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-rw-r--r--lib/io/uncompress/autodetect.c55
1 files changed, 55 insertions, 0 deletions
diff --git a/lib/io/uncompress/autodetect.c b/lib/io/uncompress/autodetect.c
new file mode 100644
index 0000000..dde33c8
--- /dev/null
+++ b/lib/io/uncompress/autodetect.c
@@ -0,0 +1,55 @@
+/* SPDX-License-Identifier: GPL-3.0-or-later */
+/*
+ * autodetect.c
+ *
+ * Copyright (C) 2019 David Oberhollenzer <goliath@infraroot.at>
+ */
+#include "../internal.h"
+
+static const struct {
+ int id;
+ const sqfs_u8 *value;
+ size_t len;
+} magic[] = {
+ { IO_COMPRESSOR_GZIP, (const sqfs_u8 *)"\x1F\x8B\x08", 3 },
+ { IO_COMPRESSOR_XZ, (const sqfs_u8 *)("\xFD" "7zXZ"), 6 },
+ { IO_COMPRESSOR_ZSTD, (const sqfs_u8 *)"\x28\xB5\x2F\xFD", 4 },
+ { IO_COMPRESSOR_BZIP2, (const sqfs_u8 *)"BZh", 3 },
+};
+
+int istream_detect_compressor(istream_t *strm,
+ int (*probe)(const sqfs_u8 *data, size_t size))
+{
+ size_t i;
+ int ret;
+
+ ret = istream_precache(strm);
+ if (ret != 0)
+ return ret;
+
+ if (probe != NULL) {
+ ret = probe(strm->buffer + strm->buffer_offset,
+ strm->buffer_used - strm->buffer_offset);
+ if (ret < 0)
+ return ret;
+
+ /* XXX: this means the data is uncompressed. We do this check
+ first since it might be perfectly OK for the uncompressed
+ data to contain a magic number from the table. */
+ if (ret > 0)
+ return 0;
+ }
+
+ for (i = 0; i < sizeof(magic) / sizeof(magic[0]); ++i) {
+ if ((strm->buffer_used - strm->buffer_offset) < magic[i].len)
+ continue;
+
+ ret = memcmp(strm->buffer + strm->buffer_offset,
+ magic[i].value, magic[i].len);
+
+ if (ret == 0)
+ return magic[i].id;
+ }
+
+ return 0;
+}