freedb.cpp

/***************************************************************************
                          freedb.cpp  -  free spaces database support
                             -------------------
    begin                : Sun Apr 29 2001
    copyright            : (C) 2001 by Alexander Bilichenko
    email                : pricer@mail.ru
 ***************************************************************************/

#include "basetypes.h"
#include "freedb.h"

#define unlock_and_freedb_io_error1() do { unlock_file(ffb); errnum = FREEDBFILE_ERROR_IO_ERROR; return FREEDBFILE_ERROR_IO_ERROR; } while (0)
#define freedb_io_error1() do { errnum = FREEDBFILE_ERROR_IO_ERROR; return FREEDBFILE_ERROR_IO_ERROR; } while (0)

/* mark free space block with size bsize and index bIndex
 * if successfull return FREEDB_ERROR_ALLOK
 */
DWORD CFreeDBFile::MarkFreeSpace(DWORD bIndex, DWORD bsize)
{
        SFreeDBEntry fs;
        DWORD rr;
        WCFILE *ffb;

        if(!init) {
                errnum = FREEDBFILE_ERROR_NOT_INITIALIZED;
                return errnum;
        }

        // ignore wasted blocks
        if(bsize < wasted_block) bsize = 0;

        if((ffb = wcfopen(fname, FILE_ACCESS_MODES_RW)) == NULL) {
                if((ffb = wcfopen(fname, FILE_ACCESS_MODES_CW)) == NULL) {
                        freedb_io_error1();
                }
                else {
                        wcfclose(ffb);
                        if((ffb = wcfopen(fname, FILE_ACCESS_MODES_RW)) == NULL) {
                                freedb_io_error1();
                        }
                }
        }
        /* seek at begining of WCFILE */
        if(wcfseek(ffb, 0, SEEK_SET) != 0) {
                freedb_io_error1();
        }

        lock_file(ffb);

        int alreadyfind = 0;
        while(!wcfeof(ffb)) {
                if((rr = (DWORD)wcfread(&fs, 1, sizeof(SFreeDBEntry), ffb)) != sizeof(SFreeDBEntry)) {
                        if(rr == 0) break;
                        unlock_and_freedb_io_error1();
                }
                if(fs.size == 0) {
                        alreadyfind = 1;
                        rr = wcftell(ffb) - sizeof(SFreeDBEntry);
                        if(wcfseek(ffb, rr, SEEK_SET) != 0) {
                                unlock_and_freedb_io_error1();
                        }
                        fs.size = bsize;
                        fs.index = bIndex;
                        if(!fCheckedWrite(&fs, sizeof(SFreeDBEntry), ffb)) {
                                unlock_and_freedb_io_error1();
                        }
                        break;
                }
        }
        if(!alreadyfind) {
                if(wcfseek(ffb, 0, SEEK_END) != 0) {
                        unlock_and_freedb_io_error1();
                }
                fs.size = bsize;
                fs.index = bIndex;
                if(!fCheckedWrite(&fs, sizeof(SFreeDBEntry), ffb)) {
                        unlock_and_freedb_io_error1();
                }
        }
        unlock_file(ffb);
        wcfclose(ffb);
        errnum = FREEDBFILE_ERROR_ALLOK;
        return FREEDBFILE_ERROR_ALLOK;
}

/* allocate size bytes of free space, and return index of it
 * otherwise return 0xFFFFFFFF and set errnum with error code
 */
DWORD CFreeDBFile::AllocFreeSpace(DWORD size)
{
        SFreeDBEntry fs;
        DWORD rr;
        WCFILE *ffb;

        if(!init) {
                errnum = FREEDBFILE_ERROR_NOT_INITIALIZED;
                return 0xFFFFFFFF;
        }

        if((ffb = wcfopen(fname, FILE_ACCESS_MODES_RW)) == NULL) {
                if((ffb = wcfopen(fname, FILE_ACCESS_MODES_CW)) == NULL) {
                        freedb_io_error1();
                }
                else {
                        wcfclose(ffb);
                        if((ffb = wcfopen(fname, FILE_ACCESS_MODES_RW)) == NULL) {
                                freedb_io_error1();
                        }
                }
        }
        /* seek at begining of WCFILE */
        if(wcfseek(ffb, 0, SEEK_SET) != 0) {
                freedb_io_error1();
        }

        lock_file(ffb);

        while(!wcfeof(ffb)) {
                if((rr = (DWORD)wcfread(&fs, 1, sizeof(SFreeDBEntry), ffb)) != sizeof(SFreeDBEntry)) {
                        if(rr == 0) {
                                break;
                        }
                        unlock_and_freedb_io_error1();
                }
                if(fs.size >= size) {
                        rr = wcftell(ffb) - sizeof(SFreeDBEntry);
                        if(wcfseek(ffb, rr, SEEK_SET) != 0) {
                                unlock_and_freedb_io_error1();
                        }

                        fs.size = fs.size - size;
                        fs.index = fs.index + size;

                        // make wasted space, if block too small
                        if(fs.size < wasted_block) fs.size = 0;

                        if(!fCheckedWrite(&fs, sizeof(SFreeDBEntry), ffb)) {
                                unlock_and_freedb_io_error1();
                        }

                        unlock_file(ffb);
                        wcfclose(ffb);
                        // unlock FFB semaphore
                        return fs.index - size;
                }
        }

        unlock_file(ffb);
        wcfclose(ffb);

        return 0xFFFFFFFF;
}

CFreeDBFile::CFreeDBFile(const char *ifname, DWORD wasted_b)
{
        init = 0;
        if(ifname == NULL || strlen(ifname) < 1) {
                errnum = FREEDBFILE_ERROR_INVALID_FILE;
                return;
        }
        fname = strdup(ifname);
        wasted_block = wasted_b;
        errnum = FREEDBFILE_ERROR_ALLOK;
        init = 1;
}

CFreeDBFile::~CFreeDBFile()
{
        if(init) {
                free(fname);
        }
}