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.TH REF 10.2
.SH NAME
Ref, incref, decref \- reference counts
.SH SYNOPSIS
.ta \w'\fLchar* 'u
.PP
.B
int incref(Ref *r)
.PP
.B
int decref(Ref *r)
.SH DESCRIPTION
A
.B Ref
structure holds a reference count for a data structure:
.IP
.EX
typedef struct
struct Ref
{
Lock;
long ref;
} Ref;
.EE
.PP
The reference count proper is found in
.BR ref ;
the
.B Lock
prevents concurrent updates
(see
.IR lock (10.2)).
.PP
.I Incref
atomically increments the reference count
.IR r ,
and returns the new count.
.PP
.I Decref
atomically decrements the reference count
.IR r ,
and returns the new count.
.SH EXAMPLES
Release a structure containing a
.B Ref
on last use.
.IP
.EX
if(decref(s) == 0)
free(s);
.EE
.SH DIAGNOSTICS
.I Decref
will
.IR panic (10.2)
if the count goes negative,
revealing a reference counting bug.
.SH SOURCE
.B /os/port/chan.c
.br
.B /emu/port/chan.c
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