error: Improve error header.

1 files changed, 24 insertions, 7 deletions

diff --git a/include/libnslayout/error.h b/include/libnslayout/error.h
index 0e2321f..5e7b87a 100644
--- a/include/libnslayout/error.h
+++ b/include/libnslayout/error.h
@@ -17,25 +17,42 @@ extern "C"
 #endif
 
 /**
+ * Number of bits in an `nslayout_error` that indicate the source of the error.
+ */
+#define NSLAYOUT_ERROR_PROV 8
+
+/**
  * Libnslayout return codes
  *
  * NSLAYOUT_OK indicates no error.
  */
 typedef enum nslayout_error {
 	/** No error code */
-	NSLAYOUT_OK				= 0,
+	NSLAYOUT_OK            = 0,
 
-	/** Error provenance */
-	NSLAYOUT_NSLAYOUT			= (1 << 0),
-	NSLAYOUT_LIBDOM				= (1 << 1),
-	NSLAYOUT_LIBCSS				= (1 << 2),
+	/** Error provenance (bits 0..7) */
+	NSLAYOUT_NSLAYOUT      = (1 << 0),
+	NSLAYOUT_LIBDOM        = (1 << 1),
+	NSLAYOUT_LIBCSS        = (1 << 2),
 
-	/** LibNSLayout errors */
-	NSLAYOUT_NO_MEM				= (1 << 8) + NSLAYOUT_NSLAYOUT,
+	/** LibNSLayout errors (bits 8..31) */
+	NSLAYOUT_NO_MEM        = (1 << NSLAYOUT_ERROR_PROV) | NSLAYOUT_NSLAYOUT,
 } nslayout_error;
 
 
 /**
+ * Get error provenance.
+ *
+ * \param[in]  err		Error code to test
+ * \return error provenance
+ */
+static inline nslayout_error nslayout_error_provenance(nslayout_error err)
+{
+	return err & ((1 << NSLAYOUT_ERROR_PROV) - 1);
+}
+
+
+/**
  * Check if error is from libnslayout
  *
  * \param[in]  err		Error code to test