mirror of
https://github.com/superseriousbusiness/gotosocial
synced 2024-12-11 08:06:46 +01:00
74 lines
1.8 KiB
Go
74 lines
1.8 KiB
Go
//go:build !amd64 || appengine || !gc || noasm
|
|
// +build !amd64 appengine !gc noasm
|
|
|
|
package zstd
|
|
|
|
import (
|
|
"errors"
|
|
"fmt"
|
|
)
|
|
|
|
// buildDtable will build the decoding table.
|
|
func (s *fseDecoder) buildDtable() error {
|
|
tableSize := uint32(1 << s.actualTableLog)
|
|
highThreshold := tableSize - 1
|
|
symbolNext := s.stateTable[:256]
|
|
|
|
// Init, lay down lowprob symbols
|
|
{
|
|
for i, v := range s.norm[:s.symbolLen] {
|
|
if v == -1 {
|
|
s.dt[highThreshold].setAddBits(uint8(i))
|
|
highThreshold--
|
|
v = 1
|
|
}
|
|
symbolNext[i] = uint16(v)
|
|
}
|
|
}
|
|
|
|
// Spread symbols
|
|
{
|
|
tableMask := tableSize - 1
|
|
step := tableStep(tableSize)
|
|
position := uint32(0)
|
|
for ss, v := range s.norm[:s.symbolLen] {
|
|
for i := 0; i < int(v); i++ {
|
|
s.dt[position].setAddBits(uint8(ss))
|
|
for {
|
|
// lowprob area
|
|
position = (position + step) & tableMask
|
|
if position <= highThreshold {
|
|
break
|
|
}
|
|
}
|
|
}
|
|
}
|
|
if position != 0 {
|
|
// position must reach all cells once, otherwise normalizedCounter is incorrect
|
|
return errors.New("corrupted input (position != 0)")
|
|
}
|
|
}
|
|
|
|
// Build Decoding table
|
|
{
|
|
tableSize := uint16(1 << s.actualTableLog)
|
|
for u, v := range s.dt[:tableSize] {
|
|
symbol := v.addBits()
|
|
nextState := symbolNext[symbol]
|
|
symbolNext[symbol] = nextState + 1
|
|
nBits := s.actualTableLog - byte(highBits(uint32(nextState)))
|
|
s.dt[u&maxTableMask].setNBits(nBits)
|
|
newState := (nextState << nBits) - tableSize
|
|
if newState > tableSize {
|
|
return fmt.Errorf("newState (%d) outside table size (%d)", newState, tableSize)
|
|
}
|
|
if newState == uint16(u) && nBits == 0 {
|
|
// Seems weird that this is possible with nbits > 0.
|
|
return fmt.Errorf("newState (%d) == oldState (%d) and no bits", newState, u)
|
|
}
|
|
s.dt[u&maxTableMask].setNewState(newState)
|
|
}
|
|
}
|
|
return nil
|
|
}
|