fakemmap.cpp

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/***************************************************************************
 *   Copyright (C) 2005 by Mario Juric   *
 *   mjuric@astro.Princeton.EDU   *
 *                                                                         *
 *   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.                          *
 *                                                                         *
 *   You should have received a copy of the GNU General Public License     *
 *   along with this program; if not, write to the                         *
 *   Free Software Foundation, Inc.,                                       *
 *   59 Temple Place - Suite 330, Boston, MA  02111-1307, USA.             *
 ***************************************************************************/

#include "fakemmap.h"
#include <map>
#include <assert.h>
#include <algorithm>
#include <stdio.h>

using std::min;

struct mapping_t {
        int fd;
        off_t offset;
};

#undef SSIZE_MAX
const size_t SSIZE_MAX = 10240UL;

std::map<size_t,mapping_t> mappings;

void *fakemmap(void *addr, size_t length, int prot, int flags, int fd, off_t offset){
        // Allocate memory for the mapping
        if(addr==0) addr = malloc(length);

        // Set up the file and memory
        char* caddr = (char*)addr;
        lseek(fd, offset, SEEK_SET);

        // Read the contents of the file into memory
        int l = 0;
        for(int i = 0; i < 10000; i++){
          int s = read(fd,caddr+l,min(length-l,SSIZE_MAX)); 
          //int s = read(fd,caddr+l,min(length-l,10240UL)); 
                if(s==-1){
                        return MAP_FAILED;
                }else if(s==0)
                        break;
                else
                        l+=s;
        }

        // Save mapping information
        mappings[(size_t)addr].fd = fd;
        mappings[(size_t)addr].offset = offset;

        // Same behavior as mmap
        return addr;
}

int fakemsync(void *addr, size_t length, int flags) {
        // Load mapping information
        int fd = mappings[(size_t)addr].fd;
        off_t offset  = mappings[(size_t)addr].offset;

        // Set up file and memory
        char* caddr = (char*)addr;
        lseek(fd, offset, SEEK_SET);

        // Write memory to file
        int l = 0;
        for(int i = 0; i < 10000; i++){
          int s = write(fd,caddr+l,min(length-l,SSIZE_MAX)); 
          //int s = write(fd,caddr+l,min(length-l,10240UL)); 
                if(s==-1)
                        return -1;
                else if( s == 0)
                        break;
                else
                        l+=s;
        }

        // Same behavior
        return 0;
}

int fakemunmap(void *addr, size_t length){
        int r = fakemsync(addr,length,0);
        free(addr);
        return r;
}