Reads a file and prints content to stdout. Uses a dynamic buffer. Is not meant to be used...

readfile.c

/*
 * readfile
 *
 * Patrick Pelletier (pp.pelletier@gmail.com) - July 2010
 *
 * Program that reads a file and outputs it's content to stdout.
 *
 * Uses a dynamic buffer to store the content temporarly.
 * It makes a good example of how to allocate a dynamic char buffer.
 * Was written as an exercice while bored with no internet connection @Recon 2010
 *
 * TODO: Maybe make some methods
 *       Extract the dynamic buffer code to make a generic module
 */

#include <stdio.h>
#include <stdlib.h>

#define INCREMENT 10

// Basic dynamic buffer structure
struct string {
	char *buffer;
	unsigned int maxLength;
	unsigned int size;
};

int main(int argc, char **argv) {

	// Argument check + usage
	char *programName = argv[0];
	if (argc != 2) {
		printf("Usage: %s <filename>\n", programName);
		exit(1);
	}

	// Open the file to read
	char *fileName = argv[1];
	FILE *file = fopen(fileName, "r");
	if (file == NULL) {
		printf("Unable to open file: %s\n", fileName);
		exit(2);
	}

	// Allocate initial space for buffer
	struct string s;
	s.buffer = malloc(INCREMENT*sizeof(char));
	if (s.buffer == NULL) {
		printf("Problem allocating memory");
		exit(3);
	}
	s.maxLength = 10;
	s.size = 0;

	// Reads file 1 char at a time and puts it in buffer, allocating space if needed
	char c;
	while ((c = fgetc(file)) != EOF) {
		if (s.size == s.maxLength) {
			s.buffer = realloc(s.buffer, sizeof(char)*(INCREMENT+s.size));
			if (s.buffer == NULL) {
				printf("Problem allocating memory");
				exit(4);
			}
			s.maxLength += INCREMENT;
		}
		s.buffer[s.size] = c;
		s.size++;
	}

	// Add missing \0
	if (s.size == s.maxLength) {
		s.buffer = realloc(s.buffer, sizeof(char *)*(1+s.size));
		if (s.buffer == NULL) {
			printf("Problem allocating memory");
			exit(4);
		}
		s.maxLength += INCREMENT;
	}
	s.buffer[s.size] = '\0';
	s.size++;

	/* Debugging messages
	printf("Size %d\n", s.size);
	printf("Max %d\n", s.maxLength);
	unsigned int j;
	for (j = 0; j <= s.maxLength; j++) {
		printf("Pos %d Char %x \n", j, s.buffer[j]);
	}
	*/

	// Print string, close everything
	printf("%s", s.buffer);
	free(s.buffer);
	fclose(file);
	return 0;
}