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package index
import (
"bufio"
"encoding/gob"
"os"
"searchEngine/core/analyzer"
"sync"
)
type Posting struct {
DocId int
BodyPositions []int
TitlePositions []int
}
type InvertedIndex struct {
Mu sync.RWMutex `gob:"-"`
Data map[string][]Posting
DocNames map[int]string
DocLengths map[int]int
}
func New() *InvertedIndex {
return &InvertedIndex{
Data: make(map[string][]Posting),
DocNames: make(map[int]string),
}
}
func (idx *InvertedIndex) Add(docID int, title string, bodyTokens []string) {
titleTokens := analyzer.ProcessText(title)
type fieldStats struct {
bodyPositions []int
titlePositions []int
}
docStats := make(map[string]fieldStats)
for position, token := range titleTokens {
stats := docStats[token]
stats.titlePositions = append(stats.titlePositions, position)
docStats[token] = stats
}
for position, token := range bodyTokens {
stats := docStats[token]
stats.bodyPositions = append(stats.bodyPositions, position)
docStats[token] = stats
}
idx.Mu.Lock()
defer idx.Mu.Unlock()
idx.DocNames[docID] = title
idx.DocLengths[docID] = len(bodyTokens)
for token, stats := range docStats {
idx.Data[token] = append(idx.Data[token], Posting{
DocId: docID,
BodyPositions: stats.bodyPositions,
TitlePositions: stats.titlePositions,
})
}
}
func (idx *InvertedIndex) Save(filepath string) error {
idx.Mu.RLock()
defer idx.Mu.RUnlock()
file, err := os.Create(filepath)
if err != nil {
return err
}
defer file.Close()
writer := bufio.NewWriter(file)
dto := struct {
Data map[string][]Posting
DocNames map[int]string
DocLengths map[int]int
}{
Data: idx.Data,
DocNames: idx.DocNames,
DocLengths: idx.DocLengths,
}
encoder := gob.NewEncoder(writer)
err = encoder.Encode(dto)
if flushErr := writer.Flush(); flushErr != nil {
return flushErr
}
return err
}
func Load(filepath string) (*InvertedIndex, error) {
file, err := os.Open(filepath)
if err != nil {
return nil, err
}
defer file.Close()
reader := bufio.NewReader(file)
var dto struct {
Data map[string][]Posting
DocNames map[int]string
DocLengths map[int]int
}
decoder := gob.NewDecoder(reader)
err = decoder.Decode(&dto)
if err != nil {
return nil, err
}
return &InvertedIndex{
Data: dto.Data,
DocNames: dto.DocNames,
DocLengths: dto.DocLengths,
}, nil
}
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