TheZZAZZGlitch's memory editor v1.2 - disassembled version

; TheZZAZZGlitch's memory editor
; v1.0 by TheZZAZZGlitch (http://pastebin.com/yTWnbPMw)
; v1.1 by ISSOtm - Reduced size by 27 bytes
; v1.2 by ISSOtm - Reduced size by 1 byte, suggested by NieDzejkob


SECTION "Main", ROM0[$DB01]

entrypoint:
mainmenu:
    push hl ; Save hl across redraw block

    ; Print memory starting 8 bytes before the current one
    ld de, -8
    add hl, de
    ld d, h
    ld e, l
.testkeys
    ldh a, [hJoyInput]
    and a
    jr nz, .testkeys ; Wait until no keys are pressed

    ld hl, wTileMap
write:
    ld [hl], $7C ; Left border
    inc hl
    ld a, d
    call writehex
    ld a, e
    call writehex
    ld [hl], $E3 ; Dash
    inc hl
    ld a, [de]
    call writehex
    ld [hl], $7C ; Right border

    ld bc, 12
    add hl, bc ; Advance to next line
    inc de
    ld a, l
    cp 8
    jr nz, write

waiting:
    ld a, $ED ; Write cursor
    ld [$C445], a ; This is in the middle of wTileMap

    pop hl ; Get back target address
.testbuttons
    halt ; Wait for VBlank
    ldh a, [hJoyInput]

    ; Now, shift A left to test all keys
    add a, a ; DOWN
    jr nc, .nodownbtn
    inc hl
.nodownbtn
    add a, a ; UP
    jr nc, .noupbtn
    dec hl
.noupbtn
    add a, a ; LEFT
    jr nc, .noleftbtn
    ld de, -$10
    add hl, de
.noleftbtn
    add a, a ; RIGHT
    jr nc,.norightbtn
    ld de, $10
    add hl, de
.norightbtn

    add a, a ; START
    jr nc, .nostartbtn
    ld de, $1000
    add hl, de
.nostartbtn
    add a, a ; SELECT
    jr nc, .noselectbtn
    inc h
.noselectbtn
    add a, a ; B
    ret c

    add a, a ; A
mainmenubounce:
    jr nc, mainmenu ; If A isn't held, go back to main loop
    ; Otherwise, slide into the byte change loop


bytechangeloop:
    ld c, [hl]
    push hl ; Save target address across this block (will be popped by return func)
    ld hl, $C445
    ld [hl], $EC ; Write new cursor

bytechangeloopentry:
    halt
    ldh a, [hJoyInput]
    and a
    jr z, storeandgotomainmenu ; Commit change if no button is held
    ld b, a
    add a, a ; Push bit 7 into carry
    ld a, c

    jr nc, .nodownbtn
    sub $10
.nodownbtn
    bit 6, b
    jr z, .noupbtn
    add $10
.noupbtn
    bit 5, b
    jr z, .noleftbtn
    dec a
.noleftbtn
    bit 4, b
    jr z, .norightbtn
    inc a
.norightbtn

    ld l, $46
    ld c, a
    call writehex ; Update target value
.waitbuttonsc
    ldh a, [hJoyInput]
    and $FE ; Wait until all buttons have been released (except a)
    jr z, bytechangeloopentry
    cp $0C
    jr nz, .waitbuttonsc
    ; If both START and SELECT (and A) are held, perform exec

specialexec:
    ; Remember : target address is on top of stack...
    call GetPredefRegisters
    ld a, [wPredefID] ; Just before wPredefRegisters, so that's where we'll pull A from (also because this will be unused)
    ; Remember: target address is on top of stack... ROP FTW !
    ret


storeandgotomainmenu:
    pop hl ; Get back target address
    ld [hl], c
    jr mainmenubounce ; Jumps to a conditional jump, but because we only jump here with C reset due to `and a`, the jump will be taken
    ; Doing a jr to another jr instead of a jp saves 1 byte


; Write byte in a at [hl] and [hl+1], advancing hl in the process
writehex:
    ld b, a
    swap a
    call writehexdigit
    ld a, b
    ; fall through to writehexdigit

writehexdigit:
    and $0F
    add $F6
    jr nc,.noadd
    add $60
.noadd
    ld [hli], a
    ret