LCOV - code coverage report
Current view: top level - include/llvm/Support - BinaryStreamArray.h (source / functions) Hit Total Coverage
Test: llvm-toolchain.info Lines: 63 67 94.0 %
Date: 2017-09-14 15:23:50 Functions: 51 53 96.2 %
Legend: Lines: hit not hit

          Line data    Source code
       1             : //===- BinaryStreamArray.h - Array backed by an arbitrary 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_SUPPORT_BINARYSTREAMARRAY_H
      11             : #define LLVM_SUPPORT_BINARYSTREAMARRAY_H
      12             : 
      13             : #include "llvm/ADT/ArrayRef.h"
      14             : #include "llvm/ADT/iterator.h"
      15             : #include "llvm/Support/BinaryStreamRef.h"
      16             : #include "llvm/Support/Error.h"
      17             : #include <cassert>
      18             : #include <cstdint>
      19             : 
      20             : /// Lightweight arrays that are backed by an arbitrary BinaryStream.  This file
      21             : /// provides two different array implementations.
      22             : ///
      23             : ///     VarStreamArray - Arrays of variable length records.  The user specifies
      24             : ///       an Extractor type that can extract a record from a given offset and
      25             : ///       return the number of bytes consumed by the record.
      26             : ///
      27             : ///     FixedStreamArray - Arrays of fixed length records.  This is similar in
      28             : ///       spirit to ArrayRef<T>, but since it is backed by a BinaryStream, the
      29             : ///       elements of the array need not be laid out in contiguous memory.
      30             : namespace llvm {
      31             : 
      32             : /// VarStreamArrayExtractor is intended to be specialized to provide customized
      33             : /// extraction logic.  On input it receives a BinaryStreamRef pointing to the
      34             : /// beginning of the next record, but where the length of the record is not yet
      35             : /// known.  Upon completion, it should return an appropriate Error instance if
      36             : /// a record could not be extracted, or if one could be extracted it should
      37             : /// return success and set Len to the number of bytes this record occupied in
      38             : /// the underlying stream, and it should fill out the fields of the value type
      39             : /// Item appropriately to represent the current record.
      40             : ///
      41             : /// You can specialize this template for your own custom value types to avoid
      42             : /// having to specify a second template argument to VarStreamArray (documented
      43             : /// below).
      44             : template <typename T> struct VarStreamArrayExtractor {
      45             :   // Method intentionally deleted.  You must provide an explicit specialization
      46             :   // with the following method implemented.
      47             :   Error operator()(BinaryStreamRef Stream, uint32_t &Len,
      48             :                    T &Item) const = delete;
      49             : };
      50             : 
      51             : /// VarStreamArray represents an array of variable length records backed by a
      52             : /// stream.  This could be a contiguous sequence of bytes in memory, it could
      53             : /// be a file on disk, or it could be a PDB stream where bytes are stored as
      54             : /// discontiguous blocks in a file.  Usually it is desirable to treat arrays
      55             : /// as contiguous blocks of memory, but doing so with large PDB files, for
      56             : /// example, could mean allocating huge amounts of memory just to allow
      57             : /// re-ordering of stream data to be contiguous before iterating over it.  By
      58             : /// abstracting this out, we need not duplicate this memory, and we can
      59             : /// iterate over arrays in arbitrarily formatted streams.  Elements are parsed
      60             : /// lazily on iteration, so there is no upfront cost associated with building
      61             : /// or copying a VarStreamArray, no matter how large it may be.
      62             : ///
      63             : /// You create a VarStreamArray by specifying a ValueType and an Extractor type.
      64             : /// If you do not specify an Extractor type, you are expected to specialize
      65             : /// VarStreamArrayExtractor<T> for your ValueType.
      66             : ///
      67             : /// By default an Extractor is default constructed in the class, but in some
      68             : /// cases you might find it useful for an Extractor to maintain state across
      69             : /// extractions.  In this case you can provide your own Extractor through a
      70             : /// secondary constructor.  The following examples show various ways of
      71             : /// creating a VarStreamArray.
      72             : ///
      73             : ///       // Will use VarStreamArrayExtractor<MyType> as the extractor.
