Decimal and Foundation (#122)

mredig · web-flow · commit a7ee11486233 · 2024-10-31T22:53:48.000+01:00
* add CustomDebugStringConvertible

* reduce Foundation dependency

* if foundation is available, add Decimal functionality

* more concise floating point init

* dry up data initialization
diff --git a/Sources/Comparable.swift b/Sources/Comparable.swift
@@ -6,9 +6,19 @@
 //  Copyright © 2016-2017 Károly Lőrentey.
 //
 
+#if canImport(Foundation)
 import Foundation
+#endif
 
 extension BigUInt: Comparable {
+    #if !canImport(Foundation)
+    public enum ComparisonResult: Sendable, Comparable, Hashable {
+        case orderedDescending
+        case orderedSame
+        case orderedAscending
+    }
+    #endif
+
     //MARK: Comparison
     
     /// Compare `a` to `b` and return an `NSComparisonResult` indicating their order.
diff --git a/Sources/Data Conversion.swift b/Sources/Data Conversion.swift
@@ -6,7 +6,9 @@
 //  Copyright © 2016-2017 Károly Lőrentey.
 //
 
+#if canImport(Foundation)
 import Foundation
+#endif
 
 extension BigUInt {
     //MARK: NSData Conversion
@@ -43,70 +45,52 @@ extension BigUInt {
         assert(c == 0 && word == 0 && index == -1)
     }
 
-
-    /// Initializes an integer from the bits stored inside a piece of `Data`.
-    /// The data is assumed to be in network (big-endian) byte order.
-    public init(_ data: Data) {
-        // This assumes Word is binary.
+    /// Return a `UnsafeRawBufferPointer` buffer that contains the base-256 representation of this integer, in network (big-endian) byte order.
+    public func serializeToBuffer() -> UnsafeRawBufferPointer {
+        // This assumes Digit is binary.
         precondition(Word.bitWidth % 8 == 0)
 
-        self.init()
+        let byteCount = (self.bitWidth + 7) / 8
 
-        let length = data.count
-        guard length > 0 else { return }
-        let bytesPerDigit = Word.bitWidth / 8
-        var index = length / bytesPerDigit
-        var c = bytesPerDigit - length % bytesPerDigit
-        if c == bytesPerDigit {
-            c = 0
-            index -= 1
-        }
-        let word: Word = data.withUnsafeBytes { buffPtr in
-            var word: Word = 0
-            let p = buffPtr.bindMemory(to: UInt8.self)
-            for byte in p {
-                word <<= 8
-                word += Word(byte)
-                c += 1
-                if c == bytesPerDigit {
-                    self[index] = word
-                    index -= 1
-                    c = 0
-                    word = 0
+        let buffer = UnsafeMutableBufferPointer<UInt8>.allocate(capacity: byteCount)
+
+        guard byteCount > 0 else { return UnsafeRawBufferPointer(start: buffer.baseAddress, count: 0) }
+
+        var i = byteCount - 1
+        for var word in self.words {
+            for _ in 0 ..< Word.bitWidth / 8 {
+                buffer[i] = UInt8(word & 0xFF)
+                word >>= 8
+                if i == 0 {
+                    assert(word == 0)
+                    break
                 }
+                i -= 1
             }
-            return word
         }
-        assert(c == 0 && word == 0 && index == -1)
+        return UnsafeRawBufferPointer(start: buffer.baseAddress, count: byteCount)
+    }
+
+    #if canImport(Foundation)
+    /// Initializes an integer from the bits stored inside a piece of `Data`.
+    /// The data is assumed to be in network (big-endian) byte order.
+    public init(_ data: Data) {
+        self = data.withUnsafeBytes({ buffer in
+            BigUInt(buffer)
+        })
     }
 
     /// Return a `Data` value that contains the base-256 representation of this integer, in network (big-endian) byte order.
     public func serialize() -> Data {
-        // This assumes Digit is binary.
-        precondition(Word.bitWidth % 8 == 0)
-
-        let byteCount = (self.bitWidth + 7) / 8
+        let buffer = serializeToBuffer()
+        defer { buffer.deallocate() }
+        guard
+            let pointer = buffer.baseAddress.map(UnsafeMutableRawPointer.init(mutating:))
+        else { return Data() }
 
