.\" -*-nroff-*-
.\"
.\" Manual for memory alignment
.\"
.\" (c) 2009, 2024 Straylight/Edgeware
.\"
.
.\"----- Licensing notice ---------------------------------------------------
.\"
.\" This file is part of the mLib utilities library.
.\"
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.\" the terms of the GNU Library General Public License as published by
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.
.\"--------------------------------------------------------------------------
.so ../defs.man \" @@@PRE@@@
.
.\"--------------------------------------------------------------------------
.TH align 3mLib "4 January 2009" "Straylight/Edgeware" "mLib utilities library"
.\" @ALIGN
.\" @ALIGNOF
.
.\"--------------------------------------------------------------------------
.SH NAME
align \- alignment utilities
.
.\"--------------------------------------------------------------------------
.SH SYNOPSIS
.
.nf
.B "#include <mLib/align.h>"
.PP
.B "union align { ...\& };"
.PP
.BI "void ALIGN(size_t &" sz ");"
.BI "size_t ALIGNOF(" type );
.fi
.
.\"--------------------------------------------------------------------------
.SH DESCRIPTION
.
The
.B "union align"
type is (a reasonable guess at) a type with the
implementation's most restrictive alignment requirements;
i.e., if a pointer is suitably aligned for
.B "union align"
value,
then it should be suitably aligned for any other value too.
.PP
The
.B ALIGNOF
macro returns the alignment required for the given
.IR type ;
i.e., if an address is suitably aligned for a
.I type
value if and only if it is a multiple of
.BR ALIGNOF( type ) \fR.
.PP
The
.B ALIGN
macro rounds its argument
.I sz
up to the next multiple of
.BR "ALIGNOF(union align)" :
so, if
.I sz
is an offset from the start of a suitably aligned chunk of memory,
e.g., returned by
.BR malloc (3),
then
.BI ALIGN( sz )
adjusts
.I sz
in place, including additional padding
so that the new offset is also suitably aligned.
The intent is to assist with writing fairly portable memory allocators,
which must return correctly-aligned memory.
.
.\"--------------------------------------------------------------------------
.SH "SEE ALSO"
.
.BR mLib (3).
.
.\"--------------------------------------------------------------------------
.SH "AUTHOR"
.
Mark Wooding, <mdw@distorted.org.uk>
.
.\"----- That's all, folks --------------------------------------------------