This is a handy helper for creating one vector from another,
mapping each element of the origin vector to an element of
the target vector with a given conversion function. It can
also be used to "concatenate" vectors by passing in a non-NULL first
argument.
Signed-off-by: Martin Wilck <mwilck@xxxxxxxx>
---
libmultipath/vector.h | 29 +++++++++++++++++++++++++++++
1 file changed, 29 insertions(+)
diff --git a/libmultipath/vector.h b/libmultipath/vector.h
index 3f6e579ae19a..6018b57525bf 100644
--- a/libmultipath/vector.h
+++ b/libmultipath/vector.h
@@ -42,6 +42,35 @@ typedef struct _vector *vector;
#define vector_foreach_slot_backwards(v,p,i) \
for (i = VECTOR_SIZE(v); i > 0 && ((p) = (v)->slot[i-1]); i--)
+#define identity(x) (x)
+/*
+ * Given a vector vec with elements of given type,
+ * return a newly allocated vector with elements conv(e) for each element
+ * e in vec. "conv" may be a macro or a function.
+ * Use "identity" for a simple copy.
+ */
+#define vector_convert(new, vec, type, conv) \
+ ({ \
+ const struct _vector *__v = (vec); \
+ vector __t = (new); \
+ type *__j; \
+ int __i; \
+ \
+ if (__t == NULL) \
+ __t = vector_alloc(); \
+ if (__t != NULL) { \
+ vector_foreach_slot(__v, __j, __i) { \
+ if (vector_alloc_slot(__t) == NULL) { \
+ vector_free(__t); \
+ __t = NULL; \
+ break; \
+ } \
+ vector_set_slot(__t, conv(__j)); \
+ } \
+ } \
+ __t; \
+ })
+
/* Prototypes */
extern vector vector_alloc(void);
extern void *vector_alloc_slot(vector v);
--
2.16.1
--
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