It is possible to integrate the Multimedia repository with third party imaging systems. Instead of specifying a location as the value in a ServerMediaPath Registry entry, we use the exec extension to specify a server-side program to be executed. For example:
System|Path|ServerMediaPath|exec imagehandler
indicates that a program called imagehandler located on the EMu server is to be used to handle all multimedia requests. The program is required to handle five service types:
get - retrieve a file
Arguments:
get filepathFailed return value:
Status: failedSuccess return value:
Status: successpathtofile
The get service is used to retrieve a file from a third party image store. The filepath argument is the generated directory component for the multimedia record's IRN with the filename appended. The filepath is the resource to be retrieved. To service this request the program must retrieve the resource from its storage area and copy it to a location in the Unix file system (normally /tmp). The full path to the temporary file must be supplied as the pathtofile return value. EMu will then copy the file onto the client machine and delete the temporary file from the server.
It is important to make sure a path to the original image is not passed back as EMu will try and remove it after copying the file to the client.
save - store a file
Arguments:
save filepath tmppathFailed return value:
Status: failedSuccess return value:
Status: successThe save service is used to save a file to the third party image store. The filepath argument is the generated resource name consisting of the multimedia IRN and the filename. The tmppath argument is a path to the file to be saved. The tmppath file is stored on the EMu server (normally in /tmp). Once the image has been copied into the third party storage area, the tmppath file must be removed as EMu does not remove it after the save is complete.
list - list all files for a given multimedia record IRN
Arguments:
list folderFailed return value:
Status: failedSuccess return value:
Status: successfile1file2...The list service is used to list all files associated with a given multimedia record IRN. The folder argument is the generated path name for a given multimedia IRN. For example, IRN 12010 would give a folder of 12/010. It is necessary to build up a list of all the files associated with this folder (or IRN). The files are returned one per line in the data section of the return message.
ping - get the size and modify time for a file
Arguments:
ping filepathFailed return value:
Status: failedSuccess return value:
Status: successLast-modified: unxitimeContent-Length: filesizeinbytesThe ping service is used to get the file size and modify time on a file. The filepath argument is the generated path to the file whose attributes are required. The returned unixtime is the time the file was last modified in seconds since 1 Jan 1970. The filesizeinbytes value is the size of the file in bytes.
remove - delete a file
Arguments:
remove filepathFailed return value:
Status: failedSuccess return value:
Status: successThe remove service is used to remove a file from a third party store. The filepath argument is the generated path to the file to be removed.
When the program is invoked on the server it is passed the service to be provided (namely get, save, list, ping or remove) as its first argument. The program is expected to pass back a status to indicate whether the operation was successful. The status is returned as the header information of the return text. An example return value is:
Status: success (header section)/tmp/filename (data section)Each return document consists of a header section and an optional data section.
Most services are called with a filepath as their argument. The filepath is the part of the directory path that is calculated from the multimedia record IRN with the filename appended. Thus if we have a file file.jpg that is associated with multimedia record IRN 12010, the filepath would be 12/010/file.jpg.
