FileHeaderReader.cpp revision 344779
1//===- FileHeaderReader.cpp - XRay File Header Reader --------------------===// 2// 3// The LLVM Compiler Infrastructure 4// 5// This file is distributed under the University of Illinois Open Source 6// License. See LICENSE.TXT for details. 7// 8//===----------------------------------------------------------------------===// 9#include "llvm/XRay/FileHeaderReader.h" 10 11namespace llvm { 12namespace xray { 13 14// Populates the FileHeader reference by reading the first 32 bytes of the file. 15Expected<XRayFileHeader> readBinaryFormatHeader(DataExtractor &HeaderExtractor, 16 uint32_t &OffsetPtr) { 17 // FIXME: Maybe deduce whether the data is little or big-endian using some 18 // magic bytes in the beginning of the file? 19 20 // First 32 bytes of the file will always be the header. We assume a certain 21 // format here: 22 // 23 // (2) uint16 : version 24 // (2) uint16 : type 25 // (4) uint32 : bitfield 26 // (8) uint64 : cycle frequency 27 // (16) - : padding 28 XRayFileHeader FileHeader; 29 auto PreReadOffset = OffsetPtr; 30 FileHeader.Version = HeaderExtractor.getU16(&OffsetPtr); 31 if (OffsetPtr == PreReadOffset) 32 return createStringError( 33 std::make_error_code(std::errc::invalid_argument), 34 "Failed reading version from file header at offset %d.", 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 %d.", OffsetPtr); 42 43 PreReadOffset = OffsetPtr; 44 uint32_t Bitfield = HeaderExtractor.getU32(&OffsetPtr); 45 if (OffsetPtr == PreReadOffset) 46 return createStringError( 47 std::make_error_code(std::errc::invalid_argument), 48 "Failed reading flag bits from file header at offset %d.", OffsetPtr); 49 50 FileHeader.ConstantTSC = Bitfield & 1uL; 51 FileHeader.NonstopTSC = Bitfield & 1uL << 1; 52 PreReadOffset = OffsetPtr; 53 FileHeader.CycleFrequency = HeaderExtractor.getU64(&OffsetPtr); 54 if (OffsetPtr == PreReadOffset) 55 return createStringError( 56 std::make_error_code(std::errc::invalid_argument), 57 "Failed reading cycle frequency from file header at offset %d.", 58 OffsetPtr); 59 60 std::memcpy(&FileHeader.FreeFormData, 61 HeaderExtractor.getData().bytes_begin() + OffsetPtr, 16); 62 63 // Manually advance the offset pointer 16 bytes, after getting a raw memcpy 64 // from the underlying data. 65 OffsetPtr += 16; 66 return std::move(FileHeader); 67} 68 69} // namespace xray 70} // namespace llvm 71