From fb8f3bcd6cec02243098ec60838ce0a7778aff38 Mon Sep 17 00:00:00 2001
From: David Thompson <dthompson2@worcester.edu>
Date: Thu, 29 Nov 2018 16:26:48 -0500
Subject: scripting: channel: Add channel-get! and channel-put! procedures.

* chickadee/scripting/channel.scm (channel-get!, channel-put!): New
  procedures.
* doc/api.texi [Channels]: Add docs.
---
 chickadee/scripting/channel.scm | 22 ++++++++++++++++++----
 doc/api.texi                    | 17 +++++++++++++----
 2 files changed, 31 insertions(+), 8 deletions(-)

diff --git a/chickadee/scripting/channel.scm b/chickadee/scripting/channel.scm
index 4d8583f..7ec11ce 100644
--- a/chickadee/scripting/channel.scm
+++ b/chickadee/scripting/channel.scm
@@ -23,7 +23,9 @@
   #:use-module (chickadee scripting script)
   #:export (make-channel
             channel?
+            channel-get!
             channel-get
+            channel-put!
             channel-put))
 
 ;; A very simplified notion of channels compared to guile-fibers.  In
@@ -55,18 +57,30 @@
              (get-cont data)
              (put-cont)))))))
 
+(define (channel-get! channel proc)
+  "Asynchronously retrieve a value from CHANNEL and call PROC with
+that value."
+  (enqueue! (channel-get-queue channel) proc)
+  (maybe-deliver channel))
+
 (define (channel-get channel)
   "Retrieve a value from CHANNEL.  The current script suspends until a
 value is available."
   (yield
    (lambda (cont)
-     (enqueue! (channel-get-queue channel) cont)
-     (maybe-deliver channel))))
+     (channel-get! channel cont))))
+
+(define noop (lambda () #t))
+
+(define* (channel-put! channel data #:optional (thunk noop))
+  "Asynchronously send DATA to CHANNEL and call THUNK after it has
+been received."
+  (enqueue! (channel-put-queue channel) (cons data thunk))
+  (maybe-deliver channel))
 
 (define (channel-put channel data)
   "Send DATA to CHANNEL.  The current script suspends until another
 script is available to retrieve the value."
   (yield
    (lambda (cont)
-     (enqueue! (channel-put-queue channel) (cons data cont))
-     (maybe-deliver channel))))
+     (channel-put! channel data cont))))
diff --git a/doc/api.texi b/doc/api.texi
index 4c34cf4..c79af20 100644
--- a/doc/api.texi
+++ b/doc/api.texi
@@ -1934,10 +1934,6 @@ procedure @var{handler}.
 Wait @var{duration} before resuming the current script.
 @end deffn
 
-@deffn {Procedure} channel-get @var{channel}
-Wait for a message from @var{channel}.
-@end deffn
-
 @deffn {Syntax} forever @var{body} @dots{}
 Evaluate @var{body} in an endless loop.
 @end deffn
@@ -2014,3 +2010,16 @@ until a value is available.
 Send @var{data} to @var{channel}.  The current script suspends until
 another script is available to retrieve the value.
 @end deffn
+
+A low-level API also exists for using channels outside of a script via
+callback procedures:
+
+@deffn {Procedure} channel-get! @var{channel} @var{proc}
+Asynchronously retrieve a value from @var{channel} and call @var{proc}
+with that value.
+@end deffn
+
+@deffn {Procedure} channel-put! @var{channel} @var{data} [@var{thunk}]
+Asynchronously send @var{data} to @var{channel} and call @var{thunk}
+after it has been received.
+@end deffn
-- 
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