i understand now,thank you very much!

can i give you the entire code?maybe you will find my answer:)

yes,but by the name of function says(database_delete),this function must delete something,and i don't know how it is deleting something

this is C code!!!

in this code?from where i need to understand that is deleting something? void Database_delete(struct Connection *conn, int id) { struct Address addr = {.id = id, .set = 0}; conn->db->rows[id] = addr;

my bad,sry about you wasted time to read my code:))

omg,sry about that badd miss,and thanks anyway!

#include #include #include #include #include #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 the 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++) { // make a prototype to initialize it struct Address addr = {.id = i, .set = 0}; // then just assign it 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"); r

thank you!!

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 the file");

return conn;

}