lib/Support/LineIterator.cpp

   1 //===- LineIterator.cpp - Implementation of line iteration ----------------===//
   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-exception
   6 //
   7 //===----------------------------------------------------------------------===//
   8
   9 #include "llvm/Support/LineIterator.h"
  10 #include "llvm/Support/MemoryBuffer.h"
  11
  12 using namespace llvm;
  13
  14 static bool isAtLineEnd(const char *P) {
  15   if (*P == '\n')
  16     return true;
  17   if (*P == '\r' && *(P + 1) == '\n')
  18     return true;
  19   return false;
  20 }
  21
  22 static bool skipIfAtLineEnd(const char *&P) {
  23   if (*P == '\n') {
  24     ++P;
  25     return true;
  26   }
  27   if (*P == '\r' && *(P + 1) == '\n') {
  28     P += 2;
  29     return true;
  30   }
  31   return false;
  32 }
  33
  34 line_iterator::line_iterator(const MemoryBuffer &Buffer, bool SkipBlanks,
  35                              char CommentMarker)
  36     : Buffer(Buffer.getBufferSize() ? &Buffer : nullptr),
  37       CommentMarker(CommentMarker), SkipBlanks(SkipBlanks), LineNumber(1),
  38       CurrentLine(Buffer.getBufferSize() ? Buffer.getBufferStart() : nullptr,
  39                   0) {
  40   // Ensure that if we are constructed on a non-empty memory buffer that it is
  41   // a null terminated buffer.
  42   if (Buffer.getBufferSize()) {
  43     assert(Buffer.getBufferEnd()[0] == '\0');
  44     // Make sure we don't skip a leading newline if we're keeping blanks
  45     if (SkipBlanks || !isAtLineEnd(Buffer.getBufferStart()))
  46       advance();
  47   }
  48 }
  49
  50 void line_iterator::advance() {
  51   assert(Buffer && "Cannot advance past the end!");
  52
  53   const char *Pos = CurrentLine.end();
  54   assert(Pos == Buffer->getBufferStart() || isAtLineEnd(Pos) || *Pos == '\0');
  55
  56   if (skipIfAtLineEnd(Pos))
  57     ++LineNumber;
  58   if (!SkipBlanks && isAtLineEnd(Pos)) {
  59     // Nothing to do for a blank line.
  60   } else if (CommentMarker == '\0') {
  61     // If we're not stripping comments, this is simpler.
  62     while (skipIfAtLineEnd(Pos))
  63       ++LineNumber;
  64   } else {
  65     // Skip comments and count line numbers, which is a bit more complex.
  66     for (;;) {
  67       if (isAtLineEnd(Pos) && !SkipBlanks)
  68         break;
  69       if (*Pos == CommentMarker)
  70         do {
  71           ++Pos;
  72         } while (*Pos != '\0' && !isAtLineEnd(Pos));
  73       if (!skipIfAtLineEnd(Pos))
  74         break;
  75       ++LineNumber;
  76     }
  77   }
  78
  79   if (*Pos == '\0') {
  80     // We've hit the end of the buffer, reset ourselves to the end state.
  81     Buffer = nullptr;
  82     CurrentLine = StringRef();
  83     return;
  84   }
  85
  86   // Measure the line.
  87   size_t Length = 0;
  88   while (Pos[Length] != '\0' && !isAtLineEnd(&Pos[Length])) {
  89     ++Length;
  90   }
  91
  92   CurrentLine = StringRef(Pos, Length);
  93 }