% PT_PKT_SYNC_FORWARD(3)

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# NAME

pt_pkt_sync_forward, pt_pkt_sync_backward, pt_pkt_sync_set - synchronize an

Intel(R) Processor Trace packet decoder

# SYNOPSIS

| **\#include `<intel-pt.h>`**

|

| **int pt_pkt_sync_forward(struct pt_packet_decoder \**decoder*);**

| **int pt_pkt_sync_backward(struct pt_packet_decoder \**decoder*);**

| **int pt_pkt_sync_set(struct pt_packet_decoder \**decoder*,**

|                     **uint64_t *offset*);**

Link with *-lipt*.

# DESCRIPTION

**pt_pkt_sync_forward**() and **pt_pkt_sync_backward**() synchronize an Intel

Processor Trace (Intel PT) packet decoder pointed to by *decoder* onto the trace

stream in *decoder*'s trace buffer.  They search for a Packet Stream Boundary

(PSB) packet in the trace stream and, if successful, set *decoder*'s current

position to that packet.

**pt_pkt_sync_forward**() searches in forward direction from *decoder*'s current

position towards the end of the trace buffer.  If *decoder* has been newly

allocated and has not been synchronized yet, the search starts from the

beginning of the trace.

**pt_pkt_sync_backward**() searches in backward direction from *decoder*'s

current position towards the beginning of the trace buffer.  If *decoder* has

been newly allocated and has not been synchronized yet, the search starts from

the end of the trace.

**pt_pkt_sync_set**() sets *decoder*'s current position to *offset* bytes from

the beginning of its trace buffer.

# RETURN VALUE

All synchronization functions return zero or a positive value on success or a

negative *pt_error_code* enumeration constant in case of an error.

# ERRORS

pte_invalid

:   The *decoder* argument is NULL.

pte_eos

:   There is no (further) PSB packet in the trace stream

    (**pt_pkt_sync_forward**() and **pt_pkt_sync_backward**()) or the *offset*

    argument is too big and the resulting position would be outside of

    *decoder*'s trace buffer (**pt_pkt_sync_set**()).

# EXAMPLE

The following example re-synchronizes an Intel PT packet decoder after decode

errors:

~~~{.c}

int foo(struct pt_packet_decoder *decoder) {

	for (;;) {

		int errcode;

		errcode = pt_pkt_sync_forward(decoder);

		if (errcode < 0)

			return errcode;

		do {

			errcode = decode(decoder);

		} while (errcode >= 0);

	}

}

~~~

# SEE ALSO

**pt_pkt_alloc_decoder**(3), **pt_pkt_free_decoder**(3),

**pt_pkt_get_offset**(3), **pt_pkt_get_sync_offset**(3),

**pt_pkt_get_config**(3), **pt_pkt_next**(3)