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BinaryStreamArray.h
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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"
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.
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>>
90  friend class VarStreamArrayIterator<ValueType, Extractor>;
91 
92 public:
94 
95  VarStreamArray() = default;
96 
97  explicit VarStreamArray(const Extractor &E) : E(E) {}
98 
99  explicit VarStreamArray(BinaryStreamRef Stream, uint32_t Skew = 0)
100  : Stream(Stream), Skew(Skew) {}
101 
102  VarStreamArray(BinaryStreamRef Stream, const Extractor &E, uint32_t Skew = 0)
103  : Stream(Stream), E(E), Skew(Skew) {}
104 
105  Iterator begin(bool *HadError = nullptr) const {
106  return Iterator(*this, E, Skew, nullptr);
107  }
108 
109  bool valid() const { return Stream.valid(); }
110 
111  uint32_t skew() const { return Skew; }
112  Iterator end() const { return Iterator(E); }
113 
114  bool empty() const { return Stream.getLength() == 0; }
115 
117  uint32_t End) const {
118  assert(Begin >= Skew);
119  // We should never cut off the beginning of the stream since it might be
120  // skewed, meaning the initial bytes are important.
121  BinaryStreamRef NewStream = Stream.slice(0, End);
122  return {NewStream, E, Begin};
123  }
124 
125  /// given an offset into the array's underlying stream, return an
126  /// iterator to the record at that offset. This is considered unsafe
127  /// since the behavior is undefined if \p Offset does not refer to the
128  /// beginning of a valid record.
129  Iterator at(uint32_t Offset) const {
130  return Iterator(*this, E, Offset, nullptr);
131  }
132 
133  const Extractor &getExtractor() const { return E; }
134  Extractor &getExtractor() { return E; }
135 
136  BinaryStreamRef getUnderlyingStream() const { return Stream; }
138  Stream = S;
139  this->Skew = Skew;
140  }
141 
142  void drop_front() { Skew += begin()->length(); }
143 
144 private:
145  BinaryStreamRef Stream;
146  Extractor E;
147  uint32_t Skew;
148 };
149 
150 template <typename ValueType, typename Extractor>
152  : public iterator_facade_base<VarStreamArrayIterator<ValueType, Extractor>,
153  std::forward_iterator_tag, ValueType> {
156 
157 public:
158  VarStreamArrayIterator(const ArrayType &Array, const Extractor &E,
159  uint32_t Offset, bool *HadError)
160  : IterRef(Array.Stream.drop_front(Offset)), Extract(E),
161  Array(&Array), AbsOffset(Offset), HadError(HadError) {
162  if (IterRef.getLength() == 0)
163  moveToEnd();
164  else {
165  auto EC = Extract(IterRef, ThisLen, ThisValue);
166  if (EC) {
167  consumeError(std::move(EC));
168  markError();
169  }
170  }
171  }
172 
173  VarStreamArrayIterator() = default;
174  explicit VarStreamArrayIterator(const Extractor &E) : Extract(E) {}
175  ~VarStreamArrayIterator() = default;
176 
177  bool operator==(const IterType &R) const {
178  if (Array && R.Array) {
179  // Both have a valid array, make sure they're same.
180  assert(Array == R.Array);
181  return IterRef == R.IterRef;
182  }
183 
184  // Both iterators are at the end.
185  if (!Array && !R.Array)
186  return true;
187 
188  // One is not at the end and one is.
189  return false;
190  }
191 
192  const ValueType &operator*() const {
193  assert(Array && !HasError);
194  return ThisValue;
195  }
196 
198  assert(Array && !HasError);
199  return ThisValue;
200  }
201 
202  IterType &operator+=(unsigned N) {
203  for (unsigned I = 0; I < N; ++I) {
204  // We are done with the current record, discard it so that we are
205  // positioned at the next record.
206  AbsOffset += ThisLen;
207  IterRef = IterRef.drop_front(ThisLen);
208  if (IterRef.getLength() == 0) {
209  // There is nothing after the current record, we must make this an end
210  // iterator.
211  moveToEnd();
212  } else {
213  // There is some data after the current record.
214  auto EC = Extract(IterRef, ThisLen, ThisValue);
215  if (EC) {
216  consumeError(std::move(EC));
217  markError();
218  } else if (ThisLen == 0) {
219  // An empty record? Make this an end iterator.
