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Home > Class Reference > %SYS namespace > %Library.FileStreamAdaptor

%Library.FileStreamAdaptor

abstract stream class %Library.FileStreamAdaptor extends %Library.AbstractStream

Stream adaptor for streams that store data in external files. Not to be used directly.

Property Inventory

Method Inventory

Parameters

parameter FILEEXT = stream;
parameter OPENAPPEND = AWUK\RAW\;
parameter OPENREAD = RUK\RAW\;
parameter OPENREADTERM = RSK\RAW\;
parameter OPENWRITE = WUNK\RAW\;
final parameter READLINE = 1;
final parameter READNORMAL = 0;
parameter STORAGE = OTHER;
final parameter WRITEAPPEND = 1;
final parameter WRITEJUSTSAVED = 4;
final parameter WRITENORMAL = 0;

Properties

property CanonicalFilename as %String (MAXLEN = 5000) [ Calculated ];
Read only property that returns the canonical filename if the file is open and "" if the file is not open. On VMS this will include the file version number
Property methods: CanonicalFilenameDisplayToLogical(), CanonicalFilenameGet(), CanonicalFilenameIsValid(), CanonicalFilenameLogicalToDisplay(), CanonicalFilenameLogicalToOdbc(), CanonicalFilenameNormalize()
property Directory as %String (MAXLEN = 5000);
Directory where stream files are located.
Property methods: DirectoryDisplayToLogical(), DirectoryGet(), DirectoryIsValid(), DirectoryLogicalToDisplay(), DirectoryLogicalToOdbc(), DirectoryNormalize(), DirectorySet()
property Filename as %String (MAXLEN = 5000) [ Calculated ];
The filename that this stream is currently using
Property methods: FilenameDisplayToLogical(), FilenameGet(), FilenameIsValid(), FilenameLogicalToDisplay(), FilenameLogicalToOdbc(), FilenameNormalize(), FilenameSet()
property LineTerminator as %String (MAXLEN = 10) [ InitialExpression = $get(^%SYS("Stream","LineTerminator"),$select($$$isUNIX:$char(10),1:$char(13,10))) , Transient ];
For file streams the line will terminate on any of the characters set in the LineTerminator, it does not support multi-character line terminators because it uses the Cache file behavior which terminates on any of the characters. Updating this in the middle of a file on VMS will rewind the file to the beginning because of the way files work on VMS.
Also for %FileCharacterStream even if you set this when you call WriteLine() as the file was opened in 'S' mode it will normalize the line terminator as the data is being written, so for example if you set LineTerminator to $char(13,10) on Unix systems when you call WriteLine() it will only write $char(10) to the file.
Property methods: LineTerminatorDisplayToLogical(), LineTerminatorGet(), LineTerminatorIsValid(), LineTerminatorLogicalToDisplay(), LineTerminatorLogicalToOdbc(), LineTerminatorNormalize(), LineTerminatorSet()
property ReadSize as %Integer;
While reading this holds the file size
Property methods: ReadSizeDisplayToLogical(), ReadSizeGet(), ReadSizeIsValid(), ReadSizeLogicalToDisplay(), ReadSizeNormalize(), ReadSizeSet()
property RemoveOnClose as %Boolean [ InitialExpression = 0 , Transient ];
If true then remove the permanent file as well as any temp file when this object is closed
Property methods: RemoveOnCloseDisplayToLogical(), RemoveOnCloseGet(), RemoveOnCloseIsValid(), RemoveOnCloseLogicalToDisplay(), RemoveOnCloseNormalize(), RemoveOnCloseSet()
property UseVMSVersion as %Boolean [ InitialExpression = 0 , Transient ];
If true then on VMS only do not delete the persistent file before replacing it with the new version. This will cause the new version to be written with a new version number and so will keep the old file version present.
Property methods: UseVMSVersionDisplayToLogical(), UseVMSVersionGet(), UseVMSVersionIsValid(), UseVMSVersionLogicalToDisplay(), UseVMSVersionNormalize(), UseVMSVersionSet()

Methods

classmethod %Exists(soid As %ObjectIdentity) as %Boolean
Inherited description: Checks to see if the object identified by the OID oid exists in the extent.

Returns %Boolean TRUE is it exists, FALSE if it does not.

method %LocationGet() as %String
method %LocationSet(value As %String) as %Status
method %NormalizeObject() as %Status
Inherited description: Normalizes all of an object's property values by invoking the data type Normalize methods. Many data types may allow many different representations of the same value. Normalization converts a value to its cannonical, or normalized, form.
classmethod %ObjectIsNull(soid As %ObjectIdentity) as %Boolean
Inherited description: Return true if this stream oid is a null stream and false if the stream is not null
method %ValidateObject(force As %Library.Integer = 0, checkserial As %Library.Boolean = 1) as %Status
Inherited description: This method validates an object. The %Save method of a persistent class calls it before filing any objects in the database. The %ValidateObject method of a referencing object can call it. You can also call it explicitly at any time.

%ValidateObject() does the following:

  1. It tests if any required property values are missing.
  2. If the PROPERTYVALIDATION class parameter is set to ValidateOnSave, it validates each non-null property value by calling the property method IsValid on each literal property and the object's %ValidateObject method for object-valued properties.
  3. If present, it will call a user-supplied %OnValidateObject() method.

