Does the program in in Exercise $14\mathrm{.}4\mathrm{.}1$ work correctly for both lowercase and uppercase alphabetic hex characters? Why or why not?

Exercise $1.$

Show that the main function in Listing $14\mathrm{.}3\mathrm{.}1$ works with the assembly language hexToInt function in Listing $14\mathrm{.}3\mathrm{.}5$

@ hexToInt$2.$s

@ Converts a hex text string to an int.

@ Calling sequence:

@ r$0<-$ address of string

@ bl hexToInt

@ returns equivalent int

@ $2017-09-29$: Bob Plantz

@ Define my Raspberry Pi

$.$cpu cortex$-$a$53$

$.$fpu neon$-$fp$-$armv$8$

$.$syntax unified @ modern syntax

@ Constant for assembler

$.$equ gap,$7$ @ between alpha and numerical

$.$equ NUL,$0$

$.$equ no$\_$ascii,$0$xf

@ The program

$.$text

$.$align $2$

$.$global hexToInt

$.$type hexToInt, $\%$function

hexToInt:

sub sp$,$ sp$,24$ @ space for saving regs

@ $($keeping $8-$byte sp align$)$

str r$4,[$sp$,4]$ @ save r$4$

str r$5,[$sp$,8]$ @ r$5$

str r$6,[$sp$,12]$ @ r$6$

str fp$,[$sp$,16]$ @ fp

str lr$,[$sp$,20]$ @ lr

add fp$,$ sp$,20$ @ set our frame pointer

mov r$4,$ r$0$ @ string pointer

mov r$5,0$ @ accumulator $=0$;

loop:

ldrb r$6,[$r$4]$ @ get char

cmp r$6,$ NUL @ end of string?

beq allDone @ yes

lsl r$5,$ r$5,4$ @ room for four bits

cmp r$6,\text{'}9$ @ alpha char?

subhi r$6,$ r$6,$ gap @ yes, remove gap

and r$6,$ r$6,$ no$\_$ascii @ strip off acsii

add r$5,$ r$5,$ r$6$ @ add in the four bits

add r$4,$ r$4,1$ @ next char

b loop

allDone:

mov r$0,$ r$5$ @ return accumulator;

ldr r$4,[$sp$,4]$ @ restore r$4$

ldr r$5,[$sp$,8]$ @ r$5$

ldr r$6,[$sp$,12]$ @ r$6$

ldr fp$,[$sp$,16]$ @ fp

ldr lr$,[$sp$,20]$ @ lr

add sp$,$ sp$,24$ @ sp

bx lr @ return

Listing $14\mathrm{.}3\mathrm{.}5.$ Function to convert a hexadecimal text string to an integer $($prog asm$).$

in$-$context

$/*$ hexConvert$1.$c

$*$ Prompts user for hex number and converts

$*$ it to an int.

$*2017-09-29$: Bob Plantz

$*/$

#include

#include "hexToInt.h$"$

int writeStr$($char $*)$;

int readLn$($char $*,$ int$)$;

int main$()$

$\{$

int theNumber;

char theString$[9]$;

writeStr$("$Enter up to $32-$bit hex number: $")$;

readLn$($theString$,9)$;

theNumber $=$ hexToInt$($theString$)$;

printf$("$The integer is: $\%$i

$",$ theNumber$)$;

return $0$;

$\}$

Listing $14\mathrm{.}3\mathrm{.}1.$ Program to input a hexadecimal text string from the keyboard and convert it to the corresponding integer. Calls the hexToInt function in Listing $14\mathrm{.}3\mathrm{.}3.($C$)$