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When skipping over the padding at the end of a record in a capture file, 

don't seek around it - some implementations of the standard I/O library
routines (e.g., the ones in Solaris 2.5.1, at least) appear not to be
clever enough to handle seeks that occur within the buffer by moving the
current buffer position; instead, they do a seek on the underlying file
descriptor *and* appear to throw out the buffer, forcing them to do
another read.

Instead, read it into a buffer.

svn path=/trunk/; revision=626
This commit is contained in:
Guy Harris 1999-09-02 00:14:06 +00:00
parent b87ec88778
commit c135be4e53
1 changed files with 28 additions and 5 deletions
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33
wiretap/snoop.c
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@ -1,6 +1,6 @@
/* snoop.c
*
* $Id: snoop.c,v 1.9 1999/08/28 01:19:45 guy Exp $
* $Id: snoop.c,v 1.10 1999/09/02 00:14:06 guy Exp $
*
* Wiretap Library
* Copyright (c) 1998 by Gilbert Ramirez <gram@verdict.uthscsa.edu>
@ -136,6 +136,9 @@ static int snoop_read(wtap *wth, int *err)
int bytes_read;
struct snooprec_hdr hdr;
int data_offset;
char padbuf[4];
int padbytes;
int bytes_to_read;
/* Read record header. */
errno = WTAP_ERR_CANT_READ;
@ -185,10 +188,30 @@ static int snoop_read(wtap *wth, int *err)
wth->phdr.len = ntohl(hdr.orig_len);
wth->phdr.pkt_encap = wth->file_encap;
/* Skip over the padding. */
fseek(wth->fh, ntohl(hdr.rec_len) - (sizeof hdr + packet_size),
SEEK_CUR);
wth->data_offset += ntohl(hdr.rec_len) - (sizeof hdr + packet_size);
/*
* Skip over the padding (don't "fseek()", as the standard
* I/O library on some platforms discards buffered data if
* you do that, which means it does a lot more reads).
* There's probably not much padding (it's probably padded only
* to a 4-byte boundary), so we probably need only do one read.
*/
padbytes = ntohl(hdr.rec_len) - (sizeof hdr + packet_size);
while (padbytes != 0) {
bytes_to_read = padbytes;
if (bytes_to_read > sizeof padbuf)
bytes_to_read = sizeof padbuf;
errno = WTAP_ERR_CANT_READ;
bytes_read = fread(padbuf, 1, bytes_to_read, wth->fh);
if (bytes_read != bytes_to_read) {
if (ferror(wth->fh))
*err = errno;
else
*err = WTAP_ERR_SHORT_READ;
return -1;
}
wth->data_offset += bytes_read;
padbytes -= bytes_read;
}
return data_offset;
}