COMPRESSION', 'OBJECT_COMPRESSED_@0@'.format(compression.to_upper()))
+
 want_xkbcommon = get_option('xkbcommon')
 if want_xkbcommon != 'false' and not skip_deps
         libxkbcommon = dependency('xkbcommon',