libsquashfs: Add sqfs_open_native_file function

Having a function to interpret the flags and open a native file handle
simplifies the istream/ostream/file code which shares that decoding
part, particularly on windows where the character set needs to be
transformed.

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

2 files changed, 41 insertions, 11 deletions

diff --git a/include/io/file.h b/include/io/file.h
index fa0abc0..5065619 100644
--- a/include/io/file.h
+++ b/include/io/file.h
@@ -7,15 +7,7 @@
 #ifndef IO_FILE_H
 #define IO_FILE_H
 
-#include "io/istream.h"
-
-#if defined(_WIN32) || defined(__WINDOWS__)
-#include <handleapi.h>
-
-typedef HANDLE os_file_t;
-#else
-typedef int os_file_t;
-#endif
+#include "sqfs/io.h"
 
 #ifdef __cplusplus
 extern "C" {
@@ -36,7 +28,7 @@ extern "C" {
  * @return A pointer to an output stream on success, NULL on failure.
  */
 SQFS_INTERNAL
-sqfs_istream_t *istream_open_handle(const char *path, os_file_t fd);
+sqfs_istream_t *istream_open_handle(const char *path, sqfs_file_handle_t fd);
 
 /**
  * @brief Create an output stream that writes to an OS native file handle.
@@ -55,7 +47,7 @@ sqfs_istream_t *istream_open_handle(const char *path, os_file_t fd);
  * @return A pointer to an output stream on success, NULL on failure.
  */
 SQFS_INTERNAL sqfs_ostream_t *ostream_open_handle(const char *path,
-						  os_file_t hnd,
+						  sqfs_file_handle_t hnd,
 						  int flags);
 
 /**
diff --git a/include/sqfs/io.h b/include/sqfs/io.h
index 4291e71..1138fc0 100644
--- a/include/sqfs/io.h
+++ b/include/sqfs/io.h
@@ -34,6 +34,20 @@
  */
 
 /**
+ * @typedef sqfs_file_handle_t
+ *
+ * @brief Native handle type for file I/O
+ */
+
+#if defined(_WIN32) || defined(__WINDOWS__)
+#include <handleapi.h>
+
+typedef HANDLE sqfs_file_handle_t;
+#else
+typedef int sqfs_file_handle_t;
+#endif
+
+/**
  * @enum SQFS_FILE_OPEN_FLAGS
  *
  * @brief Flags for @ref sqfs_open_file
@@ -273,6 +287,30 @@ extern "C" {
 #endif
 
 /**
+ * @brief Open a native file handle
+ *
+ * On Unix-like systems, this generates a file descriptor that needs to be
+ * closed with close(). If opening fails, errno is preseved.
+ *
+ * On Windows, a HANDLE is created that needs to be disposed of
+ * using CloseHandle(). If opening fails, GetLastError() is preseved.
+ * If @ref SQFS_FILE_OPEN_NO_CHARSET_XFRM is set, the given string is passed
+ * to the ANSI API that interprets the string according to the the currently
+ * set codepage. If the flag is not present, the string is assumed to be UTF-8,
+ * the function internally converts it to UTF-16 and uses the wide char API.
+ *
+ * @param out Returns a native file handle on success
+ * @param filename The path to the file to open
+ * @param flags A set of @ref SQFS_FILE_OPEN_FLAGS controlling how the
+ *              file is opened.
+ *
+ * @return Zero on success, a negative @ref SQFS_ERROR code on failure.
+ *         If an unknown flag was used, @ref SQFS_ERROR_UNSUPPORTED is returned.
+ */
+SQFS_API int sqfs_open_native_file(sqfs_file_handle_t *out,
+				   const char *filename, sqfs_u32 flags);
+
+/**
  * @brief Open a file through the operating systems filesystem API
  *
  * This function internally creates an instance of a reference implementation