import “io”
manifest
{ iosb_ichar = 0;
iosb_ochar = 1;
iosb_close = 2;
iosb_unit = 3;
iosb_buffer = 4;
iosb_pos = 5;
iosb_size = 6;
sizeof_iosb = 7;
diosb_firstbn = 7;
diosb_lastbn = 8;
diosb_length = 9;
diosb_de = 10;
sizeof_diosb = 11;
sb_rootdir_bn = 0;
sb_first_free_bn = 1;
sb_last_free_bn = 2;
de_name = 0;
de_first_bn = 5;
de_last_bn = 6;
de_length = 7;
sizeof_de = 8;
de_namelen = 5*4 – 1 }
let readch_tty(iosb) be
{ resultis inch() }
let writech_tty(iosb, c) be
{ outch(c) }
let close_tty(iosb) be
{ }
let tty = table readch_tty, writech_tty, close_tty, 0, 0, 0, 0;
let tapes = table 1, 0, 0, 0, 0, 0, 0, 0, 0;
let find_free_tape_unit() be
{ for i = 1 to 8 do
if tapes ! i = 0 then
{ tapes ! i := 1;
resultis i }
out(“All tape drives are in use
”);
finish }
let close_writetape(iosb) be
{ let r;
if iosb ! iosb_pos /= 0 then
{ let r = devctl(DC_TAPE_WRITE,
iosb ! iosb_unit,
iosb ! iosb_buffer,
iosb ! iosb_pos);
if r < 0 then{ out(“code %d from tape write
“, r);finish } }r := devctl(DC_TAPE_UNLOAD, iosb ! iosb_unit);if r < 0 then{ out(“code %d from tape unload
“, r);finish }tapes ! (iosb ! iosb_unit) := 0;freevec(iosb ! iosb_buffer);freevec(iosb) }let close_readtape(iosb) be{ let r = devctl(DC_TAPE_UNLOAD, iosb ! iosb_unit);if r < 0 then{ out(“code %d from tape unload
“, r);finish }tapes ! (iosb ! iosb_unit) := 0;freevec(iosb ! iosb_buffer);freevec(iosb) }let writechar_tape(iosb, ch) be{ if iosb ! iosb_pos = iosb ! iosb_size then{ let r = devctl(DC_TAPE_WRITE, iosb ! iosb_unit,iosb ! iosb_buffer, iosb ! iosb_size);if r < 0 then{ out(“code %d from tape write
“, r);finish }iosb ! iosb_pos := 0 }byte (iosb ! iosb_pos) of (iosb ! iosb_buffer) := ch;iosb ! iosb_pos +:= 1 }let readchar_tape(iosb) be{ let c;if iosb ! iosb_pos >= iosb ! iosb_size then
{ let r = devctl(DC_TAPE_READ,
iosb ! iosb_unit,
iosb ! iosb_buffer);
if r < 0 then{ out(“code %d from tape read
“, r);finish }iosb ! iosb_pos := 0;iosb ! iosb_size := r }if iosb ! iosb_pos = iosb ! iosb_size then{ iosb ! iosb_size := -1;resultis -1; }c := byte (iosb ! iosb_pos) of (iosb ! iosb_buffer);iosb ! iosb_pos +:= 1;resultis c }let illegal_writech(iosb, ch) be{ out(“Write performed on read-only file
“);finish }let illegal_readch(iosb) be{ out(“Read performed on write-only file
“);finish }let at_eof(iosb) be{ resultis iosb ! iosb_size = -1 }let tape_open_w(fname) be{ let t = find_free_tape_unit();let r = devctl(DC_TAPE_LOAD, t, fname, ‘W’);if r < 0 then{ out(“code %d from tape load
“, r);finish }r := newvec(sizeof_iosb);r ! iosb_ichar := illegal_readch;r ! iosb_ochar := writechar_tape;r ! iosb_close := close_writetape;r ! iosb_unit := t;r ! iosb_buffer := newvec(128);r ! iosb_pos := 0;r ! iosb_size := 512;resultis r; }let tape_open_r(fname) be{ let t = find_free_tape_unit();let r = devctl(DC_TAPE_LOAD, t, fname, ‘R’);if r < 0 then{ out(“code %d from tape load
“, r);finish }r := newvec(sizeof_iosb);r ! iosb_ichar := readchar_tape;r ! iosb_ochar := illegal_writech;r ! iosb_close := close_readtape;r ! iosb_unit := t;r ! iosb_buffer := newvec(128);r ! iosb_pos := 0;r ! iosb_size := 512;resultis r; }let stringeq(a, b) be{ let i = 0;while true do{ let ac = byte i of a, bc = byte i of b;if ac /= bc thenresultis false;if ac = 0 thenresultis true;i +:= 1 } }let strncpy(dst, src, n) be{ for i = 0 to n – 1 do{ let c = byte i of src;byte i of dst := c;if c = 0 thenreturn }byte (n – 1) of dst := 0 }let superblock = nil;let rootdir = nil;let rootdirlen = 0;let readblock(bn, addr) be{ let r = devctl(DC_DISC_READ, 1, bn, 1, addr);if r < 0 then{ out(“Error %d from disc read
“, r);finish } }let writeblock(bn, addr) be{ let r = devctl(DC_DISC_WRITE, 1, bn, 1, addr);if r < 0 then{ out(“Error %d from disc write
“, r);finish } }let disc_format() be{ let r = devctl(DC_DISC_CHECK, 1), pos;if r <= 0 then{ out(“Error %d from disc 1
