Turn the sqfs_block_writer_t into an interface

This way, everything that could be done through the hooks (and more)
can be done by simply providign a custom implementation. The result is
a lot clener that the previous hook based version.

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

4 files changed, 94 insertions, 84 deletions

diff --git a/include/sqfs/block_writer.h b/include/sqfs/block_writer.h
index 8cfb9a2..f8bc671 100644
--- a/include/sqfs/block_writer.h
+++ b/include/sqfs/block_writer.h
@@ -29,21 +29,69 @@
  */
 
 /**
- * @struct sqfs_block_writer_t
+ * @interface sqfs_block_writer_t
  *
  * @implements sqfs_object_t
  *
  * @brief Abstracts writing and deduplicating of data and fragment blocks.
  *
- * This object is not copyable, i.e. @ref sqfs_copy will always return NULL.
+ * A default reference implementation can be obtaiend
+ * through @ref sqfs_block_writer_create. The default implementation is not
+ * copyable, i.e. @ref sqfs_copy will always return NULL.
  */
+struct sqfs_block_writer_t {
+	sqfs_object_t base;
+
+	/**
+	 * @brief Submit a data block to a block writer.
+	 *
+	 * @memberof sqfs_block_writer_t
+	 *
+	 * If the @ref SQFS_BLK_FIRST_BLOCK flag is set, the data block writer
+	 * memorizes the starting location and block index of the block. If the
+	 * @ref SQFS_BLK_LAST_BLOCK flag is set, it uses those stored locations
+	 * to do block deduplication.
+	 *
+	 * If the flag @ref SQFS_BLK_ALIGN is set in combination with the
+	 * @ref SQFS_BLK_FIRST_BLOCK, the file size is padded to a multiple of
+	 * the device block size before writing. If it is set together with the
+	 * @ref SQFS_BLK_LAST_BLOCK flag, the padding is added afterwards.
+	 *
+	 * @param wr A pointer to a block writer.
+	 * @param size The size of the block to write.
+	 * @param checksum A 32 bit checksum of the block data.
+	 * @param flags A combination of @ref SQFS_BLK_FLAGS flag bits
+	 *              describing the block.
+	 * @arapm data A pointer to the data to write.
+	 * @param location Returns the location where the block has been
+	 *        written. If the @ref SQFS_BLK_LAST_BLOCK flag was set,
+	 *        deduplication is performed and this returns the (new) location
+	 *        of the first block instead.
+	 *
+	 * @return Zero on success, an @ref SQFS_ERROR error on failure.
+	 */
+	int (*write_data_block)(sqfs_block_writer_t *wr, sqfs_u32 size,
+				sqfs_u32 checksum, sqfs_u32 flags,
+				const sqfs_u8 *data, sqfs_u64 *location);
+
+	/**
+	 * @brief Get the number of blocks actually written to disk.
+	 *
+	 * @memberof sqfs_block_writer_t
+	 *
+	 * @param wr A pointer to a block writer.
+	 *
+	 * @return The number of blocks written, excluding deduplicated blocks.
+	 */
+	sqfs_u64 (*get_block_count)(const sqfs_block_writer_t *wr);
+};
 
 #ifdef __cplusplus
 extern "C" {
 #endif
 
 /**
- * @brief Create a block writer object.
+ * @brief Create an instance of a default block writer implementation.
  *
  * @memberof sqfs_block_writer_t
  *
@@ -58,47 +106,6 @@ SQFS_API sqfs_block_writer_t *sqfs_block_writer_create(sqfs_file_t *file,
 						       size_t devblksz,
 						       sqfs_u32 flags);
 
