From 34eedcb52f02f4dddccace2f0d411bc8bc396150 Mon Sep 17 00:00:00 2001
From: Omar Rizwan <omar@omar.website>
Date: Sat, 17 Jun 2023 12:41:36 -0400
Subject: fork play

---
 play/fork-play.tcl   | 23 ++++++++++++++++++++
 play/zygote-play.tcl | 60 ++++++++++++++++++++++++++++++++++++++++++++++++++++
 2 files changed, 83 insertions(+)
 create mode 100644 play/fork-play.tcl
 create mode 100644 play/zygote-play.tcl

diff --git a/play/fork-play.tcl b/play/fork-play.tcl
new file mode 100644
index 00000000..920a8987
--- /dev/null
+++ b/play/fork-play.tcl
@@ -0,0 +1,23 @@
+source "lib/c.tcl"
+set cc [c create]
+$cc include <unistd.h>
+$cc proc ::fork {} int {
+    return fork();
+}
+$cc compile
+
+puts "In parent ([pid]). Forking"
+set pid [fork]
+if {$pid == 0} {
+    puts "In child ([pid]). Forking"
+    set pid2 [fork]
+    if {$pid2 == 0} {
+        puts "In grandchild ([pid]). Done"
+        exit 0
+    }
+    puts "In child. Done"
+    exit 0
+}
+
+puts "In parent. Done"
+while true {}
diff --git a/play/zygote-play.tcl b/play/zygote-play.tcl
new file mode 100644
index 00000000..358e59cd
--- /dev/null
+++ b/play/zygote-play.tcl
@@ -0,0 +1,60 @@
+source "lib/c.tcl"
+set cc [c create]
+$cc include <unistd.h>
+$cc proc ::fork {} int {
+    return fork();
+}
+$cc compile
+
+namespace eval Zygote {
+    proc init {} {
+        variable writer
+        lassign [chan pipe] reader writer
+        set pid [fork]
+        if {$pid == 0} {
+            # We're in the child (the zygote). We will block waiting
+            # for commands from the parent (the original/main thread).
+            close $writer
+
+            fconfigure $reader -buffering line
+            # Zygote's main loop:
+            set script ""
+            while {[gets $reader line] != -1} {
+                append script $line\n
+                if {[info complete $script]} {
+                    # FIXME: This fork breaks it.
+                    set pid [fork]
+                    if {$pid == 0} {
+                        eval $script
+                        exit 0
+                    }
+                    set script ""
+                }
+            }
+            exit 0
+
+        } else {
+            # We're still in the parent. The child (the zygote) is $pid.
+            close $reader
+            # We will send the zygote a message every time we want it to
+            # fork.
+            fconfigure $writer -buffering line
+        }
+    }
+    proc spawn {code} {
+        variable writer
+        puts $writer $code
+    }
+}
+
+Zygote::init
+
+Zygote::spawn {
+    puts "hello from [pid]"
+}
+Zygote::spawn {
+    puts "wow from [pid]"
+}
+
+after 3000 { puts done; set ::done true }
+vwait ::done
-- 
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