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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 <utility>
#include "mongo/base/data_range.h"
#include "mongo/base/data_range_cursor.h"
#include "mongo/base/data_type_terminated.h"
#include "mongo/base/disallow_copying.h"
#include "mongo/bson/util/builder.h"
#include "mongo/platform/strnlen.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:
BufReader(const void* p, unsigned len)
: _start(reinterpret_cast<const char*>(p)), _pos(_start), _end(_start + len) {}
bool atEof() const {
return _pos == _end;
}
/** read in the object specified, and advance buffer pointer */
template <typename T>
void read(T& t) {
ConstDataRangeCursor cdrc(_pos, _end);
uassertStatusOK(cdrc.readAndAdvance(&t));
_pos = cdrc.data();
}
/** 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 {
uassertStatusOK(ConstDataRange(_pos, _end).read(&t));
}
/** 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 _pos - _start;
}
/** return remaining bytes */
unsigned remaining() const {
return _end - _pos;
}
/** back up by nbytes */
void rewind(unsigned nbytes) {
_pos = _pos - nbytes;
invariant(_pos >= _start);
}
/** return current position pointer, and advance by len */
const void* skip(unsigned len) {
ConstDataRangeCursor cdrc(_pos, _end);
uassertStatusOK(cdrc.advance(len));
return std::exchange(_pos, cdrc.data());
}
/// reads a NUL terminated string
StringData readCStr() {
auto range = read<Terminated<'\0', ConstDataRange>>().value;
return StringData(range.data(), range.length());
}
void readStr(std::string& s) {
s = readCStr().toString();
}
const void* pos() {
return _pos;
}
const void* start() {
return _start;
}
private:
const char* _start;
const char* _pos;
const char* _end;
};
}
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