sftp_write: buffer size is limited by 256KiB

[Павел Лобанов <lobanov.ps@xxxxxxxxx>]

Hello!

I use libssh in my project to copy files from local machine to remote by
function sftp_write. And I found that I can not use buffer large than 256
KiB in sftp_write. By that (or not?) I have small copying speed - 1MiB/s.
For comparison, by using libssh2 I get 10MiB/s for copying on same local
machine, but I used 10MiB buffer with libssh2_sftp_write (on 255KiB buffer
the speed is same that I got with libssh).

Why sftp_write function has limit of 256 KiB buffer? Is removing this limit
make upload by sftp faster?

Thanks.
Sorry for my English.