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Coprocessing Functions |
The
header file
<coproc.h>
must be included (via a
#include
statement) in any compilation that uses the coprocessing feature.
In addition to declaring the coprocessing functions, the header file also
defines certain data types and constants that are needed when coprocesses
are used. These definitions from
<coproc.h>
are as follows:
typedef unsigned coproc_t; /* cocall/coreturn error code */ #define CO_ERR (char *) -2 /* coproc argument values */ #define MAIN 0 #define SELF 1 #define CALLER 2 /* costat return values -- coprocess states */ #define ENDED 0 #define ACTIVE 1 #define BUSY 2 #define IDLE 4 #define STARTING 8
The data type
coproc_t
defines the type of a coprocess identifier. Coprocess IDs
are described in more detail in Coprocess Identifiers.
The value
CO_ERR
is returned by
cocall
and
coreturn
when the requested function cannot be performed. You should avoid passing
this value as an argument to
cocall
or
coreturn
,
because it can be misinterpreted by the paired function as indicating a program
error rather than a correct return value. Note that
NULL
can be used as a
cocall
or
coreturn
argument. This is the recommended way to signify no information.
<coproc.h>
also defines the type
struct costart_parms
, which is a structure containing start-up information
for a coprocess, such as an estimate of the required stack size. The address
of a structure of this type is passed to
costart
when a new coprocess is created. See costart for more information on
the uses for this structure.
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