Fast frequency dictionary

fast.c

#include <stdio.h>
#include <stdlib.h>
#include <fcntl.h>
#include <stdbool.h>
#include <sys/stat.h>
#include <sys/mman.h>

typedef struct freq {
	int freq;
	char* word;
} freq;
	
inline bool is_letter(char c) {
	return 'A' <= c && c <= 'Z';
}

int main(int argc, char** argv) {
	if (argc < 2) {
		fprintf(stderr, "Wrong usage");
		return 1;
	}

	struct stat st;
	int fd = open(argv[1], O_RDONLY);
	fstat(fd, &st);
	
	char* first_addr = mmap(NULL, st.st_size, PROT_READ | PROT_WRITE, MAP_PRIVATE, fd, 0);
	char* last_addr = first_addr + st.st_size;
	madvise(first_addr, st.st_size, MADV_SEQUENTIAL);

	//void* words = malloc(sizeof(freq) * 1000);

	char* addr = first_addr;
	char c;
	char* word_ptr = NULL;
	for (; addr <= last_addr;++addr) {
		c = *addr;

		if (c > 'a') {
			c -= ('a' - 'A');
			*addr = c;
		}

		continue;
		if (is_letter(c)){
			if (word_ptr == NULL) {
				word_ptr = addr;
			}
		} else {
			if (word_ptr != NULL) {
				// what about last word in memory? if there wont be any garbage at the end
				*addr = '\0';
				word_ptr = NULL;
			}
		}
	}

	printf("last addr: %p\n", addr);

	return 0;
}