read (12 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,
    boost::system::error_code & ec);

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.

ec

Set to indicate what error occurred, if any.

Return Value

The number of bytes read. If an error occurs, returns the total number of bytes successfully transferred prior to the error.