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) : SourceMgr(SM), CurBuffer(0) {
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.
getToken(const char * Buf,unsigned Len,const char * & DestPtr)33 SourceLocation ScratchBuffer::getToken(const char *Buf, unsigned Len,
34 const char *&DestPtr) {
35 if (BytesUsed+Len+2 > ScratchBufSize)
36 AllocScratchBuffer(Len+2);
37
38 // Prefix the token with a \n, so that it looks like it is the first thing on
39 // its own virtual line in caret diagnostics.
40 CurBuffer[BytesUsed++] = '\n';
41
42 // Return a pointer to the character data.
43 DestPtr = CurBuffer+BytesUsed;
44
45 // Copy the token data into the buffer.
46 memcpy(CurBuffer+BytesUsed, Buf, Len);
47
48 // Remember that we used these bytes.
49 BytesUsed += Len+1;
50
51 // Add a NUL terminator to the token. This keeps the tokens separated, in
52 // case they get relexed, and puts them on their own virtual lines in case a
53 // diagnostic points to one.
54 CurBuffer[BytesUsed-1] = '\0';
55
56 return BufferStartLoc.getFileLocWithOffset(BytesUsed-Len-1);
57 }
58
AllocScratchBuffer(unsigned RequestLen)59 void ScratchBuffer::AllocScratchBuffer(unsigned RequestLen) {
60 // Only pay attention to the requested length if it is larger than our default
61 // page size. If it is, we allocate an entire chunk for it. This is to
62 // support gigantic tokens, which almost certainly won't happen. :)
63 if (RequestLen < ScratchBufSize)
64 RequestLen = ScratchBufSize;
65
66 llvm::MemoryBuffer *Buf =
67 llvm::MemoryBuffer::getNewMemBuffer(RequestLen, "<scratch space>");
68 FileID FID = SourceMgr.createFileIDForMemBuffer(Buf);
69 BufferStartLoc = SourceMgr.getLocForStartOfFile(FID);
70 CurBuffer = const_cast<char*>(Buf->getBufferStart());
71 BytesUsed = 1;
72 CurBuffer[0] = '0'; // Start out with a \0 for cleanliness.
73 }
74