C - Write to file number of occurrences of character - c

Question

I am writing an encoding function, that takes a file descriptor from the source file, and a FILE* as the destination file. If the input file has this: AABBBccccthen I should write 2A3B4c in the output file. (number of the same consecutive character).
I managed to do this but my only problem is the number of occurrence for the first letter gets a +1... So I would get : 3A3B4c. The function returns the total number of characters written in outt.
int encode_aux(int fd1, char *buffer, FILE *outt)
{
size_t c = read(fd1, buffer, sizeof(buffer) - 1);
char previous; //to check if the next character is the same
int count = 0; //number of occurence of the same character
int total = 0; //total number of chars written in the output file
while (c != 0)
{
for (size_t i = 0; i < c; i++)
{
if (count == 0)
{
previous = buffer[i];
count += 1;
}
if (count != 0)
{
if (previous == buffer[i])
{
count += 1;
}
else
{
if (i == 0)
{
count -= 1;
}
if (count != 1)
{
total += fprintf(outt, "%d", count);
}
total += fprintf(outt, "%c", previous);
previous = buffer[i];
count = 1;
}
}
}
buffer[c] = '\0';
c = read(fd1, buffer, sizeof(buffer) - 1);
}
return total;
}
int encode(const char *file_in, const char *file_out)
{
FILE *out = fopen(file_out, "w");
char buff[4096];
int fd = open(file_in, O_RDONLY);
if (fd == -1 || out == NULL)
{
return -1;
}
int tot = encode_aux(fd, buff, out);
if (close(fd) == -1 || fclose(out) != 0)
{
return -1;
}
return tot;
}

Answer 1

if (count == 0)
{
previous = buffer[i];
count += 1;
}
if (count != 0)
{
if (previous == buffer[i])
{
count += 1;
}
When count == 0 then count = 1. Then you check count != 0, cause you just did count += 1, because count was 0. Then if (previous == buffer[i]), which also will be always true, because you just did previous = buffer[i] int he first if. Then you increment count again.
I think you miss an else:
if (count == 0)
{
previous = buffer[i];
count += 1;
} else
if (count != 0)
{
if (previous == buffer[i])
{
count += 1;
}
Notes:
I think you are mixing fgets with read calls. The buffer[c] = '\0'; is unneeded, the read call just reads bytes from the file descriptors, whatever they are, and if c will be too bug for buffer, it will be out-of-bounds access.
You are not printing the count of the last character of the file. It just so happens, that your file ends with a newline - the previous is set to newline on the last execution of your loop. If your file wouldn't end with w newline, the count of the last character won't be printed.