[squeak-dev] The Inbox: Multilingual-jr.218.mcz

H. Hirzel hannes.hirzel at gmail.com
Tue Jan 31 16:40:28 UTC 2017


On 1/27/17, Jakob Reschke <jakob.reschke at student.hpi.de> wrote:
> Well, the alternative to exploiting polymorphy like in the patch would
> be to have a nearly identical bunch of "TextConverter" classes that
> can read from binary streams and answer characters (like the Zinc UTF8
> "Encoder" that also happens to have decoding methods). But most of the
> code would be duplicated with the existing TextConverters, so I think
> it is the worse solution.

To have duplicate classes or even hierarchies for some time is
necessary if you want to do changes which cannot be done
incrementally.

See for example  the class CrLfFileStream and the subclass
HtmlFileStream which are both in the package
'51-Deprecated-Files-Kernel'.

Class comment of CrLfFileStream states
'This class is now obsolete, use MultiByteFileStream instead.'

This can be carried further ...

An option is as well to consider porting the Zinc UTF8 class(es).


>
> IMHO, a fundamental thing such as a text encoding interpreter that is
> shipped with a standard library should not be restricted by "it was
> only designed to be used with consumer xyz".
Yes.

> The TextConverter
> hierarchy is neither marked as internal/private in Multilingual by a
> category, nor by any comments, nor do the class names suggest coupling
> to the MultiByte*Streams.

The TextConverter hierarchy is in the 'Multilingual' category.


> If I were to commit this thing from scratch, I would even drop the
> support for returning the bytes as they are if the source stream
> #isBinary, because it has nothing to do with text conversion.

> Instead,
> do not use a TextConverter, if you do not want the bytes converted.

I do not understand: why would I want to use a TextConverter if I am
reading a binary stream.

> But, as Levente already wrote, we can not do this without a larger
> refactoring and compatibility issues.