“, r);finish }test superblock = nil thensuperblock := newvec(128)else{ out(“disc is mounted, unmount first
“);return }superblock ! sb_rootdir_bn := 1;superblock ! sb_first_free_bn := 2;superblock ! sb_last_free_bn := r – 1;if rootdir = nil thenrootdir := newvec(128);rootdirlen := 128;pos := 0;while pos < rootdirlen do{ let de = rootdir + pos;de ! de_name := 0;pos +:= sizeof_de } }let disc_mount() be{ let r = devctl(DC_DISC_CHECK, 1);if r <= 0 then{ out(“Error %d from disc 1
“, r);finish }test superblock = nil thensuperblock := newvec(128)else{ out(“disc is mounted, unmount first
“);return }readblock(0, superblock);if rootdir = nil thenrootdir := newvec(128);rootdirlen := 128;readblock(superblock ! sb_rootdir_bn, rootdir) }let disc_save_all() be{ if superblock = nil then{ out(“disc is not mounted
“);return }writeblock(0, superblock);writeblock(superblock ! sb_rootdir_bn, rootdir) }let disc_unmount() be{ if superblock = nil then{ out(“disc is not mounted
“);return }disc_save_all();freevec(superblock);superblock := nil;freevec(rootdir);rootdir := nil;rootdirlen := 0 }let disc_readch(iosb) be{ /* YOU IMPLEMENT THIS */ }// be careful with the value of iosb!diosb_length for the last blocklet disc_writech(iosb, ch) be{ if iosb ! iosb_pos >= iosb ! iosb_size then
{ if iosb ! diosb_firstbn <= iosb ! diosb_lastbn then{ writeblock(iosb ! diosb_firstbn, iosb ! iosb_buffer);iosb ! diosb_firstbn +:= 1;iosb ! diosb_length +:= 512 } iosb ! iosb_pos := 0;iosb ! iosb_size := 512 }byte (iosb ! iosb_pos) of (iosb ! iosb_buffer) := ch;iosb ! iosb_pos +:= 1 }let disc_close_r(iosb) be{ freevec(iosb ! iosb_buffer);freevec(iosb) }let disc_close_w(iosb) be// this is to close a file that was opened for writing{ /* YOU IMPLEMENT THIS */ }let disc_find_file(name) be{ let pos = 0;if rootdir = nil thenresultis nil;while pos < rootdirlen do{ let de = rootdir + pos;if stringeq(name, de + de_name) thenresultis de;pos +:= sizeof_de }resultis nil }let disc_create_file(name, nb) be{ let b1 = superblock ! sb_first_free_bn;let bn = b1 + nb – 1;let pos = 0;if rootdir = nil thenresultis nil;if bn > superblock ! sb_last_free_bn then
resultis nil;
while pos < rootdirlen do{ let de = rootdir + pos;if de ! de_name = 0 then{ strncpy(de + de_name, name, de_namelen);de ! de_first_bn := b1;de ! de_last_bn := bn;de ! de_length := 0;superblock ! sb_first_free_bn +:= nb;resultis de }pos +:= sizeof_de }resultis nil }let disc_delete_file(name) be{ /* YOU IMPLEMENT THIS */ }let disc_open_new_file(name, maxlen) be// this is to open a file that doesn’t exist yet, for writing{ let blocks = (maxlen + 511) / 512;let de = disc_create_file(name, blocks);let r;if de = nil thenresultis nil;r := newvec(sizeof_diosb);r ! iosb_ichar := illegal_readch;r ! iosb_ochar := disc_writech;r ! iosb_close := disc_close_w;r ! iosb_buffer := newvec(128);r ! iosb_pos := 0;r ! iosb_size := 512;r ! diosb_firstbn := de ! de_first_bn;r ! diosb_lastbn := de ! de_last_bn;r ! diosb_length := 0;r ! diosb_de := de;resultis r }let disc_open_file_write(name) be// this is to open a file that already exists and overwrite its content{ /* YOU IMPLEMENT THIS */ }let disc_open_file_read(name) be{ let de = disc_find_file(name);let r;if de = nil thenresultis nil;r := newvec(sizeof_diosb);r ! iosb_ichar := disc_readch;r ! iosb_ochar := illegal_writech;r ! iosb_close := disc_close_r;r ! iosb_buffer := newvec(128);r ! iosb_pos := 0;r ! iosb_size := 0;r ! diosb_firstbn := de ! de_first_bn;r ! diosb_lastbn := de ! de_last_bn;r ! diosb_length := de ! de_length;r ! diosb_de := de;resultis r }let disc_listdir() be{ let pos = 0;if rootdir = nil thenreturn;while pos < rootdirlen do{ let de = rootdir + pos;test de ! de_name = 0 thenout(“(unused)
