tftp

try to fix a bug Lorenz told me about
in fwrite

tests/tfpt_tests.cpp

@@ -74,4 +74,22 @@ TEST(TFTP, custom_fwrite) {
     free(write_file.data);
     write_file.data = NULL;
     write_file.len = 0;
+}
+
+TEST(TFTP, custom_fread_fwrite_suggested_by_Lorentz) {
+    write_file.data = (char*)malloc(21 * sizeof(char));
+    write_file.len = 21;
+    write_file.offset = 0;
+    tftp_custom_fwrite("1234567890123456789", 19, &write_file);
+
+    tftp_custom_fwrite("0987654321", 10, &write_file);
+    EXPECT_EQ(write_file.offset, 20);
+    EXPECT_EQ(write_file.len, 21);
+    EXPECT_EQ(memcmp(write_file.data, "12345678901234567890", 20), 0);
+    free(write_file.data);
+
+    char buf[21];
+    file.offset = 9;
+    tftp_custom_fread(buf, 20, &file);
+    EXPECT_EQ(memcmp(buf, "0", 1), 0);
 }