Format a line of log the same way as the default callback.
@param line buffer to receive the formatted line;
may be NULL if line_size is 0
@param line_size size of the buffer; at most line_size-1 characters will
be written to the buffer, plus one null terminator
@param print_prefix used to store whether the prefix must be printed;
must point to a persistent integer initially set to 1
@return Returns a negative value if an error occurred, otherwise returns
the number of characters that would have been written for a
sufficiently large buffer, not including the terminating null
character. If the return value is not less than line_size, it means
that the log message was truncated to fit the buffer.
Format a line of log the same way as the default callback. @param line buffer to receive the formatted line; may be NULL if line_size is 0 @param line_size size of the buffer; at most line_size-1 characters will be written to the buffer, plus one null terminator @param print_prefix used to store whether the prefix must be printed; must point to a persistent integer initially set to 1 @return Returns a negative value if an error occurred, otherwise returns the number of characters that would have been written for a sufficiently large buffer, not including the terminating null character. If the return value is not less than line_size, it means that the log message was truncated to fit the buffer.