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Adds Int(buffer:) initializer to FixedWidthInteger types #3047

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Adds Int(buffer:) initializer to FixedWidthInteger types #3047

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2c57a15
Adds `Int(buffer:)` initializer to FixedWidthInteger types.
natikgadzhi Jan 12, 2025
a56be34
make it fail loudly instead of returning an optional
natikgadzhi Jan 12, 2025
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14 changes: 14 additions & 0 deletions Sources/NIOCore/ByteBuffer-int.swift
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Original file line number Diff line number Diff line change
Expand Up @@ -134,6 +134,20 @@ extension FixedWidthInteger {

return 1 << ((Self.bitWidth - 1) - self.leadingZeroBitCount)
}

/// Initialize an integer from a ByteBuffer. The buffer must contain enough bytes to represent the integer.
/// The bytes will be read using the host system's endianness.
/// If the buffer doesn't contain enough bytes to represent the integer, the program will crash.
///
/// - Parameters:
/// - buffer: The ByteBuffer to read from
///
/// - Returns: The integer value read from the buffer
@inlinable
public init(buffer: ByteBuffer) {
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This should definitely be failable, so that we can avoid the force-unwrap. We also want to add tests.

There's a separate question about whether this should be exactly the right size.

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@weissi strong opinions on checking that the buffer size matches the int size exactly?

If we should verify the size match, the most straightforward way would be to check buffer.readableBytes == MemoryLayout<Self.self>.size, right?

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I'm definitely in favour of checking that this is exactly the right size. It's weird to left garbage around, if that's expected readInteger is the right tool. Endianness should also be configurable (but defaulted to .host) Something like

var buffer = buffer
guard let value = buffer.readInteger(endianness: endianness, as: Self.self), buffer.readableBytes == 0 else {
    return nil
}
return value

var buffer = buffer
self = buffer.readInteger(endianness: .host, as: Self.self)!
}
}

extension UInt32 {
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30 changes: 30 additions & 0 deletions Tests/NIOCoreTests/ByteBufferTest.swift
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Expand Up @@ -3499,6 +3499,36 @@ extension ByteBufferTest {

}

// MARK: - Int / FixedWidthInteger init
extension ByteBufferTest {
func testCreateIntegersFromByteBuffer() {
// 8-bit
let uint8Buffer = ByteBuffer(bytes: [42])
XCTAssertEqual(UInt8(buffer: uint8Buffer), 42)
XCTAssertEqual(Int8(buffer: uint8Buffer), 42)

// 16-bit
let uint16Bytes: [UInt8] = Endianness.host == .little ? [0x02, 0x01] : [0x01, 0x02]
let uint16Buffer = ByteBuffer(bytes: uint16Bytes)
XCTAssertEqual(UInt16(buffer: uint16Buffer), 0x0102)
XCTAssertEqual(Int16(buffer: uint16Buffer), 0x0102)

// 32-bit
let uint32Bytes: [UInt8] = Endianness.host == .little ? [0x04, 0x03, 0x02, 0x01] : [0x01, 0x02, 0x03, 0x04]
let uint32Buffer = ByteBuffer(bytes: uint32Bytes)
XCTAssertEqual(UInt32(buffer: uint32Buffer), 0x01020304)
XCTAssertEqual(Int32(buffer: uint32Buffer), 0x01020304)

// 64-bit
let uint64Bytes: [UInt8] = Endianness.host == .little ?
[0x08, 0x07, 0x06, 0x05, 0x04, 0x03, 0x02, 0x01] :
[0x01, 0x02, 0x03, 0x04, 0x05, 0x06, 0x07, 0x08]
let uint64Buffer = ByteBuffer(bytes: uint64Bytes)
XCTAssertEqual(UInt64(buffer: uint64Buffer), 0x0102030405060708)
XCTAssertEqual(Int64(buffer: uint64Buffer), 0x0102030405060708)
}
}

// MARK: - DispatchData init
extension ByteBufferTest {

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