Keep in the "wtap" structure the current offset into the file being

read, and maintain it ourselves as we read through the file, rather than
calling "ftell()" for every packet we read - "ftell()" may involve an
"lseek()" call, which could add a noticeable CPU overhead when reading a
large file.

svn path=/trunk/; revision=596

1 files changed, 7 insertions, 2 deletions

diff --git a/wiretap/libpcap.c b/wiretap/libpcap.c
index 50a1689c41..ccd62838e2 100644
--- a/wiretap/libpcap.c
+++ b/wiretap/libpcap.c
@@ -1,6 +1,6 @@
 /* libpcap.c
  *
- * $Id: libpcap.c,v 1.15 1999/08/24 03:19:34 guy Exp $
+ * $Id: libpcap.c,v 1.16 1999/08/28 01:19:44 guy Exp $
  *
  * Wiretap Library
  * Copyright (c) 1998 by Gilbert Ramirez <gram@verdict.uthscsa.edu>
@@ -147,6 +147,7 @@ int libpcap_open(wtap *wth, int *err)
 
 	/* Read in the number that should be at the start of a "libpcap" file */
 	fseek(wth->fh, 0, SEEK_SET);
+	wth->data_offset = 0;
 	errno = WTAP_ERR_CANT_READ;
 	bytes_read = fread(&magic, 1, sizeof magic, wth->fh);
 	if (bytes_read != sizeof magic) {
@@ -156,6 +157,7 @@ int libpcap_open(wtap *wth, int *err)
 		}
 		return 0;
 	}
+	wth->data_offset += sizeof magic;
 
 	if (magic == PCAP_SWAPPED_MAGIC) {
 		/* Host that wrote it has a byte order opposite to ours. */
@@ -176,6 +178,7 @@ int libpcap_open(wtap *wth, int *err)
 		}
 		return 0;
 	}
+	wth->data_offset += sizeof hdr;
 
 	if (byte_swapped) {
 		/* Byte-swap the header fields about which we care. */
@@ -233,6 +236,7 @@ static int libpcap_read(wtap *wth, int *err)
 		}
 		return 0;
 	}
+	wth->data_offset += sizeof hdr;
 
 	if (wth->capture.pcap->byte_swapped) {
 		/* Byte-swap the record header fields. */
@@ -274,7 +278,7 @@ static int libpcap_read(wtap *wth, int *err)
 	}
 
 	buffer_assure_space(wth->frame_buffer, packet_size);
-	data_offset = ftell(wth->fh);
+	data_offset = wth->data_offset;
 	errno = WTAP_ERR_CANT_READ;
 	bytes_read = fread(buffer_start_ptr(wth->frame_buffer), 1,
 			packet_size, wth->fh);
@@ -286,6 +290,7 @@ static int libpcap_read(wtap *wth, int *err)
 			*err = WTAP_ERR_SHORT_READ;
 		return -1;
 	}
+	wth->data_offset += packet_size;
 
 	wth->phdr.ts.tv_sec = hdr.ts_sec;
 	wth->phdr.ts.tv_usec = hdr.ts_usec;