9 files changed, 425 insertions, 281 deletions

diff --git a/include/common.h b/include/common.h
index f2431ab..bf4bc33 100644
--- a/include/common.h
+++ b/include/common.h
@@ -19,6 +19,7 @@
 #include "sqfs/meta_writer.h"
 #include "sqfs/data_reader.h"
 #include "sqfs/block_processor.h"
+#include "sqfs/block_writer.h"
 #include "sqfs/dir_writer.h"
 #include "sqfs/dir_reader.h"
 #include "sqfs/block.h"
diff --git a/include/sqfs/block_processor.h b/include/sqfs/block_processor.h
index c6dd734..a1e6f2b 100644
--- a/include/sqfs/block_processor.h
+++ b/include/sqfs/block_processor.h
@@ -43,112 +43,6 @@
  * and finally writing it to disk.
  */
 
-/**
- * @struct sqfs_block_hooks_t
- *
- * @brief A set of hooks for tapping into the data writer.
- *
- * This structure can be registered with an @ref sqfs_block_processor_t and
- * contains function pointers that will be called during various stages
- * when writing data to disk.
- *
- * The callbacks can not only be used for accounting but may also write extra
- * data to the output file or make modifications to the blocks before they are
- * writtien.
- *
- * The callbacks can be individually set to NULL to disable them.
- */
-struct sqfs_block_hooks_t {
-	/**
-	 * @brief Set this to the size of the struct.
-	 *
-	 * This is required for future expandabillity while maintaining ABI
-	 * compatibillity. At the current time, the implementation of
-	 * @ref sqfs_block_processor_set_hooks rejects any hook struct where
-	 * this isn't the exact size. If new hooks are added in the future,
-	 * the struct grows and the future implementation can tell by the size
-	 * whether the application uses the new version or the old one.
-	 */
-	size_t size;
-
-	/**
-	 * @brief Gets called before writing a block to disk.
-	 *
-	 * If this is not NULL, it gets called before a block is written to
-	 * disk. If the block has the @ref SQFS_BLK_ALIGN flag set, the
-	 * function is called before padding the file.
-	 *
-	 * The function may modify the block itself or write data to the file.
-	 * which is taken into account when padding the file.
-	 *
-	 * @param user A user pointer.
-	 * @param block The block that is about to be written.
-	 * @param file The file that the block will be written to.
-	 */
-	void (*pre_block_write)(void *user, sqfs_block_t *block,
-				sqfs_file_t *file);
-
-	/**
-	 * @brief Gets called after writing a block to disk.
-	 *
-	 * If this is not NULL, it gets called after a block is written to
-	 * disk. If the block has the @ref SQFS_BLK_ALIGN flag set, the
-	 * function is called before padding the file.
-	 *
-	 * Modifying the block is rather pointless, but the function may
-	 * write data to the file which is taken into account when padding
-	 * the file.
-	 *
-	 * @param user A user pointer.
-	 * @param block The block that is about to be written.
-	 * @param file The file that the block was written to.
-	 */
-	void (*post_block_write)(void *user, const sqfs_block_t *block,
-				 sqfs_file_t *file);
-
-	/**
-	 * @brief Gets called before storing a fragment in a fragment block.
-	 *
-	 * The function can modify the block before it is stored.
-	 *
-	 * @param user A user pointer.
-	 * @param block The data chunk that is about to be merged into the
-	 *              fragment block.
-	 */
-	void (*pre_fragment_store)(void *user, sqfs_block_t *block);
-
-	/**
-	 * @brief Gets called if block deduplication managed to get
-	 *        rid of the data blocks of a file.
-	 *
-	 * @param user A user pointer.
-	 * @param count The number of blocks that have been erased.
