lib: add `darr_strlen_fixup()` to update len based on NUL term

Signed-off-by: Christian Hopps <chopps@labn.net>

1 files changed, 17 insertions, 0 deletions

diff --git a/lib/darr.h b/lib/darr.h
index 084c2a103a..4638b904d1 100644
--- a/lib/darr.h
+++ b/lib/darr.h
@@ -62,6 +62,7 @@
  *  - darr_strdup
  *  - darr_strdup_cap
  *  - darr_strlen
+ *  - darr_strlen_fixup
  *  - darr_strnul
  *  - darr_sprintf, darr_vsprintf
  */
@@ -753,6 +754,22 @@ void *__darr_resize(void *a, uint count, size_t esize, struct memtype *mt);
 	})
 
 /**
+ * Fixup darr_len (and thus darr_strlen) for `S` based on its strlen(S)
+ * (i.e., scan for NUL byte). The dynamic array length will be set to strlen(S) + 1.
+ *
+ * Args:
+ *	S: The dynamic array with a NUL terminated string, cannot be NULL.
+ *
+ * Return:
+ *      The calculated strlen() value.
+ */
+#define darr_strlen_fixup(S)                                                                       \
+	({                                                                                         \
+		_darr_len(S) = strlen(S) + 1;                                                      \
+		darr_strlen(S);                                                                    \
+	})
+
+/**
  * darr_vsprintf() - vsprintf into a new dynamic array.
  *
  * Args: