1 files changed, 92 insertions, 0 deletions
diff --git a/lib/io/compress/gzip.c b/lib/io/compress/gzip.c
new file mode 100644
index 0000000..b73a258
--- /dev/null
+++ b/lib/io/compress/gzip.c
@@ -0,0 +1,92 @@
+/* SPDX-License-Identifier: GPL-3.0-or-later */
+/*
+ * gzip.c
+ *
+ * Copyright (C) 2019 David Oberhollenzer <goliath@infraroot.at>
+ */
+#include "../internal.h"
+
+#include <zlib.h>
+
+typedef struct {
+	ostream_comp_t base;
+
+	z_stream strm;
+} ostream_gzip_t;
+
+static int flush_inbuf(ostream_comp_t *base, bool finish)
+{
+	ostream_gzip_t *gzip = (ostream_gzip_t *)base;
+	size_t have;
+	int ret;
+
+	if (base->inbuf_used > sizeof(base->inbuf))
+		base->inbuf_used = sizeof(base->inbuf);
+
+	if (sizeof(size_t) > sizeof(uInt)) {
+		gzip->strm.avail_in = ~((uInt)0);
+
+		if ((size_t)gzip->strm.avail_in > base->inbuf_used)
+			gzip->strm.avail_in = (uInt)base->inbuf_used;
+	} else {
+		gzip->strm.avail_in = (uInt)base->inbuf_used;
+	}
+
+	gzip->strm.next_in = base->inbuf;
+
+	do {
+		gzip->strm.avail_out = BUFSZ;
+		gzip->strm.next_out = base->outbuf;
+
+		ret = deflate(&gzip->strm, finish ? Z_FINISH : Z_NO_FLUSH);
+
+		if (ret == Z_STREAM_ERROR) {
+			fprintf(stderr,
+				"%s: internal error in gzip compressor.\n",
+				base->wrapped->get_filename(base->wrapped));
+			return -1;
+		}
+
+		have = BUFSZ - gzip->strm.avail_out;
+
+		if (base->wrapped->append(base->wrapped, base->outbuf, have))
+			return -1;
+	} while (gzip->strm.avail_out == 0);
+
+	base->inbuf_used = 0;
+	return 0;
+}
+
+static void cleanup(ostream_comp_t *base)
+{
+	ostream_gzip_t *gzip = (ostream_gzip_t *)base;
+
+	deflateEnd(&gzip->strm);
+}
+
+ostream_comp_t *ostream_gzip_create(const char *filename)
+{
+	ostream_gzip_t *gzip = calloc(1, sizeof(*gzip));
+	ostream_comp_t *base = (ostream_comp_t *)gzip;
+	int ret;
+
+	if (gzip == NULL) {
+		fprintf(stderr, "%s: creating gzip wrapper: %s.\n",
+			filename, strerror(errno));
+		return NULL;
+	}
+
+	ret = deflateInit2(&gzip->strm, 9, Z_DEFLATED, 16 + 15, 8,
+			   Z_DEFAULT_STRATEGY);
+	if (ret != Z_OK) {
+		fprintf(stderr,
+			"%s: internal error creating gzip compressor.\n",
+			filename);
+		free(gzip);
+		return NULL;
+	}
+
+	base->flush_inbuf = flush_inbuf;
+	base->cleanup = cleanup;
+	return base;
+}