ex17a.c

#include <stdio.h>
#include <assert.h>
#include <stdlib.h>
#include <errno.h>
#include <string.h>

#define MAX_DATA 512
#define MAX_ROWS 100

void Database_close();

struct Address {
	int id;
	int set;
	char name[MAX_DATA];
	char email[MAX_DATA];
};

struct Database {
	struct Address rows[MAX_ROWS];
	unsigned long max_rows;
	unsigned long max_data;
};

struct Connection {
	FILE *file;
	struct Database *db;
};

struct Connection *conn;

void die(const char *message) 
{
	if(errno) {
		perror(message);
	} else {
		printf("ERROR: %s\n", message);
	}
	Database_close();
	exit(1);
}

void Address_print(struct Address *addr)
{
	printf("%d %s %s\n", 
		addr->id, addr->name, addr->email);
}

void Database_load()
{
	int rc = fread(conn->db, sizeof(struct Database), 1, conn->file);
	if(rc!=1) die("Failed to load database.");
}

void Database_open(const char *filename, char mode)
{	
	conn = malloc(sizeof(struct Connection));
	if(!conn) die("Memory error");
	
	conn->db = malloc(sizeof(struct Database));
	if(!conn->db) die("Memory error");
	
	if(mode == 'c') {
		conn->file = fopen(filename, "w");
	} else {
		conn->file = fopen(filename, "r+");
		if(conn->file) {
			Database_load();
		}
	}

	if(!conn->file) die("Failed to open the file");	
}

void Database_close()
{	
	 if(conn) {		 
		 if(conn->file) fclose(conn->file);		 
		 if(conn->db) free(conn->db);		 
		 free(conn);		 
	 }
}

void Database_write()
{
	rewind(conn->file);
	printf("size of database %d\n", sizeof(struct Database));
	printf("%lu\n", conn->db->max_rows);
	
	int rc = fwrite(conn->db, sizeof(struct Database), 1, conn->file);
	if(rc != 1) die("Failed to write database");
	
	rc = fflush(conn->file);
	if(rc == -1) die("Cannot flush database");
}

void Database_create()
{
	int i = 0;
	
	for (i = 0; i < MAX_ROWS; i++) {
		struct Address addr = { .id = i, .set = 0};		
		conn->db->rows[i] = addr;
	}
	
	conn->db->max_rows = 123;
	conn->db->max_data = 456;
}

void Database_set(int id, const char *name, const char *email)
{
	struct Address *addr = &conn->db->rows[id];
	
	if(addr->set) die("Already set, delete it first");
	
	addr->set = 1;
	//WARNING: bug, read the "How to Break It" and fix this
	char *res = strncpy(addr->name, name, MAX_DATA);
	//demonstrate the strncpy bug
	if(!res) die("Name copy failed");
	
	res = strncpy(addr->email, email, MAX_DATA);
	if(!res) die("Email copy failed");	
}

void Database_get(int id)
{
	struct Address *addr = &conn->db->rows[id];
	if(addr->set) {
		Address_print(addr);
	} else {
		die("ID is not set");
	}
}

void Database_delete(int id)
{
	struct Address addr = {.id = id, .set = 0};
	conn->db->rows[id] = addr;
}

void Database_list()
{
	int i = 0;
	struct Database *db = conn->db;
		
	for(i = 0; i < MAX_ROWS; i++) {
		struct Address *cur = &db->rows[i];
		
		if(cur->set) {
			Address_print(cur);
		}
	}
}

void Database_find(char *name)
{
	printf("You are searching for %s.\n", name);
	int i = 0;
	int found = 0;
	for(i = 0; i < MAX_ROWS; i++) {
		struct Address *address = &conn->db->rows[i];
		
		if(strcmp(address->name, name) == 0) {
			printf("Found %s in the database.\n", name);
			Address_print(address);
			found = 1;
			break;
		}		
	}
	if(found<1) { 
		printf("No Match, ffs");
	}
}

int main(int argc, char *argv[])
{
	if(argc < 3) die("USAGE: ex17 <dbfile> <action> [action params]");
	
	char *filename = argv[1];
	char action = argv[2][0];
	Database_open(filename, action);	
	int id = 0;
	
	if(argc > 3) id = atoi(argv[3]);
	if(id >= MAX_ROWS) die("There's not that many records.");
	
	switch(action) {
		case 'c':
			Database_create();
			Database_write();
			break;
			
		case 'g':
			if(argc != 4) die("Need an id to get");
			
			Database_get(id);
			break;
		
		case 's':
			if(argc != 6) die("Need id, name, email to set");
			
			Database_set(id, argv[4], argv[5]);
			Database_write();
			break;
			
		case 'd':
			if(argc != 4) die("Need an id to delete)");
			
			Database_delete(id);
			Database_write();
			break;
			
		case 'l':
			Database_list();
			break;
		
		case 'f':
			Database_find(argv[3]);
			break;
		default:
			die("Invalid action, only c=create, g=get, s=set, d=del, l=list");
	}
	
	Database_close();
	return 0;
}