Question

i am trying to write a subroutine in assembly that removes all occurrences of a given character in a string. The subroutine takes two parameters: the string pointer, and the character to be removed. Write a C code that calls this subroutine. The string is defined in the C source code file as global. Assume the assembly and C code are in separate files. Use Keil/uVision to test your program where the C code should ask the assembly subroutine to remove all occurrences of character “o” from the following global string: char str[] = “The Quick Brown Fox Jumps Over a Lazy Dog”;

Answer 1

// here is the full code
?// output is attached
?// plz comment if you need any clarification
// hit like if you liked it

// CODE

?// MAIN CODE : Chegg149.c

// This code initializes both the string and character
// If you want to take input from the user you can do it by
// using the code in the comments
#include<stdio.h>
#include<string.h>
// Declare the remove function as extern function
extern void removeAll(char *, int, const char);
char str[] = "The Quick Brown Fox Jumps Over a Lazy Dog"; // global string
// main program
int main() {
    //char str[101]; // string
    char c = 'o'; // char to remove
int len;
   
// read the string
    //printf("Enter any string(of len at most 100): ");
    //scanf("%[^\n]", &str);

len = strlen(str);
    // read the char to remove
    printf("\nEnter character to remove from string: ");
//getc(stdin);
//c = getc(stdin);

    printf("\nbefore : %s", str);
    removeAll(str, len, c); // call the function
    printf("\nafter removing '%c': %s", c, str);

    return 0;
}

?// Func.c
#include<stdio.h>

// Function to remove all occurrences of a character from the string.
void removeAll(char * str, int len, const char toRemove) {
printf("\nIn The Function : ");
printf("\nString : %s", str);
printf("\nChar to be removed : '%c' ", toRemove);

    for(int i = 0; i<len; i++) {
        //If the character to remove is found then shift all characters to one
        //place left and decrement the length of string by 1.
        if(str[i] == toRemove) {
            for(int j=i; j<len; j++) {
                str[j] = str[j+1];
            }
            len--; // decrement the length
            i--; // when a character is removed then i should not be incremented
        }
    }
}

// Func.s : ASM File

.file "Func.c"
.text
.def _printf; .scl 3; .type 32; .endef
_printf:
pushl %ebp
movl %esp, %ebp
pushl %ebx
subl $36, %esp
leal 12(%ebp), %eax
movl %eax, -12(%ebp)
movl -12(%ebp), %eax
movl %eax, 4(%esp)
movl 8(%ebp), %eax
movl %eax, (%esp)
call ___mingw_vprintf
movl %eax, %ebx
movl %ebx, %eax
addl $36, %esp
popl %ebx
popl %ebp
ret
.section .rdata,"dr"
LC0:
.ascii "\12In The Function : \0"
LC1:
.ascii "\12String : %s\0"
LC2:
.ascii "\12Char to be removed : '%c' \0"
.text
.globl _removeAll
.def _removeAll; .scl 2; .type 32; .endef
_removeAll:
pushl %ebp
movl %esp, %ebp
subl $56, %esp
movl 16(%ebp), %eax
movb %al, -28(%ebp)
movl $LC0, (%esp)
call _printf
movl 8(%ebp), %eax
movl %eax, 4(%esp)
movl $LC1, (%esp)
call _printf
movsbl -28(%ebp), %eax
movl %eax, 4(%esp)
movl $LC2, (%esp)
call _printf
movl $0, -12(%ebp)
jmp L4
L8:
movl -12(%ebp), %edx
movl 8(%ebp), %eax
addl %edx, %eax
movzbl (%eax), %eax
cmpb -28(%ebp), %al
jne L5
movl -12(%ebp), %eax
movl %eax, -16(%ebp)
jmp L6
L7:
movl -16(%ebp), %edx
movl 8(%ebp), %eax
addl %eax, %edx
movl -16(%ebp), %eax
leal 1(%eax), %ecx
movl 8(%ebp), %eax
addl %ecx, %eax
movzbl (%eax), %eax
movb %al, (%edx)
addl $1, -16(%ebp)
L6:
movl -16(%ebp), %eax
cmpl 12(%ebp), %eax
jl L7
subl $1, 12(%ebp)
subl $1, -12(%ebp)
L5:
addl $1, -12(%ebp)
L4:
movl -12(%ebp), %eax
cmpl 12(%ebp), %eax
jl L8
leave
ret
.ident "GCC: (tdm-1) 4.9.2"
.def ___mingw_vprintf; .scl 2; .type 32; .endef

?// OUTPUT
this image shows how to compile the code and how to run the code