IsamDataFileBaseT Class

An abstract class that defines the read/write capabilities for ISAM (Indexed Sequential Access Method) file.

Inheritance Hierarchy

SystemObject
  GSF.IOIsamDataFileBaseT
    GSF.Historian.FilesIntercomFile
    GSF.Historian.FilesMetadataFile
    GSF.Historian.FilesStateFile

Namespace: GSF.IO
Assembly: GSF.Core (in GSF.Core.dll) Version: 2.4.282-beta+fbfa6baa1521236175f6d73fb2eb151a42453aef

Syntax

C++

JavaScript

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public abstract class IsamDataFileBase<T> : ISupportLifecycle, 
	IDisposable, IProvideStatus, IPersistSettings
where T : ISupportBinaryImage

Public MustInherit Class IsamDataFileBase(Of T As ISupportBinaryImage)
	Implements ISupportLifecycle, IDisposable, IProvideStatus, IPersistSettings

generic<typename T>
where T : ISupportBinaryImage
public ref class IsamDataFileBase abstract : ISupportLifecycle, 
	IDisposable, IProvideStatus, IPersistSettings

[<AbstractClassAttribute>]
type IsamDataFileBase<'T when 'T : ISupportBinaryImage> = 
    class
        interface ISupportLifecycle
        interface IDisposable
        interface IProvideStatus
        interface IPersistSettings
    end

JavaScript does not support generic types or methods.

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Type Parameters

T: Type of the records the file contains. This Type must implement the ISupportBinaryImage interface.

The IsamDataFileBaseT type exposes the following members.

Constructors

	Name	Description
	IsamDataFileBaseT	Initializes a new instance of the IsamDataFileBaseT class.

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Properties

	Name	Description
	AutoSaveInterval	Gets or sets the interval in milliseconds at which the records loaded in memory are to be persisted to disk.
	Enabled	Gets or sets a boolean value that indicates whether the file is currently enabled.
	FileAccessMode	Gets or sets the FileAccess value to use when opening the file.
	FileData	Gets the underlying FileStream of the file.
	FileDataLock	Gets the locking object for the FileData stream.
	FileName	Gets or sets the name of the file.
	IsCorrupt	Gets a boolean value that indicates whether the file data on disk is corrupt.
	IsDisposed	Gets a flag that indicates whether the object has been disposed.
	IsOpen	Gets a boolean value that indicates whether the file is open.
	LoadOnOpen	Gets or sets a boolean value that indicates whether records are to be loaded automatically in memory when the file is opened.
	LoadWaitHandle	Gets wait handle for loading data.
	MemoryUsage	Gets the approximate memory consumption (in KB) of the file.
	Name	Gets the unique identifier of the file.
	PersistSettings	Gets or sets a boolean value that indicates whether the file settings are to be saved to the config file.
	RecordsInMemory	Gets the number of file records loaded in memory.
	RecordsOnDisk	Gets the number of file records on the disk.
	ReloadOnModify	Gets or sets a boolean value that indicates whether records loaded in memory are to be re-loaded when the file is modified on disk.
	SaveOnClose	Gets or sets a boolean value that indicates whether records loaded in memory are to be persisted to disk when the file is closed.
	SaveWaitHandle	Gets wait handle for saving data.
	SettingsCategory	Gets or sets the category under which the file settings are to be saved to the config file if the PersistSettings property is set to true.
	Status	Gets the descriptive status of the file.

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Methods

	Name	Description
	Close	Closes the file.
	CreateNewRecord	When overridden in a derived class, returns a new empty record.
	Dispose	Releases all the resources used by the file.
	Dispose(Boolean)	Releases the unmanaged resources used by the file and optionally releases the managed resources.
	Equals	Determines whether the specified object is equal to the current object. (Inherited from Object)
	Finalize	Releases the unmanaged resources before the file is reclaimed by GC. (Overrides ObjectFinalize)
	GetHashCode	Serves as the default hash function. (Inherited from Object)
	GetRecordSize	When overridden in a derived class, gets the size of a record (in bytes).
	GetType	Gets the Type of the current instance. (Inherited from Object)
	Initialize	Initializes the file.
	Load	Loads records from disk into memory.
	LoadSettings	Loads saved settings of the file from the config file if the PersistSettings property is set to true.
	MemberwiseClone	Creates a shallow copy of the current Object. (Inherited from Object)
	OnDataLoaded	Raises the DataLoaded event.
	OnDataLoading	Raises the DataLoading event.
	OnDataSaved	Raises the DataSaved event.
	OnDataSaving	Raises the DataSaving event.
	OnFileModified	Raises the FileModified event.
	Open	Opens the file.
	Read	Reads file records from disk if records were not loaded in memory otherwise returns the records in memory.
	Read(Int32)	Reads specified file record from disk if records were not loaded in memory otherwise returns the record in memory.
	Save	Saves records loaded in memory to disk.
	SaveSettings	Saves settings of the file to the config file if the PersistSettings property is set to true.
	ToString	Returns a string that represents the current object. (Inherited from Object)
	Write(IEnumerableT)	Writes specified records to disk if records were not loaded in memory otherwise updates the records in memory.
	Write(Int32, T)	Writes specified record to disk if records were not loaded in memory otherwise updates the record in memory.

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Events

	Name	Description
	DataLoaded	Occurs when data has been read from disk into memory.
	DataLoading	Occurs when data is being read from disk into memory.
	DataSaved	Occurs when data has been saved from memory onto disk.
	DataSaving	Occurs when data is being saved from memory onto disk.
	Disposed	Occurs when the class has been disposed.
	FileModified	Occurs when file data on the disk is modified.