-	 * @param bytes The number of bytes that have been erased. Includes
-	 *              potential padding before and after the end.
-	 */
-	void (*notify_blocks_erased)(void *user, size_t count,
-				     sqfs_u64 bytes);
-
-	/**
-	 * @brief Gets called before throwing away a fragment that turned out
-	 *        to be a duplicate.
-	 *
-	 * @param user A user pointer.
-	 * @param block The data chunk that is about to be merged into the
-	 *              fragment block.
-	 */
-	void (*notify_fragment_discard)(void *user, const sqfs_block_t *block);
-
-	/**
-	 * @brief Gets called before writing a block of padding bytes to disk.
-	 *
-	 * @param user A user pointer.
-	 * @param block The padding bytes that are about to be written.
-	 * @param count The number of padding bytes in the block.
-	 */
-	void (*prepare_padding)(void *user, sqfs_u8 *block, size_t count);
-};
-
 #ifdef __cplusplus
 extern "C" {
 #endif
diff --git a/include/sqfs/block_writer.h b/include/sqfs/block_writer.h
new file mode 100644
index 0000000..b4d804c
--- /dev/null
+++ b/include/sqfs/block_writer.h
@@ -0,0 +1,165 @@
+/* SPDX-License-Identifier: LGPL-3.0-or-later */
+/*
+ * block_writer.h - This file is part of libsquashfs
+ *
+ * Copyright (C) 2019 David Oberhollenzer <goliath@infraroot.at>
+ *
+ * This program is free software: you can redistribute it and/or modify
+ * it under the terms of the GNU Lesser General Public License as published
+ * by the Free Software Foundation, either version 3 of the License, or
+ * (at your option) any later version.
+ *
+ * This program is distributed in the hope that it will be useful,
+ * but WITHOUT ANY WARRANTY; without even the implied warranty of
+ * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+ * GNU General Public License for more details.
+ *
+ * You should have received a copy of the GNU Lesser General Public License
+ * along with this program.  If not, see <https://www.gnu.org/licenses/>.
+ */
+#ifndef SQFS_BLOCK_WRITER_H
+#define SQFS_BLOCK_WRITER_H
+
+#include "sqfs/predef.h"
+
+/**
+ * @file block_writer.h
+ *
+ * @brief Contains declarations for the @ref sqfs_block_writer_t structure.
+ */
+
+/**
+ * @struct sqfs_block_writer_t
+ *
+ * @brief Abstracts writing and deduplicating of data and fragment blocks.
+ */
+
+/**
+ * @struct sqfs_block_hooks_t
+ *
+ * @brief A set of hooks for tapping into the data writer.
+ *
+ * This structure can be registered with an @ref sqfs_block_writer_t and
+ * contains function pointers that will be called during various stages
+ * when writing data to disk.
+ *
+ * The callbacks can not only be used for accounting but may also write extra
+ * data to the output file or make modifications to the blocks before they are
+ * writtien.
+ *
+ * The callbacks can be individually set to NULL to disable them.
+ */
+struct sqfs_block_hooks_t {
+	/**
+	 * @brief Set this to the size of the struct.
+	 *
+	 * This is required for future expandabillity while maintaining ABI
+	 * compatibillity. At the current time, the implementation of
+	 * @ref sqfs_block_writer_set_hooks rejects any hook struct where
+	 * this isn't the exact size. If new hooks are added in the future,
+	 * the struct grows and the future implementation can tell by the size
+	 * whether the application uses the new version or the old one.
+	 */
+	size_t size;
+
+	/**
+	 * @brief Gets called before writing a block to disk.
+	 *
+	 * If this is not NULL, it gets called before a block is written to
+	 * disk. If the block has the @ref SQFS_BLK_ALIGN flag set, the