220  moveToEnd();
221  }
222  }
223  }
224  return *this;
225  }
226 
227  uint32_t offset() const { return AbsOffset; }
228  uint32_t getRecordLength() const { return ThisLen; }
229 
230 private:
231  void moveToEnd() {
232  Array = nullptr;
233  ThisLen = 0;
234  }
235  void markError() {
236  moveToEnd();
237  HasError = true;
238  if (HadError != nullptr)
239  *HadError = true;
240  }
241 
242  ValueType ThisValue;
243  BinaryStreamRef IterRef;
244  Extractor Extract;
245  const ArrayType *Array{nullptr};
246  uint32_t ThisLen{0};
247  uint32_t AbsOffset{0};
248  bool HasError{false};
249  bool *HadError{nullptr};
250 };
251 
252 template <typename T> class FixedStreamArrayIterator;
253 
254 /// FixedStreamArray is similar to VarStreamArray, except with each record
255 /// having a fixed-length. As with VarStreamArray, there is no upfront
256 /// cost associated with building or copying a FixedStreamArray, as the
257 /// memory for each element is not read from the backing stream until that
258 /// element is iterated.
259 template <typename T> class FixedStreamArray {
261 
262 public:
264 
265  FixedStreamArray() = default;
266  explicit FixedStreamArray(BinaryStreamRef Stream) : Stream(Stream) {
267  assert(Stream.getLength() % sizeof(T) == 0);
268  }
269 
270  bool operator==(const FixedStreamArray<T> &Other) const {
271  return Stream == Other.Stream;
272  }
273 
274  bool operator!=(const FixedStreamArray<T> &Other) const {
275  return !(*this == Other);
276  }
277 
278  FixedStreamArray &operator=(const FixedStreamArray &) = default;
279 
280  const T &operator[](uint32_t Index) const {
281  assert(Index < size());
282  uint32_t Off = Index * sizeof(T);
284  if (auto EC = Stream.readBytes(Off, sizeof(T), Data)) {
285  assert(false && "Unexpected failure reading from stream");
286  // This should never happen since we asserted that the stream length was
287  // an exact multiple of the element size.
288  consumeError(std::move(EC));
289  }
290  assert(llvm::alignmentAdjustment(Data.data(), alignof(T)) == 0);
291  return *reinterpret_cast<const T *>(Data.data());
292  }
293 
294  uint32_t size() const { return Stream.getLength() / sizeof(T); }
295 
296  bool empty() const { return size() == 0; }
297 
299  return FixedStreamArrayIterator<T>(*this, 0);
300  }
301 
303  return FixedStreamArrayIterator<T>(*this, size());
304  }
305 
306  const T &front() const { return *begin(); }
307  const T &back() const {
309  return *(--I);
310  }
311 
312  BinaryStreamRef getUnderlyingStream() const { return Stream; }
313 
314 private:
315  BinaryStreamRef Stream;
316 };
317 
318 template <typename T>
320  : public iterator_facade_base<FixedStreamArrayIterator<T>,
321  std::random_access_iterator_tag, const T> {
322 
323 public:
325  : Array(Array), Index(Index) {}
326 
329  Array = Other.Array;
330  Index = Other.Index;
331  return *this;
332  }
333 
334  const T &operator*() const { return Array[Index]; }
335  const T &operator*() { return Array[Index]; }
336 
338  assert(Array == R.Array);
339  return (Index == R.Index) && (Array == R.Array);
340  }
341 
343  Index += N;
344  return *this;
345  }
346 
348  assert(std::ptrdiff_t(Index) >= N);
349  Index -= N;
350  return *this;
351  }
352 
353  std::ptrdiff_t operator-(const FixedStreamArrayIterator<T> &R) const {
354  assert(Array == R.Array);
355  assert(Index >= R.Index);
356  return Index - R.Index;
357  }
358 
359  bool operator<(const FixedStreamArrayIterator<T> &RHS) const {
360  assert(Array == RHS.Array);
361  return Index < RHS.Index;
362  }
363 
364 private:
365  FixedStreamArray<T> Array;
366  uint32_t Index;
367 };
368 
369 } // namespace llvm
370 
371 #endif // LLVM_SUPPORT_BINARYSTREAMARRAY_H
const_iterator end(StringRef path)
Get end iterator over path.
