github.com/apache/arrow/go/v7@v7.0.1/parquet/internal/hashing/xxh3_memo_table.gen.go.tmpl

// Licensed to the Apache Software Foundation (ASF) under one
// or more contributor license agreements.  See the NOTICE file
// distributed with this work for additional information
// regarding copyright ownership.  The ASF licenses this file
// to you under the Apache License, Version 2.0 (the
// "License"); you may not use this file except in compliance
// with the License.  You may obtain a copy of the License at
//
// http://www.apache.org/licenses/LICENSE-2.0
//
// Unless required by applicable law or agreed to in writing, software
// distributed under the License is distributed on an "AS IS" BASIS,
// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
// See the License for the specific language governing permissions and
// limitations under the License.

package hashing

import (
  "github.com/apache/arrow/go/v7/arrow/bitutil"
  "github.com/apache/arrow/go/v7/parquet/internal/utils"
)

{{range .In}}
type payload{{.Name}} struct {
	val     {{.name}}
	memoIdx int32
}

type entry{{.Name}} struct {
	h       uint64
	payload payload{{.Name}}
}

func (e entry{{.Name}}) Valid() bool { return e.h != sentinel }

// {{.Name}}HashTable is a hashtable specifically for {{.name}} that
// is utilized with the MemoTable to generalize interactions for easier
// implementation of dictionaries without losing performance.
type {{.Name}}HashTable struct {
	cap     uint64
	capMask uint64
	size    uint64

	entries []entry{{.Name}}
}

// New{{.Name}}HashTable returns a new hash table for {{.name}} values
// initialized with the passed in capacity or 32 whichever is larger.
func New{{.Name}}HashTable(cap uint64) *{{.Name}}HashTable {
	initCap := uint64(bitutil.NextPowerOf2(int(max(cap, 32))))
	ret := &{{.Name}}HashTable{cap: initCap, capMask: initCap - 1, size: 0}
	ret.entries = make([]entry{{.Name}}, initCap)
	return ret
}

// Reset drops all of the values in this hash table and re-initializes it
// with the specified initial capacity as if by calling New, but without having
// to reallocate the object.
func (h *{{.Name}}HashTable) Reset(cap uint64) {
	h.cap = uint64(bitutil.NextPowerOf2(int(max(cap, 32))))
	h.capMask = h.cap - 1
	h.size = 0
	h.entries = make([]entry{{.Name}}, h.cap)
}

// CopyValues is used for copying the values out of the hash table into the
// passed in slice, in the order that they were first inserted
func (h *{{.Name}}HashTable) CopyValues(out []{{.name}}) {
  h.CopyValuesSubset(0, out)
}

// CopyValuesSubset copies a subset of the values in the hashtable out, starting
// with the value at start, in the order that they were inserted.
func (h *{{.Name}}HashTable) CopyValuesSubset(start int, out []{{.name}}) {
  h.VisitEntries(func(e *entry{{.Name}}) {
    idx := e.payload.memoIdx - int32(start)
    if idx >= 0 {
      out[idx] = e.payload.val
    }
  })
}

func (h *{{.Name}}HashTable) WriteOut(out []byte) {
  h.WriteOutSubset(0, out)
}

func (h *{{.Name}}HashTable) WriteOutSubset(start int, out []byte) {
  data := arrow.{{.Name}}Traits.CastFromBytes(out)
  h.VisitEntries(func(e *entry{{.Name}}) {
    idx := e.payload.memoIdx - int32(start)
    if idx >= 0 {
      data[idx] = utils.ToLE{{.Name}}(e.payload.val)
    }
  })
}

func (h *{{.Name}}HashTable) needUpsize() bool { return h.size*uint64(loadFactor) >= h.cap }

func ({{.Name}}HashTable) fixHash(v uint64) uint64 {
	if v == sentinel {
		return 42
	}
	return v
}

