wasm-pack utility to pack wasm files into transactions payload

src/pack.rs

@@ -0,0 +1,35 @@
+use parity_wasm::{elements, builder};
+
+pub fn pack_instance(raw_module: Vec<u8>) -> elements::Module {
+
+    let raw_len = raw_module.len();
+    let mem_required = (raw_len / (64 * 1024) + 1) as u32;
+
+    let module = builder::module()
+        .import()
+            .module("env")
+            .field("memory")
+            .external()
+            .memory(mem_required as u32, Some(mem_required as u32))
+            .build()
+        .data()
+            .offset(elements::Opcode::I32Const(0))
+            .value(raw_module)
+            .build()
+        .function()
+            .signature().param().i32().build()
+            .body().with_opcodes(elements::Opcodes::new(vec![
+                elements::Opcode::GetLocal(0),
+                elements::Opcode::I32Const(raw_len as i32),
+                elements::Opcode::I32Store(0, 12),
+                elements::Opcode::End,
+            ])).build()
+            .build()
+        .export()
+            .field("_call")
+            .internal().func(0)
+            .build()
+        .build();
+
+    module
+}