684b7a999f
* Dump: Use mholt/archive/v3 to support tar including many compressions Signed-off-by: Philipp Homann <homann.philipp@googlemail.com> * Dump: Allow dump output to stdout Signed-off-by: Philipp Homann <homann.philipp@googlemail.com> * Dump: Fixed bug present since #6677 where SessionConfig.Provider is never "file" Signed-off-by: Philipp Homann <homann.philipp@googlemail.com> * Dump: never pack RepoRootPath, LFS.ContentPath and LogRootPath when they are below AppDataPath Signed-off-by: Philipp Homann <homann.philipp@googlemail.com> * Dump: also dump LFS (fixes #10058) Signed-off-by: Philipp Homann <homann.philipp@googlemail.com> * Dump: never dump CustomPath if CustomPath is a subdir of or equal to AppDataPath (fixes #10365) Signed-off-by: Philipp Homann <homann.philipp@googlemail.com> * Use log.Info instead of fmt.Fprintf Signed-off-by: Philipp Homann <homann.philipp@googlemail.com> * import ordering * make fmt Co-authored-by: zeripath <art27@cantab.net> Co-authored-by: techknowlogick <techknowlogick@gitea.io> Co-authored-by: Matti R <matti@mdranta.net>
108 lines
2.8 KiB
Go
108 lines
2.8 KiB
Go
// Copyright 2015, Joe Tsai. All rights reserved.
|
|
// Use of this source code is governed by a BSD-style
|
|
// license that can be found in the LICENSE.md file.
|
|
|
|
// Package internal is a collection of common compression algorithms.
|
|
//
|
|
// For performance reasons, these packages lack strong error checking and
|
|
// require that the caller to ensure that strict invariants are kept.
|
|
package internal
|
|
|
|
var (
|
|
// IdentityLUT returns the input key itself.
|
|
IdentityLUT = func() (lut [256]byte) {
|
|
for i := range lut {
|
|
lut[i] = uint8(i)
|
|
}
|
|
return lut
|
|
}()
|
|
|
|
// ReverseLUT returns the input key with its bits reversed.
|
|
ReverseLUT = func() (lut [256]byte) {
|
|
for i := range lut {
|
|
b := uint8(i)
|
|
b = (b&0xaa)>>1 | (b&0x55)<<1
|
|
b = (b&0xcc)>>2 | (b&0x33)<<2
|
|
b = (b&0xf0)>>4 | (b&0x0f)<<4
|
|
lut[i] = b
|
|
}
|
|
return lut
|
|
}()
|
|
)
|
|
|
|
// ReverseUint32 reverses all bits of v.
|
|
func ReverseUint32(v uint32) (x uint32) {
|
|
x |= uint32(ReverseLUT[byte(v>>0)]) << 24
|
|
x |= uint32(ReverseLUT[byte(v>>8)]) << 16
|
|
x |= uint32(ReverseLUT[byte(v>>16)]) << 8
|
|
x |= uint32(ReverseLUT[byte(v>>24)]) << 0
|
|
return x
|
|
}
|
|
|
|
// ReverseUint32N reverses the lower n bits of v.
|
|
func ReverseUint32N(v uint32, n uint) (x uint32) {
|
|
return ReverseUint32(v << (32 - n))
|
|
}
|
|
|
|
// ReverseUint64 reverses all bits of v.
|
|
func ReverseUint64(v uint64) (x uint64) {
|
|
x |= uint64(ReverseLUT[byte(v>>0)]) << 56
|
|
x |= uint64(ReverseLUT[byte(v>>8)]) << 48
|
|
x |= uint64(ReverseLUT[byte(v>>16)]) << 40
|
|
x |= uint64(ReverseLUT[byte(v>>24)]) << 32
|
|
x |= uint64(ReverseLUT[byte(v>>32)]) << 24
|
|
x |= uint64(ReverseLUT[byte(v>>40)]) << 16
|
|
x |= uint64(ReverseLUT[byte(v>>48)]) << 8
|
|
x |= uint64(ReverseLUT[byte(v>>56)]) << 0
|
|
return x
|
|
}
|
|
|
|
// ReverseUint64N reverses the lower n bits of v.
|
|
func ReverseUint64N(v uint64, n uint) (x uint64) {
|
|
return ReverseUint64(v << (64 - n))
|
|
}
|
|
|
|
// MoveToFront is a data structure that allows for more efficient move-to-front
|
|
// transformations. This specific implementation assumes that the alphabet is
|
|
// densely packed within 0..255.
|
|
type MoveToFront struct {
|
|
dict [256]uint8 // Mapping from indexes to values
|
|
tail int // Number of tail bytes that are already ordered
|
|
}
|
|
|
|
func (m *MoveToFront) Encode(vals []uint8) {
|
|
copy(m.dict[:], IdentityLUT[:256-m.tail]) // Reset dict to be identity
|
|
|
|
var max int
|
|
for i, val := range vals {
|
|
var idx uint8 // Reverse lookup idx in dict
|
|
for di, dv := range m.dict {
|
|
if dv == val {
|
|
idx = uint8(di)
|
|
break
|
|
}
|
|
}
|
|
vals[i] = idx
|
|
|
|
max |= int(idx)
|
|
copy(m.dict[1:], m.dict[:idx])
|
|
m.dict[0] = val
|
|
}
|
|
m.tail = 256 - max - 1
|
|
}
|
|
|
|
func (m *MoveToFront) Decode(idxs []uint8) {
|
|
copy(m.dict[:], IdentityLUT[:256-m.tail]) // Reset dict to be identity
|
|
|
|
var max int
|
|
for i, idx := range idxs {
|
|
val := m.dict[idx] // Forward lookup val in dict
|
|
idxs[i] = val
|
|
|
|
max |= int(idx)
|
|
copy(m.dict[1:], m.dict[:idx])
|
|
m.dict[0] = val
|
|
}
|
|
m.tail = 256 - max - 1
|
|
}
|