1 //===--- ScratchBuffer.cpp - Scratch space for forming tokens -------------===//
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 // This file implements the ScratchBuffer interface.
11 //
12 //===----------------------------------------------------------------------===//
13
14 #include "clang/Lex/ScratchBuffer.h"
15 #include "clang/Basic/SourceManager.h"
16 #include "llvm/Support/MemoryBuffer.h"
17 #include <cstring>
18 using namespace clang;
19
20 // ScratchBufSize - The size of each chunk of scratch memory. Slightly less
21 //than a page, almost certainly enough for anything. :)
22 static const unsigned ScratchBufSize = 4060;
23
ScratchBuffer(SourceManager & SM)24 ScratchBuffer::ScratchBuffer(SourceManager &SM)
25 : SourceMgr(SM), CurBuffer(nullptr) {
26 // Set BytesUsed so that the first call to getToken will require an alloc.
27 BytesUsed = ScratchBufSize;
28 }
29
30 /// getToken - Splat the specified text into a temporary MemoryBuffer and
31 /// return a SourceLocation that refers to the token. This is just like the
32 /// method below, but returns a location that indicates the physloc of the
33 /// token.
getToken(const char * Buf,unsigned Len,const char * & DestPtr)34 SourceLocation ScratchBuffer::getToken(const char *Buf, unsigned Len,
35 const char *&DestPtr) {
36 if (BytesUsed+Len+2 > ScratchBufSize)
37 AllocScratchBuffer(Len+2);
38 else {
39 // Clear out the source line cache if it's already been computed.
40 // FIXME: Allow this to be incrementally extended.
41 auto *ContentCache = const_cast<SrcMgr::ContentCache *>(
42 SourceMgr.getSLocEntry(SourceMgr.getFileID(BufferStartLoc))
43 .getFile().getContentCache());
44 ContentCache->SourceLineCache = nullptr;
45 }
46
47 // Prefix the token with a \n, so that it looks like it is the first thing on
48 // its own virtual line in caret diagnostics.
49 CurBuffer[BytesUsed++] = '\n';
50
51 // Return a pointer to the character data.
52 DestPtr = CurBuffer+BytesUsed;
53
54 // Copy the token data into the buffer.
55 memcpy(CurBuffer+BytesUsed, Buf, Len);
56
57 // Remember that we used these bytes.
58 BytesUsed += Len+1;
59
60 // Add a NUL terminator to the token. This keeps the tokens separated, in
61 // case they get relexed, and puts them on their own virtual lines in case a
62 // diagnostic points to one.
63 CurBuffer[BytesUsed-1] = '\0';
64
65 return BufferStartLoc.getLocWithOffset(BytesUsed-Len-1);
66 }
67
AllocScratchBuffer(unsigned RequestLen)68 void ScratchBuffer::AllocScratchBuffer(unsigned RequestLen) {
69 // Only pay attention to the requested length if it is larger than our default
70 // page size. If it is, we allocate an entire chunk for it. This is to
71 // support gigantic tokens, which almost certainly won't happen. :)
72 if (RequestLen < ScratchBufSize)
73 RequestLen = ScratchBufSize;
74
75 // Get scratch buffer. Zero-initialize it so it can be dumped into a PCH file
76 // deterministically.
77 std::unique_ptr<llvm::WritableMemoryBuffer> OwnBuf =
78 llvm::WritableMemoryBuffer::getNewMemBuffer(RequestLen,
79 "<scratch space>");
80 CurBuffer = OwnBuf->getBufferStart();
81 FileID FID = SourceMgr.createFileID(std::move(OwnBuf));
82 BufferStartLoc = SourceMgr.getLocForStartOfFile(FID);
83 BytesUsed = 0;
84 }
85