+	 * function is called before padding the file.
+	 *
+	 * The function may modify the block itself or write data to the file.
+	 * which is taken into account when padding the file.
+	 *
+	 * @param user A user pointer.
+	 * @param block The block that is about to be written.
+	 * @param file The file that the block will be written to.
+	 */
+	void (*pre_block_write)(void *user, sqfs_block_t *block,
+				sqfs_file_t *file);
+
+	/**
+	 * @brief Gets called after writing a block to disk.
+	 *
+	 * If this is not NULL, it gets called after a block is written to
+	 * disk. If the block has the @ref SQFS_BLK_ALIGN flag set, the
+	 * function is called before padding the file.
+	 *
+	 * Modifying the block is rather pointless, but the function may
+	 * write data to the file which is taken into account when padding
+	 * the file.
+	 *
+	 * @param user A user pointer.
+	 * @param block The block that is about to be written.
+	 * @param file The file that the block was written to.
+	 */
+	void (*post_block_write)(void *user, const sqfs_block_t *block,
+				 sqfs_file_t *file);
+
+	/**
+	 * @brief Gets called before storing a fragment in a fragment block.
+	 *
+	 * The function can modify the block before it is stored.
+	 *
+	 * @param user A user pointer.
+	 * @param block The data chunk that is about to be merged into the
+	 *              fragment block.
+	 */
+	void (*pre_fragment_store)(void *user, sqfs_block_t *block);
+
+	/**
+	 * @brief Gets called if block deduplication managed to get
+	 *        rid of the data blocks of a file.
+	 *
+	 * @param user A user pointer.
+	 * @param count The number of blocks that have been erased.
+	 * @param bytes The number of bytes that have been erased. Includes
+	 *              potential padding before and after the end.
+	 */
+	void (*notify_blocks_erased)(void *user, size_t count,
+				     sqfs_u64 bytes);
+
+	/**
+	 * @brief Gets called before throwing away a fragment that turned out
+	 *        to be a duplicate.
+	 *
+	 * @param user A user pointer.
+	 * @param block The data chunk that is about to be merged into the
+	 *              fragment block.
+	 */
+	void (*notify_fragment_discard)(void *user, const sqfs_block_t *block);
+
+	/**
+	 * @brief Gets called before writing a block of padding bytes to disk.
+	 *
+	 * @param user A user pointer.
+	 * @param block The padding bytes that are about to be written.
+	 * @param count The number of padding bytes in the block.
+	 */
+	void (*prepare_padding)(void *user, sqfs_u8 *block, size_t count);
+};
+
+#ifdef __cplusplus
+extern "C" {
+#endif
+
+SQFS_API sqfs_block_writer_t *sqfs_block_writer_create(sqfs_file_t *file,
+						       size_t devblksz,
+						       sqfs_u32 flags);
+
+SQFS_API int sqfs_block_writer_set_hooks(sqfs_block_writer_t *wr,
+					 void *user_ptr,
+					 const sqfs_block_hooks_t *hooks);
+
+SQFS_API void sqfs_block_writer_destroy(sqfs_block_writer_t *wr);
+
+SQFS_API int sqfs_block_writer_write(sqfs_block_writer_t *wr,
+				     sqfs_block_t *block,
+				     sqfs_u64 *location);
+
+#ifdef __cplusplus
+}
+#endif
+
+#endif /* SQFS_BLOCK_WRITER_H */
diff --git a/include/sqfs/predef.h b/include/sqfs/predef.h
index 924aecc..40d0e5d 100644
--- a/include/sqfs/predef.h
+++ b/include/sqfs/predef.h
@@ -83,6 +83,7 @@ typedef struct sqfs_data_reader_t sqfs_data_reader_t;
 typedef struct sqfs_block_hooks_t sqfs_block_hooks_t;
 typedef struct sqfs_xattr_writer_t sqfs_xattr_writer_t;
 typedef struct sqfs_frag_table_t sqfs_frag_table_t;
+typedef struct sqfs_block_writer_t sqfs_block_writer_t;
 
