X-Git-Url: http://git.ozlabs.org/?a=blobdiff_plain;f=ccan%2Fmembuf%2Fmembuf.c;fp=ccan%2Fmembuf%2Fmembuf.c;h=b3b2f08ded7bd6e7f3b6d8e1906911dbf623c8d7;hb=86d30436820cacfc872de2ba518dd0b54b544647;hp=0000000000000000000000000000000000000000;hpb=a8722345053b7cd860499aa31fd6bb414c120cc8;p=ccan

diff --git a/ccan/membuf/membuf.c b/ccan/membuf/membuf.c
new file mode 100644
index 00000000..b3b2f08d
--- /dev/null
+++ b/ccan/membuf/membuf.c
@@ -0,0 +1,60 @@
+/* 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);
+}