ф >stringprnt ф -ф String passing (via CALL) demonstration (ф 2ф By Richard Murray <9ф Downloaded from http://www.heyrick.co.uk/assembler/ Fф P Z-codesize% = 180 : ф The code is 180 bytes dЮ code% codesize% nтbuild_code x ‚*и "Please enter some text: "my_string$ Њ –с '"Entering assembler..." Ц print_string, my_string$ Є#с "...returned from assembler"' ґ ѕа И Т: Ь жЭтbuild_code р г loop% = 8 ё 10 € 2 ъ P% = code% L% = code% + codesize% [ OPT loop% "9 \ Note... This is coded for CLARITY, not speed! , 6 .print_string @E CMP R10, #1 ; Check one parameter was given J! BNE wrong_parameters T ^4 LDR R0, [R9] ; Load pointer h1 LDR R1, [R9, #4] ; Load type r |7 CMP R1, #&80 ; Is it a string? † BNE wrong_var_type ђ љE \ Word giving string pointer may not be word aligned, so we ¤B \ cannot use an LDR as results for non-aligned addresses ® \ are unpredictable... ё LDRB R1, [R0], #1 В LDRB R2, [R0], #1 М" ADD R1, R1, R2, LSL#8 Ц LDRB R2, [R0], #1 а# ADD R1, R1, R2, LSL#16 к LDRB R2, [R0], #1 ф# ADD R1, R1, R2, LSL#24 ю . LDRB R2, [R0], #4 ; Length 4 CMP R2, #0 ; Check length & BEQ exit 0 :> \ Now, R1 is string pointer and R2 is string length. D .loop N LDRB R0, [R1], #1 X SWI "OS_WriteC" b@ SUBS R2, R2, #1 ; SUBS sets Z bit when = 0 l BNE loop v Ђ .exit ЉM SWI "OS_NewLine" ; So a blank string prints just that... ” MOV PC, R14 ћ Ё .wrong_parameters І SWI "OS_WriteS" ј4 EQUS "Incorrect number of parameters"+Ѕ0 Ж ALIGN Р B passed_to_call Ъ д .wrong_var_type о SWI "OS_WriteS" ш) EQUS "Wrong variable type"+Ѕ0 ALIGN H ; B passed_to_call ; Not required, will fall through .passed_to_call *) \ rudimentary optimisation! 4 SWI "OS_WriteS" >- EQUS " passed to call"+Ѕ13+Ѕ10+Ѕ0 H ALIGN R MOV PC, R14 \ ] f н pб z я