forked from osmocom/wireshark
![Guy Harris](/assets/img/avatar_default.png)
Add a "record type" field to "struct wtap_pkthdr"; currently, it can be REC_TYPE_PACKET, for a record containing a packet, or REC_TYPE_FILE_TYPE_SPECIFIC, for records containing file-type-specific data. Modify code that reads packets to be able to handle non-packet records, even if that just means ignoring them. Rename some routines to indicate that they handle more than just packets. We don't yet have any libwiretap code that supplies records other than REC_TYPE_PACKET or that supporting writing records other than REC_TYPE_PACKET, or any code to support plugins for handling REC_TYPE_FILE_TYPE_SPECIFIC records; this is just the first step for bug 8590. Change-Id: Idb40b78f17c2c3aea72031bcd252abf9bc11c813 Reviewed-on: https://code.wireshark.org/review/1773 Reviewed-by: Guy Harris <guy@alum.mit.edu>
250 lines
7.1 KiB
C
250 lines
7.1 KiB
C
/* mp2t.c
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*
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* ISO/IEC 13818-1 MPEG2-TS file format decoder for the Wiretap library.
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* Written by Weston Schmidt <weston_schmidt@alumni.purdue.edu>
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* Copyright 2012 Weston Schmidt
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*
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* Wiretap Library
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* This program is free software; you can redistribute it and/or
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* modify it under the terms of the GNU General Public License
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* as published by the Free Software Foundation; either version 2
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* of the License, or (at your option) any later version.
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*
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* This program is distributed in the hope that it will be useful,
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* but WITHOUT ANY WARRANTY; without even the implied warranty of
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* MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
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* GNU General Public License for more details.
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*
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* You should have received a copy of the GNU General Public License
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* along with this program; if not, write to the Free Software
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* Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA.
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*/
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#include "config.h"
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#ifdef HAVE_SYS_TYPES_H
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#include <sys/types.h>
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#endif
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#ifdef HAVE_UNISTD_H
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#include <unistd.h>
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#endif
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#include "mp2t.h"
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#include "wtap-int.h"
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#include "buffer.h"
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#include "file_wrappers.h"
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#include <errno.h>
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#include <stdlib.h>
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#include <string.h>
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#include <time.h>
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#define MP2T_SYNC_BYTE 0x47
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#define MP2T_SIZE 188
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#define MP2T_QAM256_BITRATE 38810700 /* bits per second */
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#define MP2T_QAM64_BITRATE 26970350 /* bits per second */
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/* we try to detect trailing data up to 40 bytes after each packet */
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#define TRAILER_LEN_MAX 40
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/* number of consecutive packets we must read to decide that a file
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is actually an mpeg2 ts */
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#define SYNC_STEPS 10
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typedef struct {
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int start_offset;
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/* length of trailing data (e.g. FEC) that's appended after each packet */
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guint8 trailer_len;
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} mp2t_filetype_t;
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static gboolean
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mp2t_read_packet(mp2t_filetype_t *mp2t, FILE_T fh, gint64 offset,
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struct wtap_pkthdr *phdr, Buffer *buf, int *err,
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gchar **err_info)
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{
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guint64 tmp;
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int bytes_read;
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buffer_assure_space(buf, MP2T_SIZE);
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errno = WTAP_ERR_CANT_READ;
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bytes_read = file_read(buffer_start_ptr(buf), MP2T_SIZE, fh);
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if (MP2T_SIZE != bytes_read) {
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*err = file_error(fh, err_info);
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/* bytes_read==0 is end of file, not a short read */
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if (bytes_read>0 && *err == 0) {
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*err = WTAP_ERR_SHORT_READ;
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}
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return FALSE;
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}
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phdr->rec_type = REC_TYPE_PACKET;
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/* XXX - relative, not absolute, time stamps */
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phdr->presence_flags = WTAP_HAS_TS;
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/*
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* Every packet in an MPEG2-TS stream is has a fixed size of
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* MP2T_SIZE plus the number of trailer bytes.
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*
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* The bitrate is constant, so the time offset, from the beginning
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* of the stream, of a given packet is the packet offset, in bits,
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* divided by the bitrate.
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*
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* It would be really cool to be able to configure the bitrate...
