[PATCH 2/2] buffer: allow limiting the amount of bytes output

[Eric Wong <e@80x24.org>]

This will aid in allowing us to create effects which affect
only a certain part of a track.
---
 lib/dtas/buffer.rb            | 6 +++---
 lib/dtas/buffer/read_write.rb | 9 +++++----
 lib/dtas/buffer/splice.rb     | 9 +++++----
 3 files changed, 13 insertions(+), 11 deletions(-)

diff --git a/lib/dtas/buffer.rb b/lib/dtas/buffer.rb
index b03ed8a..23b0b77 100644
--- a/lib/dtas/buffer.rb
+++ b/lib/dtas/buffer.rb
@@ -48,14 +48,14 @@ def __dst_error(dst, e)
   # - subset of targets array for :wait_writable
   # - some type of StandardError
   # - nil
-  def broadcast(targets)
+  def broadcast(targets, limit = nil)
     case targets.size
     when 0
       :ignore # this will pause decoders
     when 1
-      broadcast_one(targets)
+      broadcast_one(targets, limit)
     else # infinity
-      broadcast_inf(targets)
+      broadcast_inf(targets, limit)
     end
   end
 
diff --git a/lib/dtas/buffer/read_write.rb b/lib/dtas/buffer/read_write.rb
index a27b823..64ad297 100644
--- a/lib/dtas/buffer/read_write.rb
+++ b/lib/dtas/buffer/read_write.rb
@@ -26,9 +26,9 @@ def discard(bytes)
   end
 
   # always block when we have a single target
-  def broadcast_one(targets)
+  def broadcast_one(targets, limit = nil)
     buf = _rbuf
-    @to_io.read_nonblock(MAX_AT_ONCE, buf)
+    @to_io.read_nonblock(limit || MAX_AT_ONCE, buf)
     n = targets[0].write(buf) # IO#write has write-in-full behavior
     @bytes_xfer += n
     :wait_readable
@@ -42,7 +42,7 @@ def broadcast_one(targets)
     nil # do not return error here, we already spewed an error message
   end
 
-  def broadcast_inf(targets)
+  def broadcast_inf(targets, limit = nil)
     nr_nb = targets.count(&:nonblock?)
     if nr_nb == 0 || nr_nb == targets.size
       # if all targets are full, don't start until they're all writable
@@ -61,7 +61,8 @@ def broadcast_inf(targets)
 
     # don't pin too much on one target
     bytes = inflight
-    bytes = bytes > MAX_AT_ONCE ? MAX_AT_ONCE : bytes
+    limit ||= MAX_AT_ONCE
+    bytes = bytes > limit ? limit : bytes
     buf = _rbuf
     @to_io.read(bytes, buf)
     n = buf.bytesize
diff --git a/lib/dtas/buffer/splice.rb b/lib/dtas/buffer/splice.rb
index b987f3a..02ce877 100644
--- a/lib/dtas/buffer/splice.rb
+++ b/lib/dtas/buffer/splice.rb
@@ -28,9 +28,10 @@ def discard(bytes)
     IO.splice(@to_io, nil, DEVNULL, nil, bytes)
   end
 
-  def broadcast_one(targets)
+  def broadcast_one(targets, limit = nil)
     # single output is always non-blocking
-    s = IO.trysplice(@to_io, nil, targets[0], nil, MAX_AT_ONCE_1, F_MOVE)
+    limit ||= MAX_AT_ONCE_1
+    s = IO.trysplice(@to_io, nil, targets[0], nil, limit, F_MOVE)
     if Symbol === s
       targets # our one and only target blocked on write
     else
@@ -88,7 +89,7 @@ def __broadcast_tee(blocked, targets, chunk_size)
     most_teed
   end
 
-  def broadcast_inf(targets)
+  def broadcast_inf(targets, limit = nil)
     if targets.all?(&:ready_write_optimized?)
       blocked = []
     elsif targets.none?(&:nonblock?)
@@ -105,7 +106,7 @@ def broadcast_inf(targets)
     end
 
     # don't pin too much on one target
-    bytes = MAX_AT_ONCE
+    bytes = limit || MAX_AT_ONCE
     last = targets.pop # we splice to the last one, tee to the rest
 
     # this may return zero if all targets were non-blocking
-- 
EW