db.c

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#include <stdio.h>
#include <string.h>

#include "db.h"

/* 
open data base 
*/
void * open_db(char * mode)
{
    FILE * 		fp;
    
    fp = fopen(DB_NAME, mode);
    
    return fp;
}

/* 
close data base 
*/
int close_db(void * fp)
{
    if (NULL != fp)
        fclose((FILE*)fp);
    
    return 0;	
}

/* 
read record from base 
*/
int db_read_next(void * fp, RECORD * rcd)
{
    size_t		len;
    
    if (NULL == fp)
        return -1;
        
    if (feof((FILE*)fp))
        return 0;
    
    memset(rcd, 0, sizeof(RECORD));
    
    /* read header */
    len = sizeof(RECORD) - sizeof(rcd->msg);
    if (len != (int)fread(rcd, 1, len, (FILE*)fp))
        return -1;
    
    /* read message body */
    if (rcd->msg_len != fread(rcd->msg, 1, rcd->msg_len, (FILE*)fp))
        return -1;
    
    return sizeof(RECORD);
}

/* 
insert record to data base 
*/
int db_insert(void * fp, RECORD * rcd)
{
    size_t		len;
    
    if (NULL == fp || fseek((FILE*)fp, 0, SEEK_END))
        return -1;
    
    /* write header */
    rcd->msg_len = strlen(rcd->msg);
    len = sizeof(RECORD) - sizeof(rcd->msg);
    
    if (len != fwrite(rcd, 1, len, (FILE*)fp))
        return -1;
    
    /* write message body */
    if (rcd->msg_len != (fwrite(rcd->msg, 1, rcd->msg_len, (FILE*)fp)))
        return -1;
    
    return sizeof(RECORD);
}