 typedef struct sqfs_fragment_t sqfs_fragment_t;
 typedef struct sqfs_dir_header_t sqfs_dir_header_t;
diff --git a/lib/sqfs/Makemodule.am b/lib/sqfs/Makemodule.am
index cde947d..644ced2 100644
--- a/lib/sqfs/Makemodule.am
+++ b/lib/sqfs/Makemodule.am
@@ -8,7 +8,7 @@ LIBSQFS_HEARDS = include/sqfs/meta_writer.h \
 		include/sqfs/dir_writer.h include/sqfs/io.h \
 		include/sqfs/data_reader.h include/sqfs/block.h \
 		include/sqfs/xattr_reader.h include/sqfs/xattr_writer.h \
-		include/sqfs/frag_table.h
+		include/sqfs/frag_table.h include/sqfs/block_writer.h
 
 libsquashfs_la_SOURCES = $(LIBSQFS_HEARDS) lib/sqfs/id_table.c lib/sqfs/super.c
 libsquashfs_la_SOURCES += lib/sqfs/readdir.c lib/sqfs/xattr.c
@@ -28,6 +28,7 @@ libsquashfs_la_SOURCES += lib/sqfs/block_processor/fileapi.c
 libsquashfs_la_SOURCES += lib/sqfs/str_table.c lib/sqfs/str_table.h
 libsquashfs_la_SOURCES += lib/sqfs/alloc.c lib/sqfs/util.h
 libsquashfs_la_SOURCES += lib/sqfs/frag_table.c include/sqfs/frag_table.h
+libsquashfs_la_SOURCES += lib/sqfs/block_writer.c include/sqfs/block_writer.h
 libsquashfs_la_CPPFLAGS = $(AM_CPPFLAGS)
 libsquashfs_la_LDFLAGS = $(AM_LDFLAGS)
 libsquashfs_la_CFLAGS = $(AM_CFLAGS) $(PTHREAD_CFLAGS) $(ZLIB_CFLAGS)
diff --git a/lib/sqfs/block_processor/block.c b/lib/sqfs/block_processor/block.c
index 49892be..e88456a 100644
--- a/lib/sqfs/block_processor/block.c
+++ b/lib/sqfs/block_processor/block.c
@@ -9,164 +9,33 @@
 
 #include <string.h>
 
-static int store_block_location(sqfs_block_processor_t *proc, sqfs_u64 offset,
-				sqfs_u32 size, sqfs_u32 chksum)
-{
-	size_t new_sz;
-	void *new;
-
-	if (proc->num_blocks == proc->max_blocks) {
-		new_sz = proc->max_blocks * 2;
-		new = realloc(proc->blocks, sizeof(proc->blocks[0]) * new_sz);
-
-		if (new == NULL)
-			return SQFS_ERROR_ALLOC;
-
-		proc->blocks = new;
-		proc->max_blocks = new_sz;
-	}
-
-	proc->blocks[proc->num_blocks].offset = offset;
-	proc->blocks[proc->num_blocks].hash = MK_BLK_HASH(chksum, size);
-	proc->num_blocks += 1;
-	return 0;
-}
-
-static size_t deduplicate_blocks(sqfs_block_processor_t *proc, size_t count)
-{
-	size_t i, j;
-
-	for (i = 0; i < proc->file_start; ++i) {
-		for (j = 0; j < count; ++j) {
-			if (proc->blocks[i + j].hash !=
-			    proc->blocks[proc->file_start + j].hash)
-				break;
-		}
-
-		if (j == count)
-			break;
-	}
-
-	return i;
-}
-
-static int align_file(sqfs_block_processor_t *proc, sqfs_block_t *blk)
-{
-	sqfs_u32 chksum;
-	void *padding;
-	sqfs_u64 size;
-	size_t diff;
-	int ret;
-
-	if (!(blk->flags & SQFS_BLK_ALIGN))
-		return 0;
-
-	size = proc->file->get_size(proc->file);
-	diff = size % proc->devblksz;
-	if (diff == 0)
-		return 0;
-
-	padding = calloc(1, diff);
-	if (padding == 0)
-		return SQFS_ERROR_ALLOC;
-
-	if (proc->hooks != NULL && proc->hooks->prepare_padding != NULL)
-		proc->hooks->prepare_padding(proc->user_ptr, padding, diff);
-
-	chksum = crc32(0, padding, diff);
-
-	ret = proc->file->write_at(proc->file, size, padding, diff);
-	free(padding);
-	if (ret)
-		return ret;
-
-	return store_block_location(proc, size, diff | (1 << 24), chksum);
-}
-
 int process_completed_block(sqfs_block_processor_t *proc, sqfs_block_t *blk)
 {
-	sqfs_u64 offset, bytes;
-	size_t start, count;
-	sqfs_u32 out;
+	sqfs_u64 location;
+	sqfs_u32 size;
 	int err;
 
-	if (proc->hooks != NULL && proc->hooks->pre_block_write != NULL) {
-		proc->hooks->pre_block_write(proc->user_ptr, blk, proc->file);
-	}
-
-	if (blk->flags & SQFS_BLK_FIRST_BLOCK) {
-		proc->start = proc->file->get_size(proc->file);
-		proc->file_start = proc->num_blocks;
+	size = blk->size;
+	if (!(blk->flags & SQFS_BLK_IS_COMPRESSED))
+		size |= 1 << 24;
 
