xref: /OK3568_Linux_fs/kernel/tools/lib/traceevent/Documentation/libtraceevent-field_read.txt (revision 4882a59341e53eb6f0b4789bf948001014eff981)
1*4882a593Smuzhiyunlibtraceevent(3)
2*4882a593Smuzhiyun================
3*4882a593Smuzhiyun
4*4882a593SmuzhiyunNAME
5*4882a593Smuzhiyun----
6*4882a593Smuzhiyuntep_read_number_field - Reads a number from raw data.
7*4882a593Smuzhiyun
8*4882a593SmuzhiyunSYNOPSIS
9*4882a593Smuzhiyun--------
10*4882a593Smuzhiyun[verse]
11*4882a593Smuzhiyun--
12*4882a593Smuzhiyun*#include <event-parse.h>*
13*4882a593Smuzhiyun
14*4882a593Smuzhiyunint *tep_read_number_field*(struct tep_format_field pass:[*]_field_, const void pass:[*]_data_, unsigned long long pass:[*]_value_);
15*4882a593Smuzhiyun--
16*4882a593Smuzhiyun
17*4882a593SmuzhiyunDESCRIPTION
18*4882a593Smuzhiyun-----------
19*4882a593SmuzhiyunThe _tep_read_number_field()_ function reads the value of the _field_ from the
20*4882a593Smuzhiyunraw _data_ and stores it in the _value_. The function sets the _value_ according
21*4882a593Smuzhiyunto the endianness of the raw data and the current machine and stores it in
22*4882a593Smuzhiyun_value_.
23*4882a593Smuzhiyun
24*4882a593SmuzhiyunRETURN VALUE
25*4882a593Smuzhiyun------------
26*4882a593SmuzhiyunThe _tep_read_number_field()_ function retunrs 0 in case of success, or -1 in
27*4882a593Smuzhiyuncase of an error.
28*4882a593Smuzhiyun
29*4882a593SmuzhiyunEXAMPLE
30*4882a593Smuzhiyun-------
31*4882a593Smuzhiyun[source,c]
32*4882a593Smuzhiyun--
33*4882a593Smuzhiyun#include <event-parse.h>
34*4882a593Smuzhiyun...
35*4882a593Smuzhiyunstruct tep_handle *tep = tep_alloc();
36*4882a593Smuzhiyun...
37*4882a593Smuzhiyunstruct tep_event *event = tep_find_event_by_name(tep, "timer", "hrtimer_start");
38*4882a593Smuzhiyun...
39*4882a593Smuzhiyunvoid process_record(struct tep_record *record)
40*4882a593Smuzhiyun{
41*4882a593Smuzhiyun	unsigned long long pid;
42*4882a593Smuzhiyun	struct tep_format_field *field_pid = tep_find_common_field(event, "common_pid");
43*4882a593Smuzhiyun
44*4882a593Smuzhiyun	if (tep_read_number_field(field_pid, record->data, &pid) != 0) {
45*4882a593Smuzhiyun		/* Failed to get "common_pid" value */
46*4882a593Smuzhiyun	}
47*4882a593Smuzhiyun}
48*4882a593Smuzhiyun...
49*4882a593Smuzhiyun--
50*4882a593SmuzhiyunFILES
51*4882a593Smuzhiyun-----
52*4882a593Smuzhiyun[verse]
53*4882a593Smuzhiyun--
54*4882a593Smuzhiyun*event-parse.h*
55*4882a593Smuzhiyun	Header file to include in order to have access to the library APIs.
56*4882a593Smuzhiyun*-ltraceevent*
57*4882a593Smuzhiyun	Linker switch to add when building a program that uses the library.
58*4882a593Smuzhiyun--
59*4882a593Smuzhiyun
60*4882a593SmuzhiyunSEE ALSO
61*4882a593Smuzhiyun--------
62*4882a593Smuzhiyun_libtraceevent(3)_, _trace-cmd(1)_
63*4882a593Smuzhiyun
64*4882a593SmuzhiyunAUTHOR
65*4882a593Smuzhiyun------
66*4882a593Smuzhiyun[verse]
67*4882a593Smuzhiyun--
68*4882a593Smuzhiyun*Steven Rostedt* <rostedt@goodmis.org>, author of *libtraceevent*.
69*4882a593Smuzhiyun*Tzvetomir Stoyanov* <tz.stoyanov@gmail.com>, author of this man page.
70*4882a593Smuzhiyun--
71*4882a593SmuzhiyunREPORTING BUGS
72*4882a593Smuzhiyun--------------
73*4882a593SmuzhiyunReport bugs to  <linux-trace-devel@vger.kernel.org>
74*4882a593Smuzhiyun
75*4882a593SmuzhiyunLICENSE
76*4882a593Smuzhiyun-------
77*4882a593Smuzhiyunlibtraceevent is Free Software licensed under the GNU LGPL 2.1
78*4882a593Smuzhiyun
79*4882a593SmuzhiyunRESOURCES
80*4882a593Smuzhiyun---------
81*4882a593Smuzhiyunhttps://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git
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