Add SHA256 hashing (#10)

* Add SHA256 hashing

* Update ByteString.swift

* Update SHA256.swift

README.md

@@ -493,6 +493,8 @@ Although not visible when writing templates, each underlying value that is passe
   * `dropFirst() -> String`: Equivalent to Swift's `.dropFirst()`.
   * `dropLast() -> String`: Equivalent to Swift's `.dropLast()`.
   * `hash() -> String`: The hash of the string using the `CRC32` algorithm.
+  * `sha() -> String`: The SHA256 hash of the string using the `SHA256` algorithm.
+    * DO NOT rely on this to be cryptographically secure. 
   * `snakeCased() -> String`: Converts the string from camelCase to snake_case.
   * `camelCased() -> String`: Converts the string from snake_case to camelCase.
   * `withParens() -> String`: If the string is not empty, surrounds it in parenthesis.
@@ -503,6 +505,8 @@ Although not visible when writing templates, each underlying value that is passe
   * `isOdd() -> Bool`: Returns whether the integer is odd or not.
   * `isEven() -> Bool`: Returns whether the integer is even or not.
   * `hash() -> String`: The hash of the string representation of the integer using the `CRC32` algorithm.
+  * `sha() -> String`: The hash of the string using the `SHA256` algorithm.
+    * DO NOT rely on this to be cryptographically secure.
 * `Array`:
   * `first() -> Element?`: Returns the first element of the array.
   * `last() -> Element?`: Returns the last element of the array.