-        guard byteCount > 0 else { return Data() }
-
-        var data = Data(count: byteCount)
-        data.withUnsafeMutableBytes { buffPtr in
-            let p = buffPtr.bindMemory(to: UInt8.self)
-            var i = byteCount - 1
-            for var word in self.words {
-                for _ in 0 ..< Word.bitWidth / 8 {
-                    p[i] = UInt8(word & 0xFF)
-                    word >>= 8
-                    if i == 0 {
-                        assert(word == 0)
-                        break
-                    }
-                    i -= 1
-                }
-            }
-        }
-        return data
+        return Data(bytes: pointer, count: buffer.count)
     }
+    #endif
 }
 
 extension BigInt {
@@ -133,47 +117,47 @@ extension BigInt {
 
         self.magnitude = BigUInt(UnsafeRawBufferPointer(rebasing: buffer.dropFirst(1)))
     }
-    
+
+    /// Return a `Data` value that contains the base-256 representation of this integer, in network (big-endian) byte order and a prepended byte to indicate the sign (0 for positive, 1 for negative)
+    public func serializeToBuffer() -> UnsafeRawBufferPointer {
+        // Create a data object for the magnitude portion of the BigInt
+        let magnitudeBuffer = self.magnitude.serializeToBuffer()
+
+        // Similar to BigUInt, a value of 0 should return an empty buffer
+        guard magnitudeBuffer.count > 0 else { return magnitudeBuffer }
+
+        // Create a new buffer for the signed BigInt value
+        let newBuffer = UnsafeMutableRawBufferPointer.allocate(byteCount: magnitudeBuffer.count + 1, alignment: 8)
+        let magnitudeSection = UnsafeMutableRawBufferPointer(rebasing: newBuffer[1...])
+        magnitudeSection.copyBytes(from: magnitudeBuffer)
+        magnitudeBuffer.deallocate()
+
+        // The first byte should be 0 for a positive value, or 1 for a negative value
+        // i.e., the sign bit is the LSB
+        newBuffer[0] = self.sign == .plus ? 0 : 1
+
+        return UnsafeRawBufferPointer(start: newBuffer.baseAddress, count: newBuffer.count)
+    }
+
+    #if canImport(Foundation)
     /// Initializes an integer from the bits stored inside a piece of `Data`.
     /// The data is assumed to be in network (big-endian) byte order with a first
     /// byte to represent the sign (0 for positive, 1 for negative)
     public init(_ data: Data) {
-        // This assumes Word is binary.
-        // This is the same assumption made when initializing BigUInt from Data
-        precondition(Word.bitWidth % 8 == 0)
-
-        self.init()
-        
-        // Serialized data for a BigInt should contain at least 2 bytes: one representing
-        // the sign, and another for the non-zero magnitude. Zero is represented by an
-        // empty Data struct, and negative zero is not supported.
-        guard data.count > 1, let firstByte = data.first else { return }
-        
-        // The first byte gives the sign
-        // This byte is compared to a bitmask to allow additional functionality to be added
-        // to this byte in the future.
-        self.sign = firstByte & 0b1 == 0 ? .plus : .minus
-        
-        // The remaining bytes are read and stored as the magnitude
-        self.magnitude = BigUInt(data.dropFirst(1))
+        self = data.withUnsafeBytes({ buffer in
+            BigInt(buffer)
+        })
     }
     
     /// Return a `Data` value that contains the base-256 representation of this integer, in network (big-endian) byte order and a prepended byte to indicate the sign (0 for positive, 1 for negative)
     public func serialize() -> Data {
-        // Create a data object for the magnitude portion of the BigInt
-        let magnitudeData = self.magnitude.serialize()
-        
-        // Similar to BigUInt, a value of 0 should return an initialized, empty Data struct
-        guard magnitudeData.count > 0 else { return magnitudeData }
-        
-        // Create a new Data struct for the signed BigInt value
-        var data = Data(capacity: magnitudeData.count + 1)
-        
-        // The first byte should be 0 for a positive value, or 1 for a negative value
-        // i.e., the sign bit is the LSB
-        data.append(self.sign == .plus ? 0 : 1)
-        
-        data.append(magnitudeData)
-        return data
+        let buffer = serializeToBuffer()
+        defer { buffer.deallocate() }
+        guard
+            let pointer = buffer.baseAddress.map(UnsafeMutableRawPointer.init(mutating:))
+        else { return Data() }
+
+        return Data(bytes: pointer, count: buffer.count)
     }
+    #endif
 }
diff --git a/Sources/Floating Point Conversion.swift b/Sources/Floating Point Conversion.swift
@@ -6,6 +6,10 @@
 //  Copyright © 2016-2017 Károly Lőrentey.
 //
 