--Hannes

> Best regards,
> Jakob
>
> 2017-01-23 19:24 GMT+01:00 H. Hirzel <hannes.hirzel at gmail.com>:
>> Interesting in this context  the UTF8 decoding implementation of Pharo
>> 5 ZnUTF8Encoder (an alternative to UTF8TextConverter it seems)
>>
>> ZnUTF8Encoder>>
>> nextFromStream: stream
>>         | code byte next |
>>         (byte := stream next) < 128
>>                 ifTrue: [ ^ Character codePoint: byte ].
>>         (byte bitAnd: 2r11100000) == 2r11000000
>>                 ifTrue: [
>>                         code := byte bitAnd: 2r00011111.
>>                         ((next := stream next ifNil: [ self
>> errorIncomplete ]) bitAnd:
>> 2r11000000) == 2r10000000
>>                                 ifTrue: [ code := (code bitShift: 6) +
>> (next bitAnd: 2r00111111) ]
>>                                 ifFalse: [ ^ self
>> errorIllegalContinuationByte ].
>>                         code < 128 ifTrue: [ self errorOverlong ].
>>                         ^ Character codePoint: code ].
>>         (byte bitAnd: 2r11110000) == 2r11100000
>>                 ifTrue: [
>>                         code := byte bitAnd: 2r00001111.
>>                         2 timesRepeat: [
>>                                 ((next := stream next ifNil: [ self
>> errorIncomplete ]) bitAnd:
>> 2r11000000) == 2r10000000
>>                                         ifTrue: [ code := (code bitShift:
>> 6) + (next bitAnd: 2r00111111) ]
>>                                         ifFalse: [ ^ self
>> errorIllegalContinuationByte ] ].
>>                         code < 2048 ifTrue: [ self errorOverlong ].
>>                         code = 65279 "Unicode Byte Order Mark" ifTrue: [
>>                                 stream atEnd ifTrue: [ self
>> errorIncomplete ].
>>                                 ^ self nextFromStream: stream ].
>>                         ^ Character codePoint: code ].
>>         (byte bitAnd: 2r11111000) == 2r11110000
>>                 ifTrue: [
>>                         code := byte bitAnd: 2r00000111.
>>                         3 timesRepeat: [
>>                                 ((next := stream next ifNil: [ self
>> errorIncomplete ]) bitAnd:
>> 2r11000000) == 2r10000000
>>                                         ifTrue: [ code := (code bitShift:
>> 6) + (next bitAnd: 2r00111111) ]
>>                                         ifFalse: [ ^ self
>> errorIllegalContinuationByte ] ].
>>                         code < 65535 ifTrue: [ self errorOverlong ].
>>                         ^ Character codePoint: code ].
>>         self errorIllegalLeadingByte
>>
>> On 1/23/17, Levente Uzonyi <leves at caesar.elte.hu> wrote:
>>> The Pharo version seems to be the Squeak version optimized for
>>> VisualWorks (ifNil: -> isNil ifTrue:).
>>>
>>> Levente
>>>
>>> On Mon, 23 Jan 2017, H. Hirzel wrote:
>>>
>>>> Below as a comparison the version in Pharo 5.0.
>>>>
>>>> Noteworthy to say is that one can not speak about characters in an
>>>> UTF8 encoded stream which is read byte by byte until one has examined
>>>> the bytes.
>>>>
>>>> So if I read the first thing it is actually a byte. Then I can examine
>>>> if it is a one-byte character and then return the character. Then I go
>>>> for the next byte. If it indicates that we have a two byte encoded
>>>> UTF8 character then I can return the character.
>>>>
>>>> So I should have
>>>>
>>>> byte1 := aStream basicNext.
>>>>
>>>> ... check if we have a one byte character, if yes return the character
>>>>
>>>> byte2 := aStream basicNext.
>>>>
