Using Fork Commands

AFP provides these fork-level commands:

• FPGetForkParms

• FPSetForkParms

• FPOpenFork

• FPRead and FPReadExt

• FPWrite and FPWriteExt

• FPFlushFork

• FPByteRangeLock and FPByteRangeLockExt

• FPCloseFork

The AFP client uses the FPGetForkParms command to read a fork’s parameters.

The FPSetForkParms command is used to modify a fork’s parameters.

The FPOpenFork command is used to open either fork of an existing file. This command returns an open fork reference number, which is used in subsequent commands for this open fork.

The FPRead and FPReadExt commands are used to read the contents of the fork. The FPReadExt command differs from the FPRead command in that the FPReadExt command is prepared to handle large values that may be returned for volumes greater than 4 GB in size.

The FPWrite and FPWriteExt commands are used to write to a fork. The FPWriteExt command differs from the FPWrite command in that the FPWriteExt command is prepared to handle the large values that are required for writing to volumes greater than 4 GB in size.

The FPFlushFork command is used to request that server write to disk any of the fork’s data that is in the server’s internal buffers.

The FPByteRangeLock and FPByteRangeLockExt commands are used to lock ranges of bytes in the fork. The FPByteRangeLockExt command differs from the FPByteRangeLock command in that the FPByteRangeLockExt command is prepared to handle large values that are required for locking ranges on volumes greater than 4 GB in size. Locks allow multiple users to share a file’s open fork. Locking a range of bytes prevents other AFP clients from reading or writing data within the specified range. If an AFP client locks a byte range, that range is reserved for exclusive manipulation by the client that placed the lock.

The FPCloseFork command is used to close an open fork. This command invalidates the open fork reference number that was assigned when the fork was opened.