1 files changed, 83 insertions, 0 deletions
diff --git a/clang/lib/Lex/ScratchBuffer.cpp b/clang/lib/Lex/ScratchBuffer.cpp
new file mode 100644
index 0000000000000..19ab93ec54b47
--- /dev/null
+++ b/clang/lib/Lex/ScratchBuffer.cpp
@@ -0,0 +1,83 @@
+//===--- 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;
+}