“)elseout(“%s: first block = %d, last_block = %d, length = %d
“,de + de_name, de ! de_first_bn, de ! de_last_bn, de ! de_length);pos +:= sizeof_de } }let writech(iosb, ch) be{ if iosb = nil then{ out(“writech: iosb is nil
“);return }(iosb ! iosb_ochar)(iosb, ch) }let readch(iosb) be{ if iosb = nil then{ out(“readch: iosb is nil
“);resultis -1 }resultis (iosb ! iosb_ichar)(iosb) }let close(iosb) be{ if iosb = nil then{ out(“close: iosb is nil
“);return }(iosb ! iosb_close)(iosb) }let writestr(iosb, s) be{ let i = 0;while true do{ let c = byte i of s;if c = 0 then break;writech(iosb, c);i +:= 1 } }let readstr(iosb, s, max) be{ let pos = 0;while pos < max do{ let c = readch(iosb);if c < ‘ ‘ then break;byte pos of s := c;pos +:= 1 }byte pos of s := 0 }let writeno(iosb, n) be{ if n < 0 then{ writech(iosb, ‘-‘);n := -n }if n > 9 then
writeno(iosb, n / 10);
writech(iosb, ‘0’ + n rem 10) }
let readno(iosb) be
{ let n = 0, c = readch(iosb), s = 1;
while c < ‘ ‘ doc:=readch(iosb);if c = ‘-‘ then{ s := -1;c := readch(iosb) }while c >= ‘0’ / c <= ‘9’ do{ n := n * 10 + c – ‘0’; c := readch(iosb) }resultis n * s }// test of tape systemlet test_tape() be{ let fi, fo, min, max;writestr(tty, “The program is creating table.txt
“);fi := tape_open_r(“limits.txt”);fo := tape_open_w(“table.txt”);// I should check to see if fi or fo are nil.min := readno(fi);max := readno(fi);for cent = min to max do{ let fahr = cent * 9 / 5 + 32;writeno(fo, cent);writestr(fo, ” centigrade is “);writeno(fo, fahr);writestr(fo, ” fahrenheit
“) }close(fi);close(fo) }// basic test of disc system writelet test_make_table() be{ let fo = disc_open_new_file(“table.txt”, 3500);// I should check to see if fo is nil.writestr(fo, “abcdefghijklmnopqrstuvwxyz
“);for cent = 0 to 100 do{ let fahr = cent * 9 / 5 + 32;writeno(fo, cent);writestr(fo, ” centigrade is “);writeno(fo, fahr);writestr(fo, ” fahrenheit
“) }close(fo) }let test_create_any_file() be{ let fo, fname = vec(10), len;writestr(tty, “Enter file name: “);readstr(tty, fname, 39);writestr(tty, “Maximum length (in bytes): “);len := inno();fo := disc_open_new_file(fname, len);// I should check to see if fo is nil.writestr(tty, “Enter content, end with *:
“);while true do{ let c = readch(tty);if c = ‘*’ then break;writech(fo, c) }while true do{ let c = readch(tty);if c = ‘
‘ then break }close(fo) }let test_read_any_file() be{ let fi, fname = vec(10);writestr(tty, “Enter file name: “);readstr(tty, fname, 39);fi := disc_open_file_read(fname);// I should check to see if fi is nil.while true do{ let c = readch(fi);if c = -1 then break;writech(tty, c) } }let test_delete_file() be{ let fname = vec(10);writestr(tty, “Enter file name: “);readstr(tty, fname, 39);disc_delete_file(fname)/* I should check that the result is not false */ }let start() be{ let line = vec(10);init(!0x101, !0x100 – !0x101);writestr(tty, “Remember to mount or format first
And unmount when you’re done
“);while true do{ writestr(tty, “1: tape test
“);writestr(tty, “2: format disc
“);writestr(tty, “3: mount disc
“);writestr(tty, “4: unmount disc
“);writestr(tty, “5: list directory
“);writestr(tty, “6: create table.txt
“);writestr(tty, “7: create any file
“);writestr(tty, “8: read any file
“);writestr(tty, “9: delete a file
“);writestr(tty, “x: exit
“);writestr(tty, “? “);readstr(tty, line, 39);switchon line ! 0 into{ case ‘1’:test_tape();endcase;case ‘2’:disc_format();endcase;case ‘3’:disc_mount();endcase;case ‘4’:disc_unmount();endcase;case ‘5’:disc_listdir();endcase;case ‘6’:test_make_table();endcase;case ‘7’:test_create_any_file();endcase;case ‘8’:test_read_any_file();endcase;case ‘9’:test_delete_file();endcase;case ‘x’:finish;case ‘
‘:endcase;default:out(“You typed “%s”
What?
“, line); } } }
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