/
collection.go
145 lines (131 loc) · 4.32 KB
/
collection.go
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// Collection data file contains document data.
//
// Every document has a binary header and UTF-8 text content.
//
// Documents are inserted one after another, and occupies 2x original document
// size to leave room for future updates.
//
// Deleted documents are marked as deleted and the space is irrecoverable until
// a "scrub" action (in DB logic) is carried out.
//
// When update takes place, the new document may overwrite original document if
// there is enough space, otherwise the original document is marked as deleted
// and the updated document is inserted as a new document.
package data
import (
"encoding/binary"
"github.com/HouzuoGuo/tiedot/dberr"
)
// Collection file contains document headers and document text data.
type Collection struct {
*DataFile
*Config
}
// Open a collection file.
func (conf *Config) OpenCollection(path string) (col *Collection, err error) {
col = new(Collection)
col.DataFile, err = OpenDataFile(path, conf.ColFileGrowth)
col.Config = conf
col.Config.CalculateConfigConstants()
return
}
// Find and retrieve a document by ID (physical document location). Return value is a copy of the document.
func (col *Collection) Read(id int) []byte {
if id < 0 || id > col.Used-DocHeader || col.Buf[id] != 1 {
return nil
} else if room, _ := binary.Varint(col.Buf[id+1 : id+11]); room > int64(col.DocMaxRoom) {
return nil
} else if docEnd := id + DocHeader + int(room); docEnd >= col.Size {
return nil
} else {
docCopy := make([]byte, room)
copy(docCopy, col.Buf[id+DocHeader:docEnd])
return docCopy
}
}
// Insert a new document, return the new document ID.
func (col *Collection) Insert(data []byte) (id int, err error) {
room := len(data) << 1
if room > col.DocMaxRoom {
return 0, dberr.New(dberr.ErrorDocTooLarge, col.DocMaxRoom, room)
}
id = col.Used
docSize := DocHeader + room
if err = col.EnsureSize(docSize); err != nil {
return
}
col.Used += docSize
// Write validity, room, document data and padding
col.Buf[id] = 1
binary.PutVarint(col.Buf[id+1:id+11], int64(room))
copy(col.Buf[id+DocHeader:col.Used], data)
for padding := id + DocHeader + len(data); padding < col.Used; padding += col.LenPadding {
copySize := col.LenPadding
if padding+col.LenPadding >= col.Used {
copySize = col.Used - padding
}
copy(col.Buf[padding:padding+copySize], col.Padding)
}
return
}
// Overwrite or re-insert a document, return the new document ID if re-inserted.
func (col *Collection) Update(id int, data []byte) (newID int, err error) {
dataLen := len(data)
if dataLen > col.DocMaxRoom {
return 0, dberr.New(dberr.ErrorDocTooLarge, col.DocMaxRoom, dataLen)
}
if id < 0 || id >= col.Used-DocHeader || col.Buf[id] != 1 {
return 0, dberr.New(dberr.ErrorNoDoc, id)
}
currentDocRoom, _ := binary.Varint(col.Buf[id+1 : id+11])
if currentDocRoom > int64(col.DocMaxRoom) {
return 0, dberr.New(dberr.ErrorNoDoc, id)
}
if docEnd := id + DocHeader + int(currentDocRoom); docEnd >= col.Size {
return 0, dberr.New(dberr.ErrorNoDoc, id)
}
if dataLen <= int(currentDocRoom) {
padding := id + DocHeader + len(data)
paddingEnd := id + DocHeader + int(currentDocRoom)
// Overwrite data and then overwrite padding
copy(col.Buf[id+DocHeader:padding], data)
for ; padding < paddingEnd; padding += col.LenPadding {
copySize := col.LenPadding
if padding+col.LenPadding >= paddingEnd {
copySize = paddingEnd - padding
}
copy(col.Buf[padding:padding+copySize], col.Padding)
}
return id, nil
}
// No enough room - re-insert the document
col.Delete(id)
return col.Insert(data)
}
// Delete a document by ID.
func (col *Collection) Delete(id int) error {
if id < 0 || id > col.Used-DocHeader || col.Buf[id] != 1 {
return dberr.New(dberr.ErrorNoDoc, id)
}
if col.Buf[id] == 1 {
col.Buf[id] = 0
}
return nil
}
// Run the function on every document; stop when the function returns false.
func (col *Collection) ForEachDoc(fun func(id int, doc []byte) bool) {
for id := 0; id < col.Used-DocHeader && id >= 0; {
validity := col.Buf[id]
room, _ := binary.Varint(col.Buf[id+1 : id+11])
docEnd := id + DocHeader + int(room)
if (validity == 0 || validity == 1) && room <= int64(col.DocMaxRoom) && docEnd > 0 && docEnd <= col.Used {
if validity == 1 && !fun(id, col.Buf[id+DocHeader:docEnd]) {
break
}
id = docEnd
} else {
// Corrupted document - move on
id++
}
}
}