clang/lib/AST/ByteCode/BitcastBuffer.h

   1 //===--------------------- BitcastBuffer.h ----------------------*- C++ -*-===//
   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 //===----------------------------------------------------------------------===//
   8 #ifndef LLVM_CLANG_AST_INTERP_BITCAST_BUFFER_H
   9 #define LLVM_CLANG_AST_INTERP_BITCAST_BUFFER_H
  10
  11 #include <cassert>
  12 #include <cstddef>
  13 #include <memory>
  14
  15 namespace clang {
  16 namespace interp {
  17
  18 enum class Endian { Little, Big };
  19
  20 /// A quantity in bits.
  21 struct Bits {
  22   size_t N = 0;
  23   Bits() = default;
  24   static Bits zero() { return Bits(0); }
  25   explicit Bits(size_t Quantity) : N(Quantity) {}
  26   size_t getQuantity() const { return N; }
  27   size_t roundToBytes() const { return N / 8; }
  28   size_t getOffsetInByte() const { return N % 8; }
  29   bool isFullByte() const { return N % 8 == 0; }
  30   bool nonZero() const { return N != 0; }
  31
  32   Bits operator-(Bits Other) { return Bits(N - Other.N); }
  33   Bits operator+(Bits Other) { return Bits(N + Other.N); }
  34   Bits operator+=(size_t O) {
  35     N += O;
  36     return *this;
  37   }
  38
  39   bool operator>=(Bits Other) { return N >= Other.N; }
  40 };
  41
  42 /// A quantity in bytes.
  43 struct Bytes {
  44   size_t N;
  45   explicit Bytes(size_t Quantity) : N(Quantity) {}
  46   size_t getQuantity() const { return N; }
  47   Bits toBits() const { return Bits(N * 8); }
  48 };
  49
  50 /// Track what bits have been initialized to known values and which ones
  51 /// have indeterminate value.
  52 struct BitcastBuffer {
  53   Bits FinalBitSize;
  54   std::unique_ptr<std::byte[]> Data;
  55
  56   BitcastBuffer(Bits FinalBitSize) : FinalBitSize(FinalBitSize) {
  57     assert(FinalBitSize.isFullByte());
  58     unsigned ByteSize = FinalBitSize.roundToBytes();
  59     Data = std::make_unique<std::byte[]>(ByteSize);
  60   }
  61
  62   /// Returns the buffer size in bits.
  63   Bits size() const { return FinalBitSize; }
  64
  65   /// Returns \c true if all bits in the buffer have been initialized.
  66   bool allInitialized() const {
  67     // FIXME: Implement.
  68     return true;
  69   }
  70
  71   /// Push \p BitWidth bits at \p BitOffset from \p In into the buffer.
  72   /// \p TargetEndianness is the endianness of the target we're compiling for.
  73   /// \p In must hold at least \p BitWidth many bits.
  74   void pushData(const std::byte *In, Bits BitOffset, Bits BitWidth,
  75                 Endian TargetEndianness);
  76
  77   /// Copy \p BitWidth bits at offset \p BitOffset from the buffer.
  78   /// \p TargetEndianness is the endianness of the target we're compiling for.
  79   ///
  80   /// The returned output holds exactly (\p FullBitWidth / 8) bytes.
  81   std::unique_ptr<std::byte[]> copyBits(Bits BitOffset, Bits BitWidth,
  82                                         Bits FullBitWidth,
  83                                         Endian TargetEndianness) const;
  84 };
  85
  86 } // namespace interp
  87 } // namespace clang
  88 #endif