github.com/unigraph-dev/dgraph@v1.1.1-0.20200923154953-8b52b426f765/systest/_customtok/factor/main.go (about)

     1  /*
     2   * Copyright 2017-2018 Dgraph Labs, Inc. and Contributors
     3   *
     4   * Licensed under the Apache License, Version 2.0 (the "License");
     5   * you may not use this file except in compliance with the License.
     6   * You may obtain a copy of the License at
     7   *
     8   *     http://www.apache.org/licenses/LICENSE-2.0
     9   *
    10   * Unless required by applicable law or agreed to in writing, software
    11   * distributed under the License is distributed on an "AS IS" BASIS,
    12   * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
    13   * See the License for the specific language governing permissions and
    14   * limitations under the License.
    15   */
    16  
    17  package main
    18  
    19  import (
    20  	"encoding/binary"
    21  
    22  	"github.com/pkg/errors"
    23  )
    24  
    25  func Tokenizer() interface{} { return FactorTokenizer{} }
    26  
    27  type FactorTokenizer struct{}
    28  
    29  func (FactorTokenizer) Name() string     { return "factor" }
    30  func (FactorTokenizer) Type() string     { return "int" }
    31  func (FactorTokenizer) Identifier() byte { return 0xfe }
    32  
    33  func (FactorTokenizer) Tokens(value interface{}) ([]string, error) {
    34  	x := value.(int64)
    35  	if x <= 1 {
    36  		return nil, errors.Errorf("Cannot factor int <= 1: %d", x)
    37  	}
    38  	var toks []string
    39  	for p := int64(2); x > 1; p++ {
    40  		if x%p == 0 {
    41  			toks = append(toks, encodeInt(p))
    42  			for x%p == 0 {
    43  				x /= p
    44  			}
    45  		}
    46  	}
    47  	return toks, nil
    48  
    49  }
    50  
    51  func encodeInt(x int64) string {
    52  	var buf [binary.MaxVarintLen64]byte
    53  	n := binary.PutVarint(buf[:], x)
    54  	return string(buf[:n])
    55  }