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diff --git a/usr.bin/tail/read.c b/usr.bin/tail/read.c
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+/* $OpenBSD: read.c,v 1.20 2017/03/26 19:55:07 martijn Exp $ */
+/* $NetBSD: read.c,v 1.4 1994/11/23 07:42:07 jtc Exp $ */
+
+/*-
+ * Copyright (c) 1991, 1993
+ * The Regents of the University of California. All rights reserved.
+ *
+ * This code is derived from software contributed to Berkeley by
+ * Edward Sze-Tyan Wang.
+ *
+ * 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 <sys/types.h>
+#include <sys/stat.h>
+
+#include <err.h>
+#include <stdio.h>
+#include <stdint.h>
+#include <stdlib.h>
+#include <string.h>
+#include <unistd.h>
+
+#include "extern.h"
+
+/*
+ * bytes -- read bytes to an offset from the end and display.
+ *
+ * This is the function that reads to a byte offset from the end of the input,
+ * storing the data in a wrap-around buffer which is then displayed. If the
+ * rflag is set, the data is displayed in lines in reverse order, and this
+ * routine has the usual nastiness of trying to find the newlines. Otherwise,
+ * it is displayed from the character closest to the beginning of the input to
+ * the end.
+ *
+ * A non-zero return means an (non-fatal) error occurred.
+ *
+ */
+int
+bytes(struct tailfile *tf, off_t off)
+{
+ int ch;
+ size_t len, tlen;
+ char *ep, *p, *t;
+ int wrap;
+ char *sp;
+
+ if (off > SIZE_MAX)
+ errx(1, "offset too large");
+
+ if ((sp = p = malloc(off)) == NULL)
+ err(1, NULL);
+
+ for (wrap = 0, ep = p + off; (ch = getc(tf->fp)) != EOF;) {
+ *p = ch;
+ if (++p == ep) {
+ wrap = 1;
+ p = sp;
+ }
+ }
+ if (ferror(tf->fp)) {
+ ierr(tf->fname);
+ free(sp);
+ return(1);
+ }
+
+ if (rflag) {
+ for (t = p - 1, len = 0; t >= sp; --t, ++len)
+ if (*t == '\n' && len) {
+ WR(t + 1, len);
+ len = 0;
+ }
+ if (wrap) {
+ tlen = len;
+ for (t = ep - 1, len = 0; t >= p; --t, ++len)
+ if (*t == '\n') {
+ if (len) {
+ WR(t + 1, len);
+ len = 0;
+ }
+ if (tlen) {
+ WR(sp, tlen);
+ tlen = 0;
+ }
+ }
+ if (len)
+ WR(t + 1, len);
+ if (tlen)
+ WR(sp, tlen);
+ }
+ } else {
+ if (wrap && (len = ep - p))
+ WR(p, len);
+ if ((len = p - sp))
+ WR(sp, len);
+ }
+
+ free(sp);
+ return(0);
+}
+
+/*
+ * lines -- read lines to an offset from the end and display.
+ *
+ * This is the function that reads to a line offset from the end of the input,
+ * storing the data in an array of buffers which is then displayed. If the
+ * rflag is set, the data is displayed in lines in reverse order, and this
+ * routine has the usual nastiness of trying to find the newlines. Otherwise,
+ * it is displayed from the line closest to the beginning of the input to
+ * the end.
+ *
+ * A non-zero return means an (non-fatal) error occurred.
+ *
+ */
+int
+lines(struct tailfile *tf, off_t off)
+{
+ struct {
+ size_t blen;
+ size_t len;
+ char *l;
+ } *lines = NULL;
+ int ch, rc = 0;
+ char *p = NULL;
+ int wrap;
+ size_t cnt, lineno, nlineno, recno, blen, newsize;
+ char *sp = NULL, *newp = NULL;
+
+ if (off > SIZE_MAX)
+ errx(1, "offset too large");
+
+ lineno = blen = cnt = recno = wrap = 0;
+
+ while ((ch = getc(tf->fp)) != EOF) {
+ if (++cnt > blen) {
+ newsize = blen + 1024;
+ if ((newp = realloc(sp, newsize)) == NULL)
+ err(1, NULL);
+ sp = newp;
+ blen = newsize;
+ p = sp + cnt - 1;
+ }
+ *p++ = ch;
+ if (recno >= lineno) {
+ nlineno = (lineno + 1024) > off ?
+ (size_t) off : lineno + 1024;
+ if ((lines = recallocarray(lines, lineno, nlineno,
+ sizeof(*lines))) == NULL)
+ err(1, NULL);
+ lineno = nlineno;
+ }
+ if (ch == '\n') {
+ if (lines[recno].blen < cnt) {
+ newsize = cnt + 256;
+ if ((newp = realloc(lines[recno].l,
+ newsize)) == NULL)
+ err(1, NULL);
+ lines[recno].l = newp;
+ lines[recno].blen = newsize;
+ }
+ memcpy(lines[recno].l, sp, (lines[recno].len = cnt));
+ cnt = 0;
+ p = sp;
+ if (++recno == off) {
+ wrap = 1;
+ recno = 0;
+ }
+ }
+ }
+ if (ferror(tf->fp)) {
+ ierr(tf->fname);
+ rc = 1;
+ goto done;
+ }
+ if (cnt) {
+ lines[recno].l = sp;
+ lines[recno].len = cnt;
+ sp = NULL;
+ if (++recno == off) {
+ wrap = 1;
+ recno = 0;
+ }
+ }
+
+ if (rflag) {
+ for (cnt = recno; cnt > 0; --cnt)
+ WR(lines[cnt - 1].l, lines[cnt - 1].len);
+ if (wrap)
+ for (cnt = off; cnt > recno; --cnt)
+ WR(lines[cnt - 1].l, lines[cnt - 1].len);
+ } else {
+ if (wrap)
+ for (cnt = recno; cnt < off; ++cnt)
+ WR(lines[cnt].l, lines[cnt].len);
+ for (cnt = 0; cnt < recno; ++cnt)
+ WR(lines[cnt].l, lines[cnt].len);
+ }
+done:
+ for (cnt = 0; cnt < lineno; cnt++)
+ free(lines[cnt].l);
+ free(sp);
+ free(lines);
+ return(rc);
+}