stored-program computer

frustration.rs

@@ -1,24 +1,106 @@
+use std::cmp;
 use std::io;
-use std::convert::TryFrom;
+//use std::convert::TryFrom;
 use std::convert::TryInto;
 
 //const CORE_SIZE: usize = 65280
 const CORE_SIZE: usize = 128;
 
 #[derive(Debug)]
-struct Core {
-    ram: [u8; CORE_SIZE],
-    ip: usize,
-    dstack: [u16; 64],
-    tds: usize,
-    rstack: [u16; 64],
-    trs: usize
+enum State {
+    Compiling,
+    Interpreting
 }
 
+#[derive(Debug)]
+struct Core {
+    ram: [u8; CORE_SIZE],
+    ip: u16,
+    dp: u16,  // newest link field, or 0
+    here: u16, // first unused byte
+    state: State,
+    dstack: [u16; 64],
+    tds: usize,  // post-incremented; exceeds top by one
+    rstack: [u16; 64],
+    trs: usize,  // post-incremented; exceeds top by one
+}
+
+type Primitive = fn(&mut Core);
+
+struct ShortName {
+    bytes: [u8; 3],
+    length: u8
+}
+
+fn truncate_name(name: &str) -> ShortName {
+    let name_bytes = name.as_bytes();
+    let mut out = ShortName {
+        bytes: [32, 32, 32],
+        length: std::cmp::min(3, name_bytes.len()) as u8 };
+    out.bytes[0..out.length as usize].copy_from_slice(name_bytes);
+    return out;
+}
+
+struct TableEntry {
+    f: Primitive,
+    name: ShortName
+}
+
+const PRIMITIVES: [TableEntry; 8] = [
+    TableEntry {f: ret  , name: ShortName {bytes: ['r' as u8, 'e' as u8, 't' as u8], length: 1}},
+    TableEntry {f: dot  , name: ShortName {bytes: ['.' as u8, 32, 32], length: 1}},
+    TableEntry {f: store, name: ShortName {bytes: ['!' as u8, 32, 32], length: 1}},
+    TableEntry {f: load , name: ShortName {bytes: ['@' as u8, 32, 32], length: 1}},
+    TableEntry {f: add  , name: ShortName {bytes: ['+' as u8, 32, 32], length: 1}},
+    TableEntry {f: sub  , name: ShortName {bytes: ['-' as u8, 32, 32], length: 1}},
+    TableEntry {f: mul  , name: ShortName {bytes: ['*' as u8, 32, 32], length: 1}},
+    TableEntry {f: div  , name: ShortName {bytes: ['/' as u8, 32, 32], length: 1}}
+];
+
 fn new_core() -> Core {
-    return Core { ram: [0; CORE_SIZE], ip: 0,
+    let mut c = Core {
+        ram: [0; CORE_SIZE], ip: 0, dp: 0, here: 2, state: State::Interpreting,
         dstack: [0; 64], tds: 0,
         rstack: [0; 64], trs: 0 };
+    init_dictionary(&mut c);
+    return c;
+}
+
+fn create(c: &mut Core, name: ShortName) {
+    let addr: usize = c.here as usize;
+    c.ram[addr+0..=addr+1].copy_from_slice(&c.dp.to_le_bytes());
+    c.dp = addr as u16;
+    c.ram[addr+2] = name.length;
+    c.ram[addr+3..=addr+5].copy_from_slice(&name.bytes);
+    c.here = (addr+6) as u16;
+}
+
+fn init_dictionary(c: &mut Core) {
+    let mut opcode = 65535;
+    for p in PRIMITIVES {
+        create(c, p.name);
+        comma(c, opcode);
+        opcode -= 1;
+    }
+}
+
+fn step(c: &mut Core) {
+    let ip = c.ip as usize;
+    let opcode = u16::from_le_bytes(c.ram[ip..=ip+1].try_into().unwrap());
+    c.ip += 2;
+    let primitive_index = (65535 - opcode) as usize;
+    if primitive_index < PRIMITIVES.len() {
+        (PRIMITIVES[primitive_index].f)(c);
+    } else {
+        call(c, opcode);
+    }
+}
+
+fn inner(c: &mut Core) {
+    c.ip = 0;
+    while c.ip != 2 {
+        step(c);
+    }
 }
 
 fn push(c: &mut Core, val: u16) {
@@ -42,12 +124,22 @@ fn from_r(c: &mut Core) -> u16 {
 }
 
 fn call(c: &mut Core, val: u16) {
-    to_r(c, u16::try_from(c.ip).unwrap());  // or panic
-    c.ip = val as usize;
+    to_r(c, c.ip);
+    c.ip = val;
 }
 
 fn ret(c: &mut Core) {
-    c.ip = from_r(c) as usize;
+    c.ip = from_r(c);
+}
+
+fn dot(c: &mut Core) {
+    print!("{} ", pop(c));
+}
+
+fn comma(c: &mut Core, val: u16) {
+    let addr = c.here as usize;
+    c.ram[addr..=addr+1].copy_from_slice(&val.to_le_bytes());
+    c.here += 2;
 }
 
 fn store(c: &mut Core) {
@@ -85,10 +177,6 @@ fn div(c: &mut Core) {
     push(c, v2 / v1);
 }
 
-fn dot(c: &mut Core) {
-    print!("{} ", pop(c));
-}
-
 fn outer(c: &mut Core, s: &str) {
     let ss = s.trim();
     let tokens = ss.split(" ");
@@ -115,6 +203,15 @@ fn outer(c: &mut Core, s: &str) {
             "." => {
                 dot(c);
             },
+            "s" => {
+                step(c);
+            },
+            "g" => {
+                inner(c);
+            },
+            "dmp" => {
+                println!("{:?}", c);
+            },
             _ => {
                 let val = t.parse::<u16>();
                 match val {
@@ -137,5 +234,5 @@ fn main() {
     }
     //push(&mut c, 56); push(&mut c, 9); mul(&mut c); dot(&mut c);
     //let v = pop(&mut c); call(&mut c, v);
-    println!("{:?}", c);
+    //println!("{:?}", c);
 }