From 49a907da2526134d6c0349e4bb9ede4402a54b4a Mon Sep 17 00:00:00 2001
From: Chris Fallin <chris@cfallin.org>
Date: Thu, 23 Feb 2023 19:16:08 -0800
Subject: [PATCH] Working interpreter

---
 src/interp.rs | 84 +++++++++++++++++++++++++++++++++++++++++----------
 1 file changed, 68 insertions(+), 16 deletions(-)

diff --git a/src/interp.rs b/src/interp.rs
index bbf90f9..c4070cf 100644
--- a/src/interp.rs
+++ b/src/interp.rs
@@ -121,12 +121,9 @@ impl InterpContext {
                                 multivalue[0]
                             })
                             .collect::<Vec<_>>();
-                        let idx = match args[0] {
-                            ConstVal::I32(x) => x,
-                            _ => panic!(),
-                        };
-                        let func = self.tables[table_index].elements[idx as usize];
-                        self.call(module, func, &args[1..])?
+                        let idx = args.last().unwrap().as_u32().unwrap() as usize;
+                        let func = self.tables[table_index].elements[idx];
+                        self.call(module, func, &args[..args.len() - 1])?
                     }
                     &ValueDef::Operator(ref op, ref args, _) => {
                         let args = args
@@ -167,10 +164,7 @@ impl InterpContext {
                 } => {
                     let cond = body.resolve_alias(cond);
                     let cond = frame.values.get(&cond).unwrap();
-                    let cond = match cond[0] {
-                        ConstVal::I32(x) => x != 0,
-                        _ => unreachable!(),
-                    };
+                    let cond = cond[0].as_u32().unwrap() != 0;
                     if cond {
                         frame.apply_target(body, if_true);
                     } else {
@@ -184,10 +178,7 @@ impl InterpContext {
                 } => {
                     let value = body.resolve_alias(value);
                     let value = frame.values.get(&value).unwrap();
-                    let value = match value[0] {
-                        ConstVal::I32(x) => x,
-                        _ => unreachable!(),
-                    } as usize;
+                    let value = value[0].as_u32().unwrap() as usize;
                     if value < targets.len() {
                         frame.apply_target(body, &targets[value]);
                     } else {
@@ -209,8 +200,60 @@ impl InterpContext {
         }
     }
 
-    fn call_import(&mut self, name: &str, _args: &[ConstVal]) -> Option<SmallVec<[ConstVal; 2]>> {
-        todo!("call_import: {}", name);
+    fn call_import(&mut self, name: &str, args: &[ConstVal]) -> Option<SmallVec<[ConstVal; 2]>> {
+        let mem = &mut self.memories[Memory::from(0)];
+        match name {
+            "__wasi_fd_prestat_get" => {
+                Some(smallvec![ConstVal::I32(8)]) // BADF
+            }
+            "__wasi_args_sizes_get" => {
+                let p_argc = args[0].as_u32().unwrap();
+                let p_argv_size = args[1].as_u32().unwrap();
+                write_u32(mem, p_argc, 0);
+                write_u32(mem, p_argv_size, 0);
+                Some(smallvec![ConstVal::I32(0)])
+            }
+            "__wasi_args_get" => Some(smallvec![ConstVal::I32(0)]),
+            "__wasi_fd_fdstat_get" => {
+                let fd = args[0].as_u32().unwrap();
+                let p_fdstat_t = args[1].as_u32().unwrap();
+                if fd == 1 {
+                    write_u32(mem, p_fdstat_t + 0, 2); // filetype = CHAR
+                    write_u32(mem, p_fdstat_t + 4, 0); // flags = 0
+                    write_u32(mem, p_fdstat_t + 8, 0x40); // rights_base = WRITE
+                    write_u32(mem, p_fdstat_t + 12, 0); // rights_inheriting = 0
+                    Some(smallvec![ConstVal::I32(0)])
+                } else {
+                    None
+                }
+            }
+            "__wasi_fd_write" => {
+                let fd = args[0].as_u32().unwrap();
+                let p_iovs = args[1].as_u32().unwrap();
+                let iovs_len = args[2].as_u32().unwrap();
+                let p_nwritten = args[3].as_u32().unwrap();
+                if fd == 1 {
+                    let mut written = 0;
+                    for i in 0..iovs_len {
+                        let iov_entry = p_iovs + 8 * i;
+                        let base = read_u32(mem, iov_entry) as usize;
+                        let len = read_u32(mem, iov_entry + 4) as usize;
+                        let data = &mem.data[base..(base + len)];
+                        print!("{}", std::str::from_utf8(data).unwrap());
+                        written += len;
+                    }
+                    write_u32(mem, p_nwritten, written as u32);
+                    Some(smallvec![ConstVal::I32(0)])
+                } else {
+                    None
+                }
+            }
+            "__wasi_proc_exit" => {
+                eprintln!("WASI exit: {:?}", args[0]);
+                None
+            }
+            _ => panic!("Unknown import: {} with args: {:?}", name, args),
+        }
     }
 }
 
@@ -267,6 +310,15 @@ pub enum ConstVal {
     None,
 }
 
+impl ConstVal {
+    pub fn as_u32(self) -> Option<u32> {
+        match self {
+            Self::I32(x) => Some(x),
+            _ => None,
+        }
+    }
+}
+
 pub fn const_eval(
     op: &Operator,
     vals: &[ConstVal],