-		err = align_file(proc, blk);
-		if (err)
-			return err;
-	}
+	err = sqfs_block_writer_write(proc->wr, blk, &location);
+	if (err)
+		return err;
 
 	if (blk->size != 0) {
-		out = blk->size;
-		if (!(blk->flags & SQFS_BLK_IS_COMPRESSED))
-			out |= 1 << 24;
-
-		offset = proc->file->get_size(proc->file);
-
 		if (blk->flags & SQFS_BLK_FRAGMENT_BLOCK) {
 			err = sqfs_frag_table_set(proc->frag_tbl, blk->index,
-						  offset, out);
+						  location, size);
 			if (err)
 				return err;
 		} else {
-			blk->inode->extra[blk->index] = out;
+			blk->inode->extra[blk->index] = size;
 		}
-
-		err = store_block_location(proc, offset, out, blk->checksum);
-		if (err)
-			return err;
-
-		err = proc->file->write_at(proc->file, offset,
-					   blk->data, blk->size);
-		if (err)
-			return err;
-	}
-
-	if (proc->hooks != NULL && proc->hooks->post_block_write != NULL) {
-		proc->hooks->post_block_write(proc->user_ptr, blk, proc->file);
 	}
 
-	if (blk->flags & SQFS_BLK_LAST_BLOCK) {
-		err = align_file(proc, blk);
-		if (err)
-			return err;
-
-		count = proc->num_blocks - proc->file_start;
-		start = deduplicate_blocks(proc, count);
-		offset = proc->blocks[start].offset;
-
-		sqfs_inode_set_file_block_start(blk->inode, offset);
-
-		if (start >= proc->file_start)
-			return 0;
-
-		offset = start + count;
-		if (offset >= proc->file_start) {
-			count = proc->num_blocks - offset;
-			proc->num_blocks = offset;
-		} else {
-			proc->num_blocks = proc->file_start;
-		}
-
-		if (proc->hooks != NULL &&
-		    proc->hooks->notify_blocks_erased != NULL) {
-			bytes = proc->file->get_size(proc->file) - proc->start;
-
-			proc->hooks->notify_blocks_erased(proc->user_ptr,
-							  count, bytes);
-		}
-
-		err = proc->file->truncate(proc->file, proc->start);
-		if (err)
-			return err;
-	}
+	if (blk->flags & SQFS_BLK_LAST_BLOCK)
+		sqfs_inode_set_file_block_start(blk->inode, location);
 
 	return 0;
 }
diff --git a/lib/sqfs/block_processor/common.c b/lib/sqfs/block_processor/common.c
index c6375dd..806a595 100644
--- a/lib/sqfs/block_processor/common.c
+++ b/lib/sqfs/block_processor/common.c
@@ -25,19 +25,16 @@ int block_processor_init(sqfs_block_processor_t *proc, size_t max_block_size,
 	proc->max_block_size = max_block_size;
 	proc->num_workers = num_workers;
 	proc->max_backlog = max_backlog;
-	proc->devblksz = devblksz;
 	proc->cmp = cmp;
 	proc->file = file;
-	proc->max_blocks = INIT_BLOCK_COUNT;
 
 	proc->frag_tbl = sqfs_frag_table_create(0);
 	if (proc->frag_tbl == NULL)
 		return -1;
 
-	proc->blocks = alloc_array(sizeof(proc->blocks[0]), proc->max_blocks);
-	if (proc->blocks == NULL)
+	proc->wr = sqfs_block_writer_create(file, devblksz, 0);
+	if (proc->wr == NULL)
 		return -1;
-
 	return 0;
 }
 
@@ -45,11 +42,12 @@ void block_processor_cleanup(sqfs_block_processor_t *proc)
 {
 	if (proc->frag_tbl != NULL)
 		sqfs_frag_table_destroy(proc->frag_tbl);
+	if (proc->wr != NULL)
+		sqfs_block_writer_destroy(proc->wr);
 	free_blk_list(proc->queue);
 	free_blk_list(proc->done);
 	free(proc->blk_current);
 	free(proc->frag_block);
-	free(proc->blocks);
 	free(proc);
 }
 
@@ -63,10 +61,8 @@ int sqfs_block_processor_write_fragment_table(sqfs_block_processor_t *proc,
 int sqfs_block_processor_set_hooks(sqfs_block_processor_t *proc, void *user_ptr,
 				   const sqfs_block_hooks_t *hooks)
 {
-	if (hooks->size != sizeof(*hooks))
-		return SQFS_ERROR_UNSUPPORTED;
-
 	proc->hooks = hooks;
 	proc->user_ptr = user_ptr;
-	return 0;
+
+	return sqfs_block_writer_set_hooks(proc->wr, user_ptr, hooks);
 }
diff --git a/lib/sqfs/block_processor/internal.h b/lib/sqfs/block_processor/internal.h
index 40871b9..16f0edb 100644
--- a/lib/sqfs/block_processor/internal.h
+++ b/lib/sqfs/block_processor/internal.h
@@ -10,6 +10,7 @@
 #include "config.h"
 
