☜	READ Draft MDC Standard					☞

3.3 Read Command

The Read command may be used to obtain data from a socket.

A Read operation will terminate if any of the following are detected, in the order specified:

• Error condition. $Device reflects the error, $Key is assigned the empty string. The value returned by the Read command is implementation specific.
• Read timeout. $Key is assigned the empty string. The Read command returns data received up to the timeout.
• Read delimiter. $Key is assigned the delimiter string which terminated the Read. The Read command returns data received up to, but not including, the delimiter.
• Fixed-length Read requirements are satisfied. This occurs only after the specified number of characters are received. $Key is assigned the empty string. The Read command returns the characters received.
• For a stream-oriented protocol, when the buffer is empty the Read waits. When there is at least one character, the Read command returns available characters, up to the maximum string length for the implementation. Note that the number of characters returned is not predictable except to be within the range from one to the maximum string length. $Key is assigned the empty string.
• For a message-oriented protocol, when a complete message is received, Read returns the message. $Key is assigned the empty string.

For multi-character I/O delimiters, the possibility exists due to the stream nature of transmissions, that characters which would otherwise match an I/O delimiter may actually be spread across multiple ‘packets’. In the event that the last ‘n’ characters received (n > 0) match a prefix of one or more I/O delimiters, the implementation must determine if any of the additionally expected characters complete the match with the I/O delimiter(s). One implementation would be to internally issue a timed Read. A timeout of this internally issued timed Read does not affect $Test. The time associated with this internal timed Read is implementation specific and is not included in the timeout which may have been optionally specified on the actual Read command.

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Copyright © Examples: 1995-2024 Ed de Moel;
Copyright © Annotations: 2003-2008 Jacquard Systems Research
Copyright © Annotations: 2008-2024 Ed de Moel.

Some specifications are "approved for inclusion in a future standard". Note that the MUMPS Development Committee cannot guarantee that such future standards will indeed be published.

This page most recently updated on 16-Nov-2023, 14:53:28.

For comments, contact Ed de Moel (demoel@jacquardsystems.com)