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     : line_iterator(Buffer.getMemBufferRef(), SkipBlanks, CommentMarker) {}
37 
38 line_iterator::line_iterator(const MemoryBufferRef &Buffer, bool SkipBlanks,
39                              char CommentMarker)
40     : Buffer(Buffer.getBufferSize() ? std::optional<MemoryBufferRef>(Buffer)
41                                     : std::nullopt),
42       CommentMarker(CommentMarker), SkipBlanks(SkipBlanks),
43       CurrentLine(Buffer.getBufferSize() ? Buffer.getBufferStart() : nullptr,
44                   0) {
45   // Ensure that if we are constructed on a non-empty memory buffer that it is
46   // a null terminated buffer.
47   if (Buffer.getBufferSize()) {
48     assert(Buffer.getBufferEnd()[0] == '\0');
49     // Make sure we don't skip a leading newline if we're keeping blanks
50     if (SkipBlanks || !isAtLineEnd(Buffer.getBufferStart()))
51       advance();
52   }
53 }
54 
55 void line_iterator::advance() {
56   assert(Buffer && "Cannot advance past the end!");
57 
58   const char *Pos = CurrentLine.end();
59   assert(Pos == Buffer->getBufferStart() || isAtLineEnd(Pos) || *Pos == '\0');
60 
61   if (skipIfAtLineEnd(Pos))
62     ++LineNumber;
63   if (!SkipBlanks && isAtLineEnd(Pos)) {
64     // Nothing to do for a blank line.
65   } else if (CommentMarker == '\0') {
66     // If we're not stripping comments, this is simpler.
67     while (skipIfAtLineEnd(Pos))
68       ++LineNumber;
69   } else {
70     // Skip comments and count line numbers, which is a bit more complex.
71     for (;;) {
72       if (isAtLineEnd(Pos) && !SkipBlanks)
73         break;
74       if (*Pos == CommentMarker)
75         do {
76           ++Pos;
77         } while (*Pos != '\0' && !isAtLineEnd(Pos));
78       if (!skipIfAtLineEnd(Pos))
79         break;
80       ++LineNumber;
81     }
82   }
83 
84   if (*Pos == '\0') {
85     // We've hit the end of the buffer, reset ourselves to the end state.
86     Buffer = std::nullopt;
87     CurrentLine = StringRef();
88     return;
89   }
90 
91   // Measure the line.
92   size_t Length = 0;
93   while (Pos[Length] != '\0' && !isAtLineEnd(&Pos[Length])) {
94     ++Length;
95   }
96 
97   CurrentLine = StringRef(Pos, Length);
98 }
99