 #include "sqfs/block_processor.h"
+#include "sqfs/block_writer.h"
 #include "sqfs/frag_table.h"
 #include "sqfs/compressor.h"
 #include "sqfs/inode.h"
@@ -31,19 +32,6 @@
 #include <windows.h>
 #endif
 
-
-#define MK_BLK_HASH(chksum, size) \
-	(((sqfs_u64)(size) << 32) | (sqfs_u64)(chksum))
-
-#define INIT_BLOCK_COUNT (128)
-
-
-typedef struct {
-	sqfs_u64 offset;
-	sqfs_u64 hash;
-} blk_info_t;
-
-
 typedef struct compress_worker_t compress_worker_t;
 
 struct sqfs_block_processor_t {
@@ -73,24 +61,18 @@ struct sqfs_block_processor_t {
 	unsigned int num_workers;
 	size_t max_backlog;
 
-	size_t devblksz;
 	sqfs_file_t *file;
 
 	sqfs_frag_table_t *frag_tbl;
 
-	sqfs_u64 start;
-
-	size_t file_start;
-	size_t num_blocks;
-	size_t max_blocks;
-	blk_info_t *blocks;
 	sqfs_compressor_t *cmp;
 
 	sqfs_block_t *frag_block;
+	bool notify_threads;
 
+	sqfs_block_writer_t *wr;
 	const sqfs_block_hooks_t *hooks;
 	void *user_ptr;
-	bool notify_threads;
 
