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main.go
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main.go
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// Copyright 2020-2021 the Blobloom authors
//
// Licensed 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.
// This package implements a toy interactive spell checker.
//
// It reads a dictionary from /usr/share/dict/words and a text from standard
// input. It then reports any misspelled words on standard output.
package main
import (
"bufio"
"bytes"
"fmt"
"log"
"os"
"unicode"
"github.com/greatroar/blobloom"
)
func main() {
dict := loadDictionary()
sc := bufio.NewScanner(os.Stdin)
sc.Split(bufio.ScanWords)
for sc.Scan() {
word := normalize(sc.Bytes())
if !dict.Has(hash(word)) {
fmt.Printf(">>> %s\n", word)
}
}
if err := sc.Err(); err != nil {
log.Fatal(err)
}
}
// FNV1a hash function.
func hash(key []byte) uint64 {
var h uint64 = 0xcbf29ce484222325
for _, c := range key {
h ^= uint64(c)
h *= 0x100000001b3
}
return h
}
func normalize(word []byte) []byte {
word = bytes.ToLower(word)
word = bytes.TrimFunc(word, unicode.IsPunct)
return word
}
// To estimate the number of keys without scanning the file twice, we need
// an estimate of the average length of a word. This comes close for English.
const avgWordLength = 10
func loadDictionary() *blobloom.Filter {
f, err := os.Open("/usr/share/dict/words")
if err != nil {
log.Fatal(err)
}
defer f.Close()
info, err := f.Stat()
if err != nil {
log.Fatal(err)
}
filesize := uint64(info.Size())
dict := blobloom.NewOptimized(blobloom.Config{
Capacity: filesize / avgWordLength,
FPRate: .001,
})
sc := bufio.NewScanner(f)
for sc.Scan() {
dict.Add(hash(normalize(sc.Bytes())))
filesize-- // Subtract newline, for fairness.
}
if err := sc.Err(); err != nil {
log.Fatal(err)
}
log.Printf("dictionary loaded: %dkiB on disk, %dkiB in memory",
filesize/1024, dict.NumBits()/(8*1024))
return dict
}