Class: SplittingWriteStream

• Inheritance
• Description
• Related information
• Class protocol
  • instance creation
• Instance protocol
  • accessing
  • private access
  • redirect messages
  • writing
• Examples

Inheritance:

   Object
   |
   +--Stream
      |
      +--SplittingWriteStream

Package:

stx:libbasic2

Category:

Streams-Misc

Version:

rev: 1.12 date: 2019/04/01 15:17:55

user: cg

file: SplittingWriteStream.st directory: libbasic2

module: stx stc-classLibrary: libbasic2

Author:

Claus Gittinger (cg@exept)

Description:

A stream duplicator - everything written onto a splittingWriteStream
is written to two real streams.
Useful, if you have to send something to two files/destinations
simultaneously, and do not want to (or cannot) buffer it.

Especially useful, to generate a checksum, 
while sending something to a file 
(if one of the output streams is a checksummer).

Also, to duplicate some output to a Transcript.
The second stream can be closed and nilled, if no longer needed.



[instance variables:]
    outStream1      <Stream>       actual output streams
    outStream2      <Stream>

[class variables:]

Related information:

    WriteStream

Class protocol:

 on: stream1 and: stream2

Instance protocol:

 outStream1

return the value of the instance variable 'outStream1' (automatically generated)

 outStream1: aStream

set the value of the instance variable 'outStream1' (automatically generated)

 outStream2

return the value of the instance variable 'outStream2' (automatically generated)

 outStream2: aStreamOrNil

set the value of the instance variable 'outStream2' (automatically generated)

 setOutStream1: stream1 outStream2: stream2

 doesNotUnderstand: aMessage

if my superclass implements the message, it can be forwarded to both streams.

 clear

 close

(comment from inherited method)
close the stream - nothing done here.
Added for compatibility with external streams.

 contents

 cr

(comment from inherited method)
append a carriage-return to the stream.
This is only allowed, if the receiver supports writing.

 endEntry

(comment from inherited method)
ignored here - for compatibility with Transcript

 flush

(comment from inherited method)
write out all unbuffered data - ignored here, but added
to make internalStreams protocol compatible with externalStreams

 nextPut: something

(comment from inherited method)
put the argument, anObject onto the receiver
- we do not know here how to do it, it must be redefined in subclass

 nextPutAll: something

(comment from inherited method)
put all elements of the argument, aCollection onto the receiver.
This is only allowed, if the receiver supports writing.

 nextPutAll: aCollection startingAt: start to: stop

append the elements from first index to last index
of the argument, aCollection onto the receiver (i.e. both outstreams)

 nextPutAllUnicode: aString

(comment from inherited method)
normal streams can not handle multi-byte characters, so convert them to utf8

 show: something

(comment from inherited method)
append a printed representation of the argument to the stream.
This makes streams somewhat compatible to TextCollectors and
allows you to say:
Smalltalk at:#Transcript put:Stdout
or to use #show:/#showCR: with internal or external streams.

Examples:

  |s1 s2 splitter|

  s1 := '/tmp/foo1' asFilename writeStream.
  s2 := '/tmp/foo2' asFilename writeStream.
  splitter := SplittingWriteStream on:s1 and:s2.
  splitter nextPutAll:'hello world'.
  splitter close.

  |s1 s2 splitter hash|

  s1 := '/tmp/foo1' asFilename writeStream.
  s2 := SHA1Stream new.
  splitter := SplittingWriteStream on:s1 and:s2.
  splitter nextPutAll:'hello world'.
  splitter close.
  hash := s2 hashValue. 
  self assert:(hash = (SHA1Stream hashValueOf:'hello world'))