read (11 of 12 overloads)

Attempt to read a certain amount of data from a stream before returning.

template<
    typename SyncReadStream,
    typename Allocator,
    typename CompletionCondition>
std::size_t read(
    SyncReadStream & s,
    basic_streambuf< Allocator > & b,
    CompletionCondition completion_condition);

This function is used to read a certain number of bytes of data from a stream. The call will block until one of the following conditions is true:

The supplied buffer is full (that is, it has reached maximum size).
The completion_condition function object returns 0.

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

Parameters

s

The stream from which the data is to be read. The type must support the SyncReadStream concept.

b

The basic_streambuf object into which the data will be read.

completion_condition

The function object to be called to determine whether the read operation is complete. The signature of the function object must be:

std::size_t completion_condition(
  // Result of latest read_some operation.
  const boost::system::error_code& error,

  // Number of bytes transferred so far.
  std::size_t bytes_transferred
);

A return value of 0 indicates that the read operation is complete. A non-zero return value indicates the maximum number of bytes to be read on the next call to the stream's read_some function.

Return Value

The number of bytes transferred.

Exceptions

boost::system::system_error: Thrown on failure.