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Stream descriptor service requirements

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 30. 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.



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