From 5216a57797413496cf01b85c1e621ce46ef21411 Mon Sep 17 00:00:00 2001
From: =?UTF-8?q?=E5=BE=90=E6=B6=9B?= <midnite@outlook.com>
Date: Wed, 12 Jul 2023 22:55:12 +0800
Subject: [PATCH] =?UTF-8?q?feat(encrypt):=E5=A2=9E=E5=8A=A0=E9=80=9A?=
 =?UTF-8?q?=E7=94=A8=E7=9A=84=E6=95=B0=E6=8D=AE=E5=A1=AB=E5=85=85=E5=A4=84?=
 =?UTF-8?q?=E7=90=86=E3=80=82?=
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Content-Type: text/plain; charset=UTF-8
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---
 encryption/encryption.go |  2 ++
 encryption/padding.go    | 48 ++++++++++++++++++++++++++++++++++++++++
 2 files changed, 50 insertions(+)
 create mode 100644 encryption/encryption.go
 create mode 100644 encryption/padding.go

diff --git a/encryption/encryption.go b/encryption/encryption.go
new file mode 100644
index 0000000..b2435c0
--- /dev/null
+++ b/encryption/encryption.go
@@ -0,0 +1,2 @@
+// 提供用于支持加解密算法的基础功能函数。
+package encryption
diff --git a/encryption/padding.go b/encryption/padding.go
new file mode 100644
index 0000000..ba89c72
--- /dev/null
+++ b/encryption/padding.go
@@ -0,0 +1,48 @@
+package encryption
+
+import "bytes"
+
+const (
+	NoPadding = iota
+	ZeroPadding
+	PKCS7Padding
+)
+
+// 对给定的数据进行填充，默认采用填充零的方式（ZeroPadding），也可以采用填充PKCS#7的方式（PKCS7Padding）或者不填充（NoPadding）。
+func Padding(data []byte, blockSize int, padding ...int) []byte {
+	paddingMethod := append(padding, ZeroPadding)[0]
+	n := blockSize - len(data)%blockSize
+	switch paddingMethod {
+	case PKCS7Padding:
+		pad := bytes.Repeat([]byte{byte(n)}, n)
+		return append(data, pad...)
+	case NoPadding:
+		return data
+	case ZeroPadding:
+		fallthrough
+	default:
+		if n == 0 {
+			return data
+		}
+		return append(data, bytes.Repeat([]byte{0}, n)...)
+	}
+}
+
+// 对给定的数据进行去填充，默认采用去填充零的方式（对应ZeroPadding），也可以采用去填充PKCS#7的方式（对应PKCS7Padding）或者不填充（对应NoPadding）。
+func Unpadding(data []byte, padding ...int) []byte {
+	paddingMethod := append(padding, ZeroPadding)[0]
+	switch paddingMethod {
+	case PKCS7Padding:
+		length := len(data)
+		unpadding := int(data[length-1])
+		return data[:(length - unpadding)]
+	case NoPadding:
+		return data
+	case ZeroPadding:
+		fallthrough
+	default:
+		return bytes.TrimRightFunc(data, func(r rune) bool {
+			return r == rune(0)
+		})
+	}
+}