HTTP Range Requests and streams

HTTP Range Requests and streams

[gautier_niouzes]

Hi,

Is there a library supporting HTTP Range Requests (request only portions of a resource on the server: https://en.wikipedia.org/wiki/Byte_serving ) ?

Just curious...

An idea would be to map a stream type (a derived type from Ada.Streams.Root_Stream_Type, with methods Index and Set_Index) onto that mechanism.

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Re: HTTP Range Requests and streams

[Dmitry A. Kazakov]

On 2020-01-20 09:07, gautier_niouzes@hotmail.com wrote:

> Is there a library supporting HTTP Range Requests (request only portions of a resource on the server: https://en.wikipedia.org/wiki/Byte_serving ) ?
> 
> Just curious...
> 
> An idea would be to map a stream type (a derived type from Ada.Streams.Root_Stream_Type, with methods Index and Set_Index) onto that mechanism.

Do you mean file transfer built-in into the server? A HTTP server 
library merely implements the protocol. What and how the user 
implementation of the server does on top of that is not the library 
business.

The HTTP implementation in Simple Components gets you a request 
callback. In the response you can give an access to a 
Root_Stream_Type'Class object to take the body from.

Now, if you wanted not the whole stream, but a part of it, you could do

    type Stream_Slice
         (  Content : not null access Root_Stream_Type'Class;
            Start   : Stream_Element_Offset
            Size    : Stream_Element_Count
         )  is
    record
       Read_Count : Stream_Element_Count := 0;
    end record;
    overriding procedure Read (...) -- Call Set_Index when Read_Count = 0

I think you get the idea.

I am not sure of it, but I believe that GNAT AWS also allows giving a 
stream to take the response body from.

So IMO it should work relatively smoothly with either.

-- 
Regards,
Dmitry A. Kazakov
http://www.dmitry-kazakov.de