mirror of
https://github.com/awnumar/memguard.git
synced 2026-02-06 17:59:49 +00:00
64 lines
1.9 KiB
Go
64 lines
1.9 KiB
Go
/*
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Copyright 2019 Awn Umar <awn@spacetime.dev>
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Licensed under the Apache License, Version 2.0 (the "License");
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you may not use this file except in compliance with the License.
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You may obtain a copy of the License at
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http://www.apache.org/licenses/LICENSE-2.0
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Unless required by applicable law or agreed to in writing, software
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distributed under the License is distributed on an "AS IS" BASIS,
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WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
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See the License for the specific language governing permissions and
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limitations under the License.
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*/
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package stream
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import (
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"io"
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"os"
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"github.com/awnumar/memguard"
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)
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// SlowRandByte writes 16KiB of random data to a stream and then operates on it in chunks, returning a random number between 0 and 255.
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func SlowRandByte() byte {
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// Get 16KiB bytes of random data.
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// In the real world we might be reading from a socket instead.
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// Also we are free to write data in arbitrarily sized chunks.
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data := memguard.NewBufferRandom(1024 * 16)
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data.Melt() // Allow mutation so stream writer can wipe source buffer.
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// Create a stream object.
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s := memguard.NewStream() // Implements io.Reader and io.Writer interfaces.
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// Write the data to it.
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_, _ = s.Write(data.Bytes()) // Should never error or write less data.
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data.Destroy() // No longer need the source buffer. (Has been wiped.)
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// Create a buffer to work on this data in chunks.
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buf := memguard.NewBuffer(os.Getpagesize())
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defer buf.Destroy()
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// Read the data back in chunks.
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var parity byte
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for {
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n, err := s.Read(buf.Bytes()) // Reads directly into guarded allocation.
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if err != nil {
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if err == io.EOF {
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break // end of data
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}
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memguard.SafePanic(err) // other error
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}
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// Do some example computation on this data.
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for i := 0; i < n; i++ {
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parity = parity ^ buf.Bytes()[i]
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}
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}
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// Return the result.
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return parity
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}
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