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"
22 /// Interface to data which is actually streamed from a DataStreamer. In
23 /// addition to inherited members, it has the dropLeadingBytes and
24 /// setKnownObjectSize methods which are not applicable to non-streamed objects.
25 class StreamingMemoryObject : public MemoryObject {
27 StreamingMemoryObject(DataStreamer *streamer);
28 uint64_t getExtent() const override;
29 uint64_t readBytes(uint8_t *Buf, uint64_t Size,
30 uint64_t Address) const override;
31 const uint8_t *getPointer(uint64_t address, uint64_t size) const override {
32 // This could be fixed by ensuring the bytes are fetched and making a copy,
33 // requiring that the bitcode size be known, or otherwise ensuring that
34 // the memory doesn't go away/get reallocated, but it's
35 // not currently necessary. Users that need the pointer don't stream.
36 llvm_unreachable("getPointer in streaming memory objects not allowed");
39 bool isValidAddress(uint64_t address) const override;
41 /// Drop s bytes from the front of the stream, pushing the positions of the
42 /// remaining bytes down by s. This is used to skip past the bitcode header,
43 /// since we don't know a priori if it's present, and we can't put bytes
44 /// back into the stream once we've read them.
45 bool dropLeadingBytes(size_t s);
47 /// If the data object size is known in advance, many of the operations can
48 /// be made more efficient, so this method should be called before reading
49 /// starts (although it can be called anytime).
50 void setKnownObjectSize(size_t size);
53 const static uint32_t kChunkSize = 4096 * 4;
54 mutable std::vector<unsigned char> Bytes;
55 std::unique_ptr<DataStreamer> Streamer;
56 mutable size_t BytesRead; // Bytes read from stream
57 size_t BytesSkipped;// Bytes skipped at start of stream (e.g. wrapper/header)
58 mutable size_t ObjectSize; // 0 if unknown, set if wrapper seen or EOF reached
59 mutable bool EOFReached;
61 // Fetch enough bytes such that Pos can be read or EOF is reached
62 // (i.e. BytesRead > Pos). Return true if Pos can be read.
63 // Unlike most of the functions in BitcodeReader, returns true on success.
64 // Most of the requests will be small, but we fetch at kChunkSize bytes
65 // at a time to avoid making too many potentially expensive GetBytes calls
66 bool fetchToPos(size_t Pos) const {
68 return Pos < ObjectSize;
69 while (Pos >= BytesRead) {
70 Bytes.resize(BytesRead + BytesSkipped + kChunkSize);
71 size_t bytes = Streamer->GetBytes(&Bytes[BytesRead + BytesSkipped],
74 if (bytes != kChunkSize) { // reached EOF/ran out of bytes
75 ObjectSize = BytesRead;
80 return Pos < BytesRead;
83 StreamingMemoryObject(const StreamingMemoryObject&) = delete;
84 void operator=(const StreamingMemoryObject&) = delete;
87 MemoryObject *getNonStreamedMemoryObject(
88 const unsigned char *Start, const unsigned char *End);
91 #endif // STREAMINGMEMORYOBJECT_H_