Cleanup libsquashfs invalid argument error codes

 - Add an explicit "you're holding it wrong" error code.
 - Consistently return error codes and not have some special places
   where -1 is returned.

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

3 files changed, 9 insertions, 2 deletions

diff --git a/include/sqfs/compressor.h b/include/sqfs/compressor.h
index a53fbc1..4f22b0d 100644
--- a/include/sqfs/compressor.h
+++ b/include/sqfs/compressor.h
@@ -386,7 +386,8 @@ SQFS_API const char *sqfs_compressor_name_from_id(E_SQFS_COMPRESSOR id);
  * @param name The name of the compressor backend.
  * @param out Returns the coresponding @ref E_SQFS_COMPRESSOR identifier.
  *
- * @return Zero on success, -1 if the backend is unknown.
+ * @return Zero on success, @ref SQFS_ERROR_UNSUPPORTED if the backend
+ *         is unknown.
  */
 SQFS_API
 int sqfs_compressor_id_from_name(const char *name, E_SQFS_COMPRESSOR *out);
diff --git a/include/sqfs/error.h b/include/sqfs/error.h
index 9ff77d4..77e33ed 100644
--- a/include/sqfs/error.h
+++ b/include/sqfs/error.h
@@ -128,6 +128,11 @@ typedef enum {
 	 *        a regular file or a regular file inode.
 	 */
 	SQFS_ERROR_NOT_FILE = -15,
+
+	/**
+	 * @brief An invalid argument was passed to a library function.
+	 */
+	SQFS_ERROR_ARG_INVALID = -16,
 } E_SQFS_ERROR;
 
 #endif /* SQFS_ERROR_H */
diff --git a/include/sqfs/xattr.h b/include/sqfs/xattr.h
index 0f74c94..f2a87d3 100644
--- a/include/sqfs/xattr.h
+++ b/include/sqfs/xattr.h
@@ -173,7 +173,8 @@ SQFS_API const char *sqfs_get_xattr_prefix(E_SQFS_XATTR_TYPE id);
  * This function takes a key and finds the enumerator value that represents
  * its prefix. An error value is returned if the given prefix isn't supported.
  *
- * @return On success an @ref E_SQFS_XATTR_TYPE, -1 if it isn't supported.
+ * @return On success an @ref E_SQFS_XATTR_TYPE. If not supported, the
+ *         @ref SQFS_ERROR_UNSUPPORTED error code.
  */
 SQFS_API int sqfs_get_xattr_prefix_id(const char *key);