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// -*- related-file-name: "../include/lcdf/slurper.hh" -*-
/* slurper.{cc,hh} -- reading from files a line at a time
*
* Copyright (c) 1998-2011 Eddie Kohler
*
* This program is free software; you can redistribute it and/or modify it
* under the terms of the GNU General Public License as published by the Free
* Software Foundation; either version 2 of the License, or (at your option)
* any later version. This program is distributed in the hope that it will be
* useful, but WITHOUT ANY WARRANTY; without even the implied warranty of
* MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU General
* Public License for more details.
*/
#ifdef HAVE_CONFIG_H
# include <config.h>
#endif
#include <lcdf/slurper.hh>
#include <string.h>
static const int DefChunkCap = 2048;
static const int WorthMoving = 256;
Slurper::Slurper(const Filename &filename, FILE *f)
: _filename(filename), _lineno(0),
_data(new unsigned char[DefChunkCap]), _cap(DefChunkCap),
_pos(0), _len(0), _line(0), _line_len(0),
_saved_line(false), _at_eof(false)
{
if (f) {
_f = f;
_own_f = false;
} else {
_f = _filename.open_read();
_own_f = true;
}
}
Slurper::~Slurper()
{
delete[] _data;
if (_f && _own_f) fclose(_f);
}
void
Slurper::grow_buffer()
{
// If we need to keep the upper part of the buffer, shift it down (moving
// any data we care about).
if (_pos >= _cap - WorthMoving) {
// I used to move it myself, with a comment that SunOS didn't have a
// correct implementation of memmove. This should be detected by
// configure, if it's really a problem.
memmove(_data, _data + _pos, _len - _pos);
_len -= _pos;
_pos = 0;
}
// Grow the buffer if necessary.
if (_len >= _cap) {
unsigned char *new_data = new unsigned char[ 2 * _cap ];
// I can't believe I didn't have the line below!!
memcpy(new_data, _data, _len);
delete[] _data;
_data = new_data;
_cap = 2 * _cap;
}
}
inline int
Slurper::more_data()
{
grow_buffer();
// Read new data into the buffer.
int amount = fread(_data + _len, 1, _cap - _len, _f);
_len += amount;
return amount;
}
char *
Slurper::get_line_at(unsigned pos)
{
while (1) {
for (; pos < _len; pos++)
if (_data[pos] == '\n' || _data[pos] == '\r')
goto line_ends_at_pos;
// no line end? look for more data. save and reset `pos', since _pos
// may change.
int offset = pos - _pos;
bool got_more_data = more_data() != 0;
pos = _pos + offset;
if (!got_more_data) {
_at_eof = true;
goto line_ends_at_pos;
}
}
line_ends_at_pos:
// PRECONDITION: the line starts at _pos and ends at pos.
unsigned next_pos;
// Find beginning of next line. 3 cases:
// 1. line ends in \r\n -> _pos = pos + 2;
// 2. line ends in \r OR \n -> _pos = pos + 1;
// 3. neither -> must be last line in file; _pos = pos,
// since pos == _len
if (pos == _len) {
// last line in file didn't end in `\n': must have no data left
// ensure we have enough space for terminating nul
if (pos == _cap) grow_buffer();
next_pos = pos;
// if already at EOF, don't increment the line number
if (pos == _pos) _lineno--;
} else if (_data[pos] == '\n')
next_pos = pos + 1;
else {
assert(_data[pos] == '\r');
// If `\r' is last char in buffer, `\n' might be next char. Must read more
// data to check for it, or we'd report an empty line that didn't really
// exist.
if (pos == _len - 1) {
// be careful about the possible shift of _pos and _len!
int offset = pos - _pos;
more_data();
pos = _pos + offset;
}
if (pos < _len - 1 && _data[pos + 1] == '\n')
next_pos = pos + 2;
else
next_pos = pos + 1;
}
_line = _data + _pos;
_line_len = pos - _pos;
_data[pos] = 0;
_pos = next_pos;
_lineno++;
return (char *)_line;
}
char *
Slurper::next_line()
{
if (_saved_line) {
_saved_line = false;
return (char *)_line;
}
get_line_at(_pos);
if (_line_len == 0 && _at_eof)
_line = 0;
return (char *)_line;
}
char *
Slurper::peek_line()
{
next_line();
_saved_line = true;
return (char *)_line;
}
char *
Slurper::append_next_line()
{
unsigned delta = (_data + _pos) - (_line + _line_len);
if (_len - _pos > _line_len) {
memmove(_line + delta, _line, _line_len);
_line += delta;
} else {
memmove(_data + _pos - delta, _data + _pos, _len - _pos);
_pos -= delta;
_len -= delta;
}
unsigned append_at = _pos;
_pos = _line - _data;
return get_line_at(append_at);
}
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