1 //===- BinaryStream.h - Base interface for a stream of data -----*- 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_BINARYSTREAM_H
11 #define LLVM_SUPPORT_BINARYSTREAM_H
12
13 #include "llvm/ADT/ArrayRef.h"
14 #include "llvm/ADT/BitmaskEnum.h"
15 #include "llvm/Support/BinaryStreamError.h"
16 #include "llvm/Support/Endian.h"
17 #include "llvm/Support/Error.h"
18 #include <cstdint>
19
20 namespace llvm {
21
22 enum BinaryStreamFlags {
23 BSF_None = 0,
24 BSF_Write = 1, // Stream supports writing.
25 BSF_Append = 2, // Writing can occur at offset == length.
26 LLVM_MARK_AS_BITMASK_ENUM(/* LargestValue = */ BSF_Append)
27 };
28
29 /// An interface for accessing data in a stream-like format, but which
30 /// discourages copying. Instead of specifying a buffer in which to copy
31 /// data on a read, the API returns an ArrayRef to data owned by the stream's
32 /// implementation. Since implementations may not necessarily store data in a
33 /// single contiguous buffer (or even in memory at all), in such cases a it may
34 /// be necessary for an implementation to cache such a buffer so that it can
35 /// return it.
36 class BinaryStream {
37 public:
~FilterBitsBuilder()38 virtual ~BinaryStream() = default;
39
40 virtual llvm::support::endianness getEndian() const = 0;
41
42 /// Given an offset into the stream and a number of bytes, attempt to
43 /// read the bytes and set the output ArrayRef to point to data owned by the
44 /// stream.
45 virtual Error readBytes(uint32_t Offset, uint32_t Size,
46 ArrayRef<uint8_t> &Buffer) = 0;
47
48 /// Given an offset into the stream, read as much as possible without
49 /// copying any data.
50 virtual Error readLongestContiguousChunk(uint32_t Offset,
51 ArrayRef<uint8_t> &Buffer) = 0;
52
53 /// Return the number of bytes of data in this stream.
54 virtual uint32_t getLength() = 0;
55
CalculateNumEntry(const uint32_t)56 /// Return the properties of this stream.
57 virtual BinaryStreamFlags getFlags() const { return BSF_None; }
58
59 protected:
60 Error checkOffsetForRead(uint32_t Offset, uint32_t DataSize) {
61 if (Offset > getLength())
62 return make_error<BinaryStreamError>(stream_error_code::invalid_offset);
63 if (getLength() < DataSize + Offset)
64 return make_error<BinaryStreamError>(stream_error_code::stream_too_short);
65 return Error::success();
66 }
67 };
68
69 /// A BinaryStream which can be read from as well as written to. Note
70 /// that writing to a BinaryStream always necessitates copying from the input
71 /// buffer to the stream's backing store. Streams are assumed to be buffered
72 /// so that to be portable it is necessary to call commit() on the stream when
~FilterBitsReader()73 /// all data has been written.
74 class WritableBinaryStream : public BinaryStream {
75 public:
76 ~WritableBinaryStream() override = default;
77
78 /// Attempt to write the given bytes into the stream at the desired
79 /// offset. This will always necessitate a copy. Cannot shrink or grow the
80 /// stream, only writes into existing allocated space.
81 virtual Error writeBytes(uint32_t Offset, ArrayRef<uint8_t> Data) = 0;
82
83 /// For buffered streams, commits changes to the backing store.
84 virtual Error commit() = 0;
85
86 /// Return the properties of this stream.
87 BinaryStreamFlags getFlags() const override { return BSF_Write; }
88
89 protected:
90 Error checkOffsetForWrite(uint32_t Offset, uint32_t DataSize) {
91 if (!(getFlags() & BSF_Append))
92 return checkOffsetForRead(Offset, DataSize);
93
94 if (Offset > getLength())
95 return make_error<BinaryStreamError>(stream_error_code::invalid_offset);
96 return Error::success();
97 }
98 };
99
100 } // end namespace llvm
101
102 #endif // LLVM_SUPPORT_BINARYSTREAM_H
103