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*/
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tmp = ((guint64)(offset - mp2t->start_offset) * 8); /* offset, in bits */
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phdr->ts.secs = (time_t)(tmp / MP2T_QAM256_BITRATE);
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phdr->ts.nsecs = (int)((tmp % MP2T_QAM256_BITRATE) * 1000000000 / MP2T_QAM256_BITRATE);
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phdr->caplen = MP2T_SIZE;
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phdr->len = MP2T_SIZE;
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return TRUE;
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}
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static gboolean
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mp2t_read(wtap *wth, int *err, gchar **err_info, gint64 *data_offset)
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{
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mp2t_filetype_t *mp2t;
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mp2t = (mp2t_filetype_t*) wth->priv;
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*data_offset = file_tell(wth->fh);
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if (!mp2t_read_packet(mp2t, wth->fh, *data_offset, &wth->phdr,
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wth->frame_buffer, err, err_info)) {
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return FALSE;
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}
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/* if there's a trailer, skip it and go to the start of the next packet */
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if (mp2t->trailer_len!=0) {
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if (-1 == file_seek(wth->fh, mp2t->trailer_len, SEEK_CUR, err)) {
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return FALSE;
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}
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}
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return TRUE;
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}
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static gboolean
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mp2t_seek_read(wtap *wth, gint64 seek_off, struct wtap_pkthdr *phdr,
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Buffer *buf, int *err, gchar **err_info)
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{
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mp2t_filetype_t *mp2t;
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if (-1 == file_seek(wth->random_fh, seek_off, SEEK_SET, err)) {
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return FALSE;
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}
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mp2t = (mp2t_filetype_t*) wth->priv;
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if (!mp2t_read_packet(mp2t, wth->random_fh, seek_off, phdr, buf,
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err, err_info)) {
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if (*err == 0)
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*err = WTAP_ERR_SHORT_READ;
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return FALSE;
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}
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return TRUE;
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}
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int
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mp2t_open(wtap *wth, int *err, gchar **err_info)
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{
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int bytes_read;
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guint8 buffer[MP2T_SIZE+TRAILER_LEN_MAX];
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guint8 trailer_len = 0;
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guint sync_steps = 0;
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int i;
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int first;
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mp2t_filetype_t *mp2t;
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errno = WTAP_ERR_CANT_READ;
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bytes_read = file_read(buffer, MP2T_SIZE, wth->fh);
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if (MP2T_SIZE != bytes_read) {
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*err = file_error(wth->fh, err_info);
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if (*err != 0 && *err != WTAP_ERR_SHORT_READ)
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return -1;
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return 0;
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}
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first = -1;
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for (i = 0; i < MP2T_SIZE; i++) {
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if (MP2T_SYNC_BYTE == buffer[i]) {
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first = i;
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break;
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}
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}
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if (-1 == first) {
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return 0; /* wrong file type - not an mpeg2 ts file */
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}
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if (-1 == file_seek(wth->fh, first, SEEK_SET, err)) {
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return -1;
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}
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/* read some packets and make sure they all start with a sync byte */
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do {
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bytes_read = file_read(buffer, MP2T_SIZE+trailer_len, wth->fh);
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if (bytes_read < 0) {
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*err = file_error(wth->fh, err_info);
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return -1; /* read error */
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}
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if (bytes_read < MP2T_SIZE+trailer_len) {
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if(sync_steps<2) return 0; /* wrong file type - not an mpeg2 ts file */
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break; /* end of file, that's ok if we're still in sync */
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}
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if (buffer[0] == MP2T_SYNC_BYTE) {
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sync_steps++;
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}
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else {
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/* no sync byte found, check if trailing data is appended
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and we have to increase the packet size */
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/* if we've already detected a trailer field, we must remain in sync
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another mismatch means we have no mpeg2 ts file */
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if (trailer_len>0)
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return 0;
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/* check if a trailer is appended to the packet */
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for (i=0; i<TRAILER_LEN_MAX; i++) {
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if (buffer[i] == MP2T_SYNC_BYTE) {
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trailer_len = i;
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if (-1 == file_seek(wth->fh, first, SEEK_SET, err)) {
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return -1;
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}
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sync_steps = 0;
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break;
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}
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}
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/* no sync byte found in the vicinity, this is no mpeg2 ts file */
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if (i==TRAILER_LEN_MAX)
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return 0;
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}
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} while (sync_steps < SYNC_STEPS);
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if (-1 == file_seek(wth->fh, first, SEEK_SET, err)) {
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return -1;
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}
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wth->file_type_subtype = WTAP_FILE_TYPE_SUBTYPE_MPEG_2_TS;
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wth->file_encap = WTAP_ENCAP_MPEG_2_TS;
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wth->tsprecision = WTAP_FILE_TSPREC_NSEC;
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wth->subtype_read = mp2t_read;
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wth->subtype_seek_read = mp2t_seek_read;
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wth->snapshot_length = 0;
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mp2t = (mp2t_filetype_t*) g_malloc(sizeof(mp2t_filetype_t));
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if (NULL == mp2t) {
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return -1;
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}
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wth->priv = mp2t;
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mp2t->start_offset = first;
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mp2t->trailer_len = trailer_len;
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return 1;
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}
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