* 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
This changset adds a `sendfile(2)` syscall bindings to the linux bits
component. Where available, the `sendfile64(2)` syscall will be
transparently called.
A wrapping function has also been added to the std.os to transform
errno returns to Zig errors.
Change-Id: I86769fc4382c0771e3656e7b21137bafd99a4411
Michael Dusan
Andrew Kelley
Terin Stock
daurnimator
Jethro Nederhof