HashFile.c

#include<unistd.h>
#include<sys/types.h>
#include<sys/stat.h>
#include<fcntl.h>
#include<stdio.h>
#include<stdlib.h>
#include<memory.h>
#include"HashFile.h"

int hashfile_creat(const char *filename,mode_t mode,int reclen,int total_rec_num)
{
struct HashFileHeader hfh;
int fd;
int rtn;
char *buf;
int i=0;
hfh.sig = 31415926;
hfh.reclen = reclen;
hfh.total_rec_num = total_rec_num;
hfh.current_rec_num = 0;
fd = creat(filename,mode);
if(fd != -1)
{
rtn = write(fd,&hfh,sizeof(struct HashFileHeader));
if(rtn != -1)
{
buf = (char*)malloc((reclen+sizeof(struct CFTag))*total_rec_num);
memset(buf,0,(reclen+sizeof(struct CFTag))*total_rec_num);   ????
rtn = write(fd,buf,(reclen+sizeof(struct CFTag))*total_rec_num);
free(buf);
}
close(fd);
return rtn;
}
else{
close(fd);
return -1;
}
}

int hashfile_open(const char *filename,int flags,mode_t mode)
{
int fd = open(filename,flags,mode);
struct HashFileHeader hfh;
if(read(fd,&hfh,sizeof(struct HashFileHeader))!= -1)
{
lseek(fd,0,SEEK_SET);
if(hfh.sig == 31415926)
return fd;
else
return -1;
}
else return -1;
}
int hashfile_close(int fd)
{
return close(fd);
}
int hashfile_read(int fd,int keyoffset,int keylen,void *buf)
{
struct HashFileHeader hfh;
readHashFileHeader(fd,&hfh);
int offset = hashfile_findrec(fd,keyoffset,keylen,buf);
if(offset != -1)
{
lseek(fd,offset+sizeof(struct CFTag),SEEK_SET);
return read(fd,buf,hfh.reclen);
}
else
{
return -1;
}
}
int hashfile_write(int fd,int keyoffset,int keylen,void *buf)
{
return hashfile_saverec(fd,keyoffset,keylen,buf);

}
int hashfile_delrec(int fd,int keyoffset,int keylen,void *buf)
{
int offset;
offset = hashfile_findrec(fd,keyoffset,keylen,buf);
if(offset != -1)
{
struct CFTag tag;
read(fd,&tag,sizeof(struct CFTag));
tag.free =0; 
lseek(fd,offset,SEEK_SET);
write(fd,&tag,sizeof(struct CFTag));
struct HashFileHeader hfh;
readHashFileHeader(fd,&hfh);
int addr = hash(keyoffset,keylen,buf,hfh.total_rec_num);
offset = sizeof(struct HashFileHeader)+addr*(hfh.reclen+sizeof(struct CFTag));
if(lseek(fd,offset,SEEK_SET)==-1)
return -1;
read(fd,&tag,sizeof(struct CFTag));
tag.collision--; 
lseek(fd,offset,SEEK_SET);
write(fd,&tag,sizeof(struct CFTag));
hfh.current_rec_num--; 
lseek(fd,0,SEEK_SET);
write(fd,&hfh,sizeof(struct HashFileHeader));
}
else{
return -1;
}
}

int hashfile_findrec(int fd,int keyoffset,int keylen,void *buf)
{
struct HashFileHeader hfh;
readHashFileHeader(fd,&hfh);
int addr = hash(keyoffset,keylen,buf,hfh.total_rec_num);
int offset = sizeof(struct HashFileHeader)+addr*(hfh.reclen+sizeof(struct CFTag));
if(lseek(fd,offset,SEEK_SET)==-1)
return -1;
struct CFTag tag;
read(fd,&tag,sizeof(struct CFTag));
char count = tag.collision;
if(count==0)
return -1; 
recfree:
if(tag.free == 0)
{
offset += hfh.reclen+sizeof(struct CFTag);
if(lseek(fd,offset,SEEK_SET)==-1)
return -1;
read(fd,&tag,sizeof(struct CFTag));
goto recfree;
}
else{
char *p =(char*)malloc(hfh.reclen*sizeof(char));
read(fd,p,hfh.reclen);
char *p1,*p2;
p1 = (char *)buf+keyoffset;
p2 = p + keyoffset;
int j=0;
while((*p1 == *p2)&&(j<keylen))
{
p1++;
p2++;
j++;
}
if(j==keylen)
{
free(p);
p = NULL;
return(offset);
}
else{
if(addr == hash(keyoffset,keylen,p,hfh.total_rec_num))
{
count--;
if(count == 0)
{
free(p);
p = NULL;
return -1;
}
}
free(p);
p = NULL;
offset += hfh.reclen+sizeof(struct CFTag);
if(lseek(fd,offset,SEEK_SET) == -1)
return -1;
read(fd,&tag,sizeof(struct CFTag));
goto recfree;
}
}
}
int hashfile_saverec(int fd,int keyoffset,int keylen,void *buf)
{
if(checkHashFileFull(fd))
{
return -1;
}
struct HashFileHeader hfh;
readHashFileHeader(fd,&hfh);
int addr = hash(keyoffset,keylen,buf,hfh.total_rec_num);
int offset = sizeof(struct HashFileHeader)+addr*(hfh.reclen+sizeof(struct CFTag));
if(lseek(fd,offset,SEEK_SET)==-1)
return -1;
struct CFTag tag;
read(fd,&tag,sizeof(struct CFTag));
tag.collision++;
lseek(fd,sizeof(struct CFTag)*(-1),SEEK_CUR);
write(fd,&tag,sizeof(struct CFTag));
while(tag.free!=0) 
{
offset += hfh.reclen+sizeof(struct CFTag);
if(offset >= lseek(fd,0,SEEK_END))
offset = sizeof(struct HashFileHeader); //reach at and,then rewind
if(lseek(fd,offset,SEEK_SET)==-1)
return -1;
read(fd,&tag,sizeof(struct CFTag));
} 
tag.free =-1;
lseek(fd,sizeof(struct CFTag)*(-1),SEEK_CUR);
write(fd,&tag,sizeof(struct CFTag));
write(fd,buf,hfh.reclen);
hfh.current_rec_num++;
lseek(fd,0,SEEK_SET);
return write(fd,&hfh,sizeof(struct HashFileHeader));   
}

int hash(int keyoffset,int keylen,void *buf,int total_rec_num)
{
int i=0;
char *p =(char*)buf+keyoffset;
int addr =0;
for(i=0;i<keylen;i++)
{
addr += (int)(*p);
p++;
}
return addr%(int)(total_rec_num*COLLISIONFACTOR);
}

int checkHashFileFull(int fd)
{
struct HashFileHeader hfh;
readHashFileHeader(fd,&hfh);
if(hfh.current_rec_num<hfh.total_rec_num)
return 0;
else
return 1;
}
int readHashFileHeader(int fd,struct HashFileHeader *hfh)
{
lseek(fd,0,SEEK_SET);
return read(fd,hfh,sizeof(struct HashFileHeader));
}