fox32os/kernel/vfs.asm

159 lines
2.7 KiB
NASM

; virtual filesystem routines
; file struct for file:
; file_disk: 1 byte
; file_first_sector: 2 bytes
; file_seek_offset: 4 bytes
; file_system_type: 1 byte (0x00 for RYFS)
; file struct for stream:
; file_reserved_1: 1 byte
; file_reserved_2: 2 bytes
; file_reserved_4: 4 bytes
; file_system_type: 1 byte (0x01 for stream)
; file_read_call: 4 bytes
; file_write_call: 4 bytes
; open a file from a RYFS-formatted disk
; inputs:
; r0: pointer to file name string (8.3 format, for example "test txt" for test.txt)
; r1: disk ID
; r2: file struct: pointer to a blank file struct
; outputs:
; r0: first file sector, or zero if file wasn't found
open:
jmp ryfs_open
; seek specified file to the specified offset
; inputs:
; r0: byte offset
; r1: pointer to file struct
; outputs:
; none
seek:
push r1
add r1, 7
cmp.8 [r1], 0x00
pop r1
ifz jmp ryfs_seek
ret
; get the seek offset of the specified file
; inputs:
; r0: pointer to file struct
; outputs:
; r0: byte offset
tell:
push r0
add r0, 7
cmp.8 [r0], 0x00
pop r0
ifz jmp ryfs_tell
ret
; read specified number of bytes into the specified buffer
; inputs:
; r0: number of bytes to read
; r1: pointer to file struct
; r2: pointer to destination buffer
; outputs:
; r0: number of bytes left to read (streams can read short)
read:
push r3
push r1
add r1, 7
movz.8 r3, [r1]
pop r1
cmp.8 r3, 0x00
ifz pop r3
ifz jmp ryfs_read
cmp.8 r3, 0x01
ifz pop r3
ifz jmp stream_read
pop r3
ret
stream_read:
push r1
push r2
stream_read_loop:
call stream_read_char
call yield_task
cmp.8 [r2], 0
ifz jmp stream_read_out
inc r2
dec r0
ifnz jmp stream_read_loop
stream_read_out:
pop r2
pop r1
ret
stream_read_char:
push r0
push r1
push r2
; call [file_read_call]
add r1, 8
call [r1]
; put the result into [r2]
pop r2
mov.8 [r2], r0
pop r1
pop r0
ret
; write specified number of bytes into the specified file
; inputs:
; r0: number of bytes to write
; r1: pointer to file struct
; r2: pointer to source buffer
; outputs:
; none
write:
push r3
push r1
add r1, 7
movz.8 r3, [r1]
pop r1
cmp.8 r3, 0x00
ifz pop r3
ifz jmp ryfs_write
cmp.8 r3, 0x01
ifz pop r3
ifz jmp stream_write
pop r3
ret
stream_write:
push r31
push r2
mov r31, r0 ; number of bytes to write = loop count
stream_write_loop:
call stream_write_char
inc r2
loop stream_write_loop
pop r2
pop r31
ret
stream_write_char:
push r0
push r1
; call [file_write_call] with pointer to src buf in r0
add r1, 12
mov r0, r2
call [r1]
pop r1
pop r0
ret