Definition: Path.cpp:259
bool operator==(const IterType &R) const
PointerUnion< const Value *, const PseudoSourceValue * > ValueType
RefType slice(uint32_t Offset, uint32_t Len) const
Return a new BinaryStreamRef with the first Offset elements removed, and retaining exactly Len elemen...
const ValueType & operator*() const
const_iterator begin(StringRef path, Style style=Style::native)
Get begin iterator over path.
Definition: Path.cpp:250
This class represents lattice values for constants.
Definition: AllocatorList.h:24
Iterator end() const
VarStreamArray(const Extractor &E)
VarStreamArray(BinaryStreamRef Stream, const Extractor &E, uint32_t Skew=0)
bool operator!=(const FixedStreamArray< T > &Other) const
BinaryStreamRef getUnderlyingStream() const
VarStreamArray(BinaryStreamRef Stream, uint32_t Skew=0)
FixedStreamArray is similar to VarStreamArray, except with each record having a fixed-length.
VarStreamArrayExtractor is intended to be specialized to provide customized extraction logic...
VarStreamArray< ValueType, Extractor > substream(uint32_t Begin, uint32_t End) const
FixedStreamArrayIterator< T > Iterator
const T & operator[](uint32_t Index) const
void setUnderlyingStream(BinaryStreamRef S, uint32_t Skew=0)
FixedStreamArrayIterator< T > & operator=(const FixedStreamArrayIterator< T > &Other)
ELFYAML::ELF_STO Other
Definition: ELFYAML.cpp:783
#define T
Class to represent array types.
Definition: DerivedTypes.h:369
uint32_t skew() const
CRTP base class which implements the entire standard iterator facade in terms of a minimal subset of ...
Definition: iterator.h:68
VarStreamArrayIterator(const ArrayType &Array, const Extractor &E, uint32_t Offset, bool *HadError)
Extractor & getExtractor()
VarStreamArrayIterator< ValueType, Extractor > Iterator
static GCRegistry::Add< CoreCLRGC > E("coreclr", "CoreCLR-compatible GC")
size_t alignmentAdjustment(const void *Ptr, size_t Alignment)
Returns the necessary adjustment for aligning Ptr to Alignment bytes, rounding up.
Definition: MathExtras.h:634
VarStreamArrayIterator(const Extractor &E)
bool operator==(const FixedStreamArrayIterator< T > &R) const
IterType & operator+=(unsigned N)
void consumeError(Error Err)
Consume a Error without doing anything.
Definition: Error.h:982
const T & front() const
FixedStreamArray(BinaryStreamRef Stream)
uint32_t getLength() const
auto size(R &&Range, typename std::enable_if< std::is_same< typename std::iterator_traits< decltype(Range.begin())>::iterator_category, std::random_access_iterator_tag >::value, void >::type *=nullptr) -> decltype(std::distance(Range.begin(), Range.end()))
Get the size of a range.
Definition: STLExtras.h:1161
FixedStreamArrayIterator(const FixedStreamArray< T > &Array, uint32_t Index)
BinaryStreamRef is to BinaryStream what ArrayRef is to an Array.
VarStreamArray represents an array of variable length records backed by a stream. ...
FixedStreamArrayIterator< T > & operator-=(std::ptrdiff_t N)
FixedStreamArrayIterator< T > & operator+=(std::ptrdiff_t N)
const T & back() const
BinaryStreamRef getUnderlyingStream() const
#define I(x, y, z)
Definition: MD5.cpp:58
#define N
Error operator()(BinaryStreamRef Stream, uint32_t &Len, T &Item) const =delete
assert(ImpDefSCC.getReg()==AMDGPU::SCC &&ImpDefSCC.isDef())
FixedStreamArrayIterator< T > end() const
Iterator at(uint32_t Offset) const
given an offset into the array&#39;s underlying stream, return an iterator to the record at that offset...
Iterator begin(bool *HadError=nullptr) const
const Extractor & getExtractor() const
std::ptrdiff_t operator-(const FixedStreamArrayIterator< T > &R) const
Lightweight error class with error context and mandatory checking.
Definition: Error.h:158
bool operator==(const FixedStreamArray< T > &Other) const
FixedStreamArrayIterator< T > begin() const
A discriminated union of two pointer types, with the discriminator in the low bit of the pointer...
Definition: PointerUnion.h:87