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blockdev: add "type" argument to blkSeek
Allows seeking forward, backwards, to the beginning, to the end.
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@ -119,13 +119,16 @@ blkGetCW:
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; Reads B chars from blkGetC and copy them in (HL).
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; Sets Z if successful, unset Z if there was an error.
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blkRead:
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push hl
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.loop:
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call blkGetC
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ret nz
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jr nz, .end ; Z already unset
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ld (hl), a
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inc hl
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djnz .loop
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cp a ; ensure Z
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.end:
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pop hl
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ret
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; Writes character in A in current position in the selected device. Sets Z
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@ -134,8 +137,17 @@ blkPutC:
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ld iyl, 2
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jr _blkCall
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; Seeks the block device in one of 5 modes, which is the first argument:
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; 0 : Move exactly to X, X being the second argument.
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; 1 : Move forward by X bytes, X being the second argument
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; 2 : Move backwards by X bytes, X being the second argument
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; 3 : Move to the end
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; 4 : Move to the beginning
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blkSeekCmd:
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.db "seek", 0b011, 0b001, 0
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.db "seek", 0b001, 0b011, 0b001
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; First, the mode
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ld a, (hl)
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inc hl
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; HL points to two bytes that contain out address. Seek expects HL
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; to directly contain that address.
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ld a, (hl)
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@ -145,7 +157,6 @@ blkSeekCmd:
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ld l, a
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ex af, af'
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ld h, a
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xor a
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; Set position of selected device to the value specified in HL
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blkSeek:
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ld iyl, 4
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@ -57,6 +57,32 @@ mmapPutC:
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ret
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mmapSeek:
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cp 1
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jr z, .forward
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cp 2
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jr z, .backward
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cp 3
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jr z, .beginning
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cp 4
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jr z, .end
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; all other modes are considered absolute
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jr .set ; for absolute mode, HL is already correct
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.forward:
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ld de, (MMAP_PTR)
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add hl, de
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jr nc, .set
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; we have carry? out of bounds, set to maximum
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ld hl, 0xffff
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jr .set
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.backward:
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; TODO - subtraction are more complicated...
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jr .set
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.beginning:
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ld hl, 0
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jr .set
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.end:
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ld hl, 0xffff-MMAP_START
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.set:
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ld (MMAP_PTR), hl
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ret
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