| 0,0 → 1,120 |
|---|
| /* This file contains the procedures for opening, closing, and seeking on files. */ |
| |
| /* Methods: |
| * do_open: perform the OPEN system call |
| * do_close: perform the CLOSE system call |
| * do_lseek: perform the SEEK system call |
| */ |
| |
| |
| #include "fs.h" |
| #include "block.h" |
| #include "file.h" |
| #include "fproc.h" |
| #include "inode.h" |
| #include "param.h" |
| |
| |
| int do_open() |
| { |
| |
| /* Perform the open(file_name) system call */ |
| |
| int r; |
| register inode_t *rip; |
| filp_t *fil_ptr; |
| |
| |
| r = fetch_name(file_name, strlen(file_name)+1); |
| if (r != OK) |
| return err_code; /* name was bad */ |
| |
| /* See if file descriptor and filp slots are available. */ |
| if ( (r = get_fd(0, &fd, &fil_ptr)) != OK) |
| return r; |
| |
| /* Scan path name. */ |
| if ( (rip = eat_path(user_path)) == NIL_INODE) |
| return err_code; |
| |
| /* Claim the file descriptor and filp slot and fill them in. */ |
| fp->fp_filp[fd] = fil_ptr; |
| fil_ptr->filp_count = 1; |
| fil_ptr->filp_ino = rip; |
| fil_ptr->filp_flags = R_BIT; |
| |
| return fd; |
| } |
| |
| int do_close() |
| { |
| |
| /* Perform the close(fd) system call. */ |
| |
| register filp_t *rfilp; |
| register inode_t *rip; |
| |
| |
| /* First locate the inode that belongs to the file descriptor */ |
| if ( (rfilp = get_filp(fd)) == NIL_FILP) |
| return err_code; |
| |
| rip = rfilp->filp_ino; /* 'rip' points to the inode */ |
| |
| if (--rfilp->filp_count == 0) { |
| put_inode(rip); |
| } |
| |
| fp->fp_filp[fd] = NIL_FILP; |
| |
| return OK; |
| } |
| |
| int do_lseek() |
| { |
| |
| /* Perform the seek(ls_fd, offset, whence) system call. */ |
| |
| register filp_t *rfilp; |
| register offset_t pos, new_pos; |
| |
| |
| /* Check to see if the file descriptor is valid. */ |
| if ( (rfilp = get_filp(fd)) == NIL_FILP) |
| return err_code; |
| |
| |
| /* The value of 'whence' determines the start position to use. */ |
| switch(whence) { |
| case 0: pos = 0; |
| break; |
| case 1: pos = rfilp->filp_pos; |
| break; |
| case 2: pos = rfilp->filp_ino->i_size; |
| break; |
| default: return FS_EINVAL; |
| } |
| |
| /* Check for overflow. */ |
| if (((long)offset > 0) && ((long)(pos + offset) < (long)pos)) |
| return FS_EINVAL; |
| if (((long)offset < 0) && ((long)(pos + offset) > (long)pos)) |
| return FS_EINVAL; |
| |
| new_pos = pos + offset; |
| |
| /* Check for setting behind the end. */ |
| if ((new_pos) > rfilp->filp_ino->i_size) { |
| pos = rfilp->filp_ino->i_size; |
| } |
| else if (new_pos < 0) { |
| pos = 0; |
| } |
| else { |
| pos = new_pos; |
| } |
| rfilp->filp_pos = pos; |
| |
| return pos; |
| } |
| |