ConvOP1

;Attempts to convert the TI float in OP1 into an unsigned integer in HL.
;
;Throws:
; - A data type error if OP1 doesn't hold a nonnegative real number.
; - A domain error if the value cannot be exactly converted to an unsigned
;   16-bit integer.
;
; I: (OP1)=float
; O: A=0, BC=((uint)(OP1))%10, DE=OP1+8, HL=(uint)(OP1), (OP1)=(float)0
;FO: S=0, Z=1, H=0, P/V=0, N=1, C=0
;CC: 355 + 210*d
;    d = (OP1)!=0 ? floor(log10((OP1))) + 1 : 1
ConvOP1:
;Throws an error if OP1 doesn't hold a nonnegative real number.
    ld  a,(OP1)
    or  a
    jr  nz,ErrDataType
;Initializes the 16-bit accumulator to 0.
    ld  h,a
    ld  l,a
ConvOP1_Loop:
;Multiplies the 16-bit accumulator by 10, checking for overflow.
    ld  b,h
    ld  c,l
    add hl,hl
    adc a,a
    add hl,hl
    adc a,a
    add hl,bc
    adc a,a
    add hl,hl
    adc a,a
    jr  nz,ErrDomain
;Rotates the first three mantissa bytes of OP1 left by a nibble, collecting the
;highest nibble/digit rotated out.
    ex  de,hl
    ld  hl,OP1+4
    rld
    dec l
    rld
    dec l
    rld
    dec l
;Adds the highest nibble/digit rotated out to the 16-bit accumulator, checking
;for overflow. Decrements the exponent and continues looping if it doesn't
;become $7F. Doesn't care about bad exponents, as the 16-bit accumulator would
;overflow eventually.
    ld  c,a
    xor a
    ld  b,a
    dec (hl)
    ex  de,hl
    add hl,bc
    jr  c,ErrDomain
    jp  po,ConvOP1_Loop
ConvOP1_CheckIntLoop:
;Returns successfully if the last byte of the mantissa has been checked.
#ifdef 83p
    or  e
    ret m
#else
    ld  a,(OP1+8)&$FF
    sub e
    ret z
#endif
;Continues if the next byte of the mantissa is zero.
    inc e
    ld  a,(de)
    or  a
    jr  z,ConvOP1_CheckIntLoop
ErrDomain:
;Throws a domain error.
    B_CALL(_ErrDomain)
ErrDataType:
;Throws a data type error.
    B_CALL(_ErrDataType)