aboutsummaryrefslogtreecommitdiff
path: root/src/client/linux/minidump_writer/line_reader.h
blob: 9fc4b7cc887d48a984cfcedd262abed28d6d884e (plain)
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
61
62
63
64
65
66
67
68
69
70
71
72
73
74
75
76
77
78
79
80
81
82
83
84
85
86
87
88
89
90
91
92
93
94
95
96
97
98
99
100
101
102
103
104
105
106
107
108
109
110
111
112
113
114
115
116
117
118
119
120
121
122
123
124
125
126
127
128
129
130
131
// Copyright (c) 2009, Google Inc.
// All rights reserved.
//
// Redistribution and use in source and binary forms, with or without
// modification, are permitted provided that the following conditions are
// met:
//
//     * Redistributions of source code must retain the above copyright
// notice, this list of conditions and the following disclaimer.
//     * Redistributions in binary form must reproduce the above
// copyright notice, this list of conditions and the following disclaimer
// in the documentation and/or other materials provided with the
// distribution.
//     * Neither the name of Google Inc. nor the names of its
// contributors may be used to endorse or promote products derived from
// this software without specific prior written permission.
//
// THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
// "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
// LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR
// A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT
// OWNER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL,
// SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT
// LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
// DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY
// THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
// (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE
// OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.

#ifndef CLIENT_LINUX_MINIDUMP_WRITER_LINE_READER_H_
#define CLIENT_LINUX_MINIDUMP_WRITER_LINE_READER_H_

#include <stdint.h>
#include <assert.h>
#include <string.h>

#include "common/linux/linux_libc_support.h"
#include "third_party/lss/linux_syscall_support.h"

namespace google_breakpad {

// A class for reading a file, line by line, without using fopen/fgets or other
// functions which may allocate memory.
class LineReader {
 public:
  LineReader(int fd)
      : fd_(fd),
        hit_eof_(false),
        buf_used_(0) {
  }

  // The maximum length of a line.
  static const size_t kMaxLineLen = 512;

  // Return the next line from the file.
  //   line: (output) a pointer to the start of the line. The line is NUL
  //     terminated.
  //   len: (output) the length of the line (not inc the NUL byte)
  //
  // Returns true iff successful (false on EOF).
  //
  // One must call |PopLine| after this function, otherwise you'll continue to
  // get the same line over and over.
  bool GetNextLine(const char** line, unsigned* len) {
    for (;;) {
      if (buf_used_ == 0 && hit_eof_)
        return false;

      for (unsigned i = 0; i < buf_used_; ++i) {
        if (buf_[i] == '\n' || buf_[i] == 0) {
          buf_[i] = 0;
          *len = i;
          *line = buf_;
          return true;
        }
      }

      if (buf_used_ == sizeof(buf_)) {
        // we scanned the whole buffer and didn't find an end-of-line marker.
        // This line is too long to process.
        return false;
      }

      // We didn't find any end-of-line terminators in the buffer. However, if
      // this is the last line in the file it might not have one:
      if (hit_eof_) {
        assert(buf_used_);
        // There's room for the NUL because of the buf_used_ == sizeof(buf_)
        // check above.
        buf_[buf_used_] = 0;
        *len = buf_used_;
        buf_used_ += 1;  // since we appended the NUL.
        *line = buf_;
        return true;
      }

      // Otherwise, we should pull in more data from the file
      const ssize_t n = sys_read(fd_, buf_ + buf_used_,
                                 sizeof(buf_) - buf_used_);
      if (n < 0) {
        return false;
      } else if (n == 0) {
        hit_eof_ = true;
      } else {
        buf_used_ += n;
      }

      // At this point, we have either set the hit_eof_ flag, or we have more
      // data to process...
    }
  }

  void PopLine(unsigned len) {
    // len doesn't include the NUL byte at the end.

    assert(buf_used_ >= len + 1);
    buf_used_ -= len + 1;
    my_memmove(buf_, buf_ + len + 1, buf_used_);
  }

 private:
  const int fd_;

  bool hit_eof_;
  unsigned buf_used_;
  char buf_[kMaxLineLen];
};

}  // namespace google_breakpad

#endif  // CLIENT_LINUX_MINIDUMP_WRITER_LINE_READER_H_