// Inserts a row to the bottom of the table.
func (table *Table) Insert(row map[string]string) int {
// Seek to EOF
_, err := table.DataFile.Seek(0, 2)
if err == nil {
// For the columns in their order
for _, column := range table.ColumnsInOrder {
value, exists := row[column.Name]
if !exists {
value = ""
}
// Keep writing the column value.
status := table.Write(column, value)
if status != st.OK {
return status
}
}
// Write a new-line character.
_, err = table.DataFile.WriteString("\n")
if err != nil {
logg.Err("table", "Insert", err.Error())
return st.CannotWriteTableDataFile
}
} else {
logg.Err("table", "Insert", err.Error())
return st.CannotSeekTableDataFile
}
return st.OK
}
// Adds a new column.
func (table *Table) Add(name string, length int) int {
_, exists := table.Columns[name]
if exists {
return st.ColumnAlreadyExists
}
if len(name) > constant.MaxColumnNameLength {
return st.ColumnNameTooLong
}
if length <= 0 {
return st.InvalidColumnLength
}
var numberOfRows int
numberOfRows, status := table.NumberOfRows()
if status == st.OK && numberOfRows > 0 {
// Rebuild data file if there are already rows in the table.
// (To leave space for the new column)
status = table.RebuildDataFile(name, length)
table.pushNewColumn(name, length)
} else {
newColumn := table.pushNewColumn(name, length)
// Write definition of the new column into definition file.
_, err := table.DefFile.Seek(0, 2)
if err != nil {
logg.Err("table", "Add", err.Error())
return st.CannotSeekTableDefFile
}
_, err = table.DefFile.WriteString(column.ColumnToDef(newColumn))
if err != nil {
logg.Err("table", "Add", err.Error())
return st.CannotWriteTableDefFile
}
}
table.RowLength += length
return st.OK
}
// Creates a file and writes the content into it.
func CreateAndWrite(filename, content string) int {
file, err := os.Create(filename)
defer file.Close()
if err != nil {
logg.Err("util", "CreateAndWrite", err)
return st.CannotCreateFile
}
_, err = file.WriteString(content)
if err != nil {
logg.Err("util", "CreateAndWrite", err)
return st.CannotCreateFile
}
return st.OK
}
// Opens file handles.
func (table *Table) OpenFiles() int {
var err error
table.DefFile, err = os.OpenFile(table.DefFilePath, os.O_RDWR, constant.DataFilePerm)
if err == nil {
table.DataFile, err = os.OpenFile(table.DataFilePath, os.O_RDWR, constant.DataFilePerm)
if err != nil {
logg.Err("table", "OpenFiles", err.Error())
return st.CannotOpenTableDataFile
}
} else {
logg.Err("table", "OpenFiles", err.Error())
return st.CannotOpenTableDefFile
}
return st.OK
}
// Renames table files.
func Rename(path string, oldName string, newName string) int {
for _, ext := range constant.TableFiles() {
err := os.Rename(path+oldName+ext, path+newName+ext)
if err != nil {
logg.Err("tablefilemanager", "Rename", err)
return st.CannotRenameTableFile
}
}
for _, dir := range constant.TableDirs() {
err := os.Rename(path+oldName+dir, path+newName+dir)
if err != nil {
logg.Err("tablefilemanager", "Rename", err)
return st.CannotRenameTableDir
}
}
return st.OK
}
// Deletes table files
func Delete(path string, name string) int {
for _, ext := range constant.TableFiles() {
err := os.Remove(path + name + ext)
if err != nil {
logg.Err("tablefilemanager", "Delete", err)
return st.CannotRemoveTableFile
}
}
for _, dir := range constant.TableDirs() {
err := os.RemoveAll(path + name + dir)
if err != nil {
logg.Err("tablefilemanager", "Delete", err)
return st.CannotRemoveTableDir
}
}
return st.OK
}
// Returns the number of rows in this table.
func (table *Table) NumberOfRows() (int, int) {
// var numberOfRows int
// var dataFileInfo *os.FileInfo
dataFileInfo, err := table.DataFile.Stat()
if err != nil {
logg.Err("table", "NumberOfRows", err.Error())
return 0, st.CannotStatTableDataFile
}
numberOfRows := int(dataFileInfo.Size()) / table.RowLength
return numberOfRows, st.OK
}
// Seeks to a row (e.g. row number 10).
func (table *Table) Seek(rowNumber int) int {
var numberOfRows int
numberOfRows, status := table.NumberOfRows()
if status == st.OK && rowNumber < numberOfRows {
_, err := table.DataFile.Seek(int64(rowNumber*table.RowLength), 0)
if err != nil {
logg.Err("table", "Seek", err.Error())
return st.CannotSeekTableDataFile
}
}
return st.OK
}
// Constructs a Column from a column's text definition.
