84 lines · cpp
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-exception6//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>17using namespace clang;18 19// ScratchBufSize - The size of each chunk of scratch memory. Slightly less20//than a page, almost certainly enough for anything. :)21static const unsigned ScratchBufSize = 4060;22 23ScratchBuffer::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 and30/// return a SourceLocation that refers to the token. This is just like the31/// method below, but returns a location that indicates the physloc of the32/// token.33SourceLocation 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 SourceMgr.getSLocEntry(SourceMgr.getFileID(BufferStartLoc))41 .getFile()42 .getContentCache()43 .SourceLineCache = SrcMgr::LineOffsetMapping();44 }45 46 // Prefix the token with a \n, so that it looks like it is the first thing on47 // 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, in60 // case they get relexed, and puts them on their own virtual lines in case a61 // diagnostic points to one.62 CurBuffer[BytesUsed-1] = '\0';63 64 return BufferStartLoc.getLocWithOffset(BytesUsed-Len-1);65}66 67void ScratchBuffer::AllocScratchBuffer(unsigned RequestLen) {68 // Only pay attention to the requested length if it is larger than our default69 // page size. If it is, we allocate an entire chunk for it. This is to70 // 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 file75 // 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}84