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[/
/ Copyright (c) 2003-2015 Christopher M. Kohlhoff (chris at kohlhoff dot com)
/
/ Distributed under the Boost Software License, Version 1.0. (See accompanying
/ file LICENSE_1_0.txt or copy at http://www.boost.org/LICENSE_1_0.txt)
/]
[section:AsyncRandomAccessReadDevice Buffer-oriented asynchronous random-access
read device requirements]
In the table below, `a` denotes an asynchronous random access read device
object, `o` denotes an offset of type `boost::uint64_t`, `mb` denotes an object
satisfying [link boost_asio.reference.MutableBufferSequence mutable buffer sequence]
requirements, and `h` denotes an object satisfying [link
boost_asio.reference.ReadHandler read handler] requirements.
[table Buffer-oriented asynchronous random-access read device requirements
[[operation] [type] [semantics, pre/post-conditions]]
[
[`a.get_io_service();`]
[`io_service&`]
[Returns the `io_service` object through which the `async_read_some_at`
handler `h` will be invoked.]
]
[
[`a.async_read_some_at(o, mb, h);`]
[`void`]
[
Initiates an asynchronous operation to read one or more bytes of data
from the device `a` at the offset `o`. The operation is performed via the
`io_service` object `a.get_io_service()` and behaves according to [link
boost_asio.reference.asynchronous_operations asynchronous operation]
requirements.\n
\n
The mutable buffer sequence `mb` specifies memory where the data should
be placed. The `async_read_some_at` operation shall always fill a buffer
in the sequence completely before proceeding to the next.\n
\n
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:\n
\n
[mdash] the last copy of `mb` is destroyed, or\n
\n
[mdash] the handler for the asynchronous read operation is invoked,\n
\n
whichever comes first.\n
\n
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.
]
]
]
[endsect]
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