[cmp] add decompression support

* Adds .Z, .gz, .lzma, .xz and .bz2 decompression support for DD images
  using the Bled library (https://github.com/pbatard/bled).
* Closes #269

src/bled/bled.c

@@ -0,0 +1,139 @@
+/*
+ * Bled (Busybox Library for Easy Decompression)
+ *
+ * Copyright © 2014 Pete Batard <pete@akeo.ie>
+ *
+ * Licensed under GPLv2 or later, see file LICENSE in this source tree.
+ */
+
+#ifdef _CRTDBG_MAP_ALLOC
+#include <stdlib.h>
+#include <crtdbg.h>
+#endif
+
+#include "libbb.h"
+#include "bb_archive.h"
+#include "bled.h"
+
+typedef long long int(*unpacker_t)(transformer_state_t *xstate);
+
+/* Globals */
+smallint bb_got_signal;
+uint64_t bb_total_rb;
+printf_t bled_printf = NULL;
+progress_t bled_progress = NULL;
+static bool bled_initialized = 0;
+
+static long long int unpack_none(transformer_state_t *xstate)
+{
+	bb_printf("BLED_COMPRESSION_NONE is not supported");
+	return -1;
+}
+
+unpacker_t unpacker[BLED_COMPRESSION_MAX] = {
+	unpack_none,
+	inflate_unzip,
+	unpack_Z_stream,
+	unpack_gz_stream,
+	unpack_lzma_stream,
+	unpack_bz2_stream,
+	unpack_xz_stream
+};
+
+/* Uncompress file 'src', compressed using 'type', to file 'dst' */
+int64_t bled_uncompress(const char* src, const char* dst, int type)
+{
+	transformer_state_t xstate;
+	int64_t ret;
+
+	if (!bled_initialized)
+		return -1;
+
+	bb_total_rb = 0;
+	init_transformer_state(&xstate);
+	xstate.src_fd = -1;
+	xstate.dst_fd = -1;
+	xstate.check_signature = 1;
+
+	xstate.src_fd = _openU(src, _O_RDONLY | _O_BINARY, 0);
+	if (xstate.src_fd < 0) {
+		bb_printf("Could not open '%s' (errno: %d)", src, errno);
+		goto err;
+	}
+
+	xstate.dst_fd = _openU(dst, _O_WRONLY | _O_CREAT | _O_TRUNC | _O_BINARY, _S_IREAD | _S_IWRITE);
+	if (xstate.dst_fd < 0) {
+		bb_printf("Could not open '%s' (errno: %d)", dst, errno);
+		goto err;
+	}
+
+	if ((type < 0) || (type >= BLED_COMPRESSION_MAX)) {
+		bb_printf("unsupported compression format");
+		goto err;
+	}
+
+	ret = unpacker[type](&xstate);
+	_close(xstate.src_fd);
+	_close(xstate.dst_fd);
+	return ret;
+
+err:
+	if (xstate.src_fd > 0)
+		_close(xstate.src_fd);
+	if (xstate.dst_fd > 0)
+		_close(xstate.dst_fd);
+	return -1;
+}
+
+/* Uncompress using Windows handles */
+int64_t bled_uncompress_with_handles(HANDLE hSrc, HANDLE hDst, int type)
+{
+	transformer_state_t xstate;
+
+	if (!bled_initialized)
+		return -1;
+
+	bb_total_rb = 0;
+	init_transformer_state(&xstate);
+	xstate.src_fd = -1;
+	xstate.dst_fd = -1;
+	xstate.check_signature = 1;
+
+	xstate.src_fd = _open_osfhandle((intptr_t)hSrc, _O_RDONLY);
+	if (xstate.src_fd < 0) {
+		bb_printf("Could not get source descriptor (errno: %d)", errno);
+		return -1;
+	}
+
+	xstate.dst_fd = _open_osfhandle((intptr_t)hDst, 0);
+	if (xstate.dst_fd < 0) {
+		bb_printf("Could not get target descriptor (errno: %d)", errno);
+		return -1;
+	}
+
+	if ((type < 0) || (type >= BLED_COMPRESSION_MAX)) {
+		bb_printf("unsupported compression format");
+		return -1;
+	}
+
+	return unpacker[type](&xstate);
+}
+
+int bled_init(printf_t print_function, progress_t progress_function)
+{
+	if (bled_initialized)
+		return -1;
+	bled_initialized = true;
+	bled_printf = print_function;
+	bled_progress = progress_function;
+	return 0;
+}
+
+void bled_exit(void)
+{
+	bled_printf = NULL;
+	bled_progress = NULL;
+	if (global_crc32_table)
+		free(global_crc32_table);
+	bled_initialized = false;
+}