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! Copyright (C) 2018 Alexander Ilin.
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! See http://factorcode.org/license.txt for BSD license.
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USING: checksums checksums.common checksums.md5 checksums.sha
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destructors help.markup help.syntax kernel sequences ;
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IN: checksums.multi
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ABOUT: "checksums.multi"
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ARTICLE: "checksums.multi" "Checksumming with Multiple Algorithms"
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"The " { $vocab-link "checksums.multi" } " vocabulary makes it possible to calculate multiple checksums with just one pass over a data stream."
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$nl
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"The " { $link multi-checksum } " tuple holds a sequence of " { $link block-checksum } " instances, such as " { $link md5 } " or " { $link sha1 } ". When the " { $link initialize-checksum-state } " method is called on it, a new instance of " { $link block-checksum-state } " is created for all the " { $slot "checksums" } ", and returned as a new " { $link multi-state } " instance. You can then use " { $link add-checksum-bytes } " to stream data to it. When done, call " { $link get-checksum } " to finalize the process, read the resulting checksums and dispose of the tuple in one step. If you want to cancel the work without calling " { $link get-checksum } ", you must " { $link dispose } " of the tuple so that all implementation-specific resources are released."
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$nl
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"The " { $link checksum-bytes } " and the " { $link checksum-stream } " methods encapsulate the above protocol, including instantiation and disposal of the " { $link multi-state } " tuple."
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{ $examples
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{ $unchecked-example "USING: byte-arrays checksums checksums.md5 checksums.sha ;"
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"\"test\" >byte-array { md5 sha1 } <multi-checksum> checksum-bytes ."
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"{
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B{
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9 143 107 205 70 33 211 115 202 222 78 131 38 39 180 246
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}
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B{
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169 74 143 229 204 177 155 166 28 76 8 115 211 145 233
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135 152 47 187 211
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}
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}" }
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$nl
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{ $unchecked-example "USING: checksums checksums.common checksums.md5 checksums.sha"
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"io io.encodings.binary namespaces ;"
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"\"LICENSE.txt\" binary ["
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" input-stream get { md5 sha1 } <multi-checksum> checksum-stream"
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"] with-file-reader ."
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"{
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B{
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220 158 207 218 50 163 198 36 234 90 122 65 197 14 224
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16
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}
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B{
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132 132 148 224 101 202 198 114 38 53 127 18 70 170 108
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53 25 255 174 207
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}
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}" }
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} ;
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HELP: <multi-checksum>
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{ $values
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{ "checksums" sequence }
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{ "multi-checksum" multi-checksum }
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}
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{ $description "This is a simple constructor for the " { $link multi-checksum } " tuple. The " { $snippet "checksums" } " must be a sequence of " { $link block-checksum } " instances." } ;
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HELP: multi-checksum
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{ $class-description "This is an instance of the " { $link block-checksum } " mixin. It calculates multiple checksums by sequentially passing the data it receives to all the checksums in its " { $slot "checksums" } " slot. This way, even though the individual checksums are not calculated in parallel, you still can have the performance benefits of only reading a disk file once, or not having to temporarily store the data streamed from a network." } ;
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HELP: multi-state
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{ $class-description "This class represents the current state of a " { $link multi-checksum } " checksum calculation. It has an array of associated checksum states until it is disposed. You may call " { $link add-checksum-bytes } " multiple times to pipe data to all the checksums in the " { $slot "checksums" } " slot. When finished, call " { $link get-checksum } " to receive the results and release implementation-specific resources, or " { $link dispose } " to release the resources and discard the result. After the first " { $link get-checksum } " call the returned value is stored in the " { $slot "results" } " slot, and subsequent calls return the same value." }
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{ $notes "It is not possible to add more data to the checksum after the first " { $link get-checksum } " call."
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$nl
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"Most code should use " { $link with-checksum-state } " to make sure the resources are properly disposed of. Higher level words like " { $link checksum-bytes } " and " { $link checksum-stream } " use it to perform the disposal." } ;
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{ multi-checksum multi-state } related-words
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Alexander Iljin
John Benediktsson