'\" t
.\"     Title: libtraceevent
.\"    Author: [see the "AUTHOR" section]
.\" Generator: DocBook XSL Stylesheets vsnapshot <http://docbook.sf.net/>
.\"      Date: 01/14/2024
.\"    Manual: libtraceevent Manual
.\"    Source: libtraceevent 1.8.2
.\"  Language: English
.\"
.TH "LIBTRACEEVENT" "3" "01/14/2024" "libtraceevent 1\&.8\&.2" "libtraceevent Manual"
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.nh
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.SH "NAME"
tep_get_header_page_size, tep_get_header_timestamp_size, tep_is_old_format \- Get the data stored in the header page, in kernel context\&.
.SH "SYNOPSIS"
.sp
.nf
\fB#include <event\-parse\&.h>\fR

int \fBtep_get_header_page_size\fR(struct tep_handle *\fItep\fR);
int \fBtep_get_header_timestamp_size\fR(struct tep_handle *\fItep\fR);
bool \fBtep_is_old_format\fR(struct tep_handle *\fItep\fR);
.fi
.SH "DESCRIPTION"
.sp
These functions retrieve information from kernel context, stored in tracefs events/header_page\&. Old kernels do not have header page info, so default values from user space context are used\&.
.sp
The \fBtep_get_header_page_size()\fR function returns the size of a long integer, in kernel context\&. The \fItep\fR argument is trace event parser context\&. This information is retrieved from tracefs events/header_page, "commit" field\&.
.sp
The \fBtep_get_header_timestamp_size()\fR function returns the size of timestamps, in kernel context\&. The \fItep\fR argument is trace event parser context\&. This information is retrieved from tracefs events/header_page, "timestamp" field\&.
.sp
The \fBtep_is_old_format()\fR function returns true if the kernel predates the addition of events/header_page, otherwise it returns false\&.
.SH "RETURN VALUE"
.sp
The \fBtep_get_header_page_size()\fR function returns the size of a long integer, in bytes\&.
.sp
The \fBtep_get_header_timestamp_size()\fR function returns the size of timestamps, in bytes\&.
.sp
The \fBtep_is_old_format()\fR function returns true, if an old kernel is used to generate the tracing data, which has no event/header_page\&. If the kernel is new, or \fItep\fR is NULL, false is returned\&.
.SH "EXAMPLE"
.sp
.if n \{\
.RS 4
.\}
.nf
#include <event\-parse\&.h>
\&.\&.\&.
struct tep_handle *tep = tep_alloc();
\&.\&.\&.
        int longsize;
        int timesize;
        bool old;

        longsize = tep_get_header_page_size(tep);
        timesize = tep_get_header_timestamp_size(tep);
        old = tep_is_old_format(tep);

        printf ("%s kernel is used to generate the tracing data\&.\en",
                old?"Old":"New");
        printf("The size of a long integer is %d bytes\&.\en", longsize);
        printf("The timestamps size is %d bytes\&.\en", timesize);
\&.\&.\&.
.fi
.if n \{\
.RE
.\}
.SH "FILES"
.sp
.if n \{\
.RS 4
.\}
.nf
\fBevent\-parse\&.h\fR
        Header file to include in order to have access to the library APIs\&.
\fB\-ltraceevent\fR
        Linker switch to add when building a program that uses the library\&.
.fi
.if n \{\
.RE
.\}
.SH "SEE ALSO"
.sp
\fBlibtraceevent\fR(3), \fBtrace\-cmd\fR(1)
.SH "AUTHOR"
.sp
.if n \{\
.RS 4
.\}
.nf
\fBSteven Rostedt\fR <\m[blue]\fBrostedt@goodmis\&.org\fR\m[]\&\s-2\u[1]\d\s+2>, author of \fBlibtraceevent\fR\&.
\fBTzvetomir Stoyanov\fR <\m[blue]\fBtz\&.stoyanov@gmail\&.com\fR\m[]\&\s-2\u[2]\d\s+2>, author of this man page\&.
.fi
.if n \{\
.RE
.\}
.SH "REPORTING BUGS"
.sp
Report bugs to <\m[blue]\fBlinux\-trace\-devel@vger\&.kernel\&.org\fR\m[]\&\s-2\u[3]\d\s+2>
.SH "LICENSE"
.sp
libtraceevent is Free Software licensed under the GNU LGPL 2\&.1
.SH "RESOURCES"
.sp
\m[blue]\fBhttps://git\&.kernel\&.org/pub/scm/libs/libtrace/libtraceevent\&.git/\fR\m[]
.SH "NOTES"
.IP " 1." 4
rostedt@goodmis.org
.RS 4
\%mailto:rostedt@goodmis.org
.RE
.IP " 2." 4
tz.stoyanov@gmail.com
.RS 4
\%mailto:tz.stoyanov@gmail.com
.RE
.IP " 3." 4
linux-trace-devel@vger.kernel.org
.RS 4
\%mailto:linux-trace-devel@vger.kernel.org
.RE