From 3ff7aac2d2eb2cbf2f854793fc0d7bc6f1f7d927 Mon Sep 17 00:00:00 2001
From: Rose Hogenson <rhogenson@posteo.net>
Date: Sun, 9 Jan 2022 08:40:09 -0800
Subject: Initial commit.

Not sure if everything here will be needed eventually, but we have a
working bytecode interpreter. Next I will write the linker, then the
core compiler, and finish with the macro expander.
---
 bytecode/src/heap.rs | 82 ++++++++++++++++++++++++++++++++++++++++++++++++++++
 1 file changed, 82 insertions(+)
 create mode 100644 bytecode/src/heap.rs

(limited to 'bytecode/src/heap.rs')

diff --git a/bytecode/src/heap.rs b/bytecode/src/heap.rs
new file mode 100644
index 0000000..d76456a
--- /dev/null
+++ b/bytecode/src/heap.rs
@@ -0,0 +1,82 @@
+fn transmute(p: &u8) -> Result<&u64, String> {
+    let u8_p = p as *const u8;
+    let u64_p = u8_p as *const u64;
+    if u64_p as usize % 8 != 0 {
+        return Err(String::from("not aligned"));
+    }
+    unsafe {
+        return Ok(&*u64_p);
+    }
+}
+
+fn transmute_mut(p: &mut u8) -> Result<&mut u64, String> {
+    let u8_p = p as *mut u8;
+    let u64_p = u8_p as *mut u64;
+    if u64_p as usize % 8 != 0 {
+        return Err(String::from("not aligned"));
+    }
+    unsafe {
+        return Ok(&mut *u64_p);
+    }
+}
+
+pub struct Heap {
+    heap: Vec<u8>,
+}
+
+pub struct Pointer(usize);
+
+impl Heap {
+    pub fn new() -> Self {
+        Heap {
+            heap: vec![0; 128], // 1 kB
+        }
+    }
+
+    pub fn alloc(&mut self, n: usize) -> Pointer {
+        let p = Pointer(self.heap.len());
+        self.heap.append(&mut vec![0; n]);
+        p
+    }
+
+    pub fn peek(&self, p: Pointer) -> Result<u64, String> {
+        let Pointer(x) = p;
+        let u8_p = &self.heap[x];
+        let u64_p = transmute(u8_p)?;
+        Ok(*u64_p)
+    }
+
+    pub fn poke(&mut self, u: u64, p: Pointer) -> Result<(), String> {
+        let Pointer(x) = p;
+        let u8_p = &mut self.heap[x];
+        let u64_p = transmute_mut(u8_p)?;
+        *u64_p = u;
+        Ok(())
+    }
+
+    pub fn peek_byte(&self, p: Pointer) -> u8 {
+        let Pointer(x) = p;
+        self.heap[x]
+    }
+
+    pub fn poke_byte(&mut self, u: u8, p: Pointer) {
+        let Pointer(x) = p;
+        self.heap[x] = u;
+    }
+}
+
+impl Pointer {
+    pub fn from_bytes(p: u64) -> Self {
+        Pointer(usize::try_from(p).unwrap() >> 1)
+    }
+
+    pub fn bytes(&self) -> u64 {
+        let Pointer(x) = self;
+        u64::try_from(*x).unwrap() << 1
+    }
+
+    pub fn offset(&self, off: u8) -> Pointer {
+        let Pointer(x) = self;
+        Pointer(*x + usize::from(off))
+    }
+}
-- 
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