>>>> ... check if we have a two byte character, if yes return the character
>>>>
>>>> byte3 := aStream basicNext.
>>>>
>>>> ... check if we have a three byte character, if yes return the character
>>>>
>>>>
>>>> byte4 := aStream basicNext.
>>>>
>>>> ... check if we have a four byte character, if yes return the character
>>>>
>>>>
>>>>
>>>>
>>>>
>>>> nextFromStream: aStream
>>>>      | character1 value1 character2 value2 unicode character3 value3
>>>> character4 value4 |
>>>>      aStream isBinary
>>>>              ifTrue: [ ^ aStream basicNext ].
>>>>      character1 := aStream basicNext.
>>>>      character1 isNil
>>>>              ifTrue: [ ^ nil ].
>>>>      value1 := character1 asciiValue.
>>>>      value1 <= 127
>>>>              ifTrue: [
>>>>                      "1-byte character"
>>>>                      ^ character1 ]. "at least 2-byte character"
>>>>      character2 := aStream basicNext.
>>>>      character2 isNil
>>>>              ifTrue: [ ^ self errorMalformedInput ].
>>>>      value2 := character2 asciiValue.
>>>>      (value1 bitAnd: 16rE0) = 192
>>>>              ifTrue: [ ^ Unicode value: ((value1 bitAnd: 31) bitShift:
>>>> 6) +
>>>> (value2 bitAnd: 63) ].       "at least 3-byte character"
>>>>      character3 := aStream basicNext.
>>>>      character3 isNil
>>>>              ifTrue: [ ^ self errorMalformedInput ].
>>>>      value3 := character3 asciiValue.
>>>>      (value1 bitAnd: 16rF0) = 224
>>>>              ifTrue: [ unicode := ((value1 bitAnd: 15) bitShift: 12) +
>>>> ((value2
>>>> bitAnd: 63) bitShift: 6) + (value3 bitAnd: 63) ].
>>>>      (value1 bitAnd: 16rF8) = 240
>>>>              ifTrue: [
>>>>                      "4-byte character"
>>>>                      character4 := aStream basicNext.
>>>>                      character4 isNil
>>>>                              ifTrue: [ ^ self errorMalformedInput ].
>>>>                      value4 := character4 asciiValue.
>>>>                      unicode := ((value1 bitAnd: 16r7) bitShift: 18) +
>>>> ((value2 bitAnd:
>>>> 63) bitShift: 12)
>>>>                              + ((value3 bitAnd: 63) bitShift: 6) +
>>>> (value4 bitAnd: 63) ].
>>>>      unicode isNil
>>>>              ifTrue: [ ^ self errorMalformedInput ].
>>>>      unicode > 16r10FFFD
>>>>              ifTrue: [ ^ self errorMalformedInput ].
>>>>      unicode = 16rFEFF
>>>>              ifTrue: [ ^ self nextFromStream: aStream ].
>>>>      ^ Unicode value: unicode
>>>>
>>>>
>>>>
>>>>
>>>>
>>>> On 1/22/17, Tobias Pape <Das.Linux at gmx.de> wrote:
>>>>>
>>>>> On 22.01.2017, at 16:10, Levente Uzonyi <leves at caesar.elte.hu> wrote:
>>>>>
>>>>>> On Fri, 20 Jan 2017, Tobias Pape wrote:
>>>>>>
>>>>>>>
>>>>>>> On 19.01.2017, at 23:30, Levente Uzonyi <leves at caesar.elte.hu> wrote:
>>>>>>>
>>>>>>>> On Thu, 19 Jan 2017, Tobias Pape wrote:
>>>>>>>>> Thanks Jacob.
>>>>>>>>> Any objections here I put this into trunk?
>>>>>>>> Yep. TextConverters are intended to work with MultiByte*Streams
>>>>>>>> only.
>>>>>>>
>>>>>>> Didn't know that.
>>>>>>>
>>>>>>>> Therefore #basicNext is expected to return a Character, provided the
>>>>>>>> stream is not binary. This is why the #isBinary check is the first
>>>>>>>> thing
>>>>>>>> the method does.
>>>>>>>
>>>>>>> I see. however, using asInteger sounds more reasonable _even though_
>>>>>>> it
>>>>>>> is a character. Said bluntly, the responsibility of the TextConverter
>>>>>>> is
>>>>>>> to make Characters from that bloody numbers in that stream.
>>>>>>> I was confused to see that asciiValue returns something >127 in the
>>>>>>> first
>>>>>>> place.
