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* cleanup/update dependencies * add quickxorhash tests to makefile/ci
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Copyright (C) 2012 by Nick Craig-Wood http://www.craig-wood.com/nick/ | ||
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Permission is hereby granted, free of charge, to any person obtaining a copy | ||
of this software and associated documentation files (the "Software"), to deal | ||
in the Software without restriction, including without limitation the rights | ||
to use, copy, modify, merge, publish, distribute, sublicense, and/or sell | ||
copies of the Software, and to permit persons to whom the Software is | ||
furnished to do so, subject to the following conditions: | ||
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The above copyright notice and this permission notice shall be included in | ||
all copies or substantial portions of the Software. | ||
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THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR | ||
IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY, | ||
FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE | ||
AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER | ||
LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM, | ||
OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN | ||
THE SOFTWARE. | ||
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// Package quickxorhash provides the quickXorHash algorithm which is a | ||
// quick, simple non-cryptographic hash algorithm that works by XORing | ||
// the bytes in a circular-shifting fashion. | ||
// | ||
// It is used by Microsoft Onedrive for Business to hash data. | ||
// | ||
// See: https://docs.microsoft.com/en-us/onedrive/developer/code-snippets/quickxorhash | ||
package quickxorhash | ||
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// This code was ported from the code snippet linked from | ||
// https://docs.microsoft.com/en-us/onedrive/developer/code-snippets/quickxorhash | ||
// Which has the copyright | ||
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// ------------------------------------------------------------------------------ | ||
// Copyright (c) 2016 Microsoft Corporation | ||
// | ||
// Permission is hereby granted, free of charge, to any person obtaining a copy | ||
// of this software and associated documentation files (the "Software"), to deal | ||
// in the Software without restriction, including without limitation the rights | ||
// to use, copy, modify, merge, publish, distribute, sublicense, and/or sell | ||
// copies of the Software, and to permit persons to whom the Software is | ||
// furnished to do so, subject to the following conditions: | ||
// | ||
// The above copyright notice and this permission notice shall be included in | ||
// all copies or substantial portions of the Software. | ||
// | ||
// THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR | ||
// IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY, | ||
// FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE | ||
// AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER | ||
// LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM, | ||
// OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN | ||
// THE SOFTWARE. | ||
// ------------------------------------------------------------------------------ | ||
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import ( | ||
"hash" | ||
) | ||
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const ( | ||
// BlockSize is the preferred size for hashing | ||
BlockSize = 64 | ||
// Size of the output checksum | ||
Size = 20 | ||
bitsInLastCell = 32 | ||
shift = 11 | ||
widthInBits = 8 * Size | ||
dataSize = (widthInBits-1)/64 + 1 | ||
) | ||
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type quickXorHash struct { | ||
data [dataSize]uint64 | ||
lengthSoFar uint64 | ||
shiftSoFar int | ||
} | ||
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// New returns a new hash.Hash computing the quickXorHash checksum. | ||
func New() hash.Hash { | ||
return &quickXorHash{} | ||
} | ||
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// Write (via the embedded io.Writer interface) adds more data to the running hash. | ||
// It never returns an error. | ||
// | ||
// Write writes len(p) bytes from p to the underlying data stream. It returns | ||
// the number of bytes written from p (0 <= n <= len(p)) and any error | ||
// encountered that caused the write to stop early. Write must return a non-nil | ||
// error if it returns n < len(p). Write must not modify the slice data, even | ||
// temporarily. | ||
// | ||
// Implementations must not retain p. | ||
