auto import from //depot/cupcake/@135843
diff --git a/libc/stdio/fgetln.c b/libc/stdio/fgetln.c
new file mode 100644
index 0000000..946e1b7
--- /dev/null
+++ b/libc/stdio/fgetln.c
@@ -0,0 +1,150 @@
+/* $OpenBSD: fgetln.c,v 1.7 2005/08/08 08:05:36 espie Exp $ */
+/*-
+ * Copyright (c) 1990, 1993
+ * The Regents of the University of California. All rights reserved.
+ *
+ * This code is derived from software contributed to Berkeley by
+ * Chris Torek.
+ *
+ * Redistribution and use in source and binary forms, with or without
+ * modification, are permitted provided that the following conditions
+ * are met:
+ * 1. Redistributions of source code must retain the above copyright
+ * notice, this list of conditions and the following disclaimer.
+ * 2. Redistributions in binary form must reproduce the above copyright
+ * notice, this list of conditions and the following disclaimer in the
+ * documentation and/or other materials provided with the distribution.
+ * 3. Neither the name of the University nor the names of its contributors
+ * may be used to endorse or promote products derived from this software
+ * without specific prior written permission.
+ *
+ * THIS SOFTWARE IS PROVIDED BY THE REGENTS AND CONTRIBUTORS ``AS IS'' AND
+ * ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
+ * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
+ * ARE DISCLAIMED. IN NO EVENT SHALL THE REGENTS OR CONTRIBUTORS BE LIABLE
+ * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
+ * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
+ * OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
+ * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
+ * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
+ * OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
+ * SUCH DAMAGE.
+ */
+
+#include <stdio.h>
+#include <stdlib.h>
+#include <string.h>
+#include "local.h"
+
+/*
+ * Expand the line buffer. Return -1 on error.
+#ifdef notdef
+ * The `new size' does not account for a terminating '\0',
+ * so we add 1 here.
+#endif
+ */
+int
+__slbexpand(FILE *fp, size_t newsize)
+{
+ void *p;
+
+#ifdef notdef
+ ++newsize;
+#endif
+ if ((size_t)fp->_lb._size >= newsize)
+ return (0);
+ if ((p = realloc(fp->_lb._base, newsize)) == NULL)
+ return (-1);
+ fp->_lb._base = p;
+ fp->_lb._size = newsize;
+ return (0);
+}
+
+/*
+ * Get an input line. The returned pointer often (but not always)
+ * points into a stdio buffer. Fgetline does not alter the text of
+ * the returned line (which is thus not a C string because it will
+ * not necessarily end with '\0'), but does allow callers to modify
+ * it if they wish. Thus, we set __SMOD in case the caller does.
+ */
+char *
+fgetln(FILE *fp, size_t *lenp)
+{
+ unsigned char *p;
+ size_t len;
+ size_t off;
+
+ /* make sure there is input */
+ if (fp->_r <= 0 && __srefill(fp)) {
+ *lenp = 0;
+ return (NULL);
+ }
+
+ /* look for a newline in the input */
+ if ((p = memchr((void *)fp->_p, '\n', fp->_r)) != NULL) {
+ char *ret;
+
+ /*
+ * Found one. Flag buffer as modified to keep fseek from
+ * `optimising' a backward seek, in case the user stomps on
+ * the text.
+ */
+ p++; /* advance over it */
+ ret = (char *)fp->_p;
+ *lenp = len = p - fp->_p;
+ fp->_flags |= __SMOD;
+ fp->_r -= len;
+ fp->_p = p;
+ return (ret);
+ }
+
+ /*
+ * We have to copy the current buffered data to the line buffer.
+ * As a bonus, though, we can leave off the __SMOD.
+ *
+ * OPTIMISTIC is length that we (optimistically) expect will
+ * accommodate the `rest' of the string, on each trip through the
+ * loop below.
+ */
+#define OPTIMISTIC 80
+
+ for (len = fp->_r, off = 0;; len += fp->_r) {
+ size_t diff;
+
+ /*
+ * Make sure there is room for more bytes. Copy data from
+ * file buffer to line buffer, refill file and look for
+ * newline. The loop stops only when we find a newline.
+ */
+ if (__slbexpand(fp, len + OPTIMISTIC))
+ goto error;
+ (void)memcpy((void *)(fp->_lb._base + off), (void *)fp->_p,
+ len - off);
+ off = len;
+ if (__srefill(fp))
+ break; /* EOF or error: return partial line */
+ if ((p = memchr((void *)fp->_p, '\n', fp->_r)) == NULL)
+ continue;
+
+ /* got it: finish up the line (like code above) */
+ p++;
+ diff = p - fp->_p;
+ len += diff;
+ if (__slbexpand(fp, len))
+ goto error;
+ (void)memcpy((void *)(fp->_lb._base + off), (void *)fp->_p,
+ diff);
+ fp->_r -= diff;
+ fp->_p = p;
+ break;
+ }
+ *lenp = len;
+#ifdef notdef
+ fp->_lb._base[len] = '\0';
+#endif
+ return ((char *)fp->_lb._base);
+
+error:
+ *lenp = 0; /* ??? */
+ return (NULL); /* ??? */
+}