d53c412a29
This slightly changes the journal format. Currently, support is there for reading the old format, but I plan to remove that next week.
97 lines
2.8 KiB
C++
97 lines
2.8 KiB
C++
// @file bufreader.h parse a memory region into usable pieces
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/**
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* Copyright (C) 2009 10gen Inc.
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*
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* This program is free software: you can redistribute it and/or modify
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* it under the terms of the GNU Affero General Public License, version 3,
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* as published by the Free Software Foundation.
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*
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* This program is distributed in the hope that it will be useful,
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* but WITHOUT ANY WARRANTY; without even the implied warranty of
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* MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
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* GNU Affero General Public License for more details.
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*
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* You should have received a copy of the GNU Affero General Public License
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* along with this program. If not, see <http://www.gnu.org/licenses/>.
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*/
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#pragma once
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namespace mongo {
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/** helper to read and parse a block of memory
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methods throw the eof exception if the operation would pass the end of the
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buffer with which we are working.
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*/
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class BufReader : boost::noncopyable {
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public:
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class eof : public std::exception {
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public:
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virtual const char * what() { return "BufReader eof"; }
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};
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BufReader(void *p, unsigned len) : _start(p), _pos(p), _end(((char *)_pos)+len) { }
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bool atEof() const { return _pos == _end; }
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/** read in the object specified, and advance buffer pointer */
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template <typename T>
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void read(T &t) {
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T* cur = (T*) _pos;
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T *next = cur + 1;
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if( _end < next ) throw eof();
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t = *cur;
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_pos = next;
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}
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/** verify we can look at t, but do not advance */
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template <typename T>
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void peek(T &t) {
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T* cur = (T*) _pos;
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T *next = cur + 1;
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if( _end < next ) throw eof();
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t = *cur;
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}
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/** return current offset into buffer */
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unsigned offset() const { return (char*)_pos - (char*)_start; }
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/** return current position pointer, and advance by len */
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const void* skip(unsigned len) {
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char *nxt = ((char *) _pos) + len;
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if( _end < nxt ) throw eof();
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void *p = _pos;
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_pos = nxt;
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return p;
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}
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void readStr(string& s) {
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StringBuilder b;
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while( 1 ) {
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char ch;
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read(ch);
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if( ch == 0 )
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break;
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b << ch;
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}
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s = b.str();
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}
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/** skip ahead to our alignment boundary */
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void align(unsigned alignment) {
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size_t ofs = ((char*)_pos) - ((char*)_start);
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ofs = (ofs + (alignment-1)) & (~(alignment-1));
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_pos = ((char*)_start) + ofs;
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}
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void* pos() { return _pos; }
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private:
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void *_start;
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void *_pos;
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void *_end;
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};
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}
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