Up through happy path of lcthw ex17

lcthw/.ex17.argv

@@ -0,0 +1,2 @@
+ex17.db
+c

lcthw/ex17.c

@@ -0,0 +1,234 @@
+#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 {
+	struct Address rows[MAX_ROWS];
+};
+
+struct Connection {
+	FILE *file;
+	struct Database *db;
+};
+
+void die(const char *message)
+{
+	if (errno) {
+		perror(message);
+	} else {
+		printf("ERROR: %s\n", message);
+	}
+
+	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("Failed to load database.");
+	}
+}
+
+struct Connection *Database_open(const char *filename, char mode)
+{
+	struct Connection *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(conn);
+		}
+	}
+
+	if (!conn->file) {
+		die("Failed to open file");
+	}
+
+	return conn;
+}
+
+void Database_close(struct Connection *conn)
+{
+	if (conn) {
+		if (conn->file) {
+			fclose(conn->file);
+		}
+
+		if (conn->db) {
+			free(conn->db);
+		}
+
+		free(conn);
+	}
+}
+
+void Database_write(struct Connection *conn)
+{
+	rewind(conn->file);
+
+	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(struct Connection *conn)
+{
+	int i = 0;
+
+	for (i = 0; i < MAX_ROWS; i++) {
+		struct Address addr = {.id = i, .set = 0};
+		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("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(struct Connection *conn, int id)
+{
+	struct Address *addr = &conn->db->rows[id];
+
+	if (addr->set) {
+		Address_print(addr);
+	} else {
+		die("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("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("There's not that many records.");
+	}
+
+	switch (action) {
+		case 'c':
+			Database_create(conn);
+			Database_write(conn);
+			break;
+
+		case 'g':
+			if (argc != 4) {
+				die("Need an id to get");
+			}
+
+			Database_get(conn, id);
+			break;
+
+		case 's':
+			if (argc != 6) {
+				die("Need an id, name, email to set");
+			}
+
+			Database_set(conn, id, argv[4], argv[5]);
+			Database_write(conn);
+			break;
+
+		case 'd':
+			if (argc != 4) {
+				die("Need an id to delete");
+			}
+
+			Database_delete(conn, id);
+			Database_write(conn);
+			break;
+
+		case 'l':
+			Database_list(conn);
+			break;
+
+		default:
+			die("Invalid action: c=create, g=get, s=set, d=del, l=list");
+	}
+
+	Database_close(conn);
+
+	return 0;
+}