func ColumnFromDef(offset int, definition string) (*Column, int) {
var column *Column
// Extract length and name from the definition.
lengthName := strings.Split(definition, ":")
length, err := strconv.Atoi(lengthName[1])
if err != nil {
logg.Err("Column", "ColumnFromDef", "Definition malformed: "+definition)
return nil, st.InvalidColumnDefinition
}
column = &Column{Offset: offset, Length: length, Name: lengthName[0]}
return column, st.OK
}
// Opens a table.
func Open(path, name string) (*Table, int) {
var table *Table
table = new(Table)
table.Path = path
table.Name = name
status := table.Init()
if status != st.OK {
logg.Err("table", "Open", "Failed to open"+path+name+" Err: "+string(status))
return nil, status
}
return table, st.OK
}
// Creates table files.
func Create(path string, name string) int {
if len(name) > constant.MaxTableNameLength {
return st.TableNameTooLong
}
// Create table files with extension names.
for _, ext := range constant.TableFiles() {
_, err := os.Create(path + name + ext)
if err != nil {
logg.Err("tablefilemanager", "Create", err)
return st.CannotCreateTableFile
}
}
// Create table directories with name suffixes.
for _, dir := range constant.TableDirs() {
err := os.Mkdir(path+name+dir, constant.TableDirPerm)
if err != nil {
logg.Err("tablefilemanager", "Create", err)
return st.CannotCreateTableDir
}
}
return st.OK
}
// Opens a path as database.
func Open(path string) (*Database, int) {
var db *Database
db = new(Database)
db.Tables = make(map[string]*table.Table)
// Open and read content of the path (as a directory).
directory, err := os.Open(path)
if err != nil {
db = nil
logg.Err("database", "Open", err.Error())
return db, st.CannotOpenDatabaseDirectory
}
defer directory.Close()
fi, err := directory.Readdir(0)
if err != nil {
db = nil
logg.Err("database", "Open", err.Error())
return db, st.CannotReadDatabaseDirectory
}
for _, fileInfo := range fi {
// Extract extension of file name.
if !fileInfo.IsDir() {
name, ext := util.FilenameParts(fileInfo.Name())
// If extension is .data, open the file as a Table.
if ext == "data" {
_, exists := db.Tables[name]
if !exists {
var status int
// Open the table and put it into tables map.
db.Tables[name], status = table.Open(path, name)
if status != st.OK {
return nil, status
}
}
}
}
}
db.Path = path
return db, db.PrepareForTriggers(false)
}
// Flushes table's files
func (table *Table) Flush() int {
err := table.DefFile.Sync()
if err == nil {
err = table.DataFile.Sync()
if err != nil {
logg.Err("table", "Flush", err.Error())
return st.CannotFlushTableDataFile
}
} else {
return st.CannotFlushTableDefFile
}
return st.OK
}
// Removes a line's occurances from a file.
func RemoveLine(filename, line string) int {
// Open and read the file.
file, err := os.Open(filename)
if err != nil {
logg.Err("util", "RemoveLine", err)
return st.CannotReadFile
}
fi, err := file.Stat()
if err != nil {
logg.Err("util", "RemoveLine", err)
return st.CannotReadFile
}
buffer := make([]byte, fi.Size())
_, err = file.Read(buffer)
if err != nil {
logg.Err("util", "RemoveLine", err)
return st.CannotReadFile
}
file.Close()
// Re-open the file and overwrite it.
file, err = os.OpenFile(filename, os.O_WRONLY+os.O_TRUNC, 0666)
defer file.Close()
if err != nil {
logg.Err("util", "RemoveLine", err)
return st.CannotReadFile
}
lines := strings.Split(string(buffer), "\n")
for _, content := range lines {
if strings.TrimSpace(content) != strings.TrimSpace(line) {
_, err = file.WriteString(content + "\n")
if err != nil {
logg.Err("util", "RemoveLine", err)
return st.CannotWriteFile
}
}
}
return st.OK
}
// Seeks to a row and column (e.g. row number 10 column "NAME").
func (table *Table) SeekColumn(rowNumber int, columnName string) int {
status := table.Seek(rowNumber)
if status == st.OK {
column, exists := table.Columns[columnName]
if exists {
_, err := table.DataFile.Seek(int64(column.Offset), 1)
if err != nil {
logg.Err("table", "SeekColumn", err.Error())
return st.CannotSeekTableDataFile
}
}
}
return st.OK
}
// Reads a row and return a map representation (name1:value1, name2:value2...)
