| 摘要 |
In an electronic mail system comprising a local computer that can be connected to a message server over a data link, mechanisms are provided to convert large identification codes used by the message server to store and access messages and folders into shorter identification codes used by the local computer to access locally stored copies of the messages or folders. The large server identification codes, including a 46-byte folder codes and 70-byte message codes, are converted using a conversion technique that operates in one of two modes, depending on whether the data link to a master conversion map on the message server is available and operative. In the first mode, to convert the codes to 8-byte codes, the technique uses a local cache that retains mapping information produced in conversions using the master conversion map. In the second mode, three types of local maps are implemented as B-trees are used to convert the codes first to the 8-byte codes and then to 4-byte codes. In a reverse conversion using one of the B-tree maps, a 4-byte code is converted back to a 46 or 70-byte code.
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