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Question
· Jul 17

Is there a way to generate an incremental checksum?

#HL7 #Caché #Ensemble #HealthShare

Hi

Is there a way to generate an MD5 checksum of a file by performing a checksum against the file's parts? We potentially have to process large files and therefore cannot keep the entire file in memory. From what I understand checksum related logic is typically stateful, allowing file data to be passed through sequentially, however it appears cache script offers only stateless functions offering a simple method of generating a single checksum hash from a single string (or stream), correct me if I'm wrong?

Product version: HealthShare 2017.2
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Lee Butcher · Jul 17

Perfect! The source code for that class method is exactly what I need, thank you.

Just for others who have the same problem, you can do the following:

do $System.Encryption.MD5HashInit()
do $System.Encryption.MD5HashUpdate(stream.Read(...)) // Read in each chunk stream
set hash = $System.Encryption.MD5HashFinal()
set checksum = $ZCONVERT(##class(%xsd.hexBinary).LogicalToXSD(hash), "L")

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