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Fields

	Name	Description
	DefaultAutoSaveInterval	Specifies the default value for the AutoSaveInterval property.
	DefaultFileAccessMode	Specifies the default value for the FileAccessMode property.
	DefaultFileName	Specifies the default value for the FileName property.
	DefaultLoadOnOpen	Specifies the default value for the LoadOnOpen property.
	DefaultPersistSettings	Specifies the default value for the PersistSettings property.
	DefaultReloadOnModify	Specifies the default value for the ReloadOnModify property.
	DefaultSaveOnClose	Specifies the default value for the SaveOnClose property.
	DefaultSettingsCategory	Specifies the default value for the SettingsCategory property.

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Extension Methods

	Name	Description
	GetEnumValueOrDefault	Gets the enumeration constant for value, if defined in the enumeration, or a default value. (Defined by EnumExtensions)
	GetEnumValueOrDefaultT	Gets the enumeration constant for this value, if defined in the enumeration, or a default value. (Defined by EnumExtensions)

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Remarks

This ISAM implementation keeps all the records in memory, so it may not be suitable for very large files. Since data is stored in memory using a list, the maximum number of possible supported records will be 2,147,483,647 (i.e., Int32.MaxValue).

See http://en.wikipedia.org/wiki/ISAM for more information on ISAM files.

Example

This example shows a sample implementation of IsamDataFileBaseT:


            using System;
            using System.Text;
            using GSF;
            using GSF.IO;
            using GSF.Parsing;
            
            class Program
            {
                static void Main(string[] args)
                {
                    // Create a few test records.
                    TestIsamFileRecord r1 = new TestIsamFileRecord(1);
                    r1.Name = "TestRecord1";
                    r1.Value = double.MinValue;
                    r1.Description = "Test record with minimum double value";
                    TestIsamFileRecord r2 = new TestIsamFileRecord(2);
                    r2.Name = "TestRecord2";
                    r2.Value = double.MaxValue;
                    r2.Description = "Test record with maximum double value";
            
                    // Open ISAM file.
                    TestIsamFile testFile = new TestIsamFile();
                    testFile.FileName = "TestIsamFile.dat";
                    testFile.Open();
            
                    // Write test records.
                    testFile.Write(r1.Index, r1);
                    testFile.Write(r2.Index, r2);
            
                    // Read test records.
                    Console.WriteLine(testFile.Read(1));
                    Console.WriteLine(testFile.Read(2));
            
                    // Close ISAM file.
                    testFile.Close();
            
                    Console.ReadLine();
                }
            }
            
            class TestIsamFile : IsamDataFileBase<TestIsamFileRecord>
            {
                /// 
                /// Size of a single file record.
                /// 
                protected override int GetRecordSize()
                {
                    return TestIsamFileRecord.RecordLength;
                }
            
                /// 
                /// Creates a new empty file record.
                /// 
                protected override TestIsamFileRecord CreateNewRecord(int id)
                {
                    return new TestIsamFileRecord(id);
                }
            }
            
            class TestIsamFileRecord : ISupportBinaryImage
            {
                private int m_index;
                private string m_name;                  // 20  * 1 =  20
                private double m_value;                 // 1   * 8 =   8
                private string m_description;           // 100 * 1 = 100
                
                public const int RecordLength = 128;    // Total   = 128
            
                public TestIsamFileRecord(int recordIndex)
                {
                    m_index = recordIndex;
                    
                    Name = string.Empty;
                    Value = double.NaN;
                    Description = string.Empty;
                }
            
                /// 
                /// 1-based index of the record.
                /// 
                public int Index
                {
                    get { return m_index; }
                }
            
                /// 
                /// Name of the record.
                /// 
                public string Name
                {
                    get { return m_name; }
                    set { m_name = value.TruncateRight(20).PadRight(20); }
                }
            
                /// 
                /// Value of the record.
                /// 
                public double Value
                {
                    get { return m_value; }
                    set { m_value = value; }
                }
            
                /// 
                /// Description of the record.
                /// 
                public string Description
                {
                    get { return m_description; }
                    set { m_description = value.TruncateRight(100).PadRight(100); }
                }
            
                /// 
                /// Serialized record length.
                /// 
                public int BinaryLength
                {
                    get { return RecordLength; }
                }
            
                /// 
                /// Serialized record data.
                /// 
                public byte[] BinaryImage
                {
                    get
                    {
                        // Serialize TestIsamFileRecord into byte array.
                        byte[] image = new byte[RecordLength];
                        Buffer.BlockCopy(Encoding.ASCII.GetBytes(Name), 0, image, 0, 20);
                        Buffer.BlockCopy(BitConverter.GetBytes(Value), 0, image, 20, 8);
                        Buffer.BlockCopy(Encoding.ASCII.GetBytes(Description), 0, image, 28, 100);
            
                        return image;
                    }
                }
            
                /// 
                /// Deserializes the record.
                /// 
                public int Initialize(byte[] binaryImage, int startIndex, int length)
                {
                    if (length >= RecordLength)
                    {
                        // Deserialize byte array into TestIsamFileRecord.
                        Name = Encoding.ASCII.GetString(binaryImage, startIndex, 20);
                        Value = BitConverter.ToDouble(binaryImage, startIndex + 20);
                        Description = Encoding.ASCII.GetString(binaryImage, startIndex + 28, 100);
                    }
                    else
                        throw new InvalidOperationException("Invalid record size, not enough data to deserialize record"); 
            
                    return RecordLength;
                }
            
                /// 
                /// String representation of the record.
                /// 
                public override string ToString()
                {
                    return string.Format("Name: {0}, Value: {1}, Description: {2}", Name, Value, Description);
                }
            }

Reference

GSF.IO Namespace