The Slice compilers can optionally generate checksums of Slice definitions. For slice2py, the --checksum option causes the compiler to generate code that adds checksums to the dictionary Ice.sliceChecksums. The checksums are installed automatically when the Python code is first imported; no action is required by the application.
In order to verify a server's checksums, a client could simply compare the dictionaries using the comparison operator. However, this is not feasible if it is possible that the server might return a superset of the client's checksums. A more general solution is to iterate over the local checksums as demonstrated below:
{zcode:py}
serverChecksums = ...
for i in Ice.sliceChecksums:
if not serverChecksums.has_key(i):
# No match found for type id!
elif Ice.sliceChecksums[i] != serverChecksums[i]:
# Checksum mismatch!
{zcode} |
In this example, the client first verifies that the server's dictionary contains an entry for each Slice type ID, and then it proceeds to compare the checksums.