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      1 // Copyright (c) 2009, Google Inc.
      2 // All rights reserved.
      3 //
      4 // Redistribution and use in source and binary forms, with or without
      5 // modification, are permitted provided that the following conditions are
      6 // met:
      7 //
      8 //     * Redistributions of source code must retain the above copyright
      9 // notice, this list of conditions and the following disclaimer.
     10 //     * Redistributions in binary form must reproduce the above
     11 // copyright notice, this list of conditions and the following disclaimer
     12 // in the documentation and/or other materials provided with the
     13 // distribution.
     14 //     * Neither the name of Google Inc. nor the names of its
     15 // contributors may be used to endorse or promote products derived from
     16 // this software without specific prior written permission.
     17 //
     18 // THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
     19 // "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
     20 // LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR
     21 // A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT
     22 // OWNER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL,
     23 // SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT
     24 // LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
     25 // DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY
     26 // THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
     27 // (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE
     28 // OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
     29 
     30 #ifndef CLIENT_LINUX_MINIDUMP_WRITER_LINE_READER_H_
     31 #define CLIENT_LINUX_MINIDUMP_WRITER_LINE_READER_H_
     32 
     33 #include <stdint.h>
     34 #include <assert.h>
     35 #include <string.h>
     36 
     37 #include "common/linux/linux_libc_support.h"
     38 #include "third_party/lss/linux_syscall_support.h"
     39 
     40 namespace google_breakpad {
     41 
     42 // A class for reading a file, line by line, without using fopen/fgets or other
     43 // functions which may allocate memory.
     44 class LineReader {
     45  public:
     46   LineReader(int fd)
     47       : fd_(fd),
     48         hit_eof_(false),
     49         buf_used_(0) {
     50   }
     51 
     52   // The maximum length of a line.
     53   static const size_t kMaxLineLen = 512;
     54 
     55   // Return the next line from the file.
     56   //   line: (output) a pointer to the start of the line. The line is NUL
     57   //     terminated.
     58   //   len: (output) the length of the line (not inc the NUL byte)
     59   //
     60   // Returns true iff successful (false on EOF).
     61   //
     62   // One must call |PopLine| after this function, otherwise you'll continue to
     63   // get the same line over and over.
     64   bool GetNextLine(const char **line, unsigned *len) {
     65     for (;;) {
     66       if (buf_used_ == 0 && hit_eof_)
     67         return false;
     68 
     69       for (unsigned i = 0; i < buf_used_; ++i) {
     70         if (buf_[i] == '\n' || buf_[i] == 0) {
     71           buf_[i] = 0;
     72           *len = i;
     73           *line = buf_;
     74           return true;
     75         }
     76       }
     77 
     78       if (buf_used_ == sizeof(buf_)) {
     79         // we scanned the whole buffer and didn't find an end-of-line marker.
     80         // This line is too long to process.
     81         return false;
     82       }
     83 
     84       // We didn't find any end-of-line terminators in the buffer. However, if
     85       // this is the last line in the file it might not have one:
     86       if (hit_eof_) {
     87         assert(buf_used_);
     88         // There's room for the NUL because of the buf_used_ == sizeof(buf_)
     89         // check above.
     90         buf_[buf_used_] = 0;
     91         *len = buf_used_;
     92         buf_used_ += 1;  // since we appended the NUL.
     93         *line = buf_;
     94         return true;
     95       }
     96 
     97       // Otherwise, we should pull in more data from the file
     98       const ssize_t n = sys_read(fd_, buf_ + buf_used_,
     99                                  sizeof(buf_) - buf_used_);
    100       if (n < 0) {
    101         return false;
    102       } else if (n == 0) {
    103         hit_eof_ = true;
    104       } else {
    105         buf_used_ += n;
    106       }
    107 
    108       // At this point, we have either set the hit_eof_ flag, or we have more
    109       // data to process...
    110     }
    111   }
    112 
    113   void PopLine(unsigned len) {
    114     // len doesn't include the NUL byte at the end.
    115 
    116     assert(buf_used_ >= len + 1);
    117     buf_used_ -= len + 1;
    118     my_memmove(buf_, buf_ + len + 1, buf_used_);
    119   }
    120 
    121  private:
    122   const int fd_;
    123 
    124   bool hit_eof_;
    125   unsigned buf_used_;
    126   char buf_[kMaxLineLen];
    127 };
    128 
    129 }  // namespace google_breakpad
    130 
    131 #endif  // CLIENT_LINUX_MINIDUMP_WRITER_LINE_READER_H_
    132