Sources/EnumeratorMacroImpl/Types/ByteString.swift

@@ -0,0 +1,168 @@
+/*
+ This source file is part of the Swift.org open source project
+
+ Copyright (c) 2014 - 2017 Apple Inc. and the Swift project authors
+ Licensed under Apache License v2.0 with Runtime Library Exception
+
+ See http://swift.org/LICENSE.txt for license information
+ See http://swift.org/CONTRIBUTORS.txt for Swift project authors
+ */
+
+/// Borrowed from https://github.com/swiftlang/swift-tools-support-core/Sources/TSCBasic/ByteString.swift
+
+import Foundation
+
+/// A `ByteString` represents a sequence of bytes.
+///
+/// This struct provides useful operations for working with buffers of
+/// bytes. Conceptually it is just a contiguous array of bytes (UInt8), but it
+/// contains methods and default behavior suitable for common operations done
+/// using bytes strings.
+///
+/// This struct *is not* intended to be used for significant mutation of byte
+/// strings, we wish to retain the flexibility to micro-optimize the memory
+/// allocation of the storage (for example, by inlining the storage for small
+/// strings or and by eliminating wasted space in growable arrays). For
+/// construction of byte arrays, clients should use the `WritableByteStream` class
+/// and then convert to a `ByteString` when complete.
+struct ByteString: ExpressibleByArrayLiteral, Hashable, Sendable {
+    /// The buffer contents.
+    @usableFromInline
+    internal var _bytes: [UInt8]
+
+    /// Create an empty byte string.
+    @inlinable
+    init() {
+        _bytes = []
+    }
+
+    /// Create a byte string from a byte array literal.
+    @inlinable
+    init(arrayLiteral contents: UInt8...) {
+        _bytes = contents
+    }
+
+    /// Create a byte string from an array of bytes.
+    @inlinable
+    init(_ contents: [UInt8]) {
+        _bytes = contents
+    }
+
+    /// Create a byte string from an array slice.
+    @inlinable
+    init(_ contents: ArraySlice<UInt8>) {
+        _bytes = Array(contents)
+    }
+
+    /// Create a byte string from an byte buffer.
+    @inlinable
+    init<S: Sequence> (_ contents: S) where S.Iterator.Element == UInt8 {
+        _bytes = [UInt8](contents)
+    }
+
+    /// Create a byte string from the UTF8 encoding of a string.
+    @inlinable
+    init(encodingAsUTF8 string: String) {
+        _bytes = [UInt8](string.utf8)
+    }
+
+    /// Access the byte string contents as an array.
+    @inlinable
+    var contents: [UInt8] {
+        return _bytes
+    }
+
+    /// Return the byte string size.
+    @inlinable
+    var count: Int {
+        return _bytes.count
+    }
+
+    /// Gives a non-escaping closure temporary access to an immutable `Data` instance wrapping the `ByteString` without
+    /// copying any memory around.
+    ///
+    /// - Parameters:
+    ///   - closure: The closure that will have access to a `Data` instance for the duration of its lifetime.
+    @inlinable
+    func withData<T>(_ closure: (Data) throws -> T) rethrows -> T {
+        return try _bytes.withUnsafeBytes { pointer -> T in
+            let mutatingPointer = UnsafeMutableRawPointer(mutating: pointer.baseAddress!)
+            let data = Data(bytesNoCopy: mutatingPointer, count: pointer.count, deallocator: .none)
+            return try closure(data)
+        }
+    }
+
+    /// Returns a `String` lowercase hexadecimal representation of the contents of the `ByteString`.
+    @inlinable
+    var hexadecimalRepresentation: String {
+        _bytes.reduce("") {
+            var str = String($1, radix: 16)
+            // The above method does not do zero padding.
+            if str.count == 1 {
+                str = "0" + str
+            }
+            return $0 + str
+        }
+    }
+
+    /// Returns a `String` lowercase hexadecimal representation of the contents of the `ByteString`.
+    @inlinable
+    var decimalRepresentation: String {
+        _bytes.reduce("") {
+            var str = String($1, radix: 10)
+            // The above method does not do zero padding.
+            if str.count == 1 {
+                str = "0" + str
+            }
+            return $0 + str
+        }
+    }
+}
+
+/// Conform to CustomDebugStringConvertible.
+extension ByteString: CustomStringConvertible {
+    /// Return the string decoded as a UTF8 sequence, or traps if not possible.
+    var description: String {
+        return cString
+    }
+
+    /// Return the string decoded as a UTF8 sequence, if possible.
+    @available(*, deprecated, message: "Mahdi: Just so it doesn't emit a warning")
+    @inlinable
+    var validDescription: String? {
+        // FIXME: This is very inefficient, we need a way to pass a buffer. It
+        // is also wrong if the string contains embedded '\0' characters.
+        let tmp = _bytes + [UInt8(0)]
+        return tmp.withUnsafeBufferPointer { ptr in
+            return String(validatingUTF8: unsafeBitCast(ptr.baseAddress, to: UnsafePointer<CChar>.self))
+        }
+    }
+
+    /// Return the string decoded as a UTF8 sequence, substituting replacement
+    /// characters for ill-formed UTF8 sequences.
+    @inlinable
+    var cString: String {
+        return String(decoding: _bytes, as: Unicode.UTF8.self)
+    }
+
+    @available(*, deprecated, message: "use description or validDescription instead")
+    var asString: String? {
+        return validDescription
+    }
+}
+
+/// StringLiteralConvertable conformance for a ByteString.
+extension ByteString: ExpressibleByStringLiteral {
+    typealias UnicodeScalarLiteralType = StringLiteralType
+    typealias ExtendedGraphemeClusterLiteralType = StringLiteralType
+
+    init(unicodeScalarLiteral value: UnicodeScalarLiteralType) {
+        _bytes = [UInt8](value.utf8)
+    }
+    init(extendedGraphemeClusterLiteral value: ExtendedGraphemeClusterLiteralType) {
+        _bytes = [UInt8](value.utf8)
+    }
+    init(stringLiteral value: StringLiteralType) {
+        _bytes = [UInt8](value.utf8)
+    }
+}

Sources/EnumeratorMacroImpl/Types/EInt.swift

@@ -45,6 +45,8 @@ extension EInt: EMustacheTransformable {
             return (self.underlying & 1) == 1
         case "hash":
             return EString(crc32(self.description.utf8).description)
+        case "sha":
+            return EString(SHA256().hash(self.description).decimalRepresentation.prefix(10))
         default:
             RenderingContext.current.addOrReplaceFunctionDiagnostic(
                 .invalidTransform(

Sources/EnumeratorMacroImpl/Types/EString.swift

@@ -53,6 +53,8 @@ extension EString: EMustacheTransformable {
             return Bool(self)
         case "hash":
             return EString(crc32(self.utf8).description)
+        case "sha":
+            return EString(SHA256().hash(self.underlying).decimalRepresentation.prefix(10))
         case "dropFirst":
             return EString(String(self.dropFirst()))
         case "dropLast":