"

 COPYRIGHT (c) 1989 by Claus Gittinger

	      All Rights Reserved

 This software is furnished under a license and may be used

 only in accordance with the terms of that license and with the

 inclusion of the above copyright notice.   This software may not

 be provided or otherwise made available to, or used by, any

 other person.  No title to or ownership of the software is

 hereby transferred.

"

Object subclass:#Stream

	 instanceVariableNames:''

	 classVariableNames:'StreamErrorSignal PositionErrorSignal'

	 poolDictionaries:''

	 category:'Streams'

!

!Stream class methodsFor:'documentation'!

copyright

"

 COPYRIGHT (c) 1989 by Claus Gittinger

	      All Rights Reserved

 This software is furnished under a license and may be used

 only in accordance with the terms of that license and with the

 inclusion of the above copyright notice.   This software may not

 be provided or otherwise made available to, or used by, any

 other person.  No title to or ownership of the software is

 hereby transferred.

"

!

documentation

"

    An abstract class defining common behavior for all stream-like objects.

    See concrete subclasses for more detail.

    Subclasses should (at least) implement:

	#next           (if readable)

	#nextPut:       (if writable)

	#contents

	#atEnd

	#isReadable

	#isWritable

    Class variables:

	StreamErrorSignal       <Signal>        parent of all stream errors

	PositionErrorSignal     <Signal>        position attemted on a stream

						which does not support positioning

"

!

version

! !

!Stream class methodsFor:'initialization'!

initialize

    StreamErrorSignal isNil ifTrue:[

	StreamErrorSignal := ErrorSignal newSignalMayProceed:false.

	StreamErrorSignal nameClass:self message:#streamErrorSignal.

	StreamErrorSignal notifierString:'Stream error'.

	PositionErrorSignal := StreamErrorSignal newSignalMayProceed:true.

	PositionErrorSignal nameClass:self message:#positionErrorSignal.

	PositionErrorSignal notifierString:'stream as no concept of a position'.

    ]

! !

!Stream class methodsFor:'instance creation'!

new

    "report an error - Streams are created using on:-messages"

    ^ self error:'Streams cannot be created with new'

! !

!Stream class methodsFor:'Signal constants'!

positionErrorSignal

    "return the signal raised if positioning is requested for

     a stream which does not support that kind of operation"

    ^ PositionErrorSignal

!

streamErrorSignal

    "return the parent of all stream errors;

     handling this one also handles all other errors.

     Also, this one may be raised for errors not related to read/write

     operations, such as failed ioctls in externalStream etc."

    ^ StreamErrorSignal

! !

!Stream methodsFor:'accessing'!

contents

    "return the entire contents of the stream

     - we do not know here how to do it, it must be redefined in subclass"

    ^ self subclassResponsibility

! !

!Stream methodsFor:'closing'!

close

    "close the stream - nothing done here.

     Added for compatibility with external streams."

    ^ self

! !

!Stream methodsFor:'enumerating'!

do:aBlock

    "evaluate the argument, aBlock for all remaining elements,

     up to the end of the stream"

    [self atEnd] whileFalse:[

	aBlock value:(self next)

    ]

    "

     |s|

     s := ReadStream on:#(1 2 3 4 5 6 7 8 9).

     s next.

     s next.

     s do:[:element | Transcript showCr:element]

    "

! !

!Stream methodsFor:'misc'!

binary

    "switch to binary mode. ignored here, but added to make

     internalStreams protocol compatible with externStreams."

! !

!Stream methodsFor:'non homogenous reading'!

nextLine

    "for compatibility with externalStreams"

    ^ self upTo:Character cr.

!

nextLongMSB:msbFlag

    "return a signed long (4 bytes) from the stream.

     The receiver must support reading of binary bytes."

    |high uval "{ Class: SmallInteger }"|

    msbFlag ifTrue:[

	"most significant first"

	high := self next.

	uval := self next bitShift:16.

	uval := uval bitOr:(self next bitShift:8).

	uval := uval bitOr:(self next).

	uval := uval bitOr:(high bitShift:24).

    ] ifFalse:[

	"least significant first"

	uval := self next.

	uval := uval bitOr:(self next bitShift:8).

	uval := uval bitOr:(self next bitShift:16).

	uval := uval bitOr:(self next bitShift:24).

    ].

