lib/Support/LineIterator.cpp

   1 //===- LineIterator.cpp - Implementation of line iteration ----------------===//
   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 #include "llvm/Support/LineIterator.h"
  11 #include "llvm/Support/MemoryBuffer.h"
  12
  13 using namespace llvm;
  14
  15 static bool isAtLineEnd(const char *P) {
  16   if (*P == '\n')
  17     return true;
  18   if (*P == '\r' && *(P + 1) == '\n')
  19     return true;
  20   return false;
  21 }
  22
  23 static bool skipIfAtLineEnd(const char *&P) {
  24   if (*P == '\n') {
  25     ++P;
  26     return true;
  27   }
  28   if (*P == '\r' && *(P + 1) == '\n') {
  29     P += 2;
  30     return true;
  31   }
  32   return false;
  33 }
  34
  35 line_iterator::line_iterator(const MemoryBuffer &Buffer, bool SkipBlanks,
  36                              char CommentMarker)
  37     : Buffer(Buffer.getBufferSize() ? &Buffer : nullptr),
  38       CommentMarker(CommentMarker), SkipBlanks(SkipBlanks), LineNumber(1),
  39       CurrentLine(Buffer.getBufferSize() ? Buffer.getBufferStart() : nullptr,
  40                   0) {
  41   // Ensure that if we are constructed on a non-empty memory buffer that it is
  42   // a null terminated buffer.
  43   if (Buffer.getBufferSize()) {
  44     assert(Buffer.getBufferEnd()[0] == '\0');
  45     // Make sure we don't skip a leading newline if we're keeping blanks
  46     if (SkipBlanks || !isAtLineEnd(Buffer.getBufferStart()))
  47       advance();
  48   }
  49 }
  50
  51 void line_iterator::advance() {
  52   assert(Buffer && "Cannot advance past the end!");
  53
  54   const char *Pos = CurrentLine.end();
  55   assert(Pos == Buffer->getBufferStart() || isAtLineEnd(Pos) || *Pos == '\0');
  56
  57   if (skipIfAtLineEnd(Pos))
  58     ++LineNumber;
  59   if (!SkipBlanks && isAtLineEnd(Pos)) {
  60     // Nothing to do for a blank line.
  61   } else if (CommentMarker == '\0') {
  62     // If we're not stripping comments, this is simpler.
  63     while (skipIfAtLineEnd(Pos))
  64       ++LineNumber;
  65   } else {
  66     // Skip comments and count line numbers, which is a bit more complex.
  67     for (;;) {
  68       if (isAtLineEnd(Pos) && !SkipBlanks)
  69         break;
  70       if (*Pos == CommentMarker)
  71         do {
  72           ++Pos;
  73         } while (*Pos != '\0' && !isAtLineEnd(Pos));
  74       if (!skipIfAtLineEnd(Pos))
  75         break;
  76       ++LineNumber;
  77     }
  78   }
  79
  80   if (*Pos == '\0') {
  81     // We've hit the end of the buffer, reset ourselves to the end state.
  82     Buffer = nullptr;
  83     CurrentLine = StringRef();
  84     return;
  85   }
  86
  87   // Measure the line.
  88   size_t Length = 0;
  89   while (Pos[Length] != '\0' && !isAtLineEnd(&Pos[Length])) {
  90     ++Length;
  91   }
  92
  93   CurrentLine = StringRef(Pos, Length);
  94 }