 	/* file API */
 	sqfs_inode_generic_t *inode;
diff --git a/lib/sqfs/block_writer.c b/lib/sqfs/block_writer.c
new file mode 100644
index 0000000..c955532
--- /dev/null
+++ b/lib/sqfs/block_writer.c
@@ -0,0 +1,235 @@
+/* SPDX-License-Identifier: LGPL-3.0-or-later */
+/*
+ * block_writer.c
+ *
+ * Copyright (C) 2019 David Oberhollenzer <goliath@infraroot.at>
+ */
+#define SQFS_BUILDING_DLL
+#include "config.h"
+
+#include "sqfs/block_writer.h"
+#include "sqfs/error.h"
+#include "sqfs/block.h"
+#include "sqfs/io.h"
+#include "util.h"
+
+#include <stdlib.h>
+
+#define MK_BLK_HASH(chksum, size) \
+	(((sqfs_u64)(size) << 32) | (sqfs_u64)(chksum))
+
+#define INIT_BLOCK_COUNT (128)
+
+typedef struct {
+	sqfs_u64 offset;
+	sqfs_u64 hash;
+} blk_info_t;
+
+struct sqfs_block_writer_t {
+	sqfs_file_t *file;
+
+	size_t num_blocks;
+	size_t max_blocks;
+	blk_info_t *blocks;
+	size_t devblksz;
+
+	const sqfs_block_hooks_t *hooks;
+	void *user_ptr;
+
+	sqfs_u64 start;
+	size_t file_start;
+};
+
+static int store_block_location(sqfs_block_writer_t *wr, sqfs_u64 offset,
+				sqfs_u32 size, sqfs_u32 chksum)
+{
+	size_t new_sz;
+	void *new;
+
+	if (wr->num_blocks == wr->max_blocks) {
+		new_sz = wr->max_blocks * 2;
+		new = realloc(wr->blocks, sizeof(wr->blocks[0]) * new_sz);
+
+		if (new == NULL)
+			return SQFS_ERROR_ALLOC;
+
+		wr->blocks = new;
+		wr->max_blocks = new_sz;
+	}
+
+	wr->blocks[wr->num_blocks].offset = offset;
+	wr->blocks[wr->num_blocks].hash = MK_BLK_HASH(chksum, size);
+	wr->num_blocks += 1;
+	return 0;
+}
+
+static size_t deduplicate_blocks(sqfs_block_writer_t *wr, size_t count)
+{
+	size_t i, j;
+
+	for (i = 0; i < wr->file_start; ++i) {
+		for (j = 0; j < count; ++j) {
+			if (wr->blocks[i + j].hash == 0)
+				break;
+
+			if (wr->blocks[i + j].hash !=
+			    wr->blocks[wr->file_start + j].hash)
+				break;
+		}
+
+		if (j == count)
+			break;
+	}
+
+	return i;
+}
+
+static int align_file(sqfs_block_writer_t *wr, sqfs_block_t *blk)
+{
+	void *padding;
+	sqfs_u64 size;
+	size_t diff;
+	int ret;
+
+	if (!(blk->flags & SQFS_BLK_ALIGN))
+		return 0;
+
+	size = wr->file->get_size(wr->file);
+	diff = size % wr->devblksz;
+	if (diff == 0)
+		return 0;
+
+	padding = calloc(1, diff);
+	if (padding == 0)
+		return SQFS_ERROR_ALLOC;
+
+	if (wr->hooks != NULL && wr->hooks->prepare_padding != NULL)
+		wr->hooks->prepare_padding(wr->user_ptr, padding, diff);
+
+	ret = wr->file->write_at(wr->file, size, padding, diff);
+	free(padding);
+	if (ret)
+		return ret;
+
+	return store_block_location(wr, size, 0, 0);
+}
+
+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;
+
+	wr->file = file;
+	wr->devblksz = devblksz;
+	wr->max_blocks = INIT_BLOCK_COUNT;
+
+	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_set_hooks(sqfs_block_writer_t *wr, void *user_ptr,
+				const sqfs_block_hooks_t *hooks)
+{
+	if (hooks->size != sizeof(*hooks))
+		return SQFS_ERROR_UNSUPPORTED;
+
+	wr->hooks = hooks;
+	wr->user_ptr = user_ptr;
+	return 0;
+}
+
+void sqfs_block_writer_destroy(sqfs_block_writer_t *wr)
+{
+	free(wr->blocks);
+	free(wr);
+}
+
+int sqfs_block_writer_write(sqfs_block_writer_t *wr, sqfs_block_t *block,
+			    sqfs_u64 *location)
+{
+	sqfs_u64 offset, bytes;
+	size_t start, count;
+	sqfs_u32 out;
+	int err;
+
+	if (wr->hooks != NULL && wr->hooks->pre_block_write != NULL)
+		wr->hooks->pre_block_write(wr->user_ptr, block, wr->file);
+
+	if (block->flags & SQFS_BLK_FIRST_BLOCK) {
+		wr->start = wr->file->get_size(wr->file);
+		wr->file_start = wr->num_blocks;
+
+		err = align_file(wr, block);
+		if (err)
+			return err;
+	}
+
+	if (block->size != 0) {
+		out = block->size;
+		if (!(block->flags & SQFS_BLK_IS_COMPRESSED))
+			out |= 1 << 24;
+
+		offset = wr->file->get_size(wr->file);
+		*location = offset;
+
+		err = store_block_location(wr, offset, out, block->checksum);
+		if (err)
+			return err;
+
+		err = wr->file->write_at(wr->file, offset,
+					 block->data, block->size);
+		if (err)
+			return err;
+	}
+
+	if (wr->hooks != NULL && wr->hooks->post_block_write != NULL)
+		wr->hooks->post_block_write(wr->user_ptr, block, wr->file);
+
+	if (block->flags & SQFS_BLK_LAST_BLOCK) {
+		err = align_file(wr, block);
+		if (err)
+			return err;
+
+		count = wr->num_blocks - wr->file_start;
+		start = deduplicate_blocks(wr, count);
+		offset = wr->blocks[start].offset;
+
+		*location = offset;
+		if (start >= wr->file_start)
+			return 0;
+
+		offset = start + count;
+		if (offset >= wr->file_start) {
+			count = wr->num_blocks - offset;
+			wr->num_blocks = offset;
+		} else {
+			wr->num_blocks = wr->file_start;
+		}
+
+		if (wr->hooks != NULL &&
+		    wr->hooks->notify_blocks_erased != NULL) {
+			bytes = wr->file->get_size(wr->file) - wr->start;
+
+			wr->hooks->notify_blocks_erased(wr->user_ptr,
+							count, bytes);
+		}
+
+		err = wr->file->truncate(wr->file, wr->start);
+		if (err)
+			return err;
+	}
+
+	return 0;
+}