Load File Into Char* Array - c

Question

Feel silly asking this question, since this should be easy, but I can't figure out whats wrong.
void loadIniIntoMemory() {
FILE *fp ;
fp = fopen (iniFile, "r");
int ch;
int final_line_num = 0;
int char_index;
char* current_line = (char*) malloc(sizeof(char) * MAX_INI_LINE_LENGTH);
while((ch = fgetc(fp)) != EOF) {
if(ch == 10) {
// new line
*(current_line + char_index) = '\0';
char_index = 0;
iniFileData[final_line_num] = current_line;
final_line_num++;
} else {
// regular char
*(current_line + char_index) = ch; // CAN'T DO THIS, CRASH
char_index++;
if(ch == 13) {
// carriage return
continue;
}
}
}
}
Been a little while since I did C, it crashes at this line : *(current_line + char_index) = ch;
Thanks for any help.
--EDIT--
Also, no one noticed, that this code doesn't save the last line. Here is the full, correct, working code which saves a file into an array of pointers.
void loadIniIntoMemory() {
FILE *fp ;
fp = fopen (iniFile, "r");
int ch;
final_line_num = 0;
int char_index = 0;
char* current_line = (char*) malloc(sizeof(char) * MAX_INI_LINE_LENGTH);
while((ch = fgetc(fp)) != EOF) {
if(ch == '\n') {
// new line
*(current_line + char_index) = '\0';
char_index = 0;
iniFileData[final_line_num] = current_line;
final_line_num++;
current_line = (char*) malloc(sizeof(char) * MAX_INI_LINE_LENGTH);
} else if(ch != '\r') {
// regular char
*(current_line + char_index) = ch;
char_index++;
}
}
iniFileData[final_line_num] = current_line;
fclose(fp);
}

Answer 1

For starters, you don't initialize char_index, meaning it will likely have garbage in it. If you don't initialize it, your program will add some unknown number to the current_line pointer.
int char_index = 0; /* initialize to 0 */
Secondly, a bit more "natural" syntax would be:
current_line[char_index] = ...
Thirdly, you can test the characters without using their integer equivalents:
if (ch == '\n') {
/* this is the same as "ch == 10" */
Fourth, you should close the open file prior to leaving the routine:
fclose(fp);
Finally, I'm not sure what the ch == 13 ('\r') and continue is meant to handle, since the continue is effectively a no-op, but you probably don't want to copy it into the data:
if (ch != '\r') {
current_line[char_index] = ch;
char_index++;
/* or on one line: current_line[char_index++] = ch; */
}
As an aside, a powerful feature of C (and many other languages) is the switch statement:
/* substitutes your if...elseif...else */
switch (ch) {
case '\n':
current_line[char_index] = '\0';
char_index = 0;
iniFileData[final_line_num++] = current_line;
break; /* <-- very important, C allows switch cases to fall thru */
case '\r':
/* do nothing */
break;
default:
/* any character that is not a newline or linefeed */
current_line[char_index++] = ch;
break;
}

Answer 2

You didn't initialize char_index. I suppose you want to initialize it to 0. In C, uninitialized variable will contain garbage. Most likely your char_index equals some very large number.

Answer 3

Besides what others have already pointed out, you will also have to move the line buffer allocation call into the loop and immediately after the final_line_num++; statement. Otherwise, each new line you read will be overwriting the previous line.

Answer 4

And some operating systems, like most POSIX compliant ones, in particular Linux, gives you the ability to map a file segment (possibly the entire file) into virtual memory. On Linux, you could consider using the mmap system call