adb: support seamless de/compression of adb files

Add compression header of adb files. Support uncompressed and
deflate compression at this time.

1 files changed, 48 insertions, 0 deletions

diff --git a/src/adb_comp.c b/src/adb_comp.c
new file mode 100644
index 0000000..8aed95d
--- /dev/null
+++ b/src/adb_comp.c
@@ -0,0 +1,48 @@
+/* adb_comp.c - Alpine Package Keeper (APK)
+ *
+ * Copyright (C) 2021 Timo Teräs <timo.teras@iki.fi>
+ * All rights reserved.
+ *
+ * SPDX-License-Identifier: GPL-2.0-only
+ */
+
+#include "apk_defines.h"
+#include "adb.h"
+
+struct apk_istream *adb_decompress(struct apk_istream *is, adb_comp_t *compression)
+{
+	 adb_comp_t c = ADB_COMP_NONE;
+
+	if (IS_ERR_OR_NULL(is)) return is;
+
+	uint8_t *buf = apk_istream_peek(is, 4);
+	if (memcmp(buf, "ADB", 3) == 0) switch (buf[3]) {
+	case '.':
+		c = ADB_COMP_NONE;
+		break;
+	case 'd':
+		c = ADB_COMP_DEFLATE;
+		is = apk_istream_deflate(is);
+		break;
+	default:
+		apk_istream_close(is);
+		return ERR_PTR(-APKE_ADB_COMPRESSION);
+	}
+	if (compression) *compression = c;
+	return is;
+}
+
+struct apk_ostream *adb_compress(struct apk_ostream *os, adb_comp_t compression)
+{
+	if (IS_ERR_OR_NULL(os)) return os;
+	switch (compression) {
+	case ADB_COMP_NONE:
+		return os;
+	case ADB_COMP_DEFLATE:
+		if (apk_ostream_write(os, "ADBd", 4) < 0) goto err;
+		return apk_ostream_deflate(os);
+	}
+err:
+	apk_ostream_cancel(os, -APKE_ADB_COMPRESSION);
+	return ERR_PTR(apk_ostream_close(os));
+}