[src/trunk]: src/usr.bin/tail make tail -f and tail -10000 work on files > th...

[explorer <explorer%NetBSD.org@localhost>]

details:   https://anonhg.NetBSD.org/src/rev/f8e44e186a18
branches:  trunk
changeset: 517905:f8e44e186a18
user:      explorer <explorer%NetBSD.org@localhost>
date:      Wed Nov 21 06:47:07 2001 +0000

description:
make tail -f and tail -10000 work on files > those which can be mmap()ed whole.  tail -r will still not function on large files.

diffstat:

 usr.bin/tail/forward.c |  93 +++++++++++++++++++++++++++++++++++--------------
 1 files changed, 66 insertions(+), 27 deletions(-)

diffs (124 lines):

diff -r b5a7a9660344 -r f8e44e186a18 usr.bin/tail/forward.c
--- a/usr.bin/tail/forward.c    Wed Nov 21 06:28:08 2001 +0000
+++ b/usr.bin/tail/forward.c    Wed Nov 21 06:47:07 2001 +0000
@@ -1,4 +1,4 @@
-/*     $NetBSD: forward.c,v 1.16 1999/07/21 06:38:49 cgd Exp $ */
+/*     $NetBSD: forward.c,v 1.17 2001/11/21 06:47:07 explorer Exp $    */
 
 /*-
  * Copyright (c) 1991, 1993
@@ -41,7 +41,7 @@
 #if 0
 static char sccsid[] = "@(#)forward.c  8.1 (Berkeley) 6/6/93";
 #endif
-__RCSID("$NetBSD: forward.c,v 1.16 1999/07/21 06:38:49 cgd Exp $");
+__RCSID("$NetBSD: forward.c,v 1.17 2001/11/21 06:47:07 explorer Exp $");
 #endif /* not lint */
 
 #include <sys/types.h>
@@ -249,41 +249,80 @@
        long off;
        struct stat *sbp;
 {
-       off_t size;
+       off_t file_size;
+       off_t file_remaining;
        char *p;
        char *start;
+       off_t mmap_size;
+       off_t mmap_offset;
+       off_t mmap_remaining;
 
-       if (!(size = sbp->st_size))
+#define MMAP_MAXSIZE  (10 * 1024 * 1024)
+
+       if (!(file_size = sbp->st_size))
                return (0);
+       file_remaining = file_size;
 
-       if (size > SIZE_T_MAX) {
-               err(0, "%s: %s", fname, strerror(EFBIG));
+       if (mmap_size > MMAP_MAXSIZE) {
+               mmap_size = MMAP_MAXSIZE;
+               mmap_offset = file_size - MMAP_MAXSIZE;
+       } else {
+               mmap_size = file_size;
+               mmap_offset = 0;
+       }
+
+       while (off) {
+               start = mmap(NULL, (size_t)mmap_size, PROT_READ,
+                            MAP_FILE|MAP_SHARED, fileno(fp), mmap_offset);
+               if (start == MAP_FAILED) {
+                       err(0, "%s: %s", fname, strerror(EFBIG));
+                       return (1);
+               }
+
+               mmap_remaining = mmap_size;
+               /* Last char is special, ignore whether newline or not. */
+               for (p = start + mmap_remaining - 1 ; --mmap_remaining ; )
+                       if (*--p == '\n' && !--off) {
+                               ++p;
+                               break;
+                       }
+
+               file_remaining -= mmap_size - mmap_remaining;
+
+               if (off == 0)
+                       break;
+
+               if (munmap(start, mmap_size)) {
+                       err(0, "%s: %s", fname, strerror(errno));
+                       return (1);
+               }
+
+               if (mmap_offset >= MMAP_MAXSIZE) {
+                       mmap_offset -= MMAP_MAXSIZE;
+               } else {
+                       mmap_offset = 0;
+                       mmap_size = file_remaining;
+               }
+       }
+
+       /*
+        * Output the (perhaps partial) data in this mmap'd block.
+        */
+       WR(p, mmap_size - mmap_remaining);
+       file_remaining += mmap_size - mmap_remaining;
+       if (munmap(start, mmap_size)) {
+               err(0, "%s: %s", fname, strerror(errno));
                return (1);
        }
 
-       if ((start = mmap(NULL, (size_t)size, PROT_READ,
-           MAP_FILE|MAP_SHARED, fileno(fp), (off_t)0)) == (caddr_t)-1) {
-               err(0, "%s: %s", fname, strerror(EFBIG));
-               return (1);
-       }
-
-       /* Last char is special, ignore whether newline or not. */
-       for (p = start + size - 1; --size;)
-               if (*--p == '\n' && !--off) {
-                       ++p;
-                       break;
-               }
-
-       /* Set the file pointer to reflect the length displayed. */
-       size = sbp->st_size - size;
-       WR(p, size);
-       if (fseek(fp, (long)sbp->st_size, SEEK_SET) == -1) {
+       /*
+        * Set the file pointer to reflect the length displayed.
+        * This will cause the caller to redisplay the data if/when
+        * needed.
+        */
+       if (fseeko(fp, file_remaining, SEEK_SET) == -1) {
                ierr();
                return (1);
        }
-       if (munmap(start, (size_t)sbp->st_size)) {
-               err(0, "%s: %s", fname, strerror(errno));
-               return (1);
-       }
        return (0);
 }