      74             : ///       VarStreamArray<MyType> MyTypeArray;
      75             : ///
      76             : ///       // Will use a default-constructed MyExtractor as the extractor.
      77             : ///       VarStreamArray<MyType, MyExtractor> MyTypeArray2;
      78             : ///
      79             : ///       // Will use the specific instance of MyExtractor provided.
      80             : ///       // MyExtractor need not be default-constructible in this case.
      81             : ///       MyExtractor E(SomeContext);
      82             : ///       VarStreamArray<MyType, MyExtractor> MyTypeArray3(E);
      83             : ///
      84             : 
      85             : template <typename ValueType, typename Extractor> class VarStreamArrayIterator;
      86             : 
      87             : template <typename ValueType,
      88             :           typename Extractor = VarStreamArrayExtractor<ValueType>>
      89       13526 : class VarStreamArray {
      90             :   friend class VarStreamArrayIterator<ValueType, Extractor>;
      91             : 
      92             : public:
      93             :   typedef VarStreamArrayIterator<ValueType, Extractor> Iterator;
      94             : 
      95        4139 :   VarStreamArray() = default;
      96             : 
      97             :   explicit VarStreamArray(const Extractor &E) : E(E) {}
      98             : 
      99          32 :   explicit VarStreamArray(BinaryStreamRef Stream) : Stream(Stream) {}
     100             : 
     101             :   VarStreamArray(BinaryStreamRef Stream, const Extractor &E)
     102             :       : Stream(Stream), E(E) {}
     103             : 
     104             :   Iterator begin(bool *HadError = nullptr) const {
     105        2992 :     return Iterator(*this, E, HadError);
     106             :   }
     107             : 
     108         739 :   bool valid() const { return Stream.valid(); }
     109             : 
     110        3214 :   Iterator end() const { return Iterator(E); }
     111             : 
     112             :   bool empty() const { return Stream.getLength() == 0; }
     113             : 
     114             :   /// \brief given an offset into the array's underlying stream, return an
     115             :   /// iterator to the record at that offset.  This is considered unsafe
     116             :   /// since the behavior is undefined if \p Offset does not refer to the
     117             :   /// beginning of a valid record.
     118             :   Iterator at(uint32_t Offset) const {
     119        1059 :     return Iterator(*this, E, Offset, nullptr);
     120             :   }
     121             : 
     122             :   const Extractor &getExtractor() const { return E; }
     123             :   Extractor &getExtractor() { return E; }
     124             : 
     125          24 :   BinaryStreamRef getUnderlyingStream() const { return Stream; }
     126        3612 :   void setUnderlyingStream(BinaryStreamRef S) { Stream = S; }
     127             : 
     128             : private:
     129             :   BinaryStreamRef Stream;
     130             :   Extractor E;
     131             : };
     132             : 
     133             : template <typename ValueType, typename Extractor>
     134        1038 : class VarStreamArrayIterator
     135             :     : public iterator_facade_base<VarStreamArrayIterator<ValueType, Extractor>,
     136             :                                   std::forward_iterator_tag, ValueType> {
     137             :   typedef VarStreamArrayIterator<ValueType, Extractor> IterType;
     138             :   typedef VarStreamArray<ValueType, Extractor> ArrayType;
     139             : 
     140             : public:
     141             :   VarStreamArrayIterator(const ArrayType &Array, const Extractor &E,
     142             :                          bool *HadError)
     143        1496 :       : VarStreamArrayIterator(Array, E, 0, HadError) {}
     144             : 
     145        2555 :   VarStreamArrayIterator(const ArrayType &Array, const Extractor &E,
     146             :                          uint32_t Offset, bool *HadError)
     147             :       : IterRef(Array.Stream.drop_front(Offset)), Extract(E),
     148        4216 :         Array(&Array), AbsOffset(Offset), HadError(HadError) {
     149        2555 :     if (IterRef.getLength() == 0)
     150         116 :       moveToEnd();
     151             :     else {
     152        9756 :       auto EC = Extract(IterRef, ThisLen, ThisValue);
     153        2439 :       if (EC) {
     154           0 :         consumeError(std::move(EC));
     155             :         markError();
     156             :       }
     157             :     }
     158        2555 :   }
     159             : 
     160             :   VarStreamArrayIterator() = default;
     161        4491 :   explicit VarStreamArrayIterator(const Extractor &E) : Extract(E) {}
     162       11568 :   ~VarStreamArrayIterator() = default;
     163             : 
     164        8427 :   bool operator==(const IterType &R) const {
     165        8427 :     if (Array && R.Array) {
     166             :       // Both have a valid array, make sure they're same.
