1 files changed, 37 insertions, 0 deletions
diff --git a/vector.c b/vector.c
new file mode 100644
index 0000000..57f62d7
--- /dev/null
+++ b/vector.c
@@ -0,0 +1,37 @@
+#include <stddef.h>
+#include <stdint.h>
+#include <stdlib.h>
+
+#include "vector.h"
+
+#define VECTOR_TOOBIG(alloc,elemsize,arrayoff)    ((SIZE_MAX - (arrayoff)) / (alloc) < (elemsize))
+#define VECTOR_ALLOCSIZE(alloc,elemsize,arrayoff) ((arrayoff) + (alloc) * (elemsize))
+
+void *vector_init(size_t alloc, size_t elemsize, size_t arrayoff)
+{
+	if (VECTOR_TOOBIG(alloc, elemsize, arrayoff)) return NULL;
+	struct vector *v = malloc(VECTOR_ALLOCSIZE(alloc, elemsize, arrayoff));
+	if (!v) return NULL;
+
+	*v = (struct vector) {
+		.alloc    = alloc,
+		.elemsize = elemsize,
+		.arrayoff = arrayoff,
+	};
+	return v;
+}
+
+void *vector_append(struct vector **vp)
+{
+	struct vector *v = *vp;
+	if (v->count >= v->alloc) {
+		size_t alloc = 2 * v->alloc;
+		if (VECTOR_TOOBIG(alloc, v->elemsize, v->arrayoff)) return NULL;
+		v = realloc(v, VECTOR_ALLOCSIZE(alloc, v->elemsize, v->arrayoff));
+		if (!v) return NULL;
+		v->alloc = alloc;
+		*vp = v;
+	}
+	return (char*)v + v->arrayoff + v->count++ * v->elemsize;
+}
+