qsort works incorrectly (compare function) - c

Question

I write program which sort numbers like 23.44 12.4223. And almost everything works fine but it does not sort correctly numbers for instance 24.321 and 24.33 i mean for my rpgoram 24.321 is greater than 24.33
Infile contains numbers like 34.5 123.55. 56. .43 564.3
Here's my code:
#include <stdlib.h>
#include <stdio.h>
#include <string.h>
#include <ctype.h>
#define NUMBER_CHUNK 13
char* getNumber(FILE* fp)
{
int length;
int current = 0;
int c;
char *number, *number2;
number = (char*)malloc(sizeof(char)*NUMBER_CHUNK);
if(!number)
{
printf("Error while allocating memory!\n");
return NULL;
}
length = NUMBER_CHUNK;
while(!isspace(c = fgetc(fp)) && !feof(fp))
{
if(isdigit(c) || c == '.')
{
number[current] = c;
current++;
if(current >= length)
{
length+=NUMBER_CHUNK;
number2 = (char*)realloc(number,sizeof(char*)*length);
if(number2 == NULL)
{
free(number2);
return NULL;
}
else number2 = number;
}
}
else
{
return NULL;
}
}
number[current] = '\0';
return number;
}
int compare(const void *str1, const void *str2)
{
char* curr1;
char* curr2;
int value = 0;
size_t len1 = 0;
size_t len2 = 0;
curr1=*(char**)str1;
curr2=*(char**)str2;
while(*curr1=='0' || *curr1=='.') curr1++;
while(*curr2=='0' || *curr2=='.') curr2++;
while(*curr1 || *curr2)
{
while(*curr1 == '.')
curr1++;
while(*curr2 == '.')
curr2++;
if(value == 0)
{
value = *curr1 - *curr2;
}
if(*curr1)
{
curr1++;
len1++;
}
if(*curr2)
{
curr2++;
len2++;
}
}
if(len1 != len2)
{
return (len1 > len2) ? 1 : -1;
}
return value;
}
int main(int argc, char** argv)
{
FILE* fp;
char** tab;
int i = 0;
int lines = 0;
int length = 10;
if(argc != 2)
{
printf("Incorrent syntax! Use ./program_name input_file\n");
return 1;
}
if(!(fp = fopen(argv[1],"r")))
{
printf("Could not open the file! Please try again!\n");
return 2;
}
tab = (char**)malloc(length*(sizeof(char*)));
if(!tab)
{
printf("Could not allocate memory!\n");
free(tab);
return 3;
}
while(!feof(fp))
{
tab[i] = getNumber(fp);
if(i >= length)
{
length += 10;
tab = (char**)realloc(tab,sizeof(char*));
if(tab == NULL)
{
free(tab);
return 5;
}
}
if(tab[i] == NULL)
{
printf("Incorrect character in the infile! Terminating\n");
free(tab);
return 4;
}
if(*tab[i] == '\0')
{
free(tab[i]);
i--;
}
i++;
lines = i;
}
printf("\nBEFORE\n");
for(i = 0 ; i < lines; i++)
{
printf("%s\n", tab[i]);
}
qsort(tab, lines, sizeof(char*), compare);
printf("\nAFTER\n");
for(i = 0; i < lines; i++)
{
printf("%s\n",tab[i]);
free(tab[i]);
}
printf("\n");
free(tab);
fclose(fp);
return 0;
}

Answer 1

In your program 24.321 is greater than 24.33 because length of 24.321 is greater than length of 24.33.
You should stop increasing length when you read ..
Fix:
//UPDATE
while(*curr1=='0') curr1++;
while(*curr2=='0') curr2++;
//END OF UPDATE
char dot1 = 0, dot2 = 0;
char err1 = 0, err2 = 0;
while(*curr1 || *curr2)
{
if(*curr1 == '.') ++dot1; //UPDATE2
if(*curr2 == '.') ++dot2; //UPDATE2
while(*curr1 == '.')
curr1++;
while(*curr2 == '.')
curr2++;
if(value == 0)
{
value = *curr1 - *curr2;
}
if(*curr1)
{
if(*curr1 < '0' || *curr1 > '9') err1 = 1;
curr1++;
if(!dot1) len1++;
}
if(*curr2)
{
if(*curr2 < '0' || *curr2 > '9') err2 = 1;
curr2++;
if(!dot2) len2++;
}
}
if(err1 || err2 || dot1 > 1 || dot2 > 1) exit(1); // UPDATE2
UPDATE:
I updated code. Now before main comparison while only zeros are skipped. Dots will be skipped at the beginning of main while and fix with dot1 and dot2 will work.
UPDATE2:
To check if numbers are correct you should count dots and check if all chars are dots or digits.
Be aware that for longer bad numbers (more than 255 dots) my code could not work correctly (because dot1 is 1 byte long). If you need to handle these cases you should check if dot1/dot2 are equal to 1 and change err1/err2 to 1 instead of increasing dot1/dot2.

Answer 2

Your problem is here:---
if(len1 != len2)
{
return (len1 > len2) ? 1 : -1;
}
For strings "24.321" len1 = 6 ,"24.33" len2 = 5 so the longest string wins.
I thing your algorithm will also encounter problems with 123.45 vs 23.456 as you are basically ignoring the decimal point.
You could try converting to floating point (use function atof() or strtof() ) to convert the string to a real real number then compare.
Or simply return "less than" if you encounter a '.' in the first string before you encounter it in the second string.