#include <string.h>
#include <stdlib.h>
#include <stdio.h>
#include <sys/mman.h>
#include <sys/stat.h>
#include <fcntl.h>
#include <unistd.h>
#include <string.h>
#include <sys/time.h>
#include <openssl/md5.h>

#define SIZE 19*1024*1024
#define PAGE_SIZE 4096          // 4KB
#define CHUNK_SIZE 8 * 1024     // 8KB

void compute_md5(const unsigned char *data, size_t length, unsigned char *md5_hash) {
	MD5_CTX md5_ctx;

	MD5_Init(&md5_ctx);

	MD5_Update(&md5_ctx, data, length);

	MD5_Final(md5_hash, &md5_ctx);
}

void print_md5(unsigned char *md5_hash) {
	for (int i = 0; i < MD5_DIGEST_LENGTH; i++) {
		printf("%02x", md5_hash[i]);
	}
	printf("\n");
}

unsigned long long tv_to_ms(struct timeval tv)
{
	return tv.tv_sec * 1000 + tv.tv_usec / 1000;
}

int main()
{
	char c;
	pid_t pid;
	int i;
	int j = 0;
	struct timeval tv_b, tv_e;;
	unsigned char md5_hash[MD5_DIGEST_LENGTH];

	unsigned long *p = mmap(NULL, SIZE, PROT_READ | PROT_WRITE,
			MAP_PRIVATE | MAP_ANONYMOUS, -1, 0);
	if (!p) {
		perror("fail to get memory");
		exit(-1);
	}

	printf("0x%lx\n", p);

	madvise(p, SIZE, MADV_HUGEPAGE);

	for (j = 0; j < SIZE / 8; j += 8)
		*(p + j) = j;

	for (size_t offset = PAGE_SIZE; offset < SIZE; offset += CHUNK_SIZE) {
		char *str = (char *)p + offset;

		sprintf(str, "child");
	}

	for (size_t offset = PAGE_SIZE; offset < SIZE; offset += CHUNK_SIZE) {
		compute_md5((unsigned char *)p + offset, PAGE_SIZE, md5_hash);
		printf("MD5 of the buffer: ");
		print_md5(md5_hash);
	}

	gettimeofday(&tv_b, NULL);
	madvise(p, SIZE, MADV_PAGEOUT);
	gettimeofday(&tv_e, NULL);

	printf("swp out bandwidth: %ld bytes/ms\n",
			SIZE/(tv_to_ms(tv_e) - tv_to_ms(tv_b)));

	pid = fork();

	if (pid == 0) {
		printf("child: freeing some swap\n");
		for (size_t offset = 0; offset < SIZE; offset += CHUNK_SIZE) {
			if (madvise((void *)((char *)p + offset), PAGE_SIZE, MADV_DONTNEED) == -1) {
				perror("madvise failed");
				return -1;
			}
		}

		printf("child: sleep\n");
		sleep(5);

		printf("child: reading swaped data\n");

		for (size_t offset = PAGE_SIZE; offset < SIZE; offset += CHUNK_SIZE) {
			char *str = (char *)p + offset;

			if (strcmp(str, "child"))
				printf("%s\n", str);

		}
		printf("child: read done\n");

		for (size_t offset = PAGE_SIZE; offset < SIZE; offset += CHUNK_SIZE) {
			compute_md5((unsigned char *)p + offset, PAGE_SIZE, md5_hash);
			printf("MD5 of the buffer: ");
			print_md5(md5_hash);
		}
#if 2
	} else {
		printf("parent: sleeping\n");
		sleep(1);
		printf("parent: unmapping origin memory region\n");
		munmap(p, SIZE);
		printf("parent: alloc new memory region\n");

		p = mmap(NULL, 9 * 1024 * 1024, PROT_READ | PROT_WRITE,
				MAP_PRIVATE | MAP_ANONYMOUS, -1, 0);

		for (j = 0; j < 1024 * 1024; j+=8)
			*(p + j) = j + 10;

		for (size_t offset = 0; offset < 8 * 1024 * 1024; offset += CHUNK_SIZE) {
			char *str = (char *)p + offset + PAGE_SIZE;
			sprintf(str, "parent");
		}

		madvise(p, 9 * 1024 * 1024, MADV_PAGEOUT);
#endif
	}

	while(1) {
		sleep(100);
	}

	return 0;
}