Word wrap function source code

This snippet submitted by Sean Hubbard on 2012-01-22. It has been viewed 42318 times.
Rating of 5.6 with 233 votes

/*
   This function takes a string and an output buffer and a desired width. It then copies 
   the string to the buffer, inserting a new line character when a certain line
   length is reached.  If the end of the line is in the middle of a word, it will
   backtrack along the string until white space is found.
 */

#include <string.h>
#include <ctype.h>

char* word_wrap (char* buffer, char* string, int line_width) {
	int i = 0;
	int k, counter;

	while(i < strlen( string ) ) 
	{
		// copy string until the end of the line is reached
		for ( counter = 1; counter <= line_width; counter++ ) 
		{
			// check if end of string reached
			if ( i == strlen( string ) ) 
			{
				buffer[ i ] = 0;
				return buffer;
			}
			buffer[ i ] = string[ i ];
			// check for newlines embedded in the original input 
			// and reset the index
			if ( buffer[ i ] == '\n' )
			{
				counter = 1; 
			}
			i++;
		}
		// check for whitespace
		if ( isspace( string[ i ] ) ) 
		{
			buffer[i] = '\n';
			i++;
		} 
		else 
		{
			// check for nearest whitespace back in string
			for ( k = i; k > 0; k--) 
			{
				if ( isspace( string[ k ] ) ) 
				{
					buffer[ k ] = '\n';
					// set string index back to character after this one
					i = k + 1;
					break;
				}
			}
		}
	}
	buffer[ i ] = 0;

	return buffer;

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