NetBSD/share/man/man9/STACK.9

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.\" $NetBSD: STACK.9,v 1.2 2011/04/08 07:55:04 jruoho Exp $
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.\" by Jukka Ruohonen.
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.Dd April 8, 2011
.Dt STACK 9
.Os
.Sh NAME
.Nm STACK
.Nd stack macros
.Sh SYNOPSIS
.In sys/param.h
.Ft type
.Fn STACK_ALLOC "sp" "size"
.Ft type
.Fn STACK_MAX "sp" "size"
.Ft type
.Fn STACK_ALIGN "sp" "bytes"
.Ft type
.Fn STACK_GROW "sp" "size"
.Ft type
.Fn STACK_SHRINK "sp" "size"
.Sh DESCRIPTION
A stack is an area of memory with a fixed origin but with a variable size.
A stack pointer points to the most recently referenced location on the stack.
Initially, when the stack has a size of zero,
the stack pointer points to the origin of the stack.
When data items are added to the stack,
the stack pointer moves away from the origin.
.Pp
The
.Fn STACK_ALLOC
macro returns a pointer to allocated stack space of some
.Fa size .
Given the returned pointer
.Fa sp
and
.Fa size ,
.Fn STACK_MAX
returns the maximum stack address of the allocated stack space.
The
.Fn STACK_ALIGN
macro can be used to align the stack pointer
.Fa sp
by the specified amount of
.Fa bytes .
.Pp
Two basic operations are common to all stacks:
a data item is added
.Pq Dq push
to the location pointed by
.Fa sp
or a data item is removed
.Pq Dq pop
from the stack.
The stack pointer must be subsequently adjusted by the size of the data item.
The
.Fn STACK_GROW
and
.Fn STACK_SHRINK
macros adjust the stack pointer
.Fa sp
by given
.Fa size .
.Pp
A stack may grow either up or down.
The described macros take this into account by using the
.Dv __MACHINE_STACK_GROWS_UP
preprocessor define.
.Sh SEE ALSO
.Xr param 3 ,
.Xr queue 3