C struct handling for Swift

Class for packing and unpacking C structs in Swift, modeled after the struct module in Python.

Sample Code

import MVPCStruct

// Receiver expects a message with a header like this:
//  typedef struct {
//      uint16_t version;  // Message format version, currently 0x0100.
//      uint16_t reserved; // Reserved for future use.
//      uint32_t length;   // Length of data in bytes.
//      uint8_t data[];    // Binary encoded plist.
//  } __attribute__((packed)) mma_msg_t;
func sendMessageHeader(msgData: NSData) -> Bool {
    var error: NSError?
    
    let version = 0x0100
    let reserved = 0
    
    let packer = CStruct(format: "=HHI")
    if let packedHeader = packer.pack([version, reserved, msgData.length], error: &error) {
        return 8 == send(socket_fd, packedHeader.bytes, packedHeader.length)
    } else {
        return false
    }
}

Tasks

Creating CStruct Objects

- initWithFormat:

init(format: String)

Unpacking data

- unpack:format:error:

func unpack(data: NSData, format: String, error: NSErrorPointer) -> AnyObject[]?

- unpack:error:

func unpack(data: NSData, error: NSErrorPointer) -> AnyObject[]?

Packing values

- pack:format:error:

func pack(values: AnyObject[], format: String, error: NSErrorPointer) -> NSData?

- pack:error:

func pack(values: AnyObject[], error: NSErrorPointer) -> NSData? {

Format strings

Control characters

	BYTE ORDER	SIZE	ALIGNMENT
@	native	native	native
=	native	standard	none
<	little-endian	standard	none
>	big-endian	standard	none
!	network (BE)	standard	none

Format characters

FORMAT	C TYPE	SWIFT TYPE	SIZE
x	pad byte	no value
c	char	String of length 1	1
b	signed char	Int	1
B	unsigned char	UInt	1
?	_Bool	Bool	1
h	short	Int	2
H	unsigned short	UInt	2
i	int	Int	4
I	unsigned int	UInt	4
l	long	Int	4
L	unsigned long	UInt	4
q	long long	Int	8
Q	unsigned long long	UInt	8
f	float	Float	4
d	double	Double	8
s	char[]	String
p	char[]	String
P	void *	UInt	4/8