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Library function prototypes
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clear_string.s

clear_string.s 1.4 KB
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  1. ; Copyright (C) 2016 Jeremiah Orians
    2. 

  2. ; This file is part of stage0.
    3. 

  3. ;
    4. 

  4. ; stage0 is free software: you can redistribute it and/or modify
    5. 

  5. ; it under the terms of the GNU General Public License as published by
    6. 

  6. ; the Free Software Foundation, either version 3 of the License, or
    7. 

  7. ; (at your option) any later version.
    8. 

  8. ;
    9. 

  9. ; stage0 is distributed in the hope that it will be useful,
    10. 

  10. ; but WITHOUT ANY WARRANTY; without even the implied warranty of
    11. 

  11. ; MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
    12. 

  12. ; GNU General Public License for more details.
    13. 

  13. ;
    14. 

  14. ; You should have received a copy of the GNU General Public License
    15. 

  15. ; along with stage0.  If not, see <http://www.gnu.org/licenses/>.
    16. 

  16. 	
    17. 

  17. 	# We will be using R0 to pass pointer to string
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  18. 	# to cleared by the function
    19. 

  19. 	# R15 will be used as the stack pointer
    20. 

  20. :start
    21. 

  21. 	LOADUI R0 @string
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  22. 	LOADUI R1 22
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  23. 	LOADUI R2 33
    24. 

  24. 	LOADUI R3 44
    25. 

  25. 	LOADUI R4 55
    26. 

  26. 	LOADUI R15 0x600
    27. 

  27. 	CALLI R15 @clear_string
    28. 

  28. 	HALT
    29. 

  29. :string
    30. 

  30. 	HALT
    31. 

  31. 	HALT
    32. 

  32. 	NOP
    33. 

  33. 

  34. ;;  Our simple string clear function
    35. 

  35. :clear_string
    36. 

  36. 	;; Preserve registers
    37. 

  37. 	PUSHR R0 R15
    38. 

  38. 	PUSHR R1 R15
    39. 

  39. 	PUSHR R2 R15
    40. 

  40. 	PUSHR R3 R15
    41. 

  41. 	;; Setup registers
    42. 

  42. 	MOVE R1 R0
    43. 

  43. 	LOADUI R2 0
    44. 

  44. 	LOADUI R3 0
    45. 

  45. :clear_byte
    46. 

  46. 	LOADXU8 R0 R1 R2			; Get the byte
    47. 

  47. 	STOREX8 R3 R1 R2			; Overwrite with a Zero
    48. 

  48. 	ADDUI R2 R2 1				; Prep for next loop
    49. 

  49. 	JUMP.NZ R0 @clear_byte		; Stop if byte is NULL
    50. 

  50. ;; Done
    51. 

  51. 	;; Restore registers
    52. 

  52. 	POPR R3 R15
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  53. 	POPR R2 R15
    54. 

  54. 	POPR R1 R15
    55. 

  55. 	POPR R0 R15
    56. 

  56. 	RET R15
    57.