I'm dealing with small text files that i want to read into a buffer while i process them, so i've come up with the following code:
...
char source[1000000];
FILE *fp = fopen("TheFile.txt", "r");
if(fp != NULL)
{
while((symbol = getc(fp)) != EOF)
{
strcat(source, &symbol);
}
fclose(fp);
}
...
Is this the correct way of putting the contents of the file into the buffer or am i abusing strcat()?
I then iterate through the buffer thus:
for(int x = 0; (c = source[x]) != '\0'; x++)
{
//Process chars
}
See this article from JoelOnSoftware for why you don't want to use strcat.
Look at fread for an alternative. Use it with 1 for the size when you're reading bytes or characters.
Have you considered mmap()? You can read from the file directly as if it were already in memory.
Why don't you just use the array of chars you have? This ought to do it:
source[i] = getc(fp);
i++;
Not tested, but should work.. And yes, it could be better implemented with fread, I'll leave that as an exercise to the reader.
#define DEFAULT_SIZE 100
#define STEP_SIZE 100
char *buffer[DEFAULT_SIZE];
size_t buffer_sz=DEFAULT_SIZE;
size_t i=0;
while(!feof(fp)){
buffer[i]=fgetc(fp);
i++;
if(i>=buffer_sz){
buffer_sz+=STEP_SIZE;
void *tmp=buffer;
buffer=realloc(buffer,buffer_sz);
if(buffer==null){ free(tmp); exit(1);} //ensure we don't have a memory leak
}
}
buffer[i]=0;
If you're on a linux system, once you have the file descriptor you can get a lot of information about the file using fstat()
http://linux.die.net/man/2/stat
so you might have
#include <unistd.h>
void main()
{
struct stat stat;
int fd;
//get file descriptor
fstat(fd, &stat);
//the size of the file is now in stat.st_size
}
This avoids seeking to the beginning and end of the file.
Yes - you would probably be arrested for your terriable abuse of strcat !
Take a look at getline() it reads the data a line at a time but importantly it can limit the number of characters you read, so you don't overflow the buffer.
Strcat is relatively slow because it has to search the entire string for the end on every character insertion. You would normally keep a pointer to the current end of the string storage and pass that to getline as the position to read the next line into.
Methinks you want fread:
Source: Stackoverflow.com