[PATCH 2/2] uncompress: add Android sparse image support

[Juergen Borleis]

An Android sparse image file generated by the 'genimage' tool can be seen as a
kind of compression, since it contains only the data which should really be
written to a device.

This implementation writes only the intended content and skips anything else.

Signed-off-by: Juergen Borleis <jbe at pengutronix.de>
---
 lib/uncompress.c | 82 +++++++++++++++++++++++++++++++++++++++++++++---
 1 file changed, 78 insertions(+), 4 deletions(-)

diff --git a/lib/uncompress.c b/lib/uncompress.c
index 0608e9f..f17e9ce 100644
--- a/lib/uncompress.c
+++ b/lib/uncompress.c
@@ -25,6 +25,10 @@
 #include <malloc.h>
 #include <fs.h>
 #include <libfile.h>
+#ifdef CONFIG_IMAGE_SPARSE
+#include <image-sparse.h>
+#include <linux/sizes.h>
+#endif
 
 static void *uncompress_buf;
 static unsigned int uncompress_size;
@@ -60,6 +64,71 @@ static int uncompress_fill(void *buf, unsigned int len)
 	return total;
 }
 
+#ifdef CONFIG_IMAGE_SPARSE
+static int uncompress_sparse(int source, int destination)
+{
+	int ret = 0;
+	struct sparse_image_ctx *sparse;
+
+	/* rewind after checking the file type */
+	lseek(source, 0, SEEK_SET);
+
+	sparse = sparse_image_fd(source);
+	if (IS_ERR(sparse)) {
+		pr_err("Failed to open or interpret sparse image file: %m\n");
+		ret = 1;
+		goto on_error_dev;
+	}
+
+	const size_t transfer_buffer_length = SZ_128K;
+	unsigned char *buf = malloc(transfer_buffer_length);
+	if (!buf) {
+		pr_err("Failed to alloc memory for the transfers\n");
+		ret = 1;
+		goto on_error_sparse;
+	}
+
+	while (1) {
+		loff_t write_offset;
+		size_t write_length;
+
+		int rc = sparse_image_read(sparse, buf, &write_offset, transfer_buffer_length, &write_length);
+		if (rc) {
+			ret = 1;
+			goto on_error_memory;
+		}
+		if (!write_length)
+			break;
+
+		discard_range(destination, write_length, write_offset);
+
+		write_offset = lseek(destination, write_offset, SEEK_SET);
+		if (write_offset == -1) {
+			pr_err("Failed to set next data's destination offset: %m\n");
+			ret = 1;
+			goto on_error_memory;
+
+		}
+
+		rc = write_full(destination, buf, write_length);
+		if (rc < 0) {
+			pr_err("Failed to write destination's next data: %m\n");
+			ret = 1;
+			goto on_error_memory;
+		}
+	}
+
+on_error_memory:
+	free(buf);
+on_error_sparse:
+	free(sparse); /* Note: sparse_image_close(sparse); would also close the input file descriptor */
+on_error_dev:
+	return ret;
+}
+#endif
+
+static int uncompress_infd, uncompress_outfd;
+
 int uncompress(unsigned char *inbuf, int len,
 	   int(*fill)(void*, unsigned int),
 	   int(*flush)(void*, unsigned int),
@@ -121,6 +190,10 @@ int uncompress(unsigned char *inbuf, int len,
 	case filetype_xz_compressed:
 		compfn = decompress_unxz;
 		break;
+#endif
+#ifdef CONFIG_IMAGE_SPARSE
+	case filetype_android_sparse:
+		break;
 #endif
 	default:
 		err = basprintf("cannot handle filetype %s",
@@ -131,16 +204,17 @@ int uncompress(unsigned char *inbuf, int len,
 		goto err;
 	}
 
-	ret = compfn(inbuf, len, fill ? uncompress_fill : NULL,
-			flush, output, pos, error_fn);
+	if (ft == filetype_android_sparse)
+		ret = uncompress_sparse(uncompress_infd, uncompress_outfd);
+	else
+		ret = compfn(inbuf, len, fill ? uncompress_fill : NULL,
+			     flush, output, pos, error_fn);
 err:
 	free(uncompress_buf);
 
 	return ret;
 }
 
-static int uncompress_infd, uncompress_outfd;
-
 static int fill_fd(void *buf, unsigned int len)
 {
 	return read_full(uncompress_infd, buf, len);
-- 
2.30.2