abstract stream class %Library.AbstractStream extends %Stream.Object
Deprecated class, the base stream class is %Stream.Object. This is kept for legacy reasons.
A stream represents an arbitrary array of characters (or bytes) and
a current position. The basic stream interface provides the ability to
read data from a stream, write data to the stream, and rewind the
current position to the beginning of the stream.
Within InterSystems IRIS streams are used to create large (greater than 32K)
object attributes.
Type of line terminator we use for this stream, defaults to Cr/Lf. Maximum length is 10 characters.
This is stored as an attribute of the stream called 'LineTerminator'.
Inherited description: Returns true (1) if a property of this instance has been modified, otherwise false (0).
A TRUE result does not necessarily mean that any property has actually been changed. If
%IsModified() returns false then the object has not been modified. There are some
situations where we simply cannot efficiently detect a change in value. In these cases we
will set the modified status of the property.
Returns true if this is a "NULL" stream; that is, a stream which has never
been written to and saved. This is used by the InterSystems IRIS ODBC server.
Inherited description: This method is somewhat similar to %IsModified but it also checks to see if swizzled
references would cause the object to become modified should they be serialized. This works
on the assumption that a reference to a persistent object will never be modified if the ID has
already been assigned. For references to serial objects, a call to %ObjectModified indicates
whether or not the serialized value is different. If the reference to a swizzled object is
different from the initial object state then the $$$objModAll macro will already return true.
Reference the Set code.
Returns true (1) if this instance has been modified, otherwise false (0).
Deprecated method, use %Delete() instead.
Deletes the stored stream identified by oid. This will not remove the stream attributes of any
saved streams, it will just remove the stream data. If you need to clear the attributes as well you will
have to call Clear() on the stream object.
Returns true if this is a "NULL" stream; that is, a stream which has never
been written to and saved. This is used by the InterSystems IRIS ODBC server.
method LineTerminatorSet(terminator As %String) 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.
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.
Inherited description: Read a line from the stream. This will look for the line terminator in the stream and
once it finds the terminator it will return the string minus the terminator character/s. If it reaches the
end of the stream before it finds a terminator it will return the data it has so far, and if you specify a
maximum size in len it will only read up to this number of characters. On exit len
will contain the actual number of characters read. The byref argument sc will
return a %Status() if any error occured during the read and the byref argument eol
is true if it found the line terminator and false otherwise. So for example you can read in a stream
a line at a time and output the results to the current device with:
While 'stream.AtEnd { Write stream.ReadLine(,.sc,.eol) If $$$ISERR(sc) { Write "ERROR" Quit } If eol { Write ! } }
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.
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.
final method SetAttribute(name As %String, value As %String)
Inserts an attribute variable by name into the collection
Appends the string data along with a line terminator to the stream and advances the
current stream position by the number of characters in data plus the line terminator.
Returns a %Status value indicating success or failure.