实验四文件系统讲解.ppt

实验四 文件系统——Hash结构文件;实验目的;实验内容;实验准备;实验设计 ;参考代码;HashFile.h;struct CFTag { char collision; //冲突计数 char free; //空闲标志 }; int hashfile_creat(const char *filename,mode_t mode,int reclen,int recnum); //int hashfile_open(const char *filename,int flags); int hashfile_open(const char *filename,int flags, mode_t mode); int hashfile_close(int fd); int hashfile_read(int fd,int keyoffset,int keylen,void *buf); int hashfile_write(int fd,int keyoffset,int keylen,void *buf); int hashfile_delrec(int fd,int keyoffset,int keylen,void *buf); int hashfile_findrec(int fd,int keyoffset,int keylen,void *buf); int hashfile_saverec(int fd,int keyoffset,int keylen,void *buf); int hash(int keyoffset,int keylen,void *buf,int recnum); int checkHashFileFull(int fd); int readHashFileHeader(int fd,struct HashFileHeader *hfh ) ;HashFile.c;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 hfh.reclen=reclen; hfh.total_rec_num=total_rec_num; hfh.current_rec_num=0; //fd=open(filename,mode); fd=creat(filename,mode); if(fd!=-1) { rtn=write(fd,hfh,sizeof(struct HashFileHeader)); //lseek(fd,sizeof(struct HashFileHeader),SEEK_SET); 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= return fd; else return -1;