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      1 //===- StreamRef.h - A copyable reference to a stream -----------*- C++ -*-===//
      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 
     10 #ifndef LLVM_DEBUGINFO_CODEVIEW_STREAMREF_H
     11 #define LLVM_DEBUGINFO_CODEVIEW_STREAMREF_H
     12 
     13 #include "llvm/DebugInfo/CodeView/CodeViewError.h"
     14 #include "llvm/DebugInfo/CodeView/StreamInterface.h"
     15 
     16 namespace llvm {
     17 namespace codeview {
     18 
     19 class StreamRef {
     20 public:
     21   StreamRef() : Stream(nullptr), ViewOffset(0), Length(0) {}
     22   StreamRef(const StreamInterface &Stream)
     23       : Stream(&Stream), ViewOffset(0), Length(Stream.getLength()) {}
     24   StreamRef(const StreamInterface &Stream, uint32_t Offset, uint32_t Length)
     25       : Stream(&Stream), ViewOffset(Offset), Length(Length) {}
     26 
     27   // Use StreamRef.slice() instead.
     28   StreamRef(const StreamRef &S, uint32_t Offset, uint32_t Length) = delete;
     29 
     30   Error readBytes(uint32_t Offset, uint32_t Size,
     31                   ArrayRef<uint8_t> &Buffer) const {
     32     if (ViewOffset + Offset < Offset)
     33       return make_error<CodeViewError>(cv_error_code::insufficient_buffer);
     34     if (Size + Offset > Length)
     35       return make_error<CodeViewError>(cv_error_code::insufficient_buffer);
     36     return Stream->readBytes(ViewOffset + Offset, Size, Buffer);
     37   }
     38 
     39   // Given an offset into the stream, read as much as possible without copying
     40   // any data.
     41   Error readLongestContiguousChunk(uint32_t Offset,
     42                                    ArrayRef<uint8_t> &Buffer) const {
     43     if (Offset >= Length)
     44       return make_error<CodeViewError>(cv_error_code::insufficient_buffer);
     45 
     46     if (auto EC = Stream->readLongestContiguousChunk(Offset, Buffer))
     47       return EC;
     48     // This StreamRef might refer to a smaller window over a larger stream.  In
     49     // that case we will have read out more bytes than we should return, because
     50     // we should not read past the end of the current view.
     51     uint32_t MaxLength = Length - Offset;
     52     if (Buffer.size() > MaxLength)
     53       Buffer = Buffer.slice(0, MaxLength);
     54     return Error::success();
     55   }
     56 
     57   Error writeBytes(uint32_t Offset, ArrayRef<uint8_t> Data) const {
     58     if (Data.size() + Offset > Length)
     59       return make_error<CodeViewError>(cv_error_code::insufficient_buffer);
     60     return Stream->writeBytes(ViewOffset + Offset, Data);
     61   }
     62 
     63   uint32_t getLength() const { return Length; }
     64 
     65   Error commit() const { return Stream->commit(); }
     66 
     67   StreamRef drop_front(uint32_t N) const {
     68     if (!Stream)
     69       return StreamRef();
     70 
     71     N = std::min(N, Length);
     72     return StreamRef(*Stream, ViewOffset + N, Length - N);
     73   }
     74 
     75   StreamRef keep_front(uint32_t N) const {
     76     if (!Stream)
     77       return StreamRef();
     78     N = std::min(N, Length);
     79     return StreamRef(*Stream, ViewOffset, N);
     80   }
     81 
     82   StreamRef slice(uint32_t Offset, uint32_t Len) const {
     83     return drop_front(Offset).keep_front(Len);
     84   }
     85 
     86   bool operator==(const StreamRef &Other) const {
     87     if (Stream != Other.Stream)
     88       return false;
     89     if (ViewOffset != Other.ViewOffset)
     90       return false;
     91     if (Length != Other.Length)
     92       return false;
     93     return true;
     94   }
     95 
     96 private:
     97   const StreamInterface *Stream;
     98   uint32_t ViewOffset;
     99   uint32_t Length;
    100 };
    101 }
    102 }
    103 
    104 #endif // LLVM_DEBUGINFO_CODEVIEW_STREAMREF_H
    105