1 //===- StreamingMemoryObject.h - Streamable data interface -----*- C++ -*-===//
3 // The LLVM Compiler Infrastructure
5 // This file is distributed under the University of Illinois Open Source
6 // License. See LICENSE.TXT for details.
8 //===----------------------------------------------------------------------===//
10 #ifndef LLVM_SUPPORT_STREAMINGMEMORYOBJECT_H
11 #define LLVM_SUPPORT_STREAMINGMEMORYOBJECT_H
13 #include "llvm/Support/Compiler.h"
14 #include "llvm/Support/DataStream.h"
15 #include "llvm/Support/ErrorHandling.h"
16 #include "llvm/Support/MemoryObject.h"
23 /// Interface to data which is actually streamed from a DataStreamer. In
24 /// addition to inherited members, it has the dropLeadingBytes and
25 /// setKnownObjectSize methods which are not applicable to non-streamed objects.
26 class StreamingMemoryObject : public MemoryObject {
28 StreamingMemoryObject(DataStreamer *streamer);
29 uint64_t getExtent() const override;
30 uint64_t readBytes(uint8_t *Buf, uint64_t Size,
31 uint64_t Address) const override;
32 const uint8_t *getPointer(uint64_t address, uint64_t size) const override {
33 // This could be fixed by ensuring the bytes are fetched and making a copy,
34 // requiring that the bitcode size be known, or otherwise ensuring that
35 // the memory doesn't go away/get reallocated, but it's
36 // not currently necessary. Users that need the pointer don't stream.
37 llvm_unreachable("getPointer in streaming memory objects not allowed");
40 bool isValidAddress(uint64_t address) const override;
42 /// Drop s bytes from the front of the stream, pushing the positions of the
43 /// remaining bytes down by s. This is used to skip past the bitcode header,
44 /// since we don't know a priori if it's present, and we can't put bytes
45 /// back into the stream once we've read them.
46 bool dropLeadingBytes(size_t s);
48 /// If the data object size is known in advance, many of the operations can
49 /// be made more efficient, so this method should be called before reading
50 /// starts (although it can be called anytime).
51 void setKnownObjectSize(size_t size);
54 const static uint32_t kChunkSize = 4096 * 4;
55 mutable std::vector<unsigned char> Bytes;
56 std::unique_ptr<DataStreamer> Streamer;
57 mutable size_t BytesRead; // Bytes read from stream
58 size_t BytesSkipped;// Bytes skipped at start of stream (e.g. wrapper/header)
59 mutable size_t ObjectSize; // 0 if unknown, set if wrapper seen or EOF reached
60 mutable bool EOFReached;
62 // Fetch enough bytes such that Pos can be read or EOF is reached
63 // (i.e. BytesRead > Pos). Return true if Pos can be read.
64 // Unlike most of the functions in BitcodeReader, returns true on success.
65 // Most of the requests will be small, but we fetch at kChunkSize bytes
66 // at a time to avoid making too many potentially expensive GetBytes calls
67 bool fetchToPos(size_t Pos) const {
69 return Pos < ObjectSize;
70 while (Pos >= BytesRead) {
71 Bytes.resize(BytesRead + BytesSkipped + kChunkSize);
72 size_t bytes = Streamer->GetBytes(&Bytes[BytesRead + BytesSkipped],
75 if (bytes != kChunkSize) { // reached EOF/ran out of bytes
76 ObjectSize = BytesRead;
81 return Pos < BytesRead;
84 StreamingMemoryObject(const StreamingMemoryObject&) LLVM_DELETED_FUNCTION;
85 void operator=(const StreamingMemoryObject&) LLVM_DELETED_FUNCTION;
88 MemoryObject *getNonStreamedMemoryObject(
89 const unsigned char *Start, const unsigned char *End);
92 #endif // STREAMINGMEMORYOBJECT_H_