func (q *quickXorHash) Write(p []byte) (n int, err error) { | ||
currentshift := q.shiftSoFar | ||
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// The bitvector where we'll start xoring | ||
vectorArrayIndex := currentshift / 64 | ||
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// The position within the bit vector at which we begin xoring | ||
vectorOffset := currentshift % 64 | ||
iterations := len(p) | ||
if iterations > widthInBits { | ||
iterations = widthInBits | ||
} | ||
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for i := 0; i < iterations; i++ { | ||
isLastCell := vectorArrayIndex == len(q.data)-1 | ||
var bitsInVectorCell int | ||
if isLastCell { | ||
bitsInVectorCell = bitsInLastCell | ||
} else { | ||
bitsInVectorCell = 64 | ||
} | ||
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// There's at least 2 bitvectors before we reach the end of the array | ||
if vectorOffset <= bitsInVectorCell-8 { | ||
for j := i; j < len(p); j += widthInBits { | ||
q.data[vectorArrayIndex] ^= uint64(p[j]) << uint(vectorOffset) | ||
} | ||
} else { | ||
index1 := vectorArrayIndex | ||
var index2 int | ||
if isLastCell { | ||
index2 = 0 | ||
} else { | ||
index2 = vectorArrayIndex + 1 | ||
} | ||
low := byte(bitsInVectorCell - vectorOffset) | ||
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xoredByte := byte(0) | ||
for j := i; j < len(p); j += widthInBits { | ||
xoredByte ^= p[j] | ||
} | ||
q.data[index1] ^= uint64(xoredByte) << uint(vectorOffset) | ||
q.data[index2] ^= uint64(xoredByte) >> low | ||
} | ||
vectorOffset += shift | ||
for vectorOffset >= bitsInVectorCell { | ||
if isLastCell { | ||
vectorArrayIndex = 0 | ||
} else { | ||
vectorArrayIndex = vectorArrayIndex + 1 | ||
} | ||
vectorOffset -= bitsInVectorCell | ||
} | ||
} | ||
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// Update the starting position in a circular shift pattern | ||
q.shiftSoFar = (q.shiftSoFar + shift*(len(p)%widthInBits)) % widthInBits | ||
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q.lengthSoFar += uint64(len(p)) | ||
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return len(p), nil | ||
} | ||
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// Calculate the current checksum | ||
func (q *quickXorHash) checkSum() (h [Size]byte) { | ||
// Output the data as little endian bytes | ||
ph := 0 | ||
for i := 0; i < len(q.data)-1; i++ { | ||
d := q.data[i] | ||
_ = h[ph+7] // bounds check | ||
h[ph+0] = byte(d >> (8 * 0)) | ||
h[ph+1] = byte(d >> (8 * 1)) | ||
h[ph+2] = byte(d >> (8 * 2)) | ||
h[ph+3] = byte(d >> (8 * 3)) | ||
h[ph+4] = byte(d >> (8 * 4)) | ||
h[ph+5] = byte(d >> (8 * 5)) | ||
h[ph+6] = byte(d >> (8 * 6)) | ||
h[ph+7] = byte(d >> (8 * 7)) | ||
ph += 8 | ||
} | ||
// remaining 32 bits | ||
d := q.data[len(q.data)-1] | ||
h[Size-4] = byte(d >> (8 * 0)) | ||
h[Size-3] = byte(d >> (8 * 1)) | ||
h[Size-2] = byte(d >> (8 * 2)) | ||
h[Size-1] = byte(d >> (8 * 3)) | ||
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// XOR the file length with the least significant bits in little endian format | ||
d = q.lengthSoFar | ||
h[Size-8] ^= byte(d >> (8 * 0)) | ||
h[Size-7] ^= byte(d >> (8 * 1)) | ||
h[Size-6] ^= byte(d >> (8 * 2)) | ||
h[Size-5] ^= byte(d >> (8 * 3)) | ||
h[Size-4] ^= byte(d >> (8 * 4)) | ||
h[Size-3] ^= byte(d >> (8 * 5)) | ||
h[Size-2] ^= byte(d >> (8 * 6)) | ||
h[Size-1] ^= byte(d >> (8 * 7)) | ||
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return h | ||
} | ||
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// Sum appends the current hash to b and returns the resulting slice. | ||
// It does not change the underlying hash state. | ||
func (q *quickXorHash) Sum(b []byte) []byte { | ||
hash := q.checkSum() | ||
return append(b, hash[:]...) | ||
} | ||
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// Reset resets the Hash to its initial state. | ||
func (q *quickXorHash) Reset() { | ||
*q = quickXorHash{} | ||
} | ||
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// Size returns the number of bytes Sum will return. | ||
func (q *quickXorHash) Size() int { | ||
return Size | ||
} | ||
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// BlockSize returns the hash's underlying block size. | ||
// The Write method must be able to accept any amount | ||
// of data, but it may operate more efficiently if all writes | ||
// are a multiple of the block size. | ||
func (q *quickXorHash) BlockSize() int { | ||
return BlockSize | ||
} | ||
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// Sum returns the quickXorHash checksum of the data. | ||
func Sum(data []byte) [Size]byte { | ||
var d quickXorHash | ||
_, _ = d.Write(data) | ||
return d.checkSum() | ||
} |
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