add rangecheck.h

mult/range_arrayinbuf.c

@@ -0,0 +1,20 @@
+#include <rangecheck.h>
+#include <safemult.h>
+
+/* does an array of "elements" members of size "membersize" starting at
+ * "arraystart" lie inside buf1[0..len-1]? */
+int range_arrayinbuf(const void* buf1,size_t len,
+		     const void* arraystart,size_t elements,size_t membersize) {
+  size_t alen;
+  if (sizeof(alen)==8) {
+    uint64 x;
+    if (!umult64(elements,membersize,&x)) return 0;
+    alen=x;
+  } else {
+    unsigned long long t=(unsigned long long)elements*membersize;
+    alen=t;
+    if (alen!=t) return 0;
+  }
+  return range_bufinbuf(buf1,len,arraystart,alen);
+}
+