    "change from unsigned 0..FFFFFFFF to signed -80000000..7FFFFFFF"

"sorry- for now, stc cannot compile LargeInteger constants 

    uval >= 16r80000000 ifTrue:[

	^ uval - 16r100000000 

    ].

the following kludges around this"

    (uval bitShift:-16) >= 16r8000 ifTrue:[

	^ uval - (16r10000000 bitShift:8)

    ].

    ^ uval

!

nextNumber:n 

    "Return the next n bytes as a positive Integer; bytes are taken msb-first."

    |s 

     val "{ Class: SmallInteger }"

     rep "{ Class: SmallInteger }"|

    "claus: this method is central in binaryStorage -

     therefore it has been tuned a bit (and needs even more tuning)"

    n == 1 ifTrue:[

	^ self next

    ].

    n == 2 ifTrue:[

	val := self next.

	val := (val bitShift:8) + self next.

	^ val

    ].

    n == 3 ifTrue:[

	val := self next.

	val := (val bitShift:8) + self next.

	val := (val bitShift:8) + self next.

	^ val

    ].

    n == 4 ifTrue:[

	val := self next.

	val <= 16r3F ifTrue:[

	    val := (val bitShift:8) + self next.

	    val := (val bitShift:8) + self next.

	    val := (val bitShift:8) + self next.

	    ^ val

	].

	"sorry, but need a largeInteger"

	s := (val bitShift:8) + self next.

	s := (s bitShift:8) + self next.

	"the multiplication below is a temporary workaround for the

	 inability of smallintegers to handle shifts out of the 32bit range ..."

	s := (s * 256) + self next.

	^ s

    ].

    "

     arbitrary long

    "

    s := 0.

    rep := n.

    rep timesRepeat:[ 

	s := s * 256 + self next

    ].

    ^ s truncated

!

nextShortMSB:msbFlag

    "return a signed short (2 bytes) from the stream.

     The receiver must support reading of binary bytes."

    |uval "{ Class: SmallInteger }"|

    msbFlag ifTrue:[

	"most significant first"

	uval := self next bitShift:8.

	uval := uval bitOr:(self next).

    ] ifFalse:[

	"least significant first"

	uval := self next.

	uval := uval bitOr:(self next bitShift:8).

    ].

    "change from unsigned 0..FFFF to signed -8000..7FFF"

    uval >= 16r8000 ifTrue:[

	^ uval - 16r10000 

    ].

    ^ uval

!

nextUnsignedLongMSB:msbFlag

    "return an unsigned long (4 bytes) from the stream.

     The receiver must support reading of binary bytes."

    |val|

    msbFlag ifTrue:[

	val := self next.

	val := (val bitShift:8) bitOr:(self next).

	val := (val bitShift:8) bitOr:(self next).

	val := (val * 256) + (self next).

	^ val

    ].

    val := self next.

    ^ (val bitShift:24)

      + (self next bitShift:16)

      + (self next bitShift:8)

      + self next

!

nextUnsignedShortMSB:msbFlag

    "return an unsigned short (2 bytes) from the stream.

     The receiver must support reading of binary bytes."

    msbFlag ifTrue:[

	^ (self next bitShift:8) bitOr:(self next)

    ].

    ^ (self next) bitOr:(self next bitShift:8)

!

nextWord

    ^ self nextAlphaNumericWord

! !

!Stream methodsFor:'non homogenous writing'!

nextLongPut:aNumber

    "for ST-80 compatibility"

    ^ self nextPutLong:aNumber MSB:true

!

nextNumber:n put:v 

    "Append to the receiver the argument, v, which is a positive Integer,

     as the next n bytes. Bytes are written msb first. 

     Possibly pad with leading zeros.

     The receiver must support writing of binary bytes."

    |vlen i|

    "claus: this method is central in binaryStorage -

     therefore it has been tuned a bit (and needs even more tuning)"

    v class == SmallInteger ifTrue:[  "- this is a hint to stc"

	n == 1 ifTrue:[

	    (v between:0 and:16rFF) ifTrue:[

		self nextPut:v.

		^ self

	    ].

	].

	n == 2 ifTrue:[

	    (v between:0 and:16rFFFF) ifTrue:[

		self nextPut:(v bitShift:-8).

		self nextPut:(v bitAnd:16rFF).

		^ self

	    ].

