ON ERROR REPORT:PRINT" at line ";ERL:END
PROCassemble
CALL code
END
:
DEF PROCassemble
DIM code 2048
REM Allocate buffers inside code, so we don't get problems with long ADRs
in_file=code+128
out_file=code+256
code=code+384
:
REM Example of two-pass assembly; on the first time around, we
REM don't want errors reported, hence OPT 0
:
FOR pass=0 TO 2 STEP 2
P%=code
[OPT pass
:
          MOV       R12,R14             ; Keep BASIC return address in R12
          :
          ADR       R0,in_prompt
          ADR       R1,in_file
          BL        input_routine       ; Get input filename
          :
          ADR       R0,out_prompt
          ADR       R1,out_file
          BL        input_routine       ; Get output filename
          :
          MOV       R0,#&43
          ADR       R1,in_file
          SWI       "OS_Find"           ; Open input file
          CMP       R0,#0
          BEQ       file_error          ; Finish now if there's been an error
          MOV       R6,R0               ; Otherwise store the file handle in R6
          :
          MOV       R0,#&83
          ADR       R1,out_file
          SWI       "OS_Find"          ; Create and open output file
          CMP       R0,#0
          BEQ       file_error_close_input ; Finsh and close the input file if
                                           ;  there's been an error
          MOV       R7,R0               ; Otherwise store the file handle in R7
          :
.process_file                           ; Start of file processing loop
          MOV       R1,R6
          SWI       "OS_BGet"           ; Get next byte from input file into R0
          BCS       file_finished       ; Check for end-of-file, and if we've
                                        ;  reached it, jump out of the loop
          CMP       R0,#65              ; } These four comparisons make sure
          BLT       skip_byte           ; } that a byte is changed only if it
          CMP       R0,#90              ; } is less than 65 or greater than 90
          BGT       skip_byte           ; } (i.e. it is a capital letter)
          ADD       R0,R0,#32           ; Changes letter to lower case
.skip_byte
          MOV       R1,R7               ; } Put byte (altered or otherwise)
          SWI       "OS_BPut"           ; } to output file
          B         process_file        ; Loop round again
          :
.file_finished
          MOV       R0,#0
          MOV       R1,R6
          SWI       "OS_Find"           ; Close input file
          MOV       R1,R7
          SWI       "OS_Find"           ; Close output file
          MOV       R0,#18
          ADR       R1,out_file
          MOV       R2,#&1000           ; }
          SUB       R2,R2,#1            ; } &FFF is what we want (see magazine)
          SWI       "OS_File"           ; Set filetype of output to text
          :
          MOV       PC,R12              ; Return to BASIC
          :
.file_error_close_input                 ; Called when input file has been opened
                                        ;  but the output file hasn't
          MOV       R0,#0
          MOV       R1,R6
          SWI       "OS_Find"           ; Close input file
.file_error
          SWI       "OS_WriteS"         ; Display error message
          EQUS      "Couldn't open files":EQUB 0
          ALIGN
          SWI       "OS_NewLine"
          MOV       PC,R12              ; Return to BASIC
          :
.input_routine                          ; BL here with     R0  > prompt
                                        ;                  R1  > 128 byte buffer
                                        ; ARM chip does    R14 > return address
          :
          SWI       "OS_Write0"         ; Display prompt passed in R0
          MOV       R0,R1               ; Move buffer to R0 for OS_ReadLine
          MOV       R1,#128             ; 128 byte limit
          MOV       R2,#33              ; No spaces / ctrl chars allowed
          MOV       R3,#126             ; No top-bit set characters either
          SWI       "OS_ReadLine"       ; Call OS routine to get input
          MOVCS     PC,R12              ; If Escape pressed, exit to BASIC...
          MOV       PC,R14              ; ...otherwise return back to caller
          :
.in_prompt  EQUS " In filename: ":EQUB 0
.out_prompt EQUS "Out filename: ":EQUB 0
]:NEXT
ENDPROC