Replace direct file I/O with abstraction layer

This should make it easier to use libsquashfs with custom setups that
embedd a squashfs image inside something else. Also, it should make
it easier to port to non unix-like platforms.

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

13 files changed, 67 insertions, 18 deletions

diff --git a/include/data_reader.h b/include/data_reader.h
index a45c3e2..846ffd1 100644
--- a/include/data_reader.h
+++ b/include/data_reader.h
@@ -23,7 +23,7 @@ typedef struct data_reader_t data_reader_t;
 
   Prints error messsages to stderr on failure.
  */
-data_reader_t *data_reader_create(int fd, sqfs_super_t *super,
+data_reader_t *data_reader_create(sqfs_file_t *file, sqfs_super_t *super,
 				  sqfs_compressor_t *cmp);
 
 void data_reader_destroy(data_reader_t *data);
diff --git a/include/data_writer.h b/include/data_writer.h
index 89eb2c8..4d86bbf 100644
--- a/include/data_writer.h
+++ b/include/data_writer.h
@@ -36,7 +36,7 @@ enum {
   Returns NULL on failure and prints errors to stderr.
  */
 data_writer_t *data_writer_create(sqfs_super_t *super, sqfs_compressor_t *cmp,
-				  int outfd, size_t devblksize,
+				  sqfs_file_t *file, size_t devblksize,
 				  unsigned int num_jobs);
 
 void data_writer_destroy(data_writer_t *data);
diff --git a/include/highlevel.h b/include/highlevel.h
index ffcc44c..4c560f7 100644
--- a/include/highlevel.h
+++ b/include/highlevel.h
@@ -17,6 +17,7 @@
 #include "sqfs/meta_writer.h"
 #include "sqfs/xattr.h"
 #include "sqfs/dir.h"
+#include "sqfs/io.h"
 #include "data_reader.h"
 #include "fstree.h"
 
@@ -26,9 +27,9 @@
 typedef struct {
 	sqfs_compressor_t *cmp;
 	data_reader_t *data;
+	sqfs_file_t *file;
 	sqfs_super_t super;
 	fstree_t fs;
-	int sqfsfd;
 } sqfs_reader_t;
 
 enum RDTREE_FLAGS {
@@ -52,7 +53,7 @@ enum RDTREE_FLAGS {
 
   Returns 0 on success. Prints error messages to stderr on failure.
  */
-int sqfs_serialize_fstree(int outfd, sqfs_super_t *super, fstree_t *fs,
+int sqfs_serialize_fstree(sqfs_file_t *file, sqfs_super_t *super, fstree_t *fs,
 			  sqfs_compressor_t *cmp, sqfs_id_table_t *idtbl);
 
 /*
@@ -72,14 +73,14 @@ tree_node_t *tree_node_from_inode(sqfs_inode_generic_t *inode,
   Returns 0 on success. Prints error messages to stderr on failure.
  */
 int deserialize_fstree(fstree_t *out, sqfs_super_t *super,
-		       sqfs_compressor_t *cmp, int fd, int flags);
+		       sqfs_compressor_t *cmp, sqfs_file_t *file, int flags);
 
 /*
   Generate a squahfs xattr table from a file system tree.
 
   Returns 0 on success. Prints error messages to stderr on failure.
  */
-int write_xattr(int outfd, fstree_t *fs, sqfs_super_t *super,
+int write_xattr(sqfs_file_t *file, fstree_t *fs, sqfs_super_t *super,
 		sqfs_compressor_t *cmp);
 
 /*
@@ -87,7 +88,7 @@ int write_xattr(int outfd, fstree_t *fs, sqfs_super_t *super,
 
   Returns 0 on success. Prints error messages to stderr on failure.
  */
-int write_export_table(int outfd, fstree_t *fs, sqfs_super_t *super,
+int write_export_table(sqfs_file_t *file, fstree_t *fs, sqfs_super_t *super,
 		       sqfs_compressor_t *cmp);
 
 /* Print out fancy statistics for squashfs packing tools */
diff --git a/include/sqfs/compress.h b/include/sqfs/compress.h
index f0e3b76..e781e02 100644
--- a/include/sqfs/compress.h
+++ b/include/sqfs/compress.h
@@ -18,12 +18,12 @@ struct sqfs_compressor_t {
 	/* Write compressor options to the output file if necessary.
 	   Returns the number of bytes written or -1 on failure.
 	   Internally prints error messages to stderr. */
-	int (*write_options)(sqfs_compressor_t *cmp, int fd);
+	int (*write_options)(sqfs_compressor_t *cmp, sqfs_file_t *file);
 
