Add libString.

src/libString/s_read_line.c

@@ -0,0 +1,31 @@
+#include <u.h>
+#include <libc.h>
+#include <bio.h>
+#include "libString.h"
+
+/* Append an input line to a String.
+ *
+ * Returns a pointer to the character string (or 0).
+ * Trailing newline is left on.
+ */ 
+extern char *
+s_read_line(Biobuf *fp, String *to)
+{
+	char *cp;
+	int llen;
+
+	if(to->ref > 1)
+		sysfatal("can't s_read_line a shared string");
+	s_terminate(to);
+	cp = Brdline(fp, '\n');
+	if(cp == 0)
+		return 0;
+	llen = Blinelen(fp);
+	if(to->end - to->ptr < llen)
+		s_grow(to, llen);
+	memmove(to->ptr, cp, llen);
+	cp = to->ptr;
+	to->ptr += llen;
+	s_terminate(to);
+	return cp;
+}