A stream descriptor service must meet the requirements for a descriptor
service, as well as the additional requirements listed below.
In the table below, X denotes
a stream descriptor service class, a
denotes a value of type X,
b denotes a value of type
X::implementation_type, ec
denotes a value of type error_code,
mb denotes a value satisfying
mutable buffer sequence
requirements, rh denotes
a value meeting ReadHandler requirements, cb denotes a value satisfying constant
buffer sequence requirements, and wh
denotes a value meeting WriteHandler requirements.
Table 33. StreamDescriptorService requirements
|
expression
|
return type
|
assertion/note
pre/post-condition
|
|
a.read_some(b,
mb,
ec);
|
size_t
|
pre: a.is_open(b).
Reads one or more bytes of data from a descriptor b.
The mutable buffer
sequence mb specifies
memory where the data should be placed. The operation shall always
fill a buffer in the sequence completely before proceeding to the
next.
If successful, returns the number of bytes read.
Otherwise returns 0.
If the total size of all buffers in the sequence mb is 0,
the function shall return 0
immediately.
If the operation completes due to graceful
connection closure by the peer, the operation shall fail with
error::eof.
|
|
a.async_read_some(b,
mb,
rh);
|
void
|
pre: a.is_open(b).
Initiates an asynchronous operation to read one or more
bytes of data from a descriptor b.
The operation is performed via the io_service
object a.get_io_service()
and behaves according to asynchronous
operation requirements.
The mutable buffer
sequence mb specifies
memory where the data should be placed. The operation shall always
fill a buffer in the sequence completely before proceeding to the
next.
The implementation shall maintain one or more
copies of mb until
such time as the read operation no longer requires access to the
memory specified by the buffers in the sequence. The program must
ensure the memory is valid until:
— the last copy of
mb is destroyed,
or
— the handler for the asynchronous operation is invoked,
whichever comes first. If the total size of all buffers
in the sequence mb
is 0, the asynchronous
read operation shall complete immediately and pass 0 as the argument to the handler
that specifies the number of bytes read.
If the operation
completes due to graceful connection closure by the peer, the operation
shall fail with error::eof.
If the operation completes successfully, the ReadHandler object rh is invoked with the number
of bytes transferred. Otherwise it is invoked with 0.
|
|
a.write_some(b,
cb,
ec);
|
size_t
|
pre: a.is_open(b).
Writes one or more bytes of data to a descriptor b.
The constant
buffer sequence cb
specifies memory where the data to be written is located. The operation
shall always write a buffer in the sequence completely before proceeding
to the next.
If successful, returns the number of
bytes written. Otherwise returns 0.
If the total size of all buffers in the sequence cb is 0,
the function shall return 0
immediately.
|
|
a.async_write_some(b,
cb,
wh);
|
void
|
pre: a.is_open(b).
Initiates an asynchronous operation to write one or more
bytes of data to a descriptor b.
The operation is performed via the io_service
object a.get_io_service()
and behaves according to asynchronous
operation requirements.
The constant buffer
sequence cb specifies
memory where the data to be written is located. The operation shall
always write a buffer in the sequence completely before proceeding
to the next.
The implementation shall maintain one
or more copies of cb
until such time as the write operation no longer requires access
to the memory specified by the buffers in the sequence. The program
must ensure the memory is valid until:
— the last copy
of cb is destroyed,
or
— the handler for the asynchronous operation is invoked,
whichever comes first. If the total size of all buffers
in the sequence cb
is 0, the asynchronous
operation shall complete immediately and pass 0
as the argument to the handler that specifies the number of bytes
read.
If the operation completes successfully, the
WriteHandler object
wh is invoked with
the number of bytes transferred. Otherwise it is invoked with
0.
|