+#if canImport(Foundation)
+import Foundation
+#endif
+
 extension BigUInt {
     public init?<T: BinaryFloatingPoint>(exactly source: T) {
         guard source.isFinite else { return nil }
@@ -22,23 +26,69 @@ extension BigUInt {
     public init<T: BinaryFloatingPoint>(_ source: T) {
         self.init(exactly: source.rounded(.towardZero))!
     }
+
+    #if canImport(Foundation)
+    public init?(exactly source: Decimal) {
+        guard source.isFinite else { return nil }
+        guard !source.isZero else { self = 0; return }
+        guard source.sign == .plus else { return nil }
+        assert(source.floatingPointClass == .positiveNormal)
+        guard source.exponent >= 0 else { return nil }
+        let intMaxD = Decimal(UInt.max)
+        let intMaxB = BigUInt(UInt.max)
+        var start = BigUInt()
+        var value = source
+        while value >= intMaxD {
+            start += intMaxB
+            value -= intMaxD
+        }
+        start += BigUInt((value as NSNumber).uintValue)
+        self = start
+    }
+
+    public init?(truncating source: Decimal) {
+        guard source.isFinite else { return nil }
+        guard !source.isZero else { self = 0; return }
+        guard source.sign == .plus else { return nil }
+        assert(source.floatingPointClass == .positiveNormal)
+        let intMaxD = Decimal(UInt.max)
+        let intMaxB = BigUInt(UInt.max)
+        var start = BigUInt()
+        var value = source
+        while value >= intMaxD {
+            start += intMaxB
+            value -= intMaxD
+        }
+        start += BigUInt((value as NSNumber).uintValue)
+        self = start
+    }
+    #endif
 }
 
 extension BigInt {
     public init?<T: BinaryFloatingPoint>(exactly source: T) {
-        switch source.sign{
-        case .plus:
-            guard let magnitude = BigUInt(exactly: source) else { return nil }
-            self = BigInt(sign: .plus, magnitude: magnitude)
-        case .minus:
-            guard let magnitude = BigUInt(exactly: -source) else { return nil }
-            self = BigInt(sign: .minus, magnitude: magnitude)
-        }
+        guard let magnitude = BigUInt(exactly: source.magnitude) else { return nil }
+        let sign = BigInt.Sign(source.sign)
+        self.init(sign: sign, magnitude: magnitude)
     }
 
     public init<T: BinaryFloatingPoint>(_ source: T) {
         self.init(exactly: source.rounded(.towardZero))!
     }
+
+    #if canImport(Foundation)
+    public init?(exactly source: Decimal) {
+        guard let magnitude = BigUInt(exactly: source.magnitude) else { return nil }
+        let sign = BigInt.Sign(source.sign)
+        self.init(sign: sign, magnitude: magnitude)
+    }
+
+    public init?(truncating source: Decimal) {
+        guard let magnitude = BigUInt(truncating: source.magnitude) else { return nil }
+        let sign = BigInt.Sign(source.sign)
+        self.init(sign: sign, magnitude: magnitude)
+    }
+    #endif
 }
 
 extension BinaryFloatingPoint where RawExponent: FixedWidthInteger, RawSignificand: FixedWidthInteger {
@@ -71,3 +121,14 @@ extension BinaryFloatingPoint where RawExponent: FixedWidthInteger, RawSignifica
         self.init(BigInt(sign: .plus, magnitude: value))
     }
 }
+
+extension BigInt.Sign {
+    public init(_ sign: FloatingPointSign) {
+        switch sign {
+        case .plus:
+            self = .plus
+        case .minus:
+            self = .minus
+        }
+    }
+}
diff --git a/Sources/String Conversion.swift b/Sources/String Conversion.swift
@@ -221,20 +221,34 @@ extension BigInt: CustomStringConvertible {
     }
 }
 
+extension BigUInt: CustomDebugStringConvertible {
+    /// Return the decimal representation of this integer.
+    public var debugDescription: String {
+        let text = String(self)
+        return text + " (\(self.bitWidth) bits)"
+    }
+}
+
+extension BigInt: CustomDebugStringConvertible {
+    /// Return the decimal representation of this integer.
+    public var debugDescription: String {
+        let text = String(self)
+        return text + " (\(self.magnitude.bitWidth) bits)"
+    }
+}
+
 extension BigUInt: CustomPlaygroundDisplayConvertible {
 
     /// Return the playground quick look representation of this integer.
     public var playgroundDescription: Any {
-        let text = String(self)
-        return text + " (\(self.bitWidth) bits)"
+        debugDescription
     }
 }
 
 extension BigInt: CustomPlaygroundDisplayConvertible {
 
     /// Return the playground quick look representation of this integer.
     public var playgroundDescription: Any {
-        let text = String(self)
-        return text + " (\(self.magnitude.bitWidth) bits)"
+        debugDescription
     }
 }
diff --git a/Tests/BigIntTests/BigIntTests.swift b/Tests/BigIntTests/BigIntTests.swift
diff --git a/Tests/BigIntTests/BigUIntTests.swift b/Tests/BigIntTests/BigUIntTests.swift
