File download is done by a GET request to a URL from the FILE_INFO element. The file offset, if any, is given in Range: attribute of the HTTP header.
File upload is done using POST operations to a CGI program. A security mechanism prevents unauthorized upload of large amounts of data to the server. Two RPC operations are used.
1) Get file size
The request message has the form:
", htmlspecialchars("
1
1
filename
"), "
The reply message has the form:
", htmlspecialchars("
x
[ text
| nbytes ]
"), "
Status is";
list_start();
list_item("0", "Success. Nbytes is 0 if the file doesn't exist.");
list_item("1", "Transient error.
The client should try another data server, or try this one later.
");
list_item("-1", "Permanent error. The client should give up on the result.");
list_end();
echo "
In the error cases, the <file_size> element is omitted
and the <message> element gives an explanation.
2) Upload file
Request message format:
", htmlspecialchars("
1
1
...
...
x
x
... (nbytes bytes of data; may include non-ASCII data)
(no closing tags)
"), "
The <file_info> element is the exact text sent from the scheduling server to the client. It includes a signature based on the project's file upload authentication key pair. <nbytes> is the size of the file. <offset> is the offset within the file.
Reply message format:
", htmlspecialchars("
x
text
"), "
Status is ";
list_start();
list_item("0", "success");
list_item("1", "transient error;
The client should try another data server, or try this one later.
");
list_item("-1", "Permanent error.
The client should give up on the result.
");
list_end();
echo "
In the error cases, the <message> element gives an explanation.
TODO: if there's an error in the header (bad signature, or file is too large) the client should learn this without actually uploading the file. "; page_tail(); ?>