clang 10.0.0git

ScratchBuffer.cpp
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1 //===--- ScratchBuffer.cpp - Scratch space for forming tokens -------------===//
2 //
3 // Part of the LLVM Project, under the Apache License v2.0 with LLVM Exceptions.
4 // See https://llvm.org/LICENSE.txt for license information.
5 // SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
6 //
7 //===----------------------------------------------------------------------===//
8 //
9 // This file implements the ScratchBuffer interface.
10 //
11 //===----------------------------------------------------------------------===//
12
13 #include "clang/Lex/ScratchBuffer.h"
14 #include "clang/Basic/SourceManager.h"
15 #include "llvm/Support/MemoryBuffer.h"
16 #include <cstring>
17 using namespace clang;
18
19 // ScratchBufSize - The size of each chunk of scratch memory. Slightly less
20 //than a page, almost certainly enough for anything. :)
21 static const unsigned ScratchBufSize = 4060;
22
23 ScratchBuffer::ScratchBuffer(SourceManager &SM)
24 : SourceMgr(SM), CurBuffer(nullptr) {
25 // Set BytesUsed so that the first call to getToken will require an alloc.
26 BytesUsed = ScratchBufSize;
27 }
28
29 /// getToken - Splat the specified text into a temporary MemoryBuffer and
30 /// return a SourceLocation that refers to the token. This is just like the
31 /// method below, but returns a location that indicates the physloc of the
32 /// token.
33 SourceLocation ScratchBuffer::getToken(const char *Buf, unsigned Len,
34 const char *&DestPtr) {
35 if (BytesUsed+Len+2 > ScratchBufSize)
36 AllocScratchBuffer(Len+2);
37 else {
38 // Clear out the source line cache if it's already been computed.
39 // FIXME: Allow this to be incrementally extended.
40 auto *ContentCache = const_cast<SrcMgr::ContentCache *>(
41 SourceMgr.getSLocEntry(SourceMgr.getFileID(BufferStartLoc))
42 .getFile().getContentCache());
43 ContentCache->SourceLineCache = nullptr;
44 }
45
46 // Prefix the token with a \n, so that it looks like it is the first thing on
47 // its own virtual line in caret diagnostics.
48 CurBuffer[BytesUsed++] = '\n';
49
50 // Return a pointer to the character data.
51 DestPtr = CurBuffer+BytesUsed;
52
53 // Copy the token data into the buffer.
54 memcpy(CurBuffer+BytesUsed, Buf, Len);
55
56 // Remember that we used these bytes.
57 BytesUsed += Len+1;
58
59 // Add a NUL terminator to the token. This keeps the tokens separated, in
60 // case they get relexed, and puts them on their own virtual lines in case a
61 // diagnostic points to one.
62 CurBuffer[BytesUsed-1] = '\0';
63
64 return BufferStartLoc.getLocWithOffset(BytesUsed-Len-1);
65 }
66
67 void ScratchBuffer::AllocScratchBuffer(unsigned RequestLen) {
68 // Only pay attention to the requested length if it is larger than our default
69 // page size. If it is, we allocate an entire chunk for it. This is to
70 // support gigantic tokens, which almost certainly won't happen. :)
71 if (RequestLen < ScratchBufSize)
72 RequestLen = ScratchBufSize;
73
74 // Get scratch buffer. Zero-initialize it so it can be dumped into a PCH file
75 // deterministically.
76 std::unique_ptr<llvm::WritableMemoryBuffer> OwnBuf =
77 llvm::WritableMemoryBuffer::getNewMemBuffer(RequestLen,
78 "<scratch space>");
79 CurBuffer = OwnBuf->getBufferStart();
80 FileID FID = SourceMgr.createFileID(std::move(OwnBuf));
81 BufferStartLoc = SourceMgr.getLocForStartOfFile(FID);
82 BytesUsed = 0;
83 }
clang::SourceManager::getLocForStartOfFile
SourceLocation getLocForStartOfFile(FileID FID) const
Return the source location corresponding to the first byte of the specified file. ...
Definition: SourceManager.h:1109
clang::ScratchBuffer::getToken
SourceLocation getToken(const char *Buf, unsigned Len, const char *&DestPtr)
getToken - Splat the specified text into a temporary MemoryBuffer and return a SourceLocation that re...
Definition: ScratchBuffer.cpp:33
ScratchBuffer.h
clang::SourceLocation::getLocWithOffset
SourceLocation getLocWithOffset(int Offset) const
Return a source location with the specified offset from this SourceLocation.
Definition: SourceLocation.h:132
SourceManager.h
Defines the SourceManager interface.
clang::SrcMgr::ContentCache
One instance of this struct is kept for every file loaded or used.
Definition: SourceManager.h:94
ScratchBufSize
static const unsigned ScratchBufSize
Definition: ScratchBuffer.cpp:21
clang::SourceManager::createFileID
FileID createFileID(const FileEntry *SourceFile, SourceLocation IncludePos, SrcMgr::CharacteristicKind FileCharacter, int LoadedID=0, unsigned LoadedOffset=0)
Create a new FileID that represents the specified file being #included from the specified IncludePosi...
Definition: SourceManager.h:831
SM
const SourceManager & SM
Definition: Format.cpp:1685
clang::SourceLocation
Encodes a location in the source.
Definition: SourceLocation.h:86
clang::SrcMgr::ContentCache::SourceLineCache
unsigned * SourceLineCache
A bump pointer allocated array of offsets for each source line.
Definition: SourceManager.h:129
memcpy
__DEVICE__ void * memcpy(void *__a, const void *__b, size_t __c)
Definition: __clang_cuda_device_functions.h:1632
clang::FileID
An opaque identifier used by SourceManager which refers to a source file (MemoryBuffer) along with it...
Definition: SourceLocation.h:38
clang
Dataflow Directional Tag Classes.
Definition: CFGReachabilityAnalysis.h:21
clang::SourceManager::getFileID
FileID getFileID(SourceLocation SpellingLoc) const
Return the FileID for a SourceLocation.
Definition: SourceManager.h:1090
clang::SourceManager::getSLocEntry
const SrcMgr::SLocEntry & getSLocEntry(FileID FID, bool *Invalid=nullptr) const
Definition: SourceManager.h:1699
clang::ScratchBuffer::ScratchBuffer
ScratchBuffer(SourceManager &SM)
Definition: ScratchBuffer.cpp:23
clang::SourceManager
This class handles loading and caching of source files into memory.
Definition: SourceManager.h:596