Implement reading and writing of compressor options

 - gensquashfs simply asks the backend compressor to write its options
   to the file and does accounting
 - rdsquasfs simply asks the backend compressor to transparentyl snort
   the options from the file
 - not implemented in any compressor backend yet

Signed-off-by: David Oberhollenzer <david.oberhollenzer@sigma-star.at>

6 files changed, 86 insertions, 8 deletions

diff --git a/include/compress.h b/include/compress.h
index 5bb689b..a8542f2 100644
--- a/include/compress.h
+++ b/include/compress.h
@@ -19,6 +19,26 @@ typedef struct compressor_t compressor_t;
  */
 struct compressor_t {
 	/**
+	 * @brief Write compressor options to the output file if necessary
+	 *
+	 * @param cmp A pointer to the compressor object
+	 * @param fd  The file descriptor to write to
+	 *
+	 * @return The number of bytes written or -1 on failure
+	 */
+	int (*write_options)(compressor_t *cmp, int fd);
+
+	/**
+	 * @brief Read compressor options to the input file
+	 *
+	 * @param cmp A pointer to the compressor object
+	 * @param fd  The file descriptor to write to
+	 *
+	 * @return Zero on success, -1 on failure
+	 */
+	int (*read_options)(compressor_t *cmp, int fd);
+
+	/**
 	 * @brief Compress or uncompress a chunk of data
 	 *
 	 * @param cmp     A pointer to the compressor object
diff --git a/lib/comp/gzip.c b/lib/comp/gzip.c
index ea634b8..ea86f98 100644
--- a/lib/comp/gzip.c
+++ b/lib/comp/gzip.c
@@ -29,6 +29,21 @@ static void gzip_destroy(compressor_t *base)
 	free(gzip);
 }
 
+static int gzip_write_options(compressor_t *base, int fd)
+{
+	(void)base;
+	(void)fd;
+	return 0;
+}
+
+static int gzip_read_options(compressor_t *base, int fd)
+{
+	(void)base;
+	(void)fd;
+	fputs("gzip extra options are not yet implemented\n", stderr);
+	return -1;
+}
+
 static ssize_t gzip_do_block(compressor_t *base, const uint8_t *in,
 			     size_t size, uint8_t *out, size_t outsize)
 {
@@ -90,6 +105,8 @@ compressor_t *create_gzip_compressor(bool compress, size_t block_size)
 	gzip->block_size = block_size;
 	base->do_block = gzip_do_block;
 	base->destroy = gzip_destroy;
+	base->write_options = gzip_write_options;
+	base->read_options = gzip_read_options;
 
 	if (compress) {
 		ret = deflateInit(&gzip->strm, Z_BEST_COMPRESSION);
diff --git a/lib/comp/lzo.c b/lib/comp/lzo.c
index 30b14cb..95ab485 100644
--- a/lib/comp/lzo.c
+++ b/lib/comp/lzo.c
@@ -14,6 +14,21 @@ typedef struct {
 	uint8_t buffer[LZO1X_999_MEM_COMPRESS];
 } lzo_compressor_t;
 
+static int lzo_write_options(compressor_t *base, int fd)
+{
+	(void)base;
+	(void)fd;
+	return 0;
+}
+
+static int lzo_read_options(compressor_t *base, int fd)
+{
+	(void)base;
+	(void)fd;
+	fputs("lzo extra options are not yet implemented\n", stderr);
+	return -1;
+}
+
 static ssize_t lzo_comp_block(compressor_t *base, const uint8_t *in,
 			      size_t size, uint8_t *out, size_t outsize)
 {
@@ -67,5 +82,7 @@ compressor_t *create_lzo_compressor(bool compress, size_t block_size)
 
 	base->destroy = lzo_destroy;
 	base->do_block = compress ? lzo_comp_block : lzo_uncomp_block;
+	base->write_options = lzo_write_options;
+	base->read_options = lzo_read_options;
 	return base;
 }
diff --git a/lib/comp/xz.c b/lib/comp/xz.c
index 98d740c..dd608ba 100644
--- a/lib/comp/xz.c
+++ b/lib/comp/xz.c
@@ -12,6 +12,21 @@ typedef struct {
 	size_t block_size;
 } xz_compressor_t;
 
+static int xz_write_options(compressor_t *base, int fd)
+{
+	(void)base;
+	(void)fd;
+	return 0;
+}
+
+static int xz_read_options(compressor_t *base, int fd)
+{
+	(void)base;
+	(void)fd;
+	fputs("xz extra options are not yet implemented\n", stderr);
+	return -1;
+}
+
 static ssize_t xz_comp_block(compressor_t *base, const uint8_t *in,
 			       size_t size, uint8_t *out, size_t outsize)
 {
@@ -86,5 +101,7 @@ compressor_t *create_xz_compressor(bool compress, size_t block_size)
 	xz->block_size = block_size;
 	base->destroy = xz_destroy;
 	base->do_block = compress ? xz_comp_block : xz_uncomp_block;
+	base->write_options = xz_write_options;
+	base->read_options = xz_read_options;
 	return base;
 }
diff --git a/mkfs/mkfs.c b/mkfs/mkfs.c
index d708d37..ae6210b 100644
--- a/mkfs/mkfs.c
+++ b/mkfs/mkfs.c
@@ -39,7 +39,7 @@ static int padd_file(sqfs_info_t *info)
 
 int main(int argc, char **argv)
 {
-	int status = EXIT_FAILURE;
+	int status = EXIT_FAILURE, ret;
 	sqfs_info_t info;
 
 	memset(&info, 0, sizeof(info));
@@ -81,6 +81,15 @@ int main(int argc, char **argv)
 		goto out_outfd;
 	}
 
+	ret = info.cmp->write_options(info.cmp, info.outfd);
+	if (ret < 0)
+		goto out_cmp;
+
+	if (ret > 0) {
+		info.super.flags |= SQFS_FLAG_COMPRESSOR_OPTIONS;
+		info.super.bytes_used += ret;
+	}
+
 	if (write_data_to_image(&info))
 		goto out_cmp;
 
diff --git a/unpack/rdsquashfs.c b/unpack/rdsquashfs.c
index a24434c..8ee3dbd 100644
--- a/unpack/rdsquashfs.c
+++ b/unpack/rdsquashfs.c
@@ -260,13 +260,6 @@ int main(int argc, char **argv)
 		goto out_fd;
 	}
 
-	if (super.flags & SQFS_FLAG_COMPRESSOR_OPTIONS) {
-		fputs("Image has been built with compressor options.\n"
-		      "This is not yet supported.\n",
-		      stderr);
-		goto out_fd;
-	}
-
 	if (!compressor_exists(super.compression_id)) {
 		fputs("Image uses a compressor that has not been built in\n",
 		      stderr);
@@ -278,6 +271,11 @@ int main(int argc, char **argv)
 	if (info.cmp == NULL)
 		goto out_fd;
 
+	if (super.flags & SQFS_FLAG_COMPRESSOR_OPTIONS) {
+		if (info.cmp->read_options(info.cmp, info.sqfsfd))
+			goto out_cmp;
+	}
+
 	if (read_fstree(&fs, &super, &info))
 		goto out_cmp;