From 66107b4310d65b7faab0704bb1fc8311da87aa96 Mon Sep 17 00:00:00 2001
From: Jesse Brault <jbrault@mac.com>
Date: Fri, 29 Nov 2024 19:13:30 -0600
Subject: [PATCH] Begin work on write_module.

---
 src/vm/module.rs | 49 ++++++++++++++++++++++++++++++++++++++++++++++++
 1 file changed, 49 insertions(+)

diff --git a/src/vm/module.rs b/src/vm/module.rs
index 1b4de73..6595fc7 100644
--- a/src/vm/module.rs
+++ b/src/vm/module.rs
@@ -3,8 +3,13 @@ use std::collections::HashMap;
 use std::io::Read;
 
 pub const DEIMOS_MAGIC_NUMBER: u64 = 0x00_00_64_65_69_6d_6f_73; // ascii 'deimos'
+const DEIMOS_MAGIC_STRING: [u8; 6] = [0x64, 0x65, 0x69, 0x6d, 0x6f, 0x73]; // ascii 'deimos'
+
+pub const VERSION_STRING: &str = "0.1.0";
 
 pub struct DmModule {
+    name: String,
+    version: String,
     constants: HashMap<String, DmConstant>,
     functions: HashMap<String, DmFunction>,
 }
@@ -35,6 +40,47 @@ struct DmSymbol {
     address: u32,
 }
 
+macro_rules! push_byte_array {
+    ( $dest: expr, $arr: expr ) => {
+        for b in $arr {
+            $dest.push(b);
+        }
+    };
+}
+
+macro_rules! push_number_le {
+    ( $dest: expr, $num: expr ) => {
+        for b in $num.to_le_bytes() {
+            $dest.push(b);
+        }
+    };
+}
+
+macro_rules! push_string {
+    ( $dest: expr, $s: expr ) => {
+        for b in $s.len().to_le_bytes() {
+            $dest.push(b);
+        }
+        for b in $s.bytes() {
+            $dest.push(b);
+        }
+    };
+}
+
+pub fn write_module(module: DmModule) -> Vec<u8> {
+    // Push magic number
+    let mut result: Vec<u8> = Vec::new();
+    push_byte_array!(result, DEIMOS_MAGIC_STRING);
+
+    // Push version string
+    push_string!(result, module.version);
+
+    // Push module name length, little endian
+    push_string!(result, module.name);
+
+    result
+}
+
 pub fn load_module(bytes: &[u8]) -> Result<DmModule, String> {
     let mut ip: usize = 0;
     // Check for magic number at bytes 0..5
@@ -62,6 +108,9 @@ pub fn load_module(bytes: &[u8]) -> Result<DmModule, String> {
         return Err(String::from("Invalid Deimos module version."));
     }
 
+    // TODO: extract module name
+
+
     // Holder for Symbols we will extract from the symbol table bytes
     let mut symbols: Vec<DmSymbol> = Vec::new();