	].

	n == 3 ifTrue:[

	    (v between:0 and:16rFFFFFF) ifTrue:[

		self nextPut:((v bitShift:-16) bitAnd:16rFF).

		self nextPut:((v bitShift:-8) bitAnd:16rFF).

		self nextPut:(v bitAnd:16rFF).

		^ self

	    ].

	].

	n == 4 ifTrue:[

	    (v >= 0) ifTrue:[

		self nextPut:((v bitShift:-24) bitAnd:16rFF).

		self nextPut:((v bitShift:-16) bitAnd:16rFF).

		self nextPut:((v bitShift:-8) bitAnd:16rFF).

		self nextPut:(v bitAnd:16rFF).

		^ self

	    ].

	].

    ].

    "

     arbitrary long

    "

    n < (vlen := v digitLength) ifTrue: [

	"

	 the number is too big to be repesented in n bytes

	"

	self error: 'number too big'

    ].

    "pad with leading zeros"

    i := n.

    [i > vlen] whileTrue: [

	self nextPut: 0. 

	i := i - 1

    ].

    i = 1 ifTrue: [

	^ self nextPut: v

    ].

    [i > 0] whileTrue: [

	self nextPut: (v digitAt: i). 

	i := i - 1

    ]

!

nextPutLong:aNumber MSB:msbFlag

    "Write the argument, aNumber as a long (four bytes). If msbFlag is

     true, data is written most-significant byte first; otherwise least

     first. Returns the receiver on ok, nil on error.

     The receiver must support writing of binary bytes."

    msbFlag ifTrue:[

	"high word first"

	self nextShortPut:(aNumber // 16r10000) MSB:true.

	^ self nextShortPut:(aNumber \\ 16r10000) MSB:true

    ].

    "low word first"

    self nextShortPut:(aNumber \\ 16r10000) MSB:false.

    ^ self nextShortPut:(aNumber // 16r10000) MSB:false.

!

nextPutShort:aNumber MSB:msbFlag

    "Write the argument, aNumber as a short (two bytes). If msbFlag is

     true, data is written most-significant byte first; otherwise least

     first. Returns the receiver on ok, nil on error.

     The receiver must support writing of binary bytes."

    msbFlag ifTrue:[

	"most significant first"

	self nextPut:(aNumber bitShift:-8).

	^ self nextPut:(aNumber bitAnd:16rFF).

    ].

    "least significant first"

    self nextPut:(aNumber bitAnd:16rFF).

    self nextPut:(aNumber bitShift:-8).

!

nextPutWord:aNumber

    "write the argument, aNumber as a signed short (two bytes);

     write msb-first for compatibility with other smalltalks.

     The receiver must support writing of binary bytes.

     I dont know if it should be named nextPutWord: or nextWordPut:;

     one of them will vanish ..."

    ^ self nextPutShort:aNumber MSB:true

!

nextShortPut:aNumber MSB:msbFlag

    "for compatibility - this will vanish"

    ^ self nextPutShort:aNumber MSB:msbFlag

!

nextWordPut:aNumber

    "for ST-80 compatibility"

    ^ self nextPutShort:aNumber MSB:true

! !

!Stream methodsFor:'private'!

contentsSpecies

    "this should return the class of which an instance is

     returned by the #contents method. It is redefinable in subclasses"

    "return Array here - since the abstract Stream has no idea

     of the underlying collection class"

    ^ Array

! !

!Stream methodsFor:'queries'!

isBinary

    "return true, if in binary mode. Returns false here,

     to make internalStreams protocol compatible with externStreams."

    ^ false

!

isPositionable

    "return true, if the stream supports positioning (some do not)"

    ^ false

!

isReadable

    "return true, if reading is supported by the recevier.

     Assume yes here."

    ^ self subclassResponsibility

!

isStream

    "return true, if the receiver is some kind of Stream."

    ^ true

!

isWritable

    "return true, if writing is supported by the recevier.

     Assume yes here."

    ^ self subclassResponsibility

!

lineLength

    "this is just a layout hint for prettyprinting functions

     - for compatibility with TextCollectors"

    ^ 80

! !

!Stream methodsFor:'reading'!

next

    "return the next element of the stream

     - we do not know here how to do it, it must be redefined in subclass"

    ^ self subclassResponsibility

!

next:count

    "return the next count elements of the stream as a Collection."

    |answerStream 

     cnt  "{ Class: SmallInteger }" |

    answerStream := WriteStream on:(self contentsSpecies new).

    cnt := count.