From 540555d7a95f75a15f17a71f2f62f788a863ff81 Mon Sep 17 00:00:00 2001
From: Erin <erin@erindesu.cz>
Date: Tue, 1 Aug 2023 22:13:22 +0200
Subject: [PATCH] Added magic

---
 hbasm/src/lib.rs              | 28 ++++++++++++++++++++--------
 hbbytecode/src/gen_valider.rs | 11 +++++++++++
 hbvm/src/lib.rs               |  2 +-
 spec.md                       |  1 +
 4 files changed, 33 insertions(+), 9 deletions(-)

diff --git a/hbasm/src/lib.rs b/hbasm/src/lib.rs
index cf7da9e0..0b301b96 100644
--- a/hbasm/src/lib.rs
+++ b/hbasm/src/lib.rs
@@ -1,11 +1,11 @@
 //! Holey Bytes Assembler
-//! 
+//!
 //! Some people claim:
 //! > Write programs to handle text streams, because that is a universal interface.
 //!
 //! We at AbleCorp believe that nice programatic API is nicer than piping some text
 //! into a program. It's less error-prone and faster.
-//! 
+//!
 //! So this crate contains both assembleer with API for programs and a text assembler
 //! for humans to write
 
@@ -15,26 +15,37 @@ extern crate alloc;
 
 mod macros;
 
-use {alloc::vec::Vec, hashbrown::HashSet};
+use {
+    alloc::{vec, vec::Vec},
+    hashbrown::HashSet,
+};
 
 /// Assembler
-/// 
+///
 /// - Opcode-generic, instruction-type-specific methods are named `i_param_<type>`
 ///     - You likely won't need to use them, but they are here, just in case :)
 /// - Instruction-specific methods are named `i_<instruction>`
-#[derive(Default)]
 pub struct Assembler {
     pub buf: Vec<u8>,
     pub sub: HashSet<usize>,
 }
 
+impl Default for Assembler {
+    fn default() -> Self {
+        Self {
+            buf: vec![0; 3],
+            sub: Default::default(),
+        }
+    }
+}
+
 hbbytecode::invoke_with_def!(macros::text::gen_text);
 
 impl Assembler {
     hbbytecode::invoke_with_def!(macros::asm::impl_asm);
 
-    /// Append 12 zeroes (UN) at the end
-    /// 
+    /// Append 12 zeroes (UN) at the end and add magic to the begining
+    ///
     /// # HoleyBytes lore
     ///
     /// In reference HBVM implementation checks are done in
@@ -61,11 +72,12 @@ impl Assembler {
     /// Why 12 bytes? That's the size of largest instruction parameter part.
     pub fn finalise(&mut self) {
         self.buf.extend([0; 12]);
+        self.buf[0..3].copy_from_slice(&[0xAB, 0x1E, 0x0B]);
     }
 }
 
 /// Immediate value
-/// 
+///
 /// # Implementor notice
 /// It should insert exactly 8 bytes, otherwise output will be malformed.
 /// This is not checked in any way
diff --git a/hbbytecode/src/gen_valider.rs b/hbbytecode/src/gen_valider.rs
index 9149650f..c9d9ab73 100644
--- a/hbbytecode/src/gen_valider.rs
+++ b/hbbytecode/src/gen_valider.rs
@@ -23,6 +23,8 @@ macro_rules! gen_valider {
                 RegisterArrayOverflow,
                 /// Program is not validly terminated
                 InvalidEnd,
+                /// Program misses magic
+                MissingMagic
             }
 
             /// Error
@@ -37,6 +39,14 @@ macro_rules! gen_valider {
             /// Perform bytecode validation. If it passes, the program should be
             /// sound to execute.
             pub fn validate(mut program: &[u8]) -> Result<(), Error> {
+                // Validate magic
+                if program.get(0..3) != Some(&[0xAB, 0x1E, 0x0B]) {
+                    return Err(Error {
+                        kind: ErrorKind::MissingMagic,
+                        index: 0,
+                    });
+                }
+
                 // Program has to end with 12 zeroes, if there is less than
                 // 12 bytes, program is invalid.
                 if program.len() < 12 {
@@ -57,6 +67,7 @@ macro_rules! gen_valider {
                 }
 
                 let start = program;
+                program = &program[3..];
                 loop {
                     use crate::opcode::*;
                     program = match program {
diff --git a/hbvm/src/lib.rs b/hbvm/src/lib.rs
index 8e07bb55..67b1dda1 100644
--- a/hbvm/src/lib.rs
+++ b/hbvm/src/lib.rs
@@ -73,7 +73,7 @@ impl<'a, PfHandler: HandlePageFault, const TIMER_QUOTIENT: usize>
             pfhandler: traph,
             pc: 0,
             program_len: program.len() - 12,
-            program,
+            program: &program[3..],
             timer: 0,
             copier: None,
         }
diff --git a/spec.md b/spec.md
index 67094ea2..b5cbcc2d 100644
--- a/spec.md
+++ b/spec.md
@@ -1,6 +1,7 @@
 # HoleyBytes ISA Specification
 
 # Bytecode format
+- Holey Bytes program should start with following magic: `0xAB1E0B`
 - All numbers are encoded little-endian
 - There is 256 registers, they are represented by a byte
 - Immediate values are 64 bit