[#llvm-xray-XRayFileHeader]
= xref:llvm.adoc[llvm]::xref:llvm/xray.adoc[xray]::XRayFileHeader
:relfileprefix: ../../
:mrdocs:

XRay traces all have a header providing some top‐matter information useful to help tools determine how to interpret the information available in the trace.

== Synopsis

Declared in `<llvm/XRay/XRayRecord.h>`

[source,cpp,subs="verbatim,replacements,macros,-callouts"]
----
struct XRayFileHeader;
----

== Data Members

[cols="1,4"]
|===
| Name| Description
| xref:llvm/xray/XRayFileHeader/ConstantTSC.adoc[`ConstantTSC`] 
| Whether the CPU that produced the timestamp counters (TSC) move at a constant rate.
| xref:llvm/xray/XRayFileHeader/CycleFrequency.adoc[`CycleFrequency`] 
| Number of cycles per second for the CPU that produced the TSC values.
| xref:llvm/xray/XRayFileHeader/FreeFormData.adoc[`FreeFormData`] 
| Type‐dependent free‐form data whose layout varies by XRay record format.
| xref:llvm/xray/XRayFileHeader/NonstopTSC.adoc[`NonstopTSC`] 
| Whether the CPU that produced the timestamp counters (TSC) do not stop.
| xref:llvm/xray/XRayFileHeader/Type.adoc[`Type`] 
| A numeric identifier for the type of file this is. Best used in combination with Version.
| xref:llvm/xray/XRayFileHeader/Version.adoc[`Version`] 
| Version of the XRay implementation that produced this file.
|===


== Non-Member Functions

[cols="1,4"]
|===
| Name| Description
| xref:llvm/xray/readBinaryFormatHeader.adoc[`readBinaryFormatHeader`]
| Convenience function for loading the file header given a data extractor at a specified offset.
|===


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