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; Copyright 2014, Sinclair R.F., Inc.

;

; Unsigned arithmetic operations.

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;

; Add two unsigned 8-bit values to produce an unsigned 16-bit value.

; Method:  Calculate the sum of the msb of the two raw values and the msb of the

;          sums of the 7 lsbs of the two values to get the msb of the sum and

;          the lsb of the MSB of the 16-bit sum.

; 36 instructions

;

; ( u1 u2 - (u1+u2)_LSB (u1+u2)_MSB )

.function math__add_u8_u8_u16

  ; and the two 7 lsbs and put the 7 lsb of that sum on the return stack

  over 0x7F & over 0x7F & + dup 0x7F & >r

  ; add the msb of the sum of the 7 lsbs and the two inputs

  0x80 & <<msb swap 0x80 & <<msb + swap 0x80 & <<msb +

  ; construct the MSB of the sum as bit 1 of the sums of the msbs

  dup 0>> swap

  ; set the msb of the LSB if the lsb of the sum of the msbs is non-zero

  0x01 & 0<> 0x80 & r> or

  ; swap the orders so that the MSB is on the top of the data stack

  .return(swap)

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; miscellaneous unsigned addition operations

.function math__add_u16_u8_u16

  swap >r .call(math__add_u8_u8_u16) r> .return(+)

.function math__add_u16_u8_u24

  swap >r .call(math__add_u8_u8_u16) r> .call(math__add_u8_u8_u16) .return

.function math__add_u24_u8_u24

  swap >r .call(math__add_u16_u8_u24)

  r> .return(+)

.function math__add_u24_u8_u32

  swap >r .call(math__add_u16_u8_u24)

  r> .call(math__add_u8_u8_u16)

  .return

.function math__add_u32_u8_u32

  swap >r .call(math__add_u24_u8_u32)

  r> .return(+)

.function math__add_u32_u16_u32

  >r .call(math__add_u32_u8_u32)

  r> .call(math__add_u24_u8_u24)

  .return

.function math__add_u32_u24_u32

  >r .call(math__add_u32_u16_u32)

  r> .call(math__add_u16_u8_u16)

  .return

.function math__add_u32_u32_u32

  >r .call(math__add_u32_u24_u32)

  r> .return(+)