Support imports.

lib/execute/src/get.rs

@@ -0,0 +1,39 @@
+//! Support for reading the value of a wasm global from outside the module.
+
+use cranelift_codegen::ir;
+use cranelift_wasm::GlobalIndex;
+use invoke::Value;
+use std::string::String;
+use vmcontext::VMContext;
+use wasmtime_environ::{Export, Module};
+
+/// Jumps to the code region of memory and invoke the exported function
+pub fn get(module: &Module, vmctx: *mut VMContext, global_name: &str) -> Result<Value, String> {
+    let global_index = match module.exports.get(global_name) {
+        Some(Export::Global(index)) => *index,
+        Some(_) => return Err(format!("exported item \"{}\" is not a global", global_name)),
+        None => return Err(format!("no export named \"{}\"", global_name)),
+    };
+
+    get_by_index(module, vmctx, global_index)
+}
+
+pub fn get_by_index(
+    module: &Module,
+    vmctx: *mut VMContext,
+    global_index: GlobalIndex,
+) -> Result<Value, String> {
+    // TODO: Return Err if the index is out of bounds.
+    unsafe {
+        let vmctx = &mut *vmctx;
+        let vmglobal = vmctx.global(global_index);
+        let definition = vmglobal.get_definition(module.is_imported_global(global_index));
+        Ok(match module.globals[global_index].ty {
+            ir::types::I32 => Value::I32(*definition.as_i32()),
+            ir::types::I64 => Value::I64(*definition.as_i64()),
+            ir::types::F32 => Value::F32(*definition.as_f32_bits()),
+            ir::types::F64 => Value::F64(*definition.as_f64_bits()),
+            other => return Err(format!("global with type {} not supported", other)),
+        })
+    }
+}