Allow building without zstd temporarily

Eventually zstd will become the default compression method for cached
data, but for new we allow building without it as well.

Resolves: #561, #562

meson.build

@@ -46,6 +46,7 @@ conf.set('HAVE_APT_SUPPORT', get_option('apt-support'))
 conf.set('HAVE_STEMMING', get_option('stemming'))
 conf.set('HAVE_SYSTEMD', get_option('systemd'))
 conf.set('HAVE_SVG_SUPPORT', get_option('svg-support'))
+conf.set('HAVE_ZSTD', get_option('zstd-support'))
 
 configure_file(output: 'config.h', configuration: conf)
 root_inc_dir = include_directories ('.')
@@ -159,8 +160,16 @@ yaml_dep = dependency('yaml-0.1')
 xmlb_dep = dependency('xmlb', version: '>= 0.3.14',
                       fallback: ['libxmlb', 'libxmlb_dep'],
                       default_options: ['gtkdoc=false', 'introspection=false'])
-zstd_dep = dependency('libzstd')
-libsystemd_dep = dependency('libsystemd', required: get_option('systemd'))
+if get_option('zstd-support')
+    zstd_dep = dependency('libzstd', required: get_option('zstd-support'))
+else
+    zstd_dep = dependency('', required: false)
+endif
+if get_option('systemd')
+    libsystemd_dep = dependency('libsystemd', required: get_option('systemd'))
+else
+    libsystemd_dep = dependency('', required: false)
+endif
 
 if get_option ('gir')
     # ensure we have a version of GIR that isn't broken with Meson

meson_options.txt

@@ -43,6 +43,11 @@ option('svg-support',
        value : true,
        description : 'SVG graphics support for compose (only disable this for bootstrapping purposes)'
 )
+option('zstd-support',
+       type : 'boolean',
+       value : true,
+       description : 'Support Zstd for (de)compressing local / remote metadata'
+)
 
 option('docs',
        type : 'boolean',

src/as-zstd-decompressor.c

@@ -23,13 +23,17 @@
 #include "config.h"
 
 #include <gio/gio.h>
+#ifdef HAVE_ZSTD
 #include <zstd.h>
+#endif
 
 static void as_zstd_decompressor_iface_init (GConverterIface *iface);
 
 struct _AsZstdDecompressor {
 	GObject parent_instance;
+#ifdef HAVE_ZSTD
 	ZSTD_DStream *zstdstream;
+#endif
 };
 
 G_DEFINE_TYPE_WITH_CODE (AsZstdDecompressor,
@@ -40,8 +44,12 @@ G_DEFINE_TYPE_WITH_CODE (AsZstdDecompressor,
 static void
 as_zstd_decompressor_finalize (GObject *object)
 {
+#ifdef HAVE_ZSTD
 	AsZstdDecompressor *self = AS_ZSTD_DECOMPRESSOR (object);
+
 	ZSTD_freeDStream (self->zstdstream);
+#endif
+
 	G_OBJECT_CLASS (as_zstd_decompressor_parent_class)->finalize (object);
 }
 
@@ -53,8 +61,10 @@ as_zstd_decompressor_init (AsZstdDecompressor *self)
 static void
 as_zstd_decompressor_constructed (GObject *object)
 {
+#ifdef HAVE_ZSTD
 	AsZstdDecompressor *self = AS_ZSTD_DECOMPRESSOR (object);
 	self->zstdstream = ZSTD_createDStream ();
+#endif
 }
 
 static void
@@ -74,8 +84,10 @@ as_zstd_decompressor_new (void)
 static void
 as_zstd_decompressor_reset (GConverter *converter)
 {
+#ifdef HAVE_ZSTD
 	AsZstdDecompressor *self = AS_ZSTD_DECOMPRESSOR (converter);
 	ZSTD_initDStream (self->zstdstream);
+#endif
 }
 
 static GConverterResult
@@ -89,6 +101,7 @@ as_zstd_decompressor_convert (GConverter *converter,
 			      gsize *bytes_written,
 			      GError **error)
 {
+#ifdef HAVE_ZSTD
 	AsZstdDecompressor *self = AS_ZSTD_DECOMPRESSOR (converter);
 	ZSTD_outBuffer output = {
 		.dst = outbuf,
@@ -109,13 +122,20 @@ as_zstd_decompressor_convert (GConverter *converter,
 		g_set_error (error,
 			     G_IO_ERROR,
 			     G_IO_ERROR_INVALID_DATA,
-			     "cannot decompress data: %s",
+			     "can not decompress data: %s",
 			     ZSTD_getErrorName (res));
 		return G_CONVERTER_ERROR;
 	}
 	*bytes_read = input.pos;
 	*bytes_written = output.pos;
 	return G_CONVERTER_CONVERTED;
+#else
+	g_set_error_literal (error,
+			     G_IO_ERROR,
+			     G_IO_ERROR_INVALID_DATA,
+			     "AppStream was not built with Zstd support. Can not decompress data.");
+	return G_CONVERTER_ERROR;
+#endif
 }
 
 static void