--- /dev/null
+/* MIT (BSD) license - see LICENSE file for details */
+#include <ccan/membuf/membuf.h>
+#include <errno.h>
+#include <string.h>
+#include <stdlib.h>
+
+void membuf_init_(struct membuf *mb,
+ void *elems, size_t num_elems, size_t elemsize,
+ void *(*expandfn)(struct membuf *, void *, size_t))
+{
+
+ mb->start = mb->end = 0;
+ mb->max_elems = num_elems;
+ mb->elems = elems;
+ mb->expandfn = expandfn;
+}
+
+size_t membuf_prepare_space_(struct membuf *mb,
+ size_t num_extra, size_t elemsize)
+{
+ char *oldstart = membuf_elems_(mb, elemsize);
+
+ /* Always reset in the trivial empty case. */
+ if (mb->start == mb->end)
+ mb->start = mb->end = 0;
+
+ if (membuf_num_space_(mb) >= num_extra)
+ return 0;
+
+ /* There are two ways to make space: enlarge buffer, and memmove
+ * down. We use a simple heuristic: if we are using less than half
+ * the buffer, and memmove would get us sufficient space, do that. */
+ if (membuf_num_elems_(mb) <= mb->max_elems / 2
+ && membuf_num_elems_(mb) + num_extra <= mb->max_elems) {
+ memmove(mb->elems, oldstart, (mb->end - mb->start) * elemsize);
+ mb->end -= mb->start;
+ mb->start = 0;
+ } else {
+ void *expand;
+
+ /* Since we're going to expand, at least double. */
+ if (num_extra < mb->max_elems)
+ num_extra = mb->max_elems;
+
+ expand = mb->expandfn(mb, mb->elems,
+ (mb->max_elems + num_extra) * elemsize);
+ if (!expand) {
+ errno = ENOMEM;
+ } else {
+ mb->max_elems += num_extra;
+ mb->elems = expand;
+ }
+ }
+ return (char *)membuf_elems_(mb, elemsize) - oldstart;
+}
+
+void *membuf_realloc(struct membuf *mb, void *rawelems, size_t newsize)
+{
+ return realloc(rawelems, newsize);
+}