// Lookup retrieves the entry for a given hash value assuming it's payload value returns
// true when passed to the cmp func. Returns a pointer to the entry for the given hash value,
// and a boolean as to whether it was found. It is not safe to use the pointer if the bool is false.
func (h *{{.Name}}HashTable) Lookup(v uint64, cmp func({{.name}}) bool) (*entry{{.Name}}, bool) {
	idx, ok := h.lookup(v, h.capMask, cmp)
	return &h.entries[idx], ok
}

func (h *{{.Name}}HashTable) lookup(v uint64, szMask uint64, cmp func({{.name}}) bool) (uint64, bool) {
	const perturbShift uint8 = 5

	var (
		idx     uint64
		perturb uint64
		e       *entry{{.Name}}
	)

	v = h.fixHash(v)
	idx = v & szMask
	perturb = (v >> uint64(perturbShift)) + 1

	for {
		e = &h.entries[idx]
		if e.h == v && cmp(e.payload.val) {
			return idx, true
		}

		if e.h == sentinel {
			return idx, false
		}

		// perturbation logic inspired from CPython's set/dict object
		// the goal is that all 64 bits of unmasked hash value eventually
		// participate int he probing sequence, to minimize clustering
		idx = (idx + perturb) & szMask
		perturb = (perturb >> uint64(perturbShift)) + 1
	}
}

func (h *{{.Name}}HashTable) upsize(newcap uint64) error {
	newMask := newcap - 1

	oldEntries := h.entries
	h.entries = make([]entry{{.Name}}, newcap)
	for _, e := range oldEntries {
		if e.Valid() {
			idx, _ := h.lookup(e.h, newMask, func({{.name}}) bool { return false })
			h.entries[idx] = e
		}
	}
	h.cap = newcap
	h.capMask = newMask
	return nil
}

// Insert updates the given entry with the provided hash value, payload value and memo index.
// The entry pointer must have been retrieved via lookup in order to actually insert properly.
func (h *{{.Name}}HashTable) Insert(e *entry{{.Name}}, v uint64, val {{.name}}, memoIdx int32) error {
	e.h = h.fixHash(v)
	e.payload.val = val
	e.payload.memoIdx = memoIdx
	h.size++

	if h.needUpsize() {
		h.upsize(h.cap * uint64(loadFactor) * 2)
	}
	return nil
}

// VisitEntries will call the passed in function on each *valid* entry in the hash table,
// a valid entry being one which has had a value inserted into it.
func (h *{{.Name}}HashTable) VisitEntries(visit func(*entry{{.Name}})) {
	for _, e := range h.entries {
		if e.Valid() {
			visit(&e)
		}
	}
}

// {{.Name}}MemoTable is a wrapper over the appropriate hashtable to provide an interface
// conforming to the MemoTable interface defined in the encoding package for general interactions
// regarding dictionaries.
type {{.Name}}MemoTable struct {
  tbl *{{.Name}}HashTable
  nullIdx int32
}

// New{{.Name}}MemoTable returns a new memotable with num entries pre-allocated to reduce further
// allocations when inserting.
func New{{.Name}}MemoTable(num int64) *{{.Name}}MemoTable {
  return &{{.Name}}MemoTable{tbl: New{{.Name}}HashTable(uint64(num)), nullIdx: KeyNotFound}
}

// Reset allows this table to be re-used by dumping all the data currently in the table.
func (s *{{.Name}}MemoTable) Reset() {
  s.tbl.Reset(32)
  s.nullIdx = KeyNotFound
}

// Size returns the current number of inserted elements into the table including if a null
// has been inserted.
func (s *{{.Name}}MemoTable) Size() int {
  sz := int(s.tbl.size)
  if _, ok := s.GetNull(); ok {
    sz++
  }
  return sz
}

// GetNull returns the index of an inserted null or KeyNotFound along with a bool
// that will be true if found and false if not.
func (s *{{.Name}}MemoTable) GetNull() (int, bool) {
  return int(s.nullIdx), s.nullIdx != KeyNotFound
}

