Some e2e tests were disabled on iOS because they hit the Apple CFStream bug.
This commit enables e2e tests and works around the Apple bug by disabling CFStream.
on_hdr() checks if a void-return function pointer is null before jumping to it.
If it is null, it returns an error; else it executes that function and returns
success.
This change converts the void-returning function to one that returns a
grpc_error* and thus saves a branch in on_hdr() (since we're branching once by
following the function pointer anyways, we're effectively coalescing these two
branches).
In several cases, we create grpc mdelem structures using known-static
metadata inputs. Furthermore, in several cases we create a slice on
the heap (e.g. grpc_slice_from_copied_buffer) where we know we are
transferring refcount ownership. In several cases, then, we can:
1) Avoid unnecessary ref/unref operations that are no-ops (for static
slices) or superfluous (if we're transferring ownership).
2) Avoid unnecessarily comprehensive calls to grpc_slice_eq (since
they'd only be called with static or interned slice arguments,
which by construction would have equal refcounts if they were
in fact equal.
3) Avoid unnecessary checks to see if a slice is interned (when we
know that they are).
To avoid polluting the internal API, we introduce the notion of
strongly-typed grpc_slice objects. We draw a distinction between
Internal (interned and static-storage) slices and Extern (inline and
non-statically allocated). We introduce overloads to
grpc_mdelem_create() and grpc_mdelem_from_slices() for the fastpath
cases identified above based on these slice types.
From the programmer's point of view, though, nothing changes - they
need only use grpc_mdelem_create() and grpc_mdelem_from_slices() as
before, and the appropriate fastpath will be picked based on type
inference. If no special knowledge exists for the slice type (i.e. we
pass in generic grpc_slice objects), the slowpath method will still
always return correct behaviour.
This is good for:
- Roughly 1-3% reduction in CPU time for several unary/streaming
ping pong fullstack microbenchmarks.
- Reduction of about 15-20% in CPU time for some hpack parser
microbenchmarks.
- 10-12% reduction of CPU time for metadata microbenchmarks involving
interned slice comparisons.