String case: Difference between revisions

Content added Content deleted
m (→‎{{header|68000 Assembly}}: actually writes back now, it didn't before.)
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;alters the string in-place.
;alters the string in-place.


MOVE.B (A0)+,D0 ;load a letter and inc the pointer to the next letter
MOVE.B (A0),D0 ;load a letter
BEQ .Terminated ;we've reached the null terminator.
BEQ .Terminated ;we've reached the null terminator.


CMP.B #'a',D0 ;compare to ascii code for a
CMP.B #'a',D0 ;compare to ascii code for a
BCS UpperCase ;if less than a, keep looping.
BCS .overhead ;if less than a, keep looping.


CMP.B #'z',D0 ;compare to ascii code for z
CMP.B #'z',D0 ;compare to ascii code for z
BHI Uppercase ;if greater than z, keep looping
BHI .overhead ;if greater than z, keep looping


AND.B #%1101111,D0 ;this "magic constant" turns lower case to upper case, since they're always 32 apart.
AND.B #%1101111,D0 ;this "magic constant" turns lower case to upper case, since they're always 32 apart.
.overhead:
MOVE.B D0,(A0)+ ;store the letter back and increment the pointer.
;If this isn't an alphabetical character, D0 won't change and this store won't affect the string at all.
;If it was a letter, it will have been changed to upper case before storing back.

BRA UpperCase ;next letter
BRA UpperCase ;next letter

.Terminated:
.Terminated:
RTS
RTS
;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;
;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;
LowerCase:
LowerCase:
MOVE.B (A0)+,D0 ;load a letter and inc the pointer to the next letter
MOVE.B (A0),D0 ;load a letter
BEQ .Terminated ;we've reached the null terminator.
BEQ .Terminated ;we've reached the null terminator.


CMP.B #'A',D0 ;compare to ascii code for A
CMP.B #'A',D0 ;compare to ascii code for A
BCS LowerCase ;if less than A, keep looping.
BCS .overhead ;if less than A, keep looping.


CMP.B #'Z',D0 ;compare to ascii code for Z
CMP.B #'Z',D0 ;compare to ascii code for Z
BHI LowerCase ;if greater than Z, keep looping
BHI .overhead ;if greater than Z, keep looping


OR.B #%00100000,D0 ;this "magic constant" turns upper case to lower case, since they're always 32 apart.
OR.B #%00100000,D0 ;this "magic constant" turns upper case to lower case, since they're always 32 apart.
.overhead:
MOVE.B D0,(A0)+ ;store the result and get ready to read the next letter.
BRA LowerCase ;next letter
BRA LowerCase ;next letter
.Terminated:
.Terminated:
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;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;
;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;
ToggleCase:
ToggleCase:
MOVE.B (A0)+,D0 ;load a letter and inc the pointer to the next letter
MOVE.B (A0),D0 ;load a letter and inc the pointer to the next letter
BEQ .Terminated ;we've reached the null terminator.
BEQ .Terminated ;we've reached the null terminator.


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CMP.B #'A',D1 ;compare to ascii code for A
CMP.B #'A',D1 ;compare to ascii code for A
BCS ToggleCase ;if less than A, keep looping.
BCS overhead ;if less than A, keep looping.


CMP.B #'Z',D1 ;compare to ascii code for Z
CMP.B #'Z',D1 ;compare to ascii code for Z
BHI ToggleCase ;if greater than Z, keep looping
BHI overhead ;if greater than Z, keep looping


EOR.B #%00100000,D0 ;swaps the case of the letter
EOR.B #%00100000,D0 ;swaps the case of the letter
overhead:

MOVE.B D0,(A0)+ ;store the result
BRA ToggleCase ;next letter
BRA ToggleCase ;next letter
.Terminated:
.Terminated:
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