Add libString.
diff --git a/src/libString/s_alloc.c b/src/libString/s_alloc.c
new file mode 100644
index 0000000..34f8916
--- /dev/null
+++ b/src/libString/s_alloc.c
@@ -0,0 +1,86 @@
+#include <u.h>
+#include <libc.h>
+#include "libString.h"
+
+#define STRLEN 128
+
+extern void
+s_free(String *sp)
+{
+ if (sp == nil)
+ return;
+ lock(&sp->lk);
+ if(--(sp->ref) != 0){
+ unlock(&sp->lk);
+ return;
+ }
+ unlock(&sp->lk);
+
+ if(sp->fixed == 0 && sp->base != nil)
+ free(sp->base);
+ free(sp);
+}
+
+/* get another reference to a string */
+extern String *
+s_incref(String *sp)
+{
+ lock(&sp->lk);
+ sp->ref++;
+ unlock(&sp->lk);
+
+ return sp;
+}
+
+/* allocate a String head */
+extern String *
+_s_alloc(void)
+{
+ String *s;
+
+ s = mallocz(sizeof *s, 1);
+ if(s == nil)
+ return s;
+ s->ref = 1;
+ s->fixed = 0;
+ return s;
+}
+
+/* create a new `short' String */
+extern String *
+s_newalloc(int len)
+{
+ String *sp;
+
+ sp = _s_alloc();
+ if(sp == nil)
+ sysfatal("s_newalloc: %r");
+ setmalloctag(sp, getcallerpc(&len));
+ if(len < STRLEN)
+ len = STRLEN;
+ sp->base = sp->ptr = malloc(len);
+ if (sp->base == nil)
+ sysfatal("s_newalloc: %r");
+ setmalloctag(sp->base, getcallerpc(&len));
+
+ sp->end = sp->base + len;
+ s_terminate(sp);
+ return sp;
+}
+
+/* create a new `short' String */
+extern String *
+s_new(void)
+{
+ String *sp;
+
+ sp = _s_alloc();
+ if(sp == nil)
+ sysfatal("s_new: %r");
+ sp->base = sp->ptr = malloc(STRLEN);
+ if (sp->base == nil)
+ sysfatal("s_new: %r");
+ sp->end = sp->base + STRLEN;
+ s_terminate(sp);
+ return sp;
+}