>>>>>>
>>>>>> #asInteger does the same thing as #asciiValue. While #asciiValue
>>>>>> doesn't
>>>>>> do what you would expect it to do, it has the advantage to clearly
>>>>>> mark
>>>>>> the class of the receiver (in this case).
>>>>>>
>>>>>
>>>>> Yes, and that's exactly why we should use #asInteger. To _not_ limit
>>>>> the
>>>>> receiver.
>>>>> Because the receiver isn't actually a Character, but some number,
>>>>> encoded
>>>>> in
>>>>> a Character, whose meaning is to be determined by
>>>>> this very method.
>>>>>
>>>>> Also, how do we know that _basic_Next will always return a Character?
>>>>> (Yes, I know there's a binary check, but doesn't that only say
>>>>> something
>>>>> about #next, not #basicNext?)
>>>>>
>>>>>
>>>>>>>
>>>>>>>> If there are plans to make TextConverters work with more general
>>>>>>>> streams, then I persume these changes won't be enough.
>>>>>>>
>>>>>>> Clearly.
>>>>>>> But isn't this a step in the right direction?
>>>>>>
>>>>>> Yes and no. There are at least two ways to go:
>>>>>>
>>>>>> 1. Enhance the current stream library, even at the cost of breaking
>>>>>> things.
>>>>>> A patch here and there won't work. There are fundamental changes
>>>>>> required,
>>>>>> like stackable streams, to make it desirable to use it over other
>>>>>> libraries.
>>>>>>
>>>>>> 2. Integrate an existing stream library with better features (e.g.
>>>>>> Xtreams)
>>>>>> If we were to do this, we could gradually migrate existing code to the
>>>>>> new
>>>>>> library, and finally make the current stream library unloadable.
>>>>>
>>>>> I like the idea of Xtreams, but I also like going baby steps.
>>>>>
>>>>> The changes here help at least one person, won't hurt others and seem
>>>>> future
>>>>> proof.
>>>>> So?
>>>>>
>>>>> Best regards
>>>>>     -Tobias
>>>>>
>>>>>
>>>>>
>>>>>> Levente
>>>>>>
>>>>>>>
>>>>>>>> Levente
>>>>>>>>> Looks good from here.
>>>>>>>>> Best regards
>>>>>>>>>         -Tobias
>>>>>>>>> On 19.01.2017, at 17:14, commits at source.squeak.org wrote:
>>>>>>>>>> A new version of Multilingual was added to project The Inbox:
>>>>>>>>>> http://source.squeak.org/inbox/Multilingual-jr.218.mcz
>>>>>>>>>> ==================== Summary ====================
>>>>>>>>>> Name: Multilingual-jr.218
>>>>>>>>>> Author: jr
>>>>>>>>>> Time: 19 January 2017, 5:14:23.763655 pm
>>>>>>>>>> UUID: 36416c42-a4b4-554f-8203-aba25eee794f
>>>>>>>>>> Ancestors: Multilingual-tfel.217
>>>>>>>>>> support 'iso-8859-1' and do not let UTF8TextConverter expect that
>>>>>>>>>> its
>>>>>>>>>> input stream  returns Characters from basicNext
>>>>>>>>>> A stream implementation might always return bytes from basicNext
>>>>>>>>>> and
>>>>>>>>>> expect the conversion to Character to be done solely by the
>>>>>>>>>> TextConverter, so use asInteger instead of asciiValue to support
>>>>>>>>>> both
>>>>>>>>>> cases. Convert back with asCharacter.
>>>>>>>>>> =============== Diff against Multilingual-tfel.217 ===============
>>>>>>>>>> Item was changed:
>>>>>>>>>> ----- Method: Latin1TextConverter class>>encodingNames (in
>>>>>>>>>> category
>>>>>>>>>> 'utilities') -----
>>>>>>>>>> encodingNames +        ^ #('latin-1' 'latin1' 'iso-8859-1') copy.
>>>>>>>>>> -      ^ #('latin-1' 'latin1') copy.
>>>>>>>>>> !
>>>>>>>>>> Item was changed:
>>>>>>>>>> ----- Method: UTF8TextConverter>>nextFromStream: (in category
>>>>>>>>>> 'conversion') -----
>>>>>>>>>> nextFromStream: aStream
>>>>>>>>>>
>>>>>>>>>>        | char1 value1 char2 value2 unicode char3 value3 char4
>>>>>>>>>> value4 |
>>>>>>>>>>        aStream isBinary ifTrue: [^ aStream basicNext].
