//----------------------------------------------------------------------
// uppercase.s
// Author: Bob Dondero and William Ughetta
//----------------------------------------------------------------------

        .section .rodata

//----------------------------------------------------------------------

        .section .data

//----------------------------------------------------------------------

        .section .bss

cChar:
        .skip   1

//----------------------------------------------------------------------

        .section .text

        //--------------------------------------------------------------
        // Read a letter from stdin, and write its uppercase
        // equivalent to stdout.  Return 0.
        // int main(void)
        //--------------------------------------------------------------

        // Must be a multiple of 16
        .equ    MAIN_STACK_BYTECOUNT, 16

        .global main

main:
        
        // Prolog
        sub     sp, sp, MAIN_STACK_BYTECOUNT
        str     x30, [sp]
                
        // cChar = (char)getchar()
        bl      getchar
        adr     x1, cChar
        strb    w0, [x1]

        // cChar = (char)toupper((int)cChar)
        adr     x1, cChar
        ldrb    w0, [x1]
        bl      toupper
        adr     x1, cChar
        strb    w0, [x1]
        
        // putchar((int)cChar)
        adr     x1, cChar
        ldrb    w0, [x1]
        bl      putchar

        // putchar('\n')
        mov     w0, '\n'
        bl      putchar
        
        // Epilog and return 0
        mov     w0, 0
        ldr     x30, [sp]
        add     sp, sp, MAIN_STACK_BYTECOUNT
        ret

        .size   main, (. - main)