blockdev: remove a layer of indirection in block routine storage

This will facilitate "copying" blk selection in FS.
This commit is contained in:
Virgil Dupras 2019-04-23 15:03:23 -04:00
parent ad217c018e
commit 3ba0a707e7

View File

@ -26,8 +26,11 @@ BLOCKDEV_SEEK_END .equ 4
; Pointer to the selected block device. A block device is a 8 bytes block of
; memory with pointers to GetC, PutC, Seek and Tell routines, in that order.
; 0 means unsupported.
BLOCKDEV_SEL .equ BLOCKDEV_RAMSTART
BLOCKDEV_RAMEND .equ BLOCKDEV_SEL+2
BLOCKDEV_GETC .equ BLOCKDEV_RAMSTART
BLOCKDEV_PUTC .equ BLOCKDEV_GETC+2
BLOCKDEV_SEEK .equ BLOCKDEV_PUTC+2
BLOCKDEV_TELL .equ BLOCKDEV_SEEK+2
BLOCKDEV_RAMEND .equ BLOCKDEV_TELL+2
; *** CODE ***
; Select block index specified in A
@ -45,36 +48,32 @@ blkSel:
djnz .loop
pop bc
.afterloop:
ld (BLOCKDEV_SEL), hl
push hl
call intoHL
ld (BLOCKDEV_GETC), hl
pop hl
inc hl
inc hl
push hl
call intoHL
ld (BLOCKDEV_PUTC), hl
pop hl
inc hl
inc hl
push hl
call intoHL
ld (BLOCKDEV_SEEK), hl
pop hl
inc hl
inc hl
call intoHL
ld (BLOCKDEV_TELL), hl
pop hl
pop af
ret
; In those routines below, IY is destroyed (we don't push it to the stack). We
; seldom use it anyways...
; set IX to the address of the routine in BLOCKDEV_SEL with offset IYL.
_blkCallAddr:
push de
ld de, (BLOCKDEV_SEL)
; DE now points to the *address table*, not the routine addresses
; themselves. One layer of indirection left.
; slide by offset
push af
ld a, iyl
call addDE ; slide by offset
pop af
call intoDE
; Alright, now de points to what we want to call
ld ixh, d
ld ixl, e
pop de
ret
; call routine in BLOCKDEV_SEL with offset IYL.
; call IX unless it's zero
_blkCall:
push ix
call _blkCallAddr
; Before we call... is IX zero? We don't want to call a zero.
push af
xor a
@ -85,25 +84,22 @@ _blkCall:
.ok:
pop af
call callIX
jr .end
ret
.error:
pop af
ld a, BLOCKDEV_ERR_UNSUPPORTED
.end:
pop ix
ret
; Reads one character from selected device and returns its value in A.
; Sets Z according to whether read was successful: Set if successful, unset
; if not.
blkGetC:
ld iyl, 0
ld ix, (BLOCKDEV_GETC)
jr _blkCall
; Repeatedly call blkGetC until the call is a success.
blkGetCW:
ld iyl, 0
call _blkCallAddr
ld ix, (BLOCKDEV_GETC)
.loop:
call callIX
jr nz, .loop
@ -127,7 +123,7 @@ blkRead:
; Writes character in A in current position in the selected device. Sets Z
; according to whether the operation was successful.
blkPutC:
ld iyl, 2
ld ix, (BLOCKDEV_PUTC)
jr _blkCall
; Writes B chars to blkPutC from (HL).
@ -180,12 +176,12 @@ blkSeek:
ld hl, 0xffff
.seek:
pop de
ld iyl, 4
ld ix, (BLOCKDEV_SEEK)
jr _blkCall
; Returns the current position of the selected device in HL.
blkTell:
ld iyl, 6
ld ix, (BLOCKDEV_TELL)
jr _blkCall
; This label is at the end of the file on purpose: the glue file should include