UnsafeMutableRawPointer was introduced in the latest Xcode beta 6. Are there any examples of how to use UnsafeMutableRawPointer? I'm interested in the case where I need to create or decode network data packets where the one byte might indicate the type (int16, int32, cstring, network order, etc.) of the following bytes.
To start, I recommend a close reading of the Swift Evolution proposal, SE-0107 UnsafeRawPointer API.
With regards your specific situation, one option would be to use
load(fromeByteOffset:as:)Just FYI, I long ago gave up on the notion of mapping C (or Swift) data structures to network protocol formats; you inevitably end up falling into weird language or platform specific pitfalls. These days I parse network packets byte-by-byte. Swift’s ability to do low-if-not-zero-cost abstractions makes this quite palatable. I’ve pasted an example of this at the end of this post.
Share and Enjoy
—
Quinn “The Eskimo!”
Apple Developer Relations, Developer Technical Support, Core OS/Hardware
let myEmail = "eskimo" + "1" + "@apple.com"private class Input {
let bytes: [UInt8]
… lots of other stuff …
func parseUInt16() throws -> UInt16 {
return UInt16(try self.parseUInt(2))
}
func parseUInt32() throws -> UInt32 {
return UInt32(try self.parseUInt(4))
}
func parseUInt(_ size: Int) throws -> UInt64 {
precondition(size > 0)
precondition(size <= 8)
guard self.cursor + size <= limit else {
try self.throwEOF()
}
var accumulator: UInt64 = 0
for i in 0..<size {
let shift = (size - i - 1) * 8
accumulator |= UInt64(self.bytes[self.cursor + i]) << UInt64(shift)
}
self.cursor += size
return accumulator
}
@noreturn func throwEOF() throws {
if self.base == 0 {
throw ParseError.unexpectedOfPacket
} else {
throw ParseError.unexpectedEndOfResource(offset: self.limit, resourceOffset: self.base)
}
}
var base: Int
var cursor: Int
var limit: Int
var atEOF: Bool { return self.cursor == self.limit }
}