Tell what the following function is doing:

Call_000_3ef2:
Jump_000_3ef2:
    ld a, e
    ld [$c109], a
    ld a, d
    ld [$c10a], a
    ld c, [hl]
    inc hl
    ld b, [hl]
    inc hl
    push hl
    ld h, d
    ld l, e
    add hl, bc
    ld d, h
    ld e, l
    pop hl
    ld c, [hl]
    inc hl
    ld b, [hl]
    add hl, bc
    ld a, [hl-]
    ld [$c106], a
    push hl
    ld hl, $c106
    scf
    rl [hl]
    jr c, jr_000_3f54

jr_000_3f16:
    call Call_000_3f85

jr_000_3f19:
    xor a
    call Call_000_3fc9
    adc a
    call Call_000_3fc9
    adc a
    call Call_000_3fc9
    adc a
    call Call_000_3fc9
    adc a
    call Call_000_3fc9
    adc a
    call Call_000_3fc9
    adc a
    call Call_000_3fc9
    adc a
    call Call_000_3fc9
    adc a
    dec de
    ld [de], a
    dec bc
    ld a, b
    or c
    jr nz, jr_000_3f19

    ld a, [$c10a]
    cp d
    jr nz, jr_000_3f54

    ld a, [$c109]
    cp e
    jr c, jr_000_3f54

    jr jr_000_3f83

jr_000_3f4f:
    call Call_000_3fc9
    jr nc, jr_000_3f16

jr_000_3f54:
    call Call_000_3f85
    inc l
    ld [hl], c
    inc l
    ld [hl], b
    dec l
    dec l
    call Call_000_3f85
    push hl
    inc bc
    inc bc
    inc bc
    push bc
    inc l
    ld c, [hl]
    inc l
    ld b, [hl]
    ld h, d
    ld l, e
    dec hl
    add hl, bc
    pop bc

jr_000_3f6e:
    ld a, [hl-]
    dec de
    ld [de], a
    dec bc
    ld a, b
    or c
    jr nz, jr_000_3f6e

    pop hl
    ld a, [$c10a]
    cp d
    jr nz, jr_000_3f4f

    ld a, [$c109]
    cp e
    jr c, jr_000_3f4f

jr_000_3f83:
    pop hl
    ret


Call_000_3f85:
    xor a
    ld b, a
    ld c, a
    call Call_000_3fdf
    adc a
    call Call_000_3fdf
    adc a
    jr z, jr_000_3fbc

    dec a
    jr z, jr_000_3fb0

    dec a
    jr z, jr_000_3fa4

    ld a, $04

jr_000_3f9a:
    call Call_000_3fdf
    rl c
    rl b
    dec a
    jr nz, jr_000_3f9a

jr_000_3fa4:
    ld a, $04

jr_000_3fa6:
    call Call_000_3fdf
    rl c
    rl b
    dec a
    jr nz, jr_000_3fa6

jr_000_3fb0:
    ld a, $04

jr_000_3fb2:
    call Call_000_3fdf
    rl c
    rl b
    dec a
    jr nz, jr_000_3fb2

jr_000_3fbc:
    ld a, $04

jr_000_3fbe:
    call Call_000_3fdf
    rl c
    rl b
    dec a
    jr nz, jr_000_3fbe

    ret


Call_000_3fc9:
    sla [hl]
    ret nz

    di
    push af
    push hl
    add sp, $06
    pop hl
    ld a, [hl-]
    ld [$c106], a
    push hl
    add sp, -$06
    pop hl
    pop af
    rl [hl]
    ei
    ret


Call_000_3fdf:
    sla [hl]
    ret nz

    di
    push af
    push hl
    add sp, $08
    pop hl
    ld a, [hl-]
    ld [$c106], a
    push hl
    add sp, -$08
    pop hl
    pop af
    rl [hl]
    ei
    ret


    add sp, -$08
    pop hl
    pop af
    rl [hl]
    ei
    ret


    ld d, $fb
    ret