// GetOrInsertNull will return the index of the null entry or insert a null entry
// if one currently doesn't exist. The found value will be true if there was already
// a null in the table, and false if it inserted one.
func (s *{{.Name}}MemoTable) GetOrInsertNull() (idx int, found bool) {
  idx, found = s.GetNull()
  if !found {
    idx = s.Size()
    s.nullIdx = int32(idx)
  }
  return
}

// CopyValues will copy the values from the memo table out into the passed in slice
// which must be of the appropriate type.
func (s *{{.Name}}MemoTable) CopyValues(out interface{}) {
  s.CopyValuesSubset(0, out)
}

// CopyValuesSubset is like CopyValues but only copies a subset of values starting
// at the provided start index
func (s *{{.Name}}MemoTable) CopyValuesSubset(start int, out interface{}) {
  s.tbl.CopyValuesSubset(start, out.([]{{.name}}))
}

func (s *{{.Name}}MemoTable) WriteOut(out []byte) {
  s.tbl.WriteOut(out)
}

func (s *{{.Name}}MemoTable) WriteOutSubset(start int, out []byte) {
  s.tbl.WriteOutSubset(start, out)
}

// Get returns the index of the requested value in the hash table or KeyNotFound
// along with a boolean indicating if it was found or not.
func (s *{{.Name}}MemoTable) Get(val interface{}) (int, bool) {
{{if or (eq .Name "Int32") (eq .Name "Int64") }}
  h := hashInt(uint64(val.({{.name}})), 0)
  if e, ok := s.tbl.Lookup(h, func(v {{.name}}) bool { return val.({{.name}}) == v }); ok {
{{ else -}}
  var cmp func({{.name}}) bool
  {{if eq .Name "Float32"}}
  if math.IsNaN(float64(val.(float32))) {
    cmp = isNan32Cmp
    // use consistent internal bit pattern for NaN regardless of the pattern
    // that is passed to us. NaN is NaN is NaN
    val = float32(math.NaN())
  {{ else -}}
  if math.IsNaN(val.(float64)) {
    cmp = math.IsNaN
    // use consistent internal bit pattern for NaN regardless of the pattern
    // that is passed to us. NaN is NaN is NaN
    val = math.NaN()
  {{end -}}
  } else {
    cmp = func(v {{.name}}) bool { return val.({{.name}}) == v }
  }

  h := hash{{.Name}}(val.({{.name}}), 0)  
  if e, ok := s.tbl.Lookup(h, cmp); ok {
{{ end -}}
    return int(e.payload.memoIdx), ok
  }
  return KeyNotFound, false
}

// GetOrInsert will return the index of the specified value in the table, or insert the
// value into the table and return the new index. found indicates whether or not it already
// existed in the table (true) or was inserted by this call (false).
func (s *{{.Name}}MemoTable) GetOrInsert(val interface{}) (idx int, found bool, err error) {
  {{if or (eq .Name "Int32") (eq .Name "Int64") }}
  h := hashInt(uint64(val.({{.name}})), 0)
  e, ok := s.tbl.Lookup(h, func(v {{.name}}) bool {
    return val.({{.name}}) == v
  })
{{ else }}  
  var cmp func({{.name}}) bool
  {{if eq .Name "Float32"}}
  if math.IsNaN(float64(val.(float32))) {
    cmp = isNan32Cmp
    // use consistent internal bit pattern for NaN regardless of the pattern
    // that is passed to us. NaN is NaN is NaN
    val = float32(math.NaN()) 
  {{ else -}}
  if math.IsNaN(val.(float64)) {  
    cmp = math.IsNaN
    // use consistent internal bit pattern for NaN regardless of the pattern
    // that is passed to us. NaN is NaN is NaN
    val = math.NaN()
  {{end -}}
  } else {
    cmp = func(v {{.name}}) bool { return val.({{.name}}) == v }
  }
  
  h := hash{{.Name}}(val.({{.name}}), 0)
  e, ok := s.tbl.Lookup(h, cmp)
{{ end }}
  if ok {
    idx = int(e.payload.memoIdx)
    found = true
  } else {
    idx = s.Size()
    s.tbl.Insert(e, h, val.({{.name}}), int32(idx))
  }
  return
}
{{end}}