% PT_INSN_ALLOC_DECODER(3)

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# NAME

pt_insn_alloc_decoder, pt_insn_free_decoder - allocate/free an Intel(R)
Processor Trace instruction flow decoder


# SYNOPSIS

| **\#include `<intel-pt.h>`**
|
| **struct pt_insn_decoder \***
| **pt_insn_alloc_decoder(const struct pt_config \**config*);**
|
| **void pt_insn_free_decoder(struct pt_insn_decoder \**decoder*);**

Link with *-lipt*.


# DESCRIPTION

An instruction flow decoder decodes raw Intel Processor Trace (Intel PT) into a
sequence of instructions described by the *pt_insn* structure.  See
**pt_insn_next**(3).

**pt_insn_alloc_decoder**() allocates a new instruction flow decoder and returns
a pointer to it.  The *config* argument points to a *pt_config* object.  See
**pt_config**(3).  The *config* argument will not be referenced by the returned
decoder but the trace buffer defined by the *config* argument's *begin* and
*end* fields will.

The returned instruction flow decoder needs to be synchronized onto the trace
stream before it can be used.  To synchronize the instruction flow decoder, use
**pt_insn_sync_forward**(3), **pt_insn_sync_backward**(3), or
**pt_insn_sync_set**(3).

**pt_insn_free_decoder**() frees the Intel PT instruction flow decoder pointed
to by *decoder*.  The *decoder* argument must be NULL or point to a decoder that
has been allocated by a call to **pt_insn_alloc_decoder**().


# RETURN VALUE

**pt_insn_alloc_decoder**() returns a pointer to a *pt_insn_decoder* object on
success or NULL in case of an error.


# EXAMPLE

~~~{.c}
int foo(const struct pt_config *config) {
	struct pt_insn_decoder *decoder;
	errcode;

	decoder = pt_insn_alloc_decoder(config);
	if (!decoder)
		return pte_nomem;

	errcode = bar(decoder);

	pt_insn_free_decoder(decoder);
	return errcode;
}
~~~


# SEE ALSO

**pt_config**(3), **pt_insn_sync_forward**(3), **pt_insn_sync_backward**(3),
**pt_insn_sync_set**(3), **pt_insn_get_offset**(3), **pt_insn_get_sync_offset**(3),
**pt_insn_get_image**(3), **pt_insn_set_image**(3), **pt_insn_get_config**(3),
**pt_insn_time**(3), **pt_insn_core_bus_ratio**(3), **pt_insn_next**(3)