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Tutorial Files, Stores

Tutorial Files, Stores. Violeta Seretan LATL. Standard IO access. view provides visual presentation of data views are storable as files open file: Views. Old PROCEDURE Old (ask: BOOLEAN; VAR loc: Files.Locator; VAR name: Files.Name; VAR conv: Converters.Converter): View

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Tutorial Files, Stores

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  1. Tutorial Files, Stores Violeta Seretan LATL

  2. Standard IO access • view • provides visual presentation of data • views are storable as files • open file: Views.Old PROCEDURE Old (ask: BOOLEAN; VAR loc: Files.Locator; VAR name: Files.Name; VAR conv: Converters.Converter): View • save file: Views.Register PROCEDURE Register (view: View; ask: BOOLEAN; VAR loc: Files.Locator; VAR name: Files.Name; VAR conv: Converters.Converter; OUT res: INTEGER) • model • represents some data, without knowing how these data may be represented • IO access functions (for text files): • via TextMappers connected to view's model

  3. Advanced IO access. Files • Module Files • handle aspects of a hierarchical file system • Files.File • a sequence of bytes • identified by name and location (Files.Locator) • informations about file (Files. FileInfo) • indicated access: via Stores.Reader and Stores.Writer

  4. Advanced IO access. Stores • Module Stores • defines a data type Store • Stores.Store is the base type of all storableextensible objects(s.e. objects) • defining storable extensible objects e.g. TYPE MyObject = POINTER TO EXTENSIBLE RECORD (Stores.Store) int: INTEGER; string: Dialog.String END; • allows reading/writing s.e. objects to a file

  5. Internalize/Externalize Procedures • Stores.Internalize and Stores.Externalize define the IO procedures for: • reading s.e. objects, via Stores.Reader • writing s.e. objects, via Stores.Writer • These procedures are to be implemented for the s.e. objects that have been defined e.g. PROCEDURE (object: MyObject) Externalize (VAR writer: Stores.Writer), EXTENSIBLE; BEGIN writer.WriteInt(object.int); writer.WriteString(object.string) END Externalize; PROCEDURE (object: MyObject) Internalize (VAR reader: Stores.Reader), EXTENSIBLE; BEGIN reader.ReadInt(object.int); reader.ReadString(object.string) END Internalize;

  6. Store.Reader: VAR reader: Stores.Reader; file: Files.File; loc: Files.Locator; name: Files.Name; loc := Files.dir.This(""); (* default path *) fileName := "testfile"; file := Files.dir.Old(loc, name, Files.shared); IF file # NIL THEN reader.ConnectTo(file); END Stores.Writer: VAR writer: Stores.Writer; file: Files.File; loc: Files.Locator; loc := Files.dir.This(""); (* default path *) file := Files.dir.New(loc, Files.dontAsk); IF file # NIL THEN writer.ConnectTo(file); END; Reading/Writing Objects to a File • the file to be accessed isthe one connected to:

  7. writing: VAR obj: MyObject; NEW(obj); obj.int := "10"; obj.string := "Ten"; writer.WriteStore(obj) reading: VAR s: Stores.Store; obj: MyObject; reader.ReadStore(s); IF s IS MyObject THEN obj := s(MyObject); Log.Ln; Log.Int(object.int); Log.String(" " + object.string); END; Reading/Writing Objects to a File (cont) • reading/writing the objects: • WriteStore and ReadStore implicitely call Externalize/Internalize

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