From 135fbf911740e88b802d340fe3e747dd39966ec4 Mon Sep 17 00:00:00 2001
From: Julian Blake Kongslie
Date: Mon, 29 Mar 2021 13:59:45 -0700
Subject: Trivial assembler.

---
 asm.rb | 64 ++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++
 1 file changed, 64 insertions(+)
 create mode 100755 asm.rb

(limited to 'asm.rb')

diff --git a/asm.rb b/asm.rb
new file mode 100755
index 0000000..9ba1e04
--- /dev/null
+++ b/asm.rb
@@ -0,0 +1,64 @@
+#!/usr/bin/ruby -w
+
+OPCODES = {
+  "acc="  => 0x000,
+  "load"  => 0x100,
+  "store" => 0x200,
+  "ifeq"  => 0x300,
+  "jmp"   => 0x400,
+  "++acc" => 0xf01,
+  "--acc" => 0xf02,
+  "++idx" => 0xf04,
+  "--idx" => 0xf08,
+  "swap"  => 0xf10,
+  "idx"   => 0xf20,
+  "tx"    => 0xf40,
+  "halt"  => 0xf80,
+  }
+
+Line = Struct.new(:opcode, :refs, :code)
+
+$labels = {}
+$code = []
+ARGF.each_line() do | line |
+  line.chomp!()
+  next unless line =~ /\S/
+  op = 0x000
+  refs = []
+  line.scan(/\S+/).each() do | word |
+    if word =~ /^0(\d+)$/
+      op |= $1.to_i(8)
+    elsif word =~ /^-0(\d+)$/
+      op |= 0x100 - $1.to_i(8)
+    elsif word =~ /^(\d+)$/
+      op |= $1.to_i(10)
+    elsif word =~ /^-(\d+)$/
+      op |= 0x100 - $1.to_i(10)
+    elsif word =~ /^0x([0-9a-f]+)$/i
+      op |= $1.to_i(16)
+    elsif word =~ /^-0x([0-9a-f]+)$/i
+      op |= 0x100 - $1.to_i(16)
+    elsif OPCODES.key?(word)
+      op |= OPCODES[word]
+    elsif word =~ /^(.+):$/
+      $labels[$1] = $code.size()
+    else
+      refs << word
+    end
+  end
+  $code << Line.new(op, refs, line)
+end
+
+$code.each_with_index() do | line, i |
+  op = line.opcode
+  line.refs.each() do | ref |
+    if $labels.key?(ref)
+      target = $labels[ref] - (i + 1)
+      target += 0x100 if target < 0
+      op |= target
+    else
+      throw "I don't understand #{ref.inspect()}"
+    end
+  end
+  $stdout.write("#{op.to_s(16).rjust(3, "0")} // #{line.code}\n")
+end
-- 
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