Implement getpwuid_r

fakeid.c

@@ -38,6 +38,9 @@ struct passwd *getpwuid(uid_t uid) {
         return NULL;
     }
     struct passwd *pass = getpwuid(uid);
+    if (pass == NULL) {
+        return NULL;
+    }
     char *name = getenv("USER");
     if (name == NULL) {
         fprintf(stderr, "Could not find the USER environment variable. Using the real username.\n");
@@ -46,3 +49,28 @@ struct passwd *getpwuid(uid_t uid) {
     pass->pw_name = name;
     return pass;
 }
+
+int getpwuid_r(uid_t uid, struct passwd *pw, char *buf, size_t size, struct passwd **res) {
+    int prev_err = errno;
+    *res = NULL;
+    struct passwd *pass = getpwuid(uid);
+    if (pass == NULL || errno != prev_err) {
+        return errno;
+    }
+    memcpy(pw, pass, sizeof(struct passwd));
+    size_t name_len = strlen(pass->pw_name) + 1;
+    size_t passwd_len = strlen(pass->pw_passwd) + 1;
+    size_t gecos_len = strlen(pass->pw_gecos) + 1;
+    size_t dir_len = strlen(pass->pw_dir) + 1;
+    size_t shell_len = strlen(pass->pw_shell) + 1;
+    if ((name_len + passwd_len + gecos_len + dir_len + shell_len) > size) {
+        return ERANGE;
+    }
+    pw->pw_name = memcpy(buf, pass->pw_name, name_len);
+    pw->pw_passwd = memcpy(buf + name_len, pass->pw_passwd, passwd_len);
+    pw->pw_gecos = memcpy(buf + name_len + passwd_len, pass->pw_gecos, gecos_len);
+    pw->pw_dir = memcpy(buf + name_len + passwd_len + gecos_len, pass->pw_dir, dir_len);
+    pw->pw_shell = memcpy(buf + name_len + passwd_len + gecos_len + dir_len, pass->pw_shell, shell_len);
+    *res = pw;
+    return 0;
+}