-/**
- * @brief Submit a data block to a blokc writer.
- *
- * @memberof sqfs_block_writer_t
- *
- * If the @ref SQFS_BLK_FIRST_BLOCK flag is set, the data block writer
- * memorizes the starting location and block index of the block. If the
- * @ref SQFS_BLK_LAST_BLOCK flag is set, it uses those stored locations
- * to do block deduplication.
- *
- * If the flag @ref SQFS_BLK_ALIGN is set in combination with the
- * @ref SQFS_BLK_FIRST_BLOCK, the file size is padded to a multiple of the
- * device block size before writing. If it is set together with the
- * @ref SQFS_BLK_LAST_BLOCK flag, the padding is added afterwards.
- *
- * @param wr A pointer to a block writer.
- * @param block The block to write to disk next.
- * @param location Returns the location where the block has been written.
- *                 If the @ref SQFS_BLK_LAST_BLOCK flag was set, deduplication
- *                 is performed and this returns the (new) location of the
- *                 first block instead.
- *
- * @return Zero on success, an @ref SQFS_ERROR error on failure.
- */
-SQFS_API int sqfs_block_writer_write(sqfs_block_writer_t *wr,
-				     sqfs_u32 size, sqfs_u32 checksum,
-				     sqfs_u32 flags, const sqfs_u8 *data,
-				     sqfs_u64 *location);
-
-/**
- * @brief Get the number of blocks actually written to disk.
- *
- * @memberof sqfs_block_writer_t
- *
- * @param wr A pointer to a block writer.
- *
- * @return The number of blocks written, excluding deduplicated blocks.
- */
-SQFS_API
-sqfs_u64 sqfs_block_writer_get_block_count(const sqfs_block_writer_t *wr);
-
 #ifdef __cplusplus
 }
 #endif
diff --git a/lib/common/statistics.c b/lib/common/statistics.c
index 079c1b1..82e545d 100644
--- a/lib/common/statistics.c
+++ b/lib/common/statistics.c
@@ -18,7 +18,7 @@ void sqfs_print_statistics(const sqfs_super_t *super,
 	size_t ratio;
 
 	proc_stats = sqfs_block_processor_get_stats(blk);
-	blocks_written = sqfs_block_writer_get_block_count(wr);
+	blocks_written = wr->get_block_count(wr);
 
 	bytes_written = super->inode_table_start - sizeof(*super);
 
diff --git a/lib/sqfs/block_processor/common.c b/lib/sqfs/block_processor/common.c
index 757544a..e3d5486 100644
--- a/lib/sqfs/block_processor/common.c
+++ b/lib/sqfs/block_processor/common.c
@@ -68,8 +68,8 @@ int process_completed_block(sqfs_block_processor_t *proc, sqfs_block_t *blk)
 	sqfs_u32 size;
 	int err;
 
-	err = sqfs_block_writer_write(proc->wr, blk->size, blk->checksum,
-				      blk->flags, blk->data, &location);
+	err = proc->wr->write_data_block(proc->wr, blk->size, blk->checksum,
+					 blk->flags, blk->data, &location);
 	if (err)
 		goto out;
 
diff --git a/lib/sqfs/block_writer.c b/lib/sqfs/block_writer.c
index 06cbd37..a6ca4b3 100644
--- a/lib/sqfs/block_writer.c
+++ b/lib/sqfs/block_writer.c
@@ -25,8 +25,8 @@ typedef struct {
 	sqfs_u64 hash;
 } blk_info_t;
 
-struct sqfs_block_writer_t {
-	sqfs_object_t base;
+typedef struct {
+	sqfs_block_writer_t base;
 	sqfs_file_t *file;
 
 	size_t num_blocks;
@@ -39,9 +39,9 @@ struct sqfs_block_writer_t {
 
 	sqfs_u64 start;
 	size_t file_start;
-};
+} block_writer_default_t;
 
-static int store_block_location(sqfs_block_writer_t *wr, sqfs_u64 offset,
+static int store_block_location(block_writer_default_t *wr, sqfs_u64 offset,
 				sqfs_u32 size, sqfs_u32 chksum)
 {
 	size_t new_sz;
@@ -64,7 +64,7 @@ static int store_block_location(sqfs_block_writer_t *wr, sqfs_u64 offset,
 	return 0;
 }
 
