Add a "sequence error" to libsquashfs error codes

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

2 files changed, 15 insertions, 0 deletions

diff --git a/include/sqfs/error.h b/include/sqfs/error.h
index 77e33ed..055e98f 100644
--- a/include/sqfs/error.h
+++ b/include/sqfs/error.h
@@ -133,6 +133,18 @@ typedef enum {
 	 * @brief An invalid argument was passed to a library function.
 	 */
 	SQFS_ERROR_ARG_INVALID = -16,
+
+	/**
+	 * @brief Library functions were called an a nonsensical order.
+	 *
+	 * Some libsquashfs functions operate on an object with an internal
+	 * state. Depending on the state, calling a function might not make
+	 * sense at all (e.g. calling foo_end before foo_begin). In that case,
+	 * this error is returned, signifying to the caller that the sequence
+	 * makes not sense, but the object itself is unchanged, no action was
+	 * performed and the object can still be used.
+	 */
+	SQFS_ERROR_SEQUENCE = -17,
 } E_SQFS_ERROR;
 
 #endif /* SQFS_ERROR_H */
diff --git a/lib/common/perror.c b/lib/common/perror.c
index a0a86aa..c7dab08 100644
--- a/lib/common/perror.c
+++ b/lib/common/perror.c
@@ -61,6 +61,9 @@ void sqfs_perror(const char *file, const char *action, int error_code)
 	case SQFS_ERROR_ARG_INVALID:
 		errstr = "invalid argument";
 		break;
+	case SQFS_ERROR_SEQUENCE:
+		errstr = "illegal oder of operations";
+		break;
 	default:
 		errstr = "libsquashfs returned an unknown error code";
 		break;