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) 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. 34SourceLocation ScratchBuffer::getToken(const char *Buf, unsigned Len, 35 const char *&DestPtr) { 36 if (BytesUsed+Len+2 > ScratchBufSize) 37 AllocScratchBuffer(Len+2); 38 39 // Prefix the token with a \n, so that it looks like it is the first thing on 40 // its own virtual line in caret diagnostics. 41 CurBuffer[BytesUsed++] = '\n'; 42 43 // Return a pointer to the character data. 44 DestPtr = CurBuffer+BytesUsed; 45 46 // Copy the token data into the buffer. 47 memcpy(CurBuffer+BytesUsed, Buf, Len); 48 49 // Remember that we used these bytes. 50 BytesUsed += Len+1; 51 52 // Add a NUL terminator to the token. This keeps the tokens separated, in 53 // case they get relexed, and puts them on their own virtual lines in case a 54 // diagnostic points to one. 55 CurBuffer[BytesUsed-1] = '\0'; 56 57 return BufferStartLoc.getLocWithOffset(BytesUsed-Len-1); 58} 59 60void ScratchBuffer::AllocScratchBuffer(unsigned RequestLen) { 61 // Only pay attention to the requested length if it is larger than our default 62 // page size. If it is, we allocate an entire chunk for it. This is to 63 // support gigantic tokens, which almost certainly won't happen. :) 64 if (RequestLen < ScratchBufSize) 65 RequestLen = ScratchBufSize; 66 67 // Get scratch buffer. Zero-initialize it so it can be dumped into a PCH file 68 // deterministically. 69 std::unique_ptr<llvm::MemoryBuffer> OwnBuf = 70 llvm::MemoryBuffer::getNewMemBuffer(RequestLen, "<scratch space>"); 71 llvm::MemoryBuffer &Buf = *OwnBuf; 72 FileID FID = SourceMgr.createFileID(std::move(OwnBuf)); 73 BufferStartLoc = SourceMgr.getLocForStartOfFile(FID); 74 CurBuffer = const_cast<char*>(Buf.getBufferStart()); 75 BytesUsed = 0; 76} 77