[fpc-devel] zstream, fpc and lazarus

[Paul Ishenin]

Daniël Mantione wrote:
> Op Sun, 2 Dec 2007, schreef Paul Ishenin:
>
>   
>> Daniël Mantione ?????:
>>     
>>>  Ok, read with me. If we seek backwards (which is the case with offset 0
>>> from beginning), we call reset:
>>>
>>> if origin=sofrombeginning then
>>>  dec(offset,raw_read);
>>> if offset<0 then
>>> begin
>>> inc(offset,raw_read);
>>> reset;
>>> end;
>>>
>>> Inside reset, we set the source stream position to 0:
>>>
>>>       
>> No, Daniel. When we just create TDecompressionStream we seeks to
>> soFromBeginning, 0. We have raw_read = 0, so offset = 0 too after dec(offset,
>> raw_read). And next condition with offset < 0 then is false 
>> =>  so no reset call.
>>
>> I fixed that locally after your commit and lazarus works.
>>     
>
> This seems extremely strange to me. Are you telling that the source stream 
> is not at the start of the Zstream when you create the decompression stream?
>   
Exactly. At least when I debugged pngreader it was at the end.
> By the way, I'm getting some doubts about position:=0. This basically 
>   
This is according codegear help. We should folow it since many code 
depends on it.
> seeks the source file to its begin. But what happens if the Zstream does 
> not start at the beginning of the file?
>   
My assumption is that zstream must be at the begining or one should use 
temporary memory stream to achieve that.

Best regards,
Paul Ishenin.