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// @file bufreader.h parse a memory region into usable pieces
/**
* Copyright (C) 2009 10gen Inc.
*
* This program is free software: you can redistribute it and/or modify
* it under the terms of the GNU Affero General Public License, version 3,
* as published by the Free Software Foundation.
*
* 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 Affero General Public License for more details.
*
* You should have received a copy of the GNU Affero General Public License
* along with this program. If not, see <http://www.gnu.org/licenses/>.
*/
#pragma once
namespace mongo {
/** helper to read and parse a block of memory
methods throw the eof exception if the operation would pass the end of the
buffer with which we are working.
*/
class BufReader : boost::noncopyable {
public:
class eof : public std::exception {
public:
eof() { }
virtual const char * what() const throw() { return "BufReader eof"; }
};
BufReader(const void *p, unsigned len) : _start(p), _pos(p), _end(((char *)_pos)+len) { }
bool atEof() const { return _pos == _end; }
/** read in the object specified, and advance buffer pointer */
template <typename T>
void read(T &t) {
T* cur = (T*) _pos;
T *next = cur + 1;
if( _end < next ) throw eof();
t = *cur;
_pos = next;
}
/** verify we can look at t, but do not advance */
template <typename T>
void peek(T &t) {
T* cur = (T*) _pos;
T *next = cur + 1;
if( _end < next ) throw eof();
t = *cur;
}
/** return current offset into buffer */
unsigned offset() const { return (char*)_pos - (char*)_start; }
/** return remaining bytes */
unsigned remaining() const { return (char*)_end -(char*)_pos; }
/** back up by nbytes */
void rewind(unsigned nbytes) {
_pos = ((char *) _pos) - nbytes;
verify( _pos >= _start );
}
/** return current position pointer, and advance by len */
const void* skip(unsigned len) {
const char *nxt = ((char *) _pos) + len;
if( _end < nxt ) throw eof();
const void *p = _pos;
_pos = nxt;
return p;
}
void readStr(string& s) {
StringBuilder b;
while( 1 ) {
char ch;
read(ch);
if( ch == 0 )
break;
b << ch;
}
s = b.str();
}
const void* pos() { return _pos; }
const void* start() { return _start; }
private:
const void *_start;
const void *_pos;
const void *_end;
};
}
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