Start implementing https://github.com/ziglang/zig/issues/4917 which is to rename instream/outstream to reader/writer. This first change allows code to use Writer/writer instead of OutStream/outStream, but still maintains the old outstream names with "Deprecated" comments.
The main goal here is to make the function pointers comptime, so that we
don't have to do the crazy stuff with async function frames.
Since InStream, OutStream, and SeekableStream are already generic
across error sets, it's not really worse to make them generic across the
vtable as well.
See #764 for the open issue acknowledging that using generics for these
abstractions is a design flaw.
See #130 for the efforts to make these abstractions non-generic.
This commit also changes the OutStream API so that `write` returns
number of bytes written, and `writeAll` is the one that loops until the
whole buffer is written.
* rework os.sendfile and add macosx support, and a fallback
implementation for any OS.
* fix sendto compile error
* std.os write functions support partial writes. closes#3443.
* std.os pread / pwrite functions can now return `error.Unseekable`.
* std.fs.File read/write functions now have readAll/writeAll variants
which loop to complete operations even when partial reads/writes
happen.
* Audit std.os read/write functions with respect to Linux returning
EINVAL for lengths greater than 0x7fff0000.
* std.os read/write shim functions do not unnecessarily loop. Since
partial reads/writes are part of the API, the caller will be forced
to loop anyway, and so that would just be code bloat.
* Improve doc comments
* Add a non-trivial test for std.os.sendfile
* Fix std.os.pread on 32 bit Linux
* Add missing SYS_sendfile bit on aarch64