>>>>>>>>>>        char1 := aStream basicNext.
>>>>>>>>>>        char1 ifNil:[^ nil].
>>>>>>>>>> +      value1 := char1 asInteger.
>>>>>>>>>> -      value1 := char1 asciiValue.
>>>>>>>>>>        value1 <= 127 ifTrue: [
>>>>>>>>>>                "1-byte char"
>>>>>>>>>> +              ^ char1 asCharacter
>>>>>>>>>> -              ^ char1
>>>>>>>>>>        ].
>>>>>>>>>>
>>>>>>>>>>        "at least 2-byte char"
>>>>>>>>>>        char2 := aStream basicNext.
>>>>>>>>>> +      char2 ifNil:[^self errorMalformedInput: (String with: char1
>>>>>>>>>> asCharacter)].
>>>>>>>>>> +      value2 := char2 asInteger.
>>>>>>>>>> -      char2 ifNil:[^self errorMalformedInput: (String with:
>>>>>>>>>> char1)].
>>>>>>>>>> -      value2 := char2 asciiValue.
>>>>>>>>>>
>>>>>>>>>>        (value1 bitAnd: 16rE0) = 192 ifTrue: [
>>>>>>>>>>                ^ Unicode value: ((value1 bitAnd: 31) bitShift: 6)
>>>>>>>>>> + (value2
>>>>>>>>>> bitAnd:
>>>>>>>>>> 63).
>>>>>>>>>>        ].
>>>>>>>>>>
>>>>>>>>>>        "at least 3-byte char"
>>>>>>>>>>        char3 := aStream basicNext.
>>>>>>>>>> +      char3 ifNil:[^self errorMalformedInput: (String with: char1
>>>>>>>>>> asCharacter with: char2 asCharacter)].
>>>>>>>>>> +      value3 := char3 asInteger.
>>>>>>>>>> -      char3 ifNil:[^self errorMalformedInput: (String with: char1
>>>>>>>>>> with:
>>>>>>>>>> char2)].
>>>>>>>>>> -      value3 := char3 asciiValue.
>>>>>>>>>>        (value1 bitAnd: 16rF0) = 224 ifTrue: [
>>>>>>>>>>                unicode := ((value1 bitAnd: 15) bitShift: 12) +
>>>>>>>>>> ((value2 bitAnd:
>>>>>>>>>> 63)
>>>>>>>>>> bitShift: 6)
>>>>>>>>>>                                + (value3 bitAnd: 63).
>>>>>>>>>>        ].
>>>>>>>>>>
>>>>>>>>>>        (value1 bitAnd: 16rF8) = 240 ifTrue: [
>>>>>>>>>>                "4-byte char"
>>>>>>>>>>                char4 := aStream basicNext.
>>>>>>>>>> +              char4 ifNil:[^self errorMalformedInput: (String
>>>>>>>>>> with: char1
>>>>>>>>>> asCharacter with: char2 asCharacter with: char3 asCharacter)].
>>>>>>>>>> +              value4 := char4 asInteger.
>>>>>>>>>> -              char4 ifNil:[^self errorMalformedInput: (String
>>>>>>>>>> with: char1
>>>>>>>>>> with:
>>>>>>>>>> char2 with: char3)].
>>>>>>>>>> -              value4 := char4 asciiValue.
>>>>>>>>>>                unicode := ((value1 bitAnd: 16r7) bitShift: 18) +
>>>>>>>>>>                                        ((value2 bitAnd: 63)
>>>>>>>>>> bitShift: 12) +
>>>>>>>>>>                                        ((value3 bitAnd: 63)
>>>>>>>>>> bitShift: 6) +
>>>>>>>>>>                                        (value4 bitAnd: 63).
>>>>>>>>>>        ].
>>>>>>>>>> +      unicode ifNil:[^self errorMalformedInput: (String with:
>>>>>>>>>> char1
>>>>>>>>>> asCharacter with: char2 asCharacter with: char3 asCharacter)].
>>>>>>>>>> -      unicode ifNil:[^self errorMalformedInput: (String with:
>>>>>>>>>> char1
>>>>>>>>>> with:
>>>>>>>>>> char2 with: char3)].
>>>>>>>>>>        unicode > 16r10FFFD ifTrue: [
>>>>>>>>>> +              ^self errorMalformedInput: (String with: char1
>>>>>>>>>> asCharacter with:
>>>>>>>>>> char2 asCharacter with: char3 asCharacter).
>>>>>>>>>> -              ^self errorMalformedInput: (String with: char1
>>>>>>>>>> with: char2 with:
>>>>>>>>>> char3).
>>>>>>>>>>        ].
>>>>>>>>>>
>>>>>>>>>>        unicode = 16rFEFF ifTrue: [^ self nextFromStream: aStream].
>>>>>>>>>>        ^ Unicode value: unicode.
>>>>>>>>>> !
>>>>>
>>>>>
>>>>>
>>>
>>>
>>
>
>


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