     167             :       assert(Array == R.Array);
     168           0 :       return IterRef == R.IterRef;
     169             :     }
     170             : 
     171             :     // Both iterators are at the end.
     172        8427 :     if (!Array && !R.Array)
     173             :       return true;
     174             : 
     175             :     // One is not at the end and one is.
     176        7133 :     return false;
     177             :   }
     178             : 
     179             :   const ValueType &operator*() const {
     180             :     assert(Array && !HasError);
     181             :     return ThisValue;
     182             :   }
     183             : 
     184             :   ValueType &operator*() {
     185             :     assert(Array && !HasError);
     186             :     return ThisValue;
     187             :   }
     188             : 
     189        9032 :   IterType &operator+=(unsigned N) {
     190       18064 :     for (unsigned I = 0; I < N; ++I) {
     191             :       // We are done with the current record, discard it so that we are
     192             :       // positioned at the next record.
     193        9032 :       AbsOffset += ThisLen;
     194       27096 :       IterRef = IterRef.drop_front(ThisLen);
     195        9032 :       if (IterRef.getLength() == 0) {
     196             :         // There is nothing after the current record, we must make this an end
     197             :         // iterator.
     198        1266 :         moveToEnd();
     199             :       } else {
     200             :         // There is some data after the current record.
     201       31064 :         auto EC = Extract(IterRef, ThisLen, ThisValue);
     202        7766 :         if (EC) {
     203           3 :           consumeError(std::move(EC));
     204             :           markError();
     205        7765 :         } else if (ThisLen == 0) {
     206             :           // An empty record? Make this an end iterator.
     207           1 :           moveToEnd();
     208             :         }
     209             :       }
     210             :     }
     211        9032 :     return *this;
     212             :   }
     213             : 
     214             :   uint32_t offset() const { return AbsOffset; }
     215             :   uint32_t getRecordLength() const { return ThisLen; }
     216             : 
     217             : private:
     218             :   void moveToEnd() {
     219        1384 :     Array = nullptr;
     220        1268 :     ThisLen = 0;
     221             :   }
     222             :   void markError() {
     223           1 :     moveToEnd();
     224           1 :     HasError = true;
     225           1 :     if (HadError != nullptr)
     226           0 :       *HadError = true;
     227             :   }
     228             : 
     229             :   ValueType ThisValue;
     230             :   BinaryStreamRef IterRef;
     231             :   Extractor Extract;
     232             :   const ArrayType *Array{nullptr};
     233             :   uint32_t ThisLen{0};
     234             :   uint32_t AbsOffset{0};
     235             :   bool HasError{false};
     236             :   bool *HadError{nullptr};
     237             : };
     238             : 
     239             : template <typename T> class FixedStreamArrayIterator;
     240             : 
     241             : /// FixedStreamArray is similar to VarStreamArray, except with each record
     242             : /// having a fixed-length.  As with VarStreamArray, there is no upfront
     243             : /// cost associated with building or copying a FixedStreamArray, as the
     244             : /// memory for each element is not read from the backing stream until that
     245             : /// element is iterated.
     246       34420 : template <typename T> class FixedStreamArray {
     247             :   friend class FixedStreamArrayIterator<T>;
     248             : 
     249             : public:
     250             :   typedef FixedStreamArrayIterator<T> Iterator;
     251             : 
     252        3780 :   FixedStreamArray() = default;
     253        2590 :   explicit FixedStreamArray(BinaryStreamRef Stream) : Stream(Stream) {
     254             :     assert(Stream.getLength() % sizeof(T) == 0);
     255             :   }
     256             : 
     257             :   bool operator==(const FixedStreamArray<T> &Other) const {
     258         602 :     return Stream == Other.Stream;
     259             :   }
     260             : 
     261             :   bool operator!=(const FixedStreamArray<T> &Other) const {
     262             :     return !(*this == Other);
     263             :   }
     264             : 
     265             :   FixedStreamArray &operator=(const FixedStreamArray &) = default;
     266             : 
     267        5224 :   const T &operator[](uint32_t Index) const {
     268             :     assert(Index < size());
     269        5224 :     uint32_t Off = Index * sizeof(T);
     270        5224 :     ArrayRef<uint8_t> Data;
     271       15672 :     if (auto EC = Stream.readBytes(Off, sizeof(T), Data)) {
     272             :       assert(false && "Unexpected failure reading from stream");
     273             :       // This should never happen since we asserted that the stream length was
     274             :       // an exact multiple of the element size.