-static size_t deduplicate_blocks(sqfs_block_writer_t *wr, size_t count)
+static size_t deduplicate_blocks(block_writer_default_t *wr, size_t count)
 {
 	size_t i, j;
 
@@ -85,7 +85,7 @@ static size_t deduplicate_blocks(sqfs_block_writer_t *wr, size_t count)
 	return i;
 }
 
-static int align_file(sqfs_block_writer_t *wr)
+static int align_file(block_writer_default_t *wr)
 {
 	void *padding;
 	sqfs_u64 size;
@@ -111,41 +111,15 @@ static int align_file(sqfs_block_writer_t *wr)
 
 static void block_writer_destroy(sqfs_object_t *wr)
 {
-	free(((sqfs_block_writer_t *)wr)->blocks);
+	free(((block_writer_default_t *)wr)->blocks);
 	free(wr);
 }
 
-sqfs_block_writer_t *sqfs_block_writer_create(sqfs_file_t *file,
-					      size_t devblksz, sqfs_u32 flags)
-{
-	sqfs_block_writer_t *wr;
-
-	if (flags != 0)
-		return NULL;
-
-	wr = calloc(1, sizeof(*wr));
-	if (wr == NULL)
-		return NULL;
-
-	((sqfs_object_t *)wr)->destroy = block_writer_destroy;
-	wr->file = file;
-	wr->devblksz = devblksz;
-	wr->max_blocks = INIT_BLOCK_COUNT;
-	wr->data_area_start = wr->file->get_size(wr->file);
-
-	wr->blocks = alloc_array(sizeof(wr->blocks[0]), wr->max_blocks);
-	if (wr->blocks == NULL) {
-		free(wr);
-		return NULL;
-	}
-
-	return wr;
-}
-
-int sqfs_block_writer_write(sqfs_block_writer_t *wr, sqfs_u32 size,
+static int write_data_block(sqfs_block_writer_t *base, sqfs_u32 size,
 			    sqfs_u32 checksum, sqfs_u32 flags,
 			    const sqfs_u8 *data, sqfs_u64 *location)
 {
+	block_writer_default_t *wr = (block_writer_default_t *)base;
 	size_t start, count;
 	sqfs_u64 offset;
 	sqfs_u32 out;
@@ -219,7 +193,36 @@ int sqfs_block_writer_write(sqfs_block_writer_t *wr, sqfs_u32 size,
 	return 0;
 }
 
-sqfs_u64 sqfs_block_writer_get_block_count(const sqfs_block_writer_t *wr)
+static sqfs_u64 get_block_count(const sqfs_block_writer_t *wr)
 {
-	return wr->blocks_written;
+	return ((const block_writer_default_t *)wr)->blocks_written;
+}
+
+sqfs_block_writer_t *sqfs_block_writer_create(sqfs_file_t *file,
+					      size_t devblksz, sqfs_u32 flags)
+{
+	block_writer_default_t *wr;
+
+	if (flags != 0)
+		return NULL;
+
+	wr = calloc(1, sizeof(*wr));
+	if (wr == NULL)
+		return NULL;
+
+	((sqfs_block_writer_t *)wr)->write_data_block = write_data_block;
+	((sqfs_block_writer_t *)wr)->get_block_count = get_block_count;
+	((sqfs_object_t *)wr)->destroy = block_writer_destroy;
+	wr->file = file;
+	wr->devblksz = devblksz;
+	wr->max_blocks = INIT_BLOCK_COUNT;
+	wr->data_area_start = wr->file->get_size(wr->file);
+
+	wr->blocks = alloc_array(sizeof(wr->blocks[0]), wr->max_blocks);
+	if (wr->blocks == NULL) {
+		free(wr);
+		return NULL;
+	}
+
+	return (sqfs_block_writer_t *)wr;
 }