LLVM 20.0.0git
FileHeaderReader.cpp
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1//===- FileHeaderReader.cpp - XRay File Header Reader --------------------===//
2//
3// Part of the LLVM Project, under the Apache License v2.0 with LLVM Exceptions.
4// See https://llvm.org/LICENSE.txt for license information.
5// SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
6//
7//===----------------------------------------------------------------------===//
9
10namespace llvm {
11namespace xray {
12
13// Populates the FileHeader reference by reading the first 32 bytes of the file.
15 uint64_t &OffsetPtr) {
16 // FIXME: Maybe deduce whether the data is little or big-endian using some
17 // magic bytes in the beginning of the file?
18
19 // First 32 bytes of the file will always be the header. We assume a certain
20 // format here:
21 //
22 // (2) uint16 : version
23 // (2) uint16 : type
24 // (4) uint32 : bitfield
25 // (8) uint64 : cycle frequency
26 // (16) - : padding
27 XRayFileHeader FileHeader;
28 auto PreReadOffset = OffsetPtr;
29 FileHeader.Version = HeaderExtractor.getU16(&OffsetPtr);
30 if (OffsetPtr == PreReadOffset)
31 return createStringError(
32 std::make_error_code(std::errc::invalid_argument),
33 "Failed reading version from file header at offset %" PRId64 ".",
34 OffsetPtr);
35
36 PreReadOffset = OffsetPtr;
37 FileHeader.Type = HeaderExtractor.getU16(&OffsetPtr);
38 if (OffsetPtr == PreReadOffset)
39 return createStringError(
40 std::make_error_code(std::errc::invalid_argument),
41 "Failed reading file type from file header at offset %" PRId64 ".",
42 OffsetPtr);
43
44 PreReadOffset = OffsetPtr;
45 uint32_t Bitfield = HeaderExtractor.getU32(&OffsetPtr);
46 if (OffsetPtr == PreReadOffset)
47 return createStringError(
48 std::make_error_code(std::errc::invalid_argument),
49 "Failed reading flag bits from file header at offset %" PRId64 ".",
50 OffsetPtr);
51
52 FileHeader.ConstantTSC = Bitfield & 1uL;
53 FileHeader.NonstopTSC = Bitfield & 1uL << 1;
54 PreReadOffset = OffsetPtr;
55 FileHeader.CycleFrequency = HeaderExtractor.getU64(&OffsetPtr);
56 if (OffsetPtr == PreReadOffset)
57 return createStringError(
58 std::make_error_code(std::errc::invalid_argument),
59 "Failed reading cycle frequency from file header at offset %" PRId64
60 ".",
61 OffsetPtr);
62
63 std::memcpy(&FileHeader.FreeFormData,
64 HeaderExtractor.getData().bytes_begin() + OffsetPtr, 16);
65
66 // Manually advance the offset pointer 16 bytes, after getting a raw memcpy
67 // from the underlying data.
68 OffsetPtr += 16;
69 return std::move(FileHeader);
70}
71
72} // namespace xray
73} // namespace llvm
uint32_t getU32(uint64_t *offset_ptr, Error *Err=nullptr) const
Extract a uint32_t value from *offset_ptr.
StringRef getData() const
Get the data pointed to by this extractor.
Definition: DataExtractor.h:95
uint16_t getU16(uint64_t *offset_ptr, Error *Err=nullptr) const
Extract a uint16_t value from *offset_ptr.
uint64_t getU64(uint64_t *offset_ptr, Error *Err=nullptr) const
Extract a uint64_t value from *offset_ptr.
Tagged union holding either a T or a Error.
Definition: Error.h:481
const unsigned char * bytes_begin() const
Definition: StringRef.h:115
Expected< XRayFileHeader > readBinaryFormatHeader(DataExtractor &HeaderExtractor, uint64_t &OffsetPtr)
Convenience function for loading the file header given a data extractor at a specified offset.
This is an optimization pass for GlobalISel generic memory operations.
Definition: AddressRanges.h:18
Error createStringError(std::error_code EC, char const *Fmt, const Ts &... Vals)
Create formatted StringError object.
Definition: Error.h:1286
Holds functions to get, set or test bitfields.
Definition: Bitfields.h:212
XRay traces all have a header providing some top-matter information useful to help tools determine ho...
Definition: XRayRecord.h:27
bool ConstantTSC
Whether the CPU that produced the timestamp counters (TSC) move at a constant rate.
Definition: XRayRecord.h:37
uint16_t Type
A numeric identifier for the type of file this is.
Definition: XRayRecord.h:33
uint64_t CycleFrequency
The number of cycles per second for the CPU that produced the timestamp counter (TSC) values.
Definition: XRayRecord.h:45
bool NonstopTSC
Whether the CPU that produced the timestamp counters (TSC) do not stop.
Definition: XRayRecord.h:40
uint16_t Version
Version of the XRay implementation that produced this file.
Definition: XRayRecord.h:29