     275           0 :       consumeError(std::move(EC));
     276             :     }
     277             :     assert(llvm::alignmentAdjustment(Data.data(), alignof(T)) == 0);
     278        5224 :     return *reinterpret_cast<const T *>(Data.data());
     279             :   }
     280             : 
     281        2284 :   uint32_t size() const { return Stream.getLength() / sizeof(T); }
     282             : 
     283         216 :   bool empty() const { return size() == 0; }
     284             : 
     285             :   FixedStreamArrayIterator<T> begin() const {
     286         644 :     return FixedStreamArrayIterator<T>(*this, 0);
     287             :   }
     288             : 
     289             :   FixedStreamArrayIterator<T> end() const {
     290        1344 :     return FixedStreamArrayIterator<T>(*this, size());
     291             :   }
     292             : 
     293             :   const T &front() const { return *begin(); }
     294             :   const T &back() const {
     295             :     FixedStreamArrayIterator<T> I = end();
     296             :     return *(--I);
     297             :   }
     298             : 
     299             :   BinaryStreamRef getUnderlyingStream() const { return Stream; }
     300             : 
     301             : private:
     302             :   BinaryStreamRef Stream;
     303             : };
     304             : 
     305             : template <typename T>
     306       18501 : class FixedStreamArrayIterator
     307             :     : public iterator_facade_base<FixedStreamArrayIterator<T>,
     308             :                                   std::random_access_iterator_tag, const T> {
     309             : 
     310             : public:
     311             :   FixedStreamArrayIterator(const FixedStreamArray<T> &Array, uint32_t Index)
     312        2632 :       : Array(Array), Index(Index) {}
     313             : 
     314             :   FixedStreamArrayIterator<T> &
     315             :   operator=(const FixedStreamArrayIterator<T> &Other) {
     316         120 :     Array = Other.Array;
     317          60 :     Index = Other.Index;
     318             :     return *this;
     319             :   }
     320             : 
     321         301 :   const T &operator*() const { return Array[Index]; }
     322        1630 :   const T &operator*() { return Array[Index]; }
     323             : 
     324             :   bool operator==(const FixedStreamArrayIterator<T> &R) const {
     325             :     assert(Array == R.Array);
     326        2219 :     return (Index == R.Index) && (Array == R.Array);
     327             :   }
     328             : 
     329             :   FixedStreamArrayIterator<T> &operator+=(std::ptrdiff_t N) {
     330        1883 :     Index += N;
     331             :     return *this;
     332             :   }
     333             : 
     334             :   FixedStreamArrayIterator<T> &operator-=(std::ptrdiff_t N) {
     335             :     assert(std::ptrdiff_t(Index) >= N);
     336             :     Index -= N;
     337             :     return *this;
     338             :   }
     339             : 
     340             :   std::ptrdiff_t operator-(const FixedStreamArrayIterator<T> &R) const {
     341             :     assert(Array == R.Array);
     342             :     assert(Index >= R.Index);
     343         369 :     return Index - R.Index;
     344             :   }
     345             : 
     346             :   bool operator<(const FixedStreamArrayIterator<T> &RHS) const {
     347             :     assert(Array == RHS.Array);
     348             :     return Index < RHS.Index;
     349             :   }
     350             : 
     351             : private:
     352             :   FixedStreamArray<T> Array;
     353             :   uint32_t Index;
     354             : };
     355             : 
     356             : } // namespace llvm
     357             : 
     358             : #endif // LLVM_SUPPORT_BINARYSTREAMARRAY_H

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