Technotes


Arbitrating the Use of afpMiscUserCommand and afpMiscUserWrite


Technote NW 15September 1992


Written by: Jim Luther September 1992

This Technical Note discusses a scheme for arbitrating the use of the afpMiscUserCommand and afpMiscUserWrite AppleTalk Filing Protocol (AFP) commands.


Inside Macintosh Volume V lists two AFP command codes that are reserved for developers. They are afpMiscUserCommand (call number 191) and afpMiscUserWrite (call number 254). Several developers have asked that Apple arbitrate the use of those two AFP calls. This Technical Note describes our recommended solution.

Because afpMiscUserCommand and afpMiscUserWrite are reserved for developers, the format of the AFP request and reply blocks are undefined except for the first byte of the request block which contains the AFP call number. If the request block is further defined to include a word-aligned long value, that long value can be used to identify a specific developer request. Since most developers have probably already been assigned a unique 4-byte file creator type, we suggest reusing that creator type for the long value. Figure 1 shows the request blocks for afpMiscUserCommand and afpMiscUserWrite with the creator type value. The value of aspMaxCmdSize in the figure is returned by the ASPGetParms function.

Figure 1 afpMiscUserCommand and afpMiscUserWrite Request Blocks With Creator Type Identifier

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