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//===--- ScratchBuffer.cpp - Scratch space for forming tokens -------------===//
//
// Part of the LLVM Project, under the Apache License v2.0 with LLVM Exceptions.
// See https://llvm.org/LICENSE.txt for license information.
// SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
//
//===----------------------------------------------------------------------===//
//
// This file implements the ScratchBuffer interface.
//
//===----------------------------------------------------------------------===//
#include "clang/Lex/ScratchBuffer.h"
#include "clang/Basic/SourceManager.h"
#include "llvm/Support/MemoryBuffer.h"
#include <cstring>
using namespace clang;
// ScratchBufSize - The size of each chunk of scratch memory. Slightly less
//than a page, almost certainly enough for anything. :)
static const unsigned ScratchBufSize = 4060;
ScratchBuffer::ScratchBuffer(SourceManager &SM)
: SourceMgr(SM), CurBuffer(nullptr) {
// Set BytesUsed so that the first call to getToken will require an alloc.
BytesUsed = ScratchBufSize;
}
/// getToken - Splat the specified text into a temporary MemoryBuffer and
/// return a SourceLocation that refers to the token. This is just like the
/// method below, but returns a location that indicates the physloc of the
/// token.
SourceLocation ScratchBuffer::getToken(const char *Buf, unsigned Len,
const char *&DestPtr) {
if (BytesUsed+Len+2 > ScratchBufSize)
AllocScratchBuffer(Len+2);
else {
// Clear out the source line cache if it's already been computed.
// FIXME: Allow this to be incrementally extended.
auto *ContentCache = const_cast<SrcMgr::ContentCache *>(
SourceMgr.getSLocEntry(SourceMgr.getFileID(BufferStartLoc))
.getFile().getContentCache());
ContentCache->SourceLineCache = nullptr;
}
// Prefix the token with a \n, so that it looks like it is the first thing on
// its own virtual line in caret diagnostics.
CurBuffer[BytesUsed++] = '\n';
// Return a pointer to the character data.
DestPtr = CurBuffer+BytesUsed;
// Copy the token data into the buffer.
memcpy(CurBuffer+BytesUsed, Buf, Len);
// Remember that we used these bytes.
BytesUsed += Len+1;
// Add a NUL terminator to the token. This keeps the tokens separated, in
// case they get relexed, and puts them on their own virtual lines in case a
// diagnostic points to one.
CurBuffer[BytesUsed-1] = '\0';
return BufferStartLoc.getLocWithOffset(BytesUsed-Len-1);
}
void ScratchBuffer::AllocScratchBuffer(unsigned RequestLen) {
// Only pay attention to the requested length if it is larger than our default
// page size. If it is, we allocate an entire chunk for it. This is to
// support gigantic tokens, which almost certainly won't happen. :)
if (RequestLen < ScratchBufSize)
RequestLen = ScratchBufSize;
// Get scratch buffer. Zero-initialize it so it can be dumped into a PCH file
// deterministically.
std::unique_ptr<llvm::WritableMemoryBuffer> OwnBuf =
llvm::WritableMemoryBuffer::getNewMemBuffer(RequestLen,
"<scratch space>");
CurBuffer = OwnBuf->getBufferStart();
FileID FID = SourceMgr.createFileID(std::move(OwnBuf));
BufferStartLoc = SourceMgr.getLocForStartOfFile(FID);
BytesUsed = 0;
}
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