read_at (6 of 8 overloads)

Attempt to read a certain amount of data at the specified offset before returning.

template<
    typename SyncRandomAccessReadDevice,
    typename Allocator>
std::size_t read_at(
    SyncRandomAccessReadDevice & d,
    uint64_t offset,
    basic_streambuf< Allocator > & b,
    boost::system::error_code & ec);

This function is used to read a certain number of bytes of data from a random access device at the specified offset. The call will block until one of the following conditions is true:

An error occurred.

This operation is implemented in terms of zero or more calls to the device's read_some_at function.

Parameters

d: The device from which the data is to be read. The type must support the SyncRandomAccessReadDevice concept.
offset: The offset at which the data will be read.
b: The basic_streambuf object into which the data will be read.
ec: Set to indicate what error occurred, if any.

Return Value

The number of bytes transferred.

Remarks

This overload is equivalent to calling:

boost::asio::read_at(
   d, 42, b,
   boost::asio::transfer_all(), ec);