Removing extra blanks from a string in C

1

I have a string that is actually a Y86-64 instruction set:

   rmmovq             %r0           ,        0   (     %rB)

So I want to remove extra spaces from it and convert it to:

rmmovq %r0, 0(%rB)

I have tried lots of things, but I am out of option now. Help please!

2

What have you tried? You could try something like

for (int i = 0; myString[i] != '\0'; i++) {
  if (myString[i] == " ")
    while (myString[i+1] == " ")
      for (int j = i + 1; myString[j] != '\0'; j++)
        myString[j] = myString[j+1];
}

I have not verified that it is portable, works well, etc.

This will just reduce down to single spaces. If you know your data absolutely will conform to a specific pattern, you can probably add in a bunch of special logic, but the code gets very fragile very fast in that case.

You probably want regex, but that’s not directly part of vanilla C.

3

What is line[i] here?

4

The best I got was this:

int i, x;
    for (i = x = 0; str[i]; ++i)
        if (!isspace(str[i]) || (i > 0 && !isspace(str[i - 1])))
            str[x++] = str[i];
    str[x] = '\0';

But it was still leaving one blank space before comma and brackets.

5

Woops, I meant myString instead of line.

Eliminating the extra spaces in

rmmovq %r0 , 0 ( %rB)

is what I mean about wanting to put in extra special logic that’s somewhat fragile.

// Strip multiple spaces
for (int i = 0; myString[i] != '\0'; i++) {
  if (isSpace(myString[i]))
    while (isSpace(myString[i+1]))
      for (int j = i + 1; myString[j] != '\0'; j++)
        myString[j] = myString[j+1];
}

// Strip space before commas
for (int i = 0; myString[i] != '\0'; i++) {
  if (isSpace(myString[i]))
    if (myString[i+1] == ",")
      for (int j = i; myString[j] != '\0'; j++)
        myString[j] = myString[j+1];
}

// Strip space before and after (
for (int i = 0; myString[i] != '\0'; i++) {
  if (isSpace(myString[i]))
    if (myString[i+1] == "(") {
      myString[i] = myString[i + 1]
      for (int j = i + 1; myString[j] != '\0'; j++)
        myString[j] = myString[j+2];
    }
}

Again, not checked, optimized, etc, just rough thoughts. Without regex this will end up being pretty fragile code.

1 Like
6

Well, this works, I mixed your code and mine, and I got the result. :smiley: :rofl:

1 Like
7

Working is the first step to clean and pretty : )