Make the slow path faster by reducing input- and output-end
coordination. Also, avoid retaining one end just because the other end
is retained.
This change involves adding an indirection for the fast-path buffers
so that management for both ends of a pipe can be centralized
independent of the ports.
Sortof. This is where we especially take advantage of vtable
flexibility. The methods of the vtable are really closures,
because that's far more convenient for custom ports.
Change the internal port representation to an object-with-vtable
representation. The syntax looks similar to the class system of
`racket/class`, but everything is first-order: no class values, no
mixins, etc. Also, the vtable can contain non-procedures (like #f for
"not supported" or a port to mean a direcirection).
Using objects will make port instaces smaller and support a
reorganization to eliminate ad hoc `data`-field extensions. It will
also replace a half-step was was in place for byte input
Along with the conversion, change the way the fast path for writing
works: When possible, expose a shared buffer and index into that
buffer.
Only byte string input ports are really converted, so far. A
compatibility layer maps the old protocol to the new one, so
conversion can continue piecewise.
Show the compile-time value that is not a procedure. While
this runs some risk of exposing details that are meant
to be private to a macro/language, a macro/language can
use an applicable structure to provide a more specific
error message. Meanwhile, showing the value is likely to
help for someone who needs to debug a macro problem.
When the desired reference is not an advertised commit, then try
pulling just a few commits --- at depth 8, 16, and 32 -- from the
"master" branch to check whether the commit can be found that way. If
not, fall back to the exhaustive search that requires a full download.
This should help with the common case that a package reference into
the Racket repo is a few commits behind the current master branch
(because the package server hasn't scanned the repo recently enough).
It's much faster to disover that the commit is within the first 32,
which is almost always is, than to download the entire repository.
Upgrading an auto install to an explicit install runs into trouble if
the auto install is in a wider scope. It doens't seem necessary to
promote already-installed packages for migration, anyway.
