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Zeda

rand (eZ80 optimized)

Jan 12th, 2017
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  1. rand:
  2. ;;Input: A is the range.
  3. ;;Output: Returns in A a random number from 0 to (input)A-1.
  4. ;;  B=0
  5. ;;  DE is a pseudo-random 16-bit integer.
  6. ;;Destroys:
  7. ;;  HL
  8. ;;Speed:
  9.     push af
  10.     call prng24
  11.     ex de,hl
  12.     pop af
  13.     or a \ sbc hl,hl
  14.     ld b,h
  15.     add a,a \ jr nc,$+5 \ push de \ pop hl
  16.     add hl,hl \ rla \ jr nc,$+4 \ add hl,de \ adc a,b
  17.     add hl,hl \ rla \ jr nc,$+4 \ add hl,de \ adc a,b
  18.     add hl,hl \ rla \ jr nc,$+4 \ add hl,de \ adc a,b
  19.     add hl,hl \ rla \ jr nc,$+4 \ add hl,de \ adc a,b
  20.     add hl,hl \ rla \ jr nc,$+4 \ add hl,de \ adc a,b
  21.     add hl,hl \ rla \ jr nc,$+4 \ add hl,de \ adc a,b
  22.     add hl,hl \ rla \ ret nc \ add hl,de \ adc a,b
  23.     ret
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