 	/* Read compressor options to the input file.
 	   Returns zero on success, -1 on failure.
 	   Internally prints error messages to stderr. */
-	int (*read_options)(sqfs_compressor_t *cmp, int fd);
+	int (*read_options)(sqfs_compressor_t *cmp, sqfs_file_t *file);
 
 	/*
 	  Compress or uncompress a chunk of data.
diff --git a/include/sqfs/id_table.h b/include/sqfs/id_table.h
index 3610640..6b058ae 100644
--- a/include/sqfs/id_table.h
+++ b/include/sqfs/id_table.h
@@ -25,12 +25,12 @@ SQFS_API int sqfs_id_table_id_to_index(sqfs_id_table_t *tbl, uint32_t id,
 
 /* Write an ID table to a SquashFS image.
    Returns 0 on success. Internally prints error message to stderr. */
-SQFS_API int sqfs_id_table_write(sqfs_id_table_t *tbl, int outfd,
+SQFS_API int sqfs_id_table_write(sqfs_id_table_t *tbl, sqfs_file_t *file,
 				 sqfs_super_t *super, sqfs_compressor_t *cmp);
 
 /* Read an ID table from a SquashFS image.
    Returns 0 on success. Internally prints error messages to stderr. */
-SQFS_API int sqfs_id_table_read(sqfs_id_table_t *tbl, int fd,
+SQFS_API int sqfs_id_table_read(sqfs_id_table_t *tbl, sqfs_file_t *file,
 				sqfs_super_t *super, sqfs_compressor_t *cmp);
 
 SQFS_API int sqfs_id_table_index_to_id(const sqfs_id_table_t *tbl,
diff --git a/include/sqfs/io.h b/include/sqfs/io.h
new file mode 100644
index 0000000..f290c2d
--- /dev/null
+++ b/include/sqfs/io.h
@@ -0,0 +1,44 @@
+/* SPDX-License-Identifier: GPL-3.0-or-later */
+/*
+ * io.h
+ *
+ * Copyright (C) 2019 David Oberhollenzer <goliath@infraroot.at>
+ */
+#ifndef SQFS_IO_H
+#define SQFS_IO_H
+
+#include "sqfs/predef.h"
+
+typedef enum {
+	SQFS_FILE_OPEN_READ_ONLY = 0x01,
+
+	SQFS_FILE_OPEN_OVERWRITE = 0x02,
+
+	SQFS_FILE_OPEN_ALL_FLAGS = 0x03,
+} E_SQFS_FILE_OPEN_FLAGS;
+
+struct sqfs_file_t {
+	void (*destroy)(sqfs_file_t *file);
+
+	int (*read_at)(sqfs_file_t *file, uint64_t offset,
+		       void *buffer, size_t size);
+
+	int (*write_at)(sqfs_file_t *file, uint64_t offset,
+			const void *buffer, size_t size);
+
+	uint64_t (*get_size)(sqfs_file_t *file);
+
+	int (*truncate)(sqfs_file_t *file, uint64_t size);
+};
+
+#ifdef __cplusplus
+extern "C" {
+#endif
+
+SQFS_API sqfs_file_t *sqfs_open_file(const char *filename, int flags);
+
+#ifdef __cplusplus
+}
+#endif
+
+#endif /* SQFS_IO_H */
diff --git a/include/sqfs/meta_reader.h b/include/sqfs/meta_reader.h
index f5008d4..00a6d65 100644
--- a/include/sqfs/meta_reader.h
+++ b/include/sqfs/meta_reader.h
@@ -19,7 +19,7 @@ extern "C" {
    Start offset and limit can be specified to do bounds checking against
    a subregion of the filesystem image.
 */
-SQFS_API sqfs_meta_reader_t *sqfs_meta_reader_create(int fd,
+SQFS_API sqfs_meta_reader_t *sqfs_meta_reader_create(sqfs_file_t *file,
 						     sqfs_compressor_t *cmp,
 						     uint64_t start,
 						     uint64_t limit);
diff --git a/include/sqfs/meta_writer.h b/include/sqfs/meta_writer.h
index 9cd1598..3b255f2 100644
--- a/include/sqfs/meta_writer.h
+++ b/include/sqfs/meta_writer.h
@@ -18,7 +18,7 @@ extern "C" {
    If keep_in_mem is true, the blocks are collected in memory and must
    be explicitly flushed to disk using meta_write_write_to_file.
 */
-SQFS_API sqfs_meta_writer_t *sqfs_meta_writer_create(int fd,
+SQFS_API sqfs_meta_writer_t *sqfs_meta_writer_create(sqfs_file_t *file,
 						     sqfs_compressor_t *cmp,
 						     bool keep_in_mem);
 
