lib/XRay/FileHeaderReader.cpp

   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
  11 namespace llvm {
  12 namespace xray {
  13
  14 // Populates the FileHeader reference by reading the first 32 bytes of the file.
  15 Expected<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   if (FileHeader.Version != 1 && FileHeader.Version != 2 &&
  67       FileHeader.Version != 3)
  68     return createStringError(std::make_error_code(std::errc::invalid_argument),
  69                              "Unsupported XRay file version: %d at offset %d",
  70                              FileHeader.Version, OffsetPtr);
  71   return std::move(FileHeader);
  72 }
  73
  74 } // namespace xray
  75 } // namespace llvm