c - Convert white space to tabs -

i decided learn c, started going through k&r, got stuck on problem 21 in chapter 1. supposed write program, given string without tabs , tabwidth, converts white space equivalent spacing using tabs , white space.

so far, i've got this:

void entab (char from[], char to[], int length, int tabwidth) {     int i, j, tabpos, flag, count;      j = tabpos = flag = count = 0;     (i = 0; from[i] != '\0' && j < length - count - 2; i++) {         if (from[i] == ' ') {             // if see space, set flag true , increment             // whitespace counter. don't add characters until reach             // next tabstop.             count++;             tabpos = (tabpos + 1) % tabwidth;             flag = 1;             if (count >= tabwidth - tabpos) {                 to[j] = '\t';                 j++;                 count = count - tabwidth + tabpos;                 tabpos = 0;             }         } else {             if (flag == 1) {                 // if see other space , flag true,                 // there weren't enough spaces reach tabstop. add count                 // spaces string.                 flag = 0;                 tabpos = (tabpos + count + 1) % tabwidth;                 while (count > 0) {                     to[j] = ' ';                     j++;                     count--;                 }             } else {                 tabpos = (tabpos + 1) % tabwidth;             }             count = 0;             to[j] = from[i];             j++;         }     }     to[j] = '\0';     return; } 

which, unfortunaly, seems produce larger spacing it's supposed to. ideas screwed up?

ps i've looked @ other solutions online , understand there better approach problem, fix error in mine well.

edit: setting tabwidth=4 , using:

    foobar         foo  bar      foo bar     foo     bar 

as input, get:

/t/tfoobar /t/t/t/tfoo  bar/t/t/t foo bar /t/tfoo/t/t bar 

as output, while correct output be:

/tfoobar /t/tfoo/t bar/t/t foo bar /tfoo/t/tbar 

if (count >= tabwidth - tabpos) 

this starts outputting tabs soon. consider input string:

"aa              "  

with 8 tabwidth. character 5 (i 4, count 3) when tabpos becomes 5, therefore triggering condition. don't want output tabs before variable reaches tabwidth.

i won't fix code either. instead of making general statements "refactor code" 21st century way of saying "rewrite code", can point out 1 obvious mistake. don't need tabpos variable. use (i % tabwidth). here on things should start falling place.