If any of these tests fail, %ValidateObject() immediately returns an error value. It is up to the caller of %ValidateObject to process the error value.

Returns a %Status value indicating success or failure.

method CanonicalFilenameGet() as %String
method Clear(permanent As %Boolean = 1) as %Status
Inherited description: Clear the contents of this Stream from permanent storage. This will remove the permanent stream storage and any temporary stream and initialise the stream to its initial state that it starts in, including removing all the stream attributes.

Returns a %Status value indicating success or failure.

method CopyFrom(source As %AbstractStream) as %Status
Inherited description: Copies the contents of source into this Stream.

For example, you can copy oldstream into a new stream:

  Set newstream=##class(%GlobalCharacterStream).%New()
  Do newstream.CopyFrom(oldstream)
  

Returns a %Status value indicating success or failure.

method FileBinarySize() as %Integer
Return the current size of the file in bytes.
method FilenameGet() as %String
method FilenameSet(file As %String) as Status
method Flush() as %Status
Inherited description: Flush any output in the stream not already saved.
classmethod GetStreamIdForFile(file As %String, contenttype As %String = "", charset As %String = "") as %String
Generate a stream OId that links to this file. This can be used by the CSP server to generate an OID that can be embedded in a web page and later used to display this file. The contenttype is an optional parameter to specify the content type of this stream for display with a stream server. If I have a file called 'C:\Test.txt' then I can create a stream linked to this by:
  Set id=##class(%FileCharacterStream).GetStreamIdForFile("c:\Test.txt")
  Set stream=##class(%FileCharacterStream).%Open(id)
  Do stream.OutputToDevice()
  
method LastModifiedGet() as %TimeStamp
method LineTerminatorSet(terminator As %String) as %Status
method LinkToFile(filename As %String) as %Status
This method lets you connect a file stream to a file called filename without making a copy of it. If the file does not already exist it will still allow you to link to this file, and %IsNull() will return true until you write to this file.
  Do object.Image.LinkToFile("\temp\image.jpg")
  Do object.%Save()
  
The method as its name suggests creates a LINK to an EXISTING file. So this is a 'shared public' file, as it can be shared by several instances of a class, or even several classes. Using the CopyFrom() method, on the contrary, creates a 'private' image, not sharable by other instances/classes, so these two methods are really different.

The problems with shared public images are that several instances are all allowed to update and even delete the image, causing problems for other instances.

For example, if dog #2 has image 'test.gif', I can also assign that image to dog #5 or even person #24 If I change the image for dog #5, then the image is changed in place to another image, thus upsetting dog#2 and person#24. If I delete dog#5, the image is also deleted and thus dog#2 and person#24 are changed.

Also note that if there is currently some temporary data in the old stream when the LinkToFile() is called this temporary data will be removed before the stream is linked to this filename.

method MoveToEnd() as %Status
Inherited description: Move to the end of the stream so the next Write will be appended to the end. This allows you to read from a stream, then MoveToEnd() and append new data, where just calling Write() after a read will clear the stream before writing new data.

Returns a %Status value indicating success or failure.

classmethod NewFileName(ext As %String = "", directory As %String = "") as %String
method OpenStream(sid As %String) as %Status
Open a stream given a stream id
method OutputToDevice(ByRef len As %Integer = -1) as %Status
Inherited description: Write out len characters of the stream to the current device starting from the current position. This method is optimised for performance by the various sub classes. If len is omitted or set to -1 then it will write out the entire stream starting at the beginning.
method Read(ByRef len As %Integer = 32000, ByRef sc As %Status) as %CacheString
Inherited description: Reads up to len characters from the current position in the stream. The current position is advanced by the number of characters read. Upon exit, len is set to the actual number of characters read. If a read occurs when the stream position is at the end of the stream, len will be set to -1 and Read() will return a null string (""). If no len is passed in, ie. 'Read()' then it is up to the Read implementation as to how much data to return. Some stream classes use this to optimize the amount of data returned to align this with the underlying storage of the stream.

You must call Rewind() if you want to read a stream from the beginning again. Calling Read() after Write() implicitly ends the Write() operation and rewinds to the start of the stream.

Returns a string up to len characters long. The byref argument sc will return a %Status if any error occurred during the read.

method ReadLine(ByRef len As %Integer = 32000, ByRef sc As %Status, ByRef eol As %Boolean, ByRef term As %String) as %CacheString
Read a line from the file. Note that besides the normal ReadLine arguments this can also be passed a term which will return the termintor that completed the line if we read in a whole line.
method ReadLineIntoStream(ByRef sc As %Status) as %AbstractStream
Inherited description: This reads from the stream until it find the LineTerminator and returns this as a stream. If the stream does not contain the line terminator this can potentially be the entire stream.
method Rewind() as %Status
Inherited description: Go back to the start of the stream.
method SaveStream() as %Status
Inherited description: Deprecated method, use %Save() instead. Saves the temporary copy of the stream data to a persistent location. Note that any locking or transaction handling must be done by the caller.

Returns a %Status value indicating success or failure.

method SizeGet() as %Integer
Return the current size of the data stream.
method Write(data As %CacheString = "") as %Status
Inherited description: Appends the string data to the stream and advances the current stream position by the number of characters in data.

Note that a write operation immediately following a read or rewind will clear out the existing data in the stream.

Returns a %Status value indicating success or failure.

Inherited Members

Inherited Properties

Inherited Methods

Subclasses

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