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//
// CryptoSwift
//
// Copyright (C) 2014-2017 Marcin Krzyżanowski <marcin@krzyzanowskim.com>
// This software is provided 'as-is', without any express or implied warranty.
//
// In no event will the authors be held liable for any damages arising from the use of this software.
//
// Permission is granted to anyone to use this software for any purpose,including commercial applications, and to alter it and redistribute it freely, subject to the following restrictions:
//
// - The origin of this software must not be misrepresented; you must not claim that you wrote the original software. If you use this software in a product, an acknowledgment in the product documentation is required.
// - Altered source versions must be plainly marked as such, and must not be misrepresented as being the original software.
// - This notice may not be removed or altered from any source or binary distribution.
//
// PKCS is a group of public-key cryptography standards devised
// and published by RSA Security Inc, starting in the early 1990s.
//
struct PKCS7Padding: PaddingProtocol {
enum Error: Swift.Error {
case invalidPaddingValue
}
init() {
}
func add(to bytes: Array<UInt8>, blockSize: Int) -> Array<UInt8> {
let padding = UInt8(blockSize - (bytes.count % blockSize))
var withPadding = bytes
if padding == 0 {
// If the original data is a multiple of N bytes, then an extra block of bytes with value N is added.
for _ in 0..<blockSize {
withPadding += Array<UInt8>(arrayLiteral: UInt8(blockSize))
}
} else {
// The value of each added byte is the number of bytes that are added
for _ in 0..<padding {
withPadding += Array<UInt8>(arrayLiteral: UInt8(padding))
}
}
return withPadding
}
func remove(from bytes: Array<UInt8>, blockSize _: Int?) -> Array<UInt8> {
guard !bytes.isEmpty, let lastByte = bytes.last else {
return bytes
}
assert(!bytes.isEmpty, "Need bytes to remove padding")
let padding = Int(lastByte) // last byte
let finalLength = bytes.count - padding
if finalLength < 0 {
return bytes
}
if padding >= 1 {
return Array(bytes[0..<finalLength])
}
return bytes
}
}