Following Lua's source code as closely as possible

1 files changed, 67 insertions, 0 deletions

diff --git a/src/lundump.js b/src/lundump.js
new file mode 100644
index 0000000..69445d4
--- /dev/null
+++ b/src/lundump.js
@@ -0,0 +1,67 @@
+/*jshint esversion: 6 */
+"use strict";
+
+const DataView  = require('buffer-dataview');
+const fs        = require('fs');
+const lua_State = require('./lstate.js').lua_State;
+const LClosure  = require('./lobject.js').LClosure;
+
+/**
+ * Parse Lua 5.3 bytecode
+ * @see {@link http://www.lua.org/source/5.3/lundump.c.html|lundump.c}
+ */
+class BytecodeParser {
+
+    /**
+     * Initilialize bytecode parser
+     * @constructor
+     * @param {DataView} dataView Contains the binary data
+     */
+    constructor(dataView) {
+        this.dataView = dataView;
+        this.offset = 0;
+    }
+
+    peekByte() {
+        return this.dataView.getUint8(this.offset, true);
+    }
+
+    readByte() {
+        let byte = this.peekByte();
+        this.offset++;
+        return byte;
+    }
+
+    peekWord() {
+        return this.dataView.getUint32(this.offset, true);
+    }
+
+    readWord() {
+        let word = this.peekWord();
+        this.offset += 4;
+
+        return word;
+    }
+
+    checkHeader() {
+        if (this.readByte() !== 0x1b
+            || this.readByte() !== 0x4c
+            || this.readByte() !== 0x75
+            || this.readByte() !== 0x61)
+            throw new Error("Bad LUA_SIGNATURE, expected [1b 4c 75 61]");
+
+        if (this.readByte() !== 0x53)
+            throw new Error("Bad Lua version, expected 5.3");
+
+        if (this.readByte() !== 0)
+            throw new Error("Supports only official PUC-Rio implementation")
+    }
+
+    luaU_undump() {
+        checkHeader();
+        let cl = new LClosure(L, this.readByte());
+
+        return cl;
+    }
+
+}
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