func (table *Table) Read(rowNumber int) (map[string]string, int) {
row := make(map[string]string)
status := table.Seek(rowNumber)
if status == st.OK {
rowInBytes := make([]byte, table.RowLength)
_, err := table.DataFile.Read(rowInBytes)
if err == nil {
// For the columns in their order
for _, column := range table.ColumnsInOrder {
// column1:value2, column2:value2...
row[column.Name] = strings.TrimSpace(string(rowInBytes[column.Offset : column.Offset+column.Length]))
}
} else {
logg.Err("table", "Read", err.Error())
return nil, st.CannotReadTableDataFile
}
}
return row, st.OK
}
// Load the table (column definitions, etc.).
func (table *Table) Init() int {
// This function may be called multiple times, thus clear previous state.
table.RowLength = 0
table.Columns = make(map[string]*column.Column)
table.ColumnsInOrder = make([]*column.Column, 0)
table.DefFilePath = table.Path + table.Name + ".def"
table.DataFilePath = table.Path + table.Name + ".data"
status := table.OpenFiles()
if status != st.OK {
return status
}
defFileInfo, err := table.DefFile.Stat()
if err != nil {
logg.Err("table", "Init", err.Error())
return st.CannotStatTableDefFile
}
// Read definition file into memeory.
content := make([]byte, defFileInfo.Size())
table.DefFile.Read(content)
// Each line contains one column definition.
lines := strings.Split(string(content), "\n")
for _, line := range lines {
if line != "" {
var aColumn *column.Column
// Convert the definition into a Column.
aColumn, status = column.ColumnFromDef(table.RowLength, line)
if status != st.OK {
return status
}
table.Columns[aColumn.Name] = aColumn
table.ColumnsInOrder = append(table.ColumnsInOrder[:], aColumn)
table.RowLength += aColumn.Length
}
}
table.RowLength++
return st.OK
}
// Returns existing shared and exclusive locks of a table.
func LocksOf(t *table.Table) (*Locks, int) {
// Read files in .shared directory.
sharedLocksPath := t.Path + t.Name + ".shared"
sharedLocksDir, err := os.Open(sharedLocksPath)
if err != nil {
return nil, st.CannotReadSharedLocksDir
}
defer sharedLocksDir.Close()
fi, err := sharedLocksDir.Readdir(0)
if err != nil {
logg.Err("transaction", "LocksOf", err)
return nil, st.CannotReadSharedLocksDir
}
locks := new(Locks)
locks.Shared = make([]int64, 0)
for _, fileInfo := range fi {
// File name represents a transaction ID (also a timestamp).
theID, err := strconv.ParseInt(fileInfo.Name(), 10, 64)
// tt := time.Now().Nanosecond() + constant.LockTimeout
if err != nil || theID > int64(time.Now().Nanosecond()+constant.LockTimeout) {
// Remove expired shared lock.
err = os.Remove(sharedLocksPath + "/" + fileInfo.Name())
logg.Warn("transaction", "LocksOf", "Expired shared lock ID "+
fileInfo.Name()+" file "+sharedLocksPath+"/"+fileInfo.Name()+" is removed")
if err != nil {
logg.Err("transaction", "LocksOf", err)
return nil, st.CannotUnlockSharedLock
}
} else {
locks.Shared = append(locks.Shared[:], theID)
}
}
// Read the content of exclusive lock.
exclusiveLockPath := t.Path + t.Name + ".exclusive"
exclusiveFile, err := os.Open(exclusiveLockPath)
if err != nil {
return locks, st.OK
}
fi2, err := exclusiveFile.Stat()
if err != nil {
logg.Err("transaction", "LocksOf", err)
return nil, st.CannotReadExclusiveLocksFile
}
// The file content is a transaction ID
buffer := make([]byte, fi2.Size())
_, err = exclusiveFile.Read(buffer)
if err != nil {
logg.Err("transaction", "LocksOf", err)
return nil, st.CannotReadExclusiveLocksFile
}
theID, err := strconv.ParseInt(string(buffer), 10, 64)
if err != nil || theID > int64(time.Now().Nanosecond()+constant.LockTimeout) {
// Remove expired exclusive lock.
err = os.Remove(exclusiveLockPath)
logg.Debug("transaction", "LocksOf", err)
logg.Warn("transaction", "LocksOf", "Expired exclusive lock ID "+
string(buffer)+" file "+exclusiveLockPath+" is removed")
if err != nil {
logg.Err("transaction", "LocksOf", err)
return nil, st.CannotUnlockExclusiveLock
}
} else {
locks.Exclusive = theID
}
return locks, st.OK
}