PPCaching.cpp revision d6aba06861c41ccbc4926e5fe3cecd97b20410c0 
1//===--- PPCaching.cpp - Handle caching lexed 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 pieces of the Preprocessor interface that manage the
11// caching of lexed tokens.
12//
13//===----------------------------------------------------------------------===//
14
15#include "clang/Lex/Preprocessor.h"
16using namespace clang;
17
18/// EnableBacktrackAtThisPos - From the point that this method is called, and
19/// until CommitBacktrackedTokens() or Backtrack() is called, the Preprocessor
20/// keeps track of the lexed tokens so that a subsequent Backtrack() call will
21/// make the Preprocessor re-lex the same tokens.
22///
23/// Nested backtracks are allowed, meaning that EnableBacktrackAtThisPos can
24/// be called multiple times and CommitBacktrackedTokens/Backtrack calls will
25/// be combined with the EnableBacktrackAtThisPos calls in reverse order.
26void Preprocessor::EnableBacktrackAtThisPos() {
27  BacktrackPositions.push_back(CachedLexPos);
28  EnterCachingLexMode();
29}
30
31/// CommitBacktrackedTokens - Disable the last EnableBacktrackAtThisPos call.
32void Preprocessor::CommitBacktrackedTokens() {
33  assert(!BacktrackPositions.empty()
34         && "EnableBacktrackAtThisPos was not called!");
35  BacktrackPositions.pop_back();
36}
37
38/// Backtrack - Make Preprocessor re-lex the tokens that were lexed since
39/// EnableBacktrackAtThisPos() was previously called.
40void Preprocessor::Backtrack() {
41  assert(!BacktrackPositions.empty()
42         && "EnableBacktrackAtThisPos was not called!");
43  CachedLexPos = BacktrackPositions.back();
44  BacktrackPositions.pop_back();
45  recomputeCurLexerKind();
46}
47
48void Preprocessor::CachingLex(Token &Result) {
49  if (!InCachingLexMode())
50    return;
51
52  if (CachedLexPos < CachedTokens.size()) {
53    Result = CachedTokens[CachedLexPos++];
54    return;
55  }
56
57  ExitCachingLexMode();
58  Lex(Result);
59
60  if (!isBacktrackEnabled()) {
61    // All cached tokens were consumed.
62    CachedTokens.clear();
63    CachedLexPos = 0;
64    return;
65  }
66
67  // Cache the lexed token.
68  EnterCachingLexMode();
69  CachedTokens.push_back(Result);
70  ++CachedLexPos;
71}
72
73void Preprocessor::EnterCachingLexMode() {
74  if (InCachingLexMode())
75    return;
76
77  PushIncludeMacroStack();
78  CurLexerKind = CLK_CachingLexer;
79}
80
81
82const Token &Preprocessor::PeekAhead(unsigned N) {
83  assert(CachedLexPos + N > CachedTokens.size() && "Confused caching.");
84  ExitCachingLexMode();
85  for (unsigned C = CachedLexPos + N - CachedTokens.size(); C > 0; --C) {
86    CachedTokens.push_back(Token());
87    Lex(CachedTokens.back());
88  }
89  EnterCachingLexMode();
90  return CachedTokens.back();
91}
92
93void Preprocessor::AnnotatePreviousCachedTokens(const Token &Tok) {
94  assert(Tok.isAnnotation() && "Expected annotation token");
95  assert(CachedLexPos != 0 && "Expected to have some cached tokens");
96  assert(CachedTokens[CachedLexPos-1].getLastLoc() == Tok.getAnnotationEndLoc()
97         && "The annotation should be until the most recent cached token");
98
99  // Start from the end of the cached tokens list and look for the token
100  // that is the beginning of the annotation token.
101  for (CachedTokensTy::size_type i = CachedLexPos; i != 0; --i) {
102    CachedTokensTy::iterator AnnotBegin = CachedTokens.begin() + i-1;
103    if (AnnotBegin->getLocation() == Tok.getLocation()) {
104      assert((BacktrackPositions.empty() || BacktrackPositions.back() < i) &&
105             "The backtrack pos points inside the annotated tokens!");
106      // Replace the cached tokens with the single annotation token.
107      if (i < CachedLexPos)
108        CachedTokens.erase(AnnotBegin + 1, CachedTokens.begin() + CachedLexPos);
109      *AnnotBegin = Tok;
110      CachedLexPos = i;
111      return;
112    }
113  }
114}
115