pair.h File Reference

It is sometimes useful to return two values from a function. By exploiting the EABI for 64-bit integer values, we can efficiently return two 32-bit values, in ‘C’. More...

#include "stdint.h"

Go to the source code of this file.

Data Structures
union	pair_union_t
	The implementation of a pair. More...
struct	pair_union_t.__unnamed1__

Macros
#define	pair(x, y)   __pair((void*)(x), (void*)(y))
	Create a pair, with automatic casting.

Typedefs
typedef uint64_t	pair_t
	Give a useful name to the return type, indicating it's use.

Functions
static pair_t	__pair (void *x, void *y)
	Create a pair from two generic 32-bit objects.
static void *	fst (pair_t p)
	Return the first component of a pair.
static void *	snd (pair_t p)
	Return the second component of a pair.

Detailed Description

It is sometimes useful to return two values from a function. By exploiting the EABI for 64-bit integer values, we can efficiently return two 32-bit values, in ‘C’.

The returned values are in r0, and r1 respectively. This obviates the need to use pointers to return pairs of values.

Author

Dave Lester (david.nosp@m..r.l.nosp@m.ester.nosp@m.@man.nosp@m.chest.nosp@m.er.a.nosp@m.c.uk)

Copyright

Copyright © Dave Lester and The University of Manchester, 2014. All rights reserved.
SpiNNaker Project
Advanced Processor Technologies Group
School of Computer Science
The University of Manchester
Manchester M13 9PL, UK

Date

27 April, 2014

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Data Structure Documentation

pair_union_t

union pair_union_t

The implementation of a pair.

Data Fields
pair_t	pair	The paired value.
struct pair_union_t.__unnamed1__	__unnamed__

pair_union_t.__unnamed1__

struct pair_union_t.__unnamed1__

Data Fields
void *	lo	Low word of the pair.
void *	hi	High word of the pair.

Function Documentation

__pair()

static pair_t __pair ( void *  x, void *  y  )

inlinestatic

Create a pair from two generic 32-bit objects.

Parameters

[in]	x	is a void* object
[in]	y	is a void* object

Returns

A pair of values as a 64-bit unsigned int (pair_t).

fst()

static void * fst ( pair_t  p )

inlinestatic

Return the first component of a pair.

Parameters

[in]

p

is a pair_t object

Returns

The first component: n.b. this is void*, so will need casting.

snd()

static void * snd ( pair_t  p )

inlinestatic

Return the second component of a pair.

Parameters

[in]

p

is a pair_t object

Returns

The second component: n.b. this is void*, so will need casting.