diff --git a/include/sqfs/predef.h b/include/sqfs/predef.h
index 6df257c..df08b1b 100644
--- a/include/sqfs/predef.h
+++ b/include/sqfs/predef.h
@@ -47,6 +47,7 @@ typedef struct sqfs_id_table_t sqfs_id_table_t;
 typedef struct sqfs_meta_reader_t sqfs_meta_reader_t;
 typedef struct sqfs_meta_writer_t sqfs_meta_writer_t;
 typedef struct sqfs_xattr_reader_t sqfs_xattr_reader_t;
+typedef struct sqfs_file_t sqfs_file_t;
 
 typedef struct sqfs_fragment_t sqfs_fragment_t;
 typedef struct sqfs_dir_header_t sqfs_dir_header_t;
diff --git a/include/sqfs/super.h b/include/sqfs/super.h
index b1ce82b..a8697a1 100644
--- a/include/sqfs/super.h
+++ b/include/sqfs/super.h
@@ -73,10 +73,10 @@ SQFS_API int sqfs_super_init(sqfs_super_t *super, size_t block_size,
 			     E_SQFS_COMPRESSOR compressor);
 
 /* Returns 0 on success. Prints error messages to stderr on failure. */
-SQFS_API int sqfs_super_write(sqfs_super_t *super, int fd);
+SQFS_API int sqfs_super_write(sqfs_super_t *super, sqfs_file_t *file);
 
 /* Returns 0 on success. Prints error messages to stderr on failure. */
-SQFS_API int sqfs_super_read(sqfs_super_t *super, int fd);
+SQFS_API int sqfs_super_read(sqfs_super_t *super, sqfs_file_t *file);
 
 #ifdef __cplusplus
 }
diff --git a/include/sqfs/table.h b/include/sqfs/table.h
index f837f6b..7767b9a 100644
--- a/include/sqfs/table.h
+++ b/include/sqfs/table.h
@@ -24,12 +24,12 @@ extern "C" {
 
   Returns 0 on success. Internally prints error messages to stderr.
  */
-SQFS_API int sqfs_write_table(int outfd, sqfs_super_t *super,
+SQFS_API int sqfs_write_table(sqfs_file_t *file, sqfs_super_t *super,
 			      sqfs_compressor_t *cmp,
 			      const void *data, size_t table_size,
 			      uint64_t *start);
 
-SQFS_API int sqfs_read_table(int fd, sqfs_compressor_t *cmp,
+SQFS_API int sqfs_read_table(sqfs_file_t *file, sqfs_compressor_t *cmp,
 			     size_t table_size, uint64_t location,
 			     uint64_t lower_limit, uint64_t upper_limit,
 			     void **out);
diff --git a/include/sqfs/xattr.h b/include/sqfs/xattr.h
index 0f9cf32..23587d1 100644
--- a/include/sqfs/xattr.h
+++ b/include/sqfs/xattr.h
@@ -58,7 +58,7 @@ SQFS_API int sqfs_xattr_reader_load_locations(sqfs_xattr_reader_t *xr);
 
 SQFS_API void sqfs_xattr_reader_destroy(sqfs_xattr_reader_t *xr);
 
-SQFS_API sqfs_xattr_reader_t *sqfs_xattr_reader_create(int sqfsfd,
+SQFS_API sqfs_xattr_reader_t *sqfs_xattr_reader_create(sqfs_file_t *file,
 						       sqfs_super_t *super,
 						       sqfs_compressor_t *cmp);
 
diff --git a/include/util.h b/include/util.h
index 93b8a04..e2089da 100644
--- a/include/util.h
+++ b/include/util.h
@@ -109,6 +109,9 @@ int popd(void);
 SQFS_INTERNAL
 int padd_file(int outfd, uint64_t size, size_t blocksize);
 
+SQFS_INTERNAL
+int padd_sqfs(sqfs_file_t *file, uint64_t size, size_t blocksize);
+
 /*
   Helper for allocating data structures with flexible array members.