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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/>.
*
* As a special exception, the copyright holders give permission to link the
* code of portions of this program with the OpenSSL library under certain
* conditions as described in each individual source file and distribute
* linked combinations including the program with the OpenSSL library. You
* must comply with the GNU Affero General Public License in all respects
* for all of the code used other than as permitted herein. If you modify
* file(s) with this exception, you may extend this exception to your
* version of the file(s), but you are not obligated to do so. If you do not
* wish to do so, delete this exception statement from your version. If you
* delete this exception statement from all source files in the program,
* then also delete it in the license file.
*/
#pragma once
#include "mongo/bson/util/builder.h"
#include "mongo/util/assert_util.h"
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 {
MONGO_DISALLOW_COPYING(BufReader);
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;
}
/** read in and return an object of the specified type, and advance buffer pointer */
template <typename T>
T read() {
T out;
read(out);
return out;
}
/** read in the object specified, but do not advance buffer pointer */
template <typename T>
void peek(T& t) const {
T* cur = (T*)_pos;
T* next = cur + 1;
if (_end < next)
throw eof();
t = *cur;
}
/** read in and return an object of the specified type, but do not advance buffer pointer */
template <typename T>
T peek() const {
T out;
peek(out);
return out;
}
/** 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;
}
/// reads a NUL terminated string
StringData readCStr() {
const char* start = static_cast<const char*>(pos());
size_t len = strnlen(start, remaining() - 1);
if (start[len] != '\0')
throw eof(); // no NUL byte in remaining bytes
skip(len + 1 /*NUL byte*/);
return StringData(start, len);
}
void readStr(std::string& s) {
s = readCStr().toString();
}
const void* pos() {
return _pos;
}
const void* start() {
return _start;
}
private:
const void* _start;
const void* _pos;
const void* _end;
};
}
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