Copying over the ex17 bits so that I can revert the main file to pre-extra-credit state

ex17-ec.c

@@ -0,0 +1,239 @@
+#include <stdio.h>
+#include <assert.h>
+#include <stdlib.h>
+#include <errno.h>
+#include <string.h>
+
+#define DEFAULT_MAX_DATA 512
+#define DEFAULT_MAX_ROWS 100
+
+struct Address {
+    int id;
+    int set;
+    char *name;
+    char *email;
+};
+
+struct Database {
+    size_t size;
+    int max_data;
+    int max_rows;
+    struct Address *rows;
+};
+
+struct Connection {
+    FILE *file;
+    struct Database *db;
+};
+
+void Database_close(struct Connection *conn);
+
+void die(const char *message, struct Connection *conn)
+{
+    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)
+{
+    rewind(conn->file);
+
+    int rc = fread(&conn->db->max_rows, sizeof(int), 1, conn->file);
+    if(rc != 1) die("Failed to load database max_rows.", conn);
+
+    rc = fread(&conn->db->max_data, sizeof(int), 1, conn->file);
+    if(rc != 1) die("Failed to load database max_data.", conn);
+
+    rc = fread(conn->db->rows, sizeof(struct Address), conn->db->max_rows, conn->file);
+    if(rc != 1) die("Failed to load database rows.", conn);
+}
+
+struct Connection* Database_open(const char *filename, char mode, int max_rows)
+{
+    struct Connection *conn = malloc(sizeof(struct Connection));
+    if(!conn) die("Memory error", conn);
+
+    conn->db = malloc(sizeof(struct Database));
+    if(!conn->db) die("Memory error", conn);
+
+    size_t rowsize = max_rows * sizeof(struct Address);
+    conn->db->size = rowsize;
+    conn->db->rows = malloc(rowsize);
+    if(!conn->db->rows) die("Memory error", conn);
+
+    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", conn);
+
+    return conn;
+}
+
+void Database_close(struct Connection *conn)
+{
+    if(conn != NULL) {
+        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->size, sizeof(size_t), 1, conn->file);
+    if(rc != 1) die("Failed to write database size.", conn);
+
+    rc = fwrite(&conn->db->max_rows, sizeof(int), 1, conn->file);
+    if(rc != 1) die("Failed to write database max_rows.", conn);
+
+    rc = fwrite(&conn->db->max_data, sizeof(int), 1, conn->file);
+    if(rc != 1) die("Failed to write database max_data.", conn);
+
+    rc = fwrite(conn->db->rows, conn->db->size, 1, conn->file);
+    if(rc != 1) die("Failed to write database rows.", conn);
+
+    rc = fflush(conn->file);
+    if(rc == -1) die("Cannot flush database.", conn);
+}
+
+void Database_create(struct Connection *conn, int max_rows, int max_data)
+{
+    int i = 0;
+    conn->db->max_rows = max_rows;
+    conn->db->max_data = max_data;
+
+    for(i = 0; i < conn->db->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)
+{
+    int max_data = conn->db->max_data;
+    struct Address *addr = &conn->db->rows[id];
+    if(addr->set) die("Already set, delete it first", conn);
+
+    addr->set = 1;
+    char *res = strncpy(addr->name, name, max_data);
+    if(!res) die("Name copy failed", conn);
+    addr->name[max_data - 1] = '\0';
+
+    res = strncpy(addr->email, email, max_data);
+    if(!res) die("Email copy failed", conn);
+    addr->email[max_data - 1] = '\0';
+}
+
+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", conn);
+    }
+}
+
+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 < conn->db->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>[:max_data,max_rows] [action params]", NULL);
+
+    char *filename = argv[1];
+
+    int max_data = DEFAULT_MAX_DATA;
+    int max_rows = DEFAULT_MAX_ROWS;
+
+    char action = argv[2][0];
+    if(':' == argv[2][1]) {
+        sscanf(argv[2], "%c:%d,%d", &action, &max_data, &max_rows);
+    }
+
+    struct Connection *conn = Database_open(filename, action, max_rows);
+    int id = 0;
+
+    if(argc > 3) id = atoi(argv[3]);
+    if(id >= max_rows) die("There's not that many records.", conn);
+
+    switch(action) {
+        case 'c':
+            Database_create(conn, max_rows, max_data);
+            Database_write(conn);
+            break;
+
+        case 'g':
+            if(argc != 4) die("Need an id to get", conn);
+
+            Database_get(conn, id);
+            break;
+
+        case 's':
+            if(argc != 6) die("Need id, name, email to set", conn);
+
+            Database_set(conn, id, argv[4], argv[5]);
+            Database_write(conn);
+            break;
+
+        case 'd':
+            if(argc != 4) die("Need id to delete", conn);
+
+            Database_delete(conn, id);
+            Database_write(conn);
+            break;
+
+        case 'l':
+            Database_list(conn);
+            break;
+        default:
+            die("Invalid action, only: c=create, g=get, s=set, d=del, l=list", conn);
+    }
+
+    Database_close(conn);
+
+    return 0;
+}
+