util: convenience utilities for fscrypt

This commit adds in the util package. This package provides
two functions for creating errors. These functions are:
	- InvalidInputErrorF - bad input from user or caller
	- SystemErrorF - low level failure

It also adds in a small function for converting Go byte slices into C
void pointers. This will be very useful for interoperating with C.

Change-Id: I87ad7946dd5fa26e28927590aff4bcc9fd5ce4f7

1 files changed, 50 insertions, 0 deletions

diff --git a/util/errors.go b/util/errors.go
new file mode 100644
index 0000000..aafeadd
--- /dev/null
+++ b/util/errors.go
@@ -0,0 +1,50 @@
+/*
+ * errors.go - Custom errors and error functions used by fscrypt
+ *
+ * Copyright 2017 Google Inc.
+ * Author: Joe Richey (joerichey@google.com)
+ *
+ * Licensed under the Apache License, Version 2.0 (the "License"); you may not
+ * use this file except in compliance with the License. You may obtain a copy of
+ * the License at
+ *
+ *     http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS, WITHOUT
+ * WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied. See the
+ * License for the specific language governing permissions and limitations under
+ * the License.
+ */
+
+package util
+
+import (
+	"fmt"
+	"log"
+)
+
+// InvalidInputF creates an error that should indicate either bad input from a
+// caller of a public library function or bad user input.
+func InvalidInputF(format string, a ...interface{}) error {
+	return fmt.Errorf("invalid input: "+format, a...)
+}
+
+// InvalidLengthError indicates name should have had length expected.
+func InvalidLengthError(name string, expected int, actual int) error {
+	return InvalidInputF("expected %s of length %d, actual length was %d", name, expected, actual)
+}
+
+// SystemErrorF creates an error that should indicate something has gone wrong
+// in the underlying system (syscall failure, bad ioctl, etc...).
+func SystemErrorF(format string, a ...interface{}) error {
+	return fmt.Errorf("system error: "+format, a...)
+}
+
+// NeverError panics if a non-nil error is passed in. It should be used to check
+// for logic errors, not to handle recoverable errors.
+func NeverError(err error) {
+	if err != nil {
+		log.Panicf("NeverError() check failed: %v", err)
+	}
+}