Write an ARM assembly language which accepts an integer and

Write an ARM assembly language which accepts an integer and returns a string which is the hexadecimal representation of the integer.

The signature of the routine is:
char * int2hex( int conv ) ;

The input is a 32 bit integer. The output is a pointer to a character string of the format 0Xdddddddd. Do not suppress leading zeroes.

The C program is:

#include <stdlib.h>
#include <stdio.h>

extern char * int2hex( int convert ) ;

int main( int argc, char * argv[] )
{
   int convert = 1194684 ;
   char * result ;
  
   result = int2hex( convert ) ;
   printf( \"Integer to hex string: %s\ \", result ) ;
}

A string in C is terminated by a null byte (a byte of zero).
You will need to use the shift instructions. You need to separate the integer into 4 bit sections each representing the individual hex digits. These need to be turned into printable characters.
You need to ‘adjust’ the resulting values for the digits A-F.
Use the strb instruction and an auto increment of 1 since you are storing bytes into memory.
Use the malloc library routine to obtain space for the character string (11 bytes: 2 for 0x, 8 for the hex digits, and one for the null byte).

Solution

TTL          Ch5Ex1

AREA      Program, CODE, READONLY

ENTRY

MOV   v2, #’0’                  ; store ‘0’ at the beginning

LDR   v2, [V2, #8]

MOV   v2, #’X’                  ; store ‘X’ after ‘0’

htoa

STMFD sp!, {v1, v2, lr}          ;function entry - save some v-registers

                                  ;and the return address.

MOV    v1, a1                   ; preserve arguments over following

MOV    v2, a2                   ; function calls

MOV    a1, a2

BL     div16                         ; a1 = a1 / 16

SUB    v2, v2, a1, LSL #3             ; number - 8*quotient

SUB    v2, v2, a1, LSL #1             ; - 2*quotient = remainder

CMP    a1, #0                         ; quotient non-zero?

MOVNE a2, a1                         ; quotient to a2...

MOV    a1, v1                         ; buffer ptr unconditionally to a1

BLNE   htoa                           ; conditional recursive call to utoa

ADD    v2, v2, #\'0\'                   ; NUL character

STRB   v2, [a1], #1                   ; store NUL character at end

LDMFD sp!, {v1, v2, pc}              ; function exit - restore and return