While I get a little over my head with the Ex17 extra credit for working the variable sizes into the database file, but I had a really productive day breaking Ex17 about as horribly as anyone can. The first hurdle I’m finally over is making everything use the Database rows as a pointer instead of a fixed sized declaration. I think I nailed all the memory errors in Valgrind too. I thought I would share and shout out for any feedback if anyone else is working on this or has before. I obviously still have a lot of work to do. But I like to think it’s coming together nicely so far.
#include <stdio.h>
#include <assert.h>
#include <stdlib.h>
#include <errno.h>
#include <string.h>
#define MAX_DATA 512
#define MAX_ROWS 100
struct Address {
int id;
int set;
char name[MAX_DATA];
char email[MAX_DATA];
};
struct Database {
size_t max_data;
size_t max_rows;
struct Address *rows;
};
struct Connection {
FILE *file;
struct Database *db;
};
void Database_close(struct Connection *conn);
void die(struct Connection *conn, const char *message)
{
if (errno) {
perror(message);
} else {
printf("ERROR: %s\n", message);
}
Database_close(conn);
exit(1);
}
void Address_print(struct Address *addr)
{
printf("%d %s %s\n", addr->id, addr->name, addr->email);
}
void Database_load(struct Connection *conn)
{
int rc = fread(conn->db, sizeof(struct Database), 1, conn->file);
if (rc != 1)
die(conn, "Failed to load database.");
conn->db->rows = (struct Address *)malloc(sizeof(struct Address) * MAX_ROWS);
if (!conn->db->rows)
die(conn, "memory error: rows");
rc = fread(conn->db->rows, sizeof(struct Address) * MAX_ROWS, 1, conn->file);
if (rc != 1)
die(conn, "Failed to load rows.");
}
struct Connection *Database_open(const char *filename, char mode)
{
struct Connection *conn = malloc(sizeof(struct Connection));
if (!conn)
die(conn, "Memory error");
conn->db = calloc(1, sizeof(struct Database));
if (!conn->db)
die(conn, "Memory error");
if (mode == 'c') {
conn->file = fopen(filename, "w");
} else {
conn->file = fopen(filename, "r+");
if (conn->file) {
Database_load(conn);
}
}
if (!conn->file)
die(conn, "Failed to open the file");
return conn;
}
void Database_close(struct Connection *conn)
{
if (conn) {
if (conn->file)
fclose(conn->file);
if (conn->db->rows)
free(conn->db->rows);
if (conn->db)
free(conn->db);
free(conn);
}
}
void Database_write(struct Connection *conn)
{
rewind(conn->file);
if (errno)
die(conn, "rewind error");
int rc = fwrite(conn->db, sizeof(struct Database), 1, conn->file);
if (rc != 1)
die(conn, "Failed to write database.");
rc = fwrite(conn->db->rows, (sizeof(struct Address) * MAX_ROWS), 1, conn->file);
if (rc != 1)
die(conn, "Failed to write rows.");
rc = fflush(conn->file);
if (rc == -1)
die(conn, "Cannot flush database.");
}
void Database_create(struct Connection *conn)
{
int i = 0;
conn->db->rows = (struct Address *)malloc(sizeof(struct Address) * MAX_ROWS);
for (i = 0; i < MAX_ROWS; i++) {
struct Address addr = {.id = i,.set = 0 };
strncpy(addr.name, " ", MAX_DATA);
strncpy(addr.email, " ", MAX_DATA);
conn->db->rows[i] = addr;
}
}
void Database_set(struct Connection *conn, int id, const char *name,
const char *email)
{
struct Address *addr = &conn->db->rows[id];
if (addr->set)
die(conn, "Already set, delete it first");
addr->set = 1;
char *res = strncpy(addr->name, name, MAX_DATA);
if (!res)
die(conn, "Name copy failed");
res = strncpy(addr->email, email, MAX_DATA);
if (!res)
die(conn, "Email copy failed");
}
void Database_get(struct Connection *conn, int id)
{
struct Address *addr = &conn->db->rows[id];
if (addr->set) {
Address_print(addr);
} else {
die(conn, "ID is not set");
}
}
void Database_delete(struct Connection *conn, int id)
{
struct Address addr = {.id = id,.set = 0 };
conn->db->rows[id] = addr;
}
void Database_list(struct Connection *conn)
{
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);
}
}
}
int main(int argc, char *argv[])
{
if (argc < 3)
die(NULL, "USAGE: ex17 <dbfile> <action> [action params]");
char *filename = argv[1];
char action = argv[2][0];
struct Connection *conn = Database_open(filename, action);
int id = 0;
if (argc > 3) id = atoi(argv[3]);
if (id >= MAX_ROWS) die(conn, "There's not that many records.");
switch (action) {
case 'c':
Database_create(conn);
Database_write(conn);
break;
case 'g':
if (argc != 4)
die(conn, "Need an id to get");
Database_get(conn, id);
break;
case 's':
if (argc != 6)
die(conn, "Need id, name, email to set");
Database_set(conn, id, argv[4], argv[5]);
Database_write(conn);
break;
case 'd':
if (argc != 4)
die(conn, "Need id to delete");
Database_delete(conn, id);
Database_write(conn);
break;
case 'l':
Database_list(conn);
break;
default:
die(conn, "Invalid action: c=create, g=get, s=set, d=del, l=list");
}
Database_close(conn);
return 0;
}
exactly! And it really has. I’m starting to really learn my way around in the debugging tools. And it keeps me reflecting on the basics because sometimes it makes you question everything you know because everything LOOKS right, but is horribly wrong in some (tiny?) way.