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> 18using namespace clang; 19 20// ScratchBufSize - The size of each chunk of scratch memory. Slightly less 21//than a page, almost certainly enough for anything. :) 22static const unsigned ScratchBufSize = 4060; 23 24ScratchBuffer::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. 33SourceLocation 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.getLocWithOffset(BytesUsed-Len-1); 57} 58 59void 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