diff --git a/gas/src/main.rs b/gas/src/main.rs
index b6eba3a..dd50747 100644
--- a/gas/src/main.rs
+++ b/gas/src/main.rs
@@ -1,38 +1,7 @@
 extern crate parity_wasm;
+extern crate wasm_utils;
 
 use std::env;
-use parity_wasm::{builder, elements};
-
-pub fn update_call_index(opcodes: &mut elements::Opcodes, inserted_index: u32) {
-    use parity_wasm::elements::Opcode::*;
-    for opcode in opcodes.elements_mut().iter_mut() {
-        match opcode {
-            &mut Block(_, ref mut block) | &mut If(_, ref mut block) | &mut Loop(_, ref mut block) => {
-                update_call_index(block, inserted_index)
-            },
-            &mut Call(ref mut call_index) => {
-                if *call_index >= inserted_index { *call_index += 1}
-            },
-            _ => { }
-        }
-    }
-}
-
-pub fn inject_counter(opcodes: &mut elements::Opcodes, gas_func: u32) {
-    use parity_wasm::elements::Opcode::*;
-    for opcode in opcodes.elements_mut().iter_mut() {
-        match opcode {
-            &mut Block(_, ref mut block) | &mut If(_, ref mut block) | &mut Loop(_, ref mut block) => {
-                inject_counter(block, gas_func)
-            },
-            _ => { }
-        }
-    }
-
-    let ops = opcodes.elements_mut().len() as u32;
-    opcodes.elements_mut().insert(0, I32Const(ops as i32));
-    opcodes.elements_mut().insert(1, Call(gas_func));
-}
 
 fn main() {
 
@@ -43,69 +12,9 @@ fn main() {
     }
 
     // Loading module
-    let module = parity_wasm::deserialize_file(&args[1]).unwrap();
+    let module = parity_wasm::deserialize_file(&args[1]).expect("Module deserialization to succeed");
 
-    // Injecting gas counting external
-    let mut mbuilder = builder::from_module(module);
-    let import_sig = mbuilder.push_signature(
-        builder::signature()
-            .param().i32()
-            .build_sig()
-        );
+    let result = wasm_utils::inject_gas_counter(module);
 
-    let mut gas_func = mbuilder.push_import(
-        builder::import()
-            .module("env")
-            .field("gas")
-            .external().func(import_sig)
-            .build()
-        );
-
-    // back to plain module
-    let mut module = mbuilder.build();
-
-    assert!(module.global_section().is_some());
-
-    // calculate actual function index of the imported definition
-    //    (substract all imports that are NOT functions)
-
-    for import_entry in module.import_section().expect("Builder should have insert the import section").entries() {
-        match *import_entry.external() {
-            elements::External::Function(_) => {},
-            _ => { gas_func -= 1; }
-        }
-    }
-
-    // Updating calling addresses (all calls to function index >= `gas_func` should be incremented)
-    for section in module.sections_mut() {
-        match section {
-            &mut elements::Section::Code(ref mut code_section) => {
-                for ref mut func_body in code_section.bodies_mut() {
-                    update_call_index(func_body.code_mut(), gas_func);
-                    inject_counter(func_body.code_mut(), gas_func);
-                }
-            },
-            &mut elements::Section::Export(ref mut export_section) => {
-                for ref mut export in export_section.entries_mut() {
-                    match export.internal_mut() {
-                        &mut elements::Internal::Function(ref mut func_index) => {
-                            if *func_index >= gas_func { *func_index += 1}
-                        },
-                        _ => {}
-                    } 
-                }
-            },
-            &mut elements::Section::Element(ref mut elements_section) => {
-                for ref mut segment in elements_section.entries_mut() {
-                    // update all indirect call addresses initial values
-                    for func_index in segment.members_mut() {
-                        if *func_index >= gas_func { *func_index += 1}
-                    }
-                }
-            },
-            _ => { }
-        }
-    }
-
-    parity_wasm::serialize_to_file(&args[2], module).unwrap();    
+    parity_wasm::serialize_to_file(&args[2], result).expect("Module serialization to succeed")    
 }
diff --git a/runner/build.sh b/runner/build.sh
index 6b79c6e..eb08957 100755
--- a/runner/build.sh
+++ b/runner/build.sh
@@ -21,7 +21,7 @@ then
 
 else
     # c/c++ can be compiled directly by emcc
-    emcc $file -O3 -s WASM=1 -s SIDE_MODULE=1 -o out/contract.wasm -s
+    emcc $file -O3 -s WASM=1 -s SIDE_MODULE=1 -o out/contract.wasm
 
     # Gas injector
     cargo run --manifest-path=./../gas/Cargo.toml --release -- ./out/contract.wasm ./out/contract.wasm
diff --git a/samples/logger_contract.rs b/samples/logger_contract.rs
index 030eb2b..f454bb5 100644
--- a/samples/logger_contract.rs
+++ b/samples/logger_contract.rs
@@ -6,7 +6,7 @@
 
 use std::slice;
 
-#[link_args = "-s WASM=1 -s NO_EXIT_RUNTIME=1 -s NO_FILESYSTEM=1"]
+#[link_args = "-s NO_EXIT_RUNTIME=1 -s NO_FILESYSTEM=1"]
 extern {}
 
 /// Wrapper over storage read/write/size externs
diff --git a/src/gas.rs b/src/gas.rs
new file mode 100644
index 0000000..e69c288
--- /dev/null
+++ b/src/gas.rs
@@ -0,0 +1,99 @@
+use parity_wasm::{elements, builder};
+
+
+pub fn update_call_index(opcodes: &mut elements::Opcodes, inserted_index: u32) {
+    use parity_wasm::elements::Opcode::*;
+    for opcode in opcodes.elements_mut().iter_mut() {
+        match opcode {
+            &mut Block(_, ref mut block) | &mut If(_, ref mut block) | &mut Loop(_, ref mut block) => {
+                update_call_index(block, inserted_index)
+            },
+            &mut Call(ref mut call_index) => {
+                if *call_index >= inserted_index { *call_index += 1}
+            },
+            _ => { }
+        }
+    }
+}
+
+pub fn inject_counter(opcodes: &mut elements::Opcodes, gas_func: u32) {
+    use parity_wasm::elements::Opcode::*;
+    for opcode in opcodes.elements_mut().iter_mut() {
+        match opcode {
+            &mut Block(_, ref mut block) | &mut If(_, ref mut block) | &mut Loop(_, ref mut block) => {
+                inject_counter(block, gas_func)
+            },
+            _ => { }
+        }
+    }
+
+    let ops = opcodes.elements_mut().len() as u32;
+    opcodes.elements_mut().insert(0, I32Const(ops as i32));
+    opcodes.elements_mut().insert(1, Call(gas_func));
+}
+
+pub fn inject_gas_counter(module: elements::Module) -> elements::Module {
+   // Injecting gas counting external
+    let mut mbuilder = builder::from_module(module);
+    let import_sig = mbuilder.push_signature(
+        builder::signature()
+            .param().i32()
+            .build_sig()
+        );
+
+    let mut gas_func = mbuilder.push_import(
+        builder::import()
+            .module("env")
+            .field("gas")
+            .external().func(import_sig)
+            .build()
+        );
+
+    // back to plain module
+    let mut module = mbuilder.build();
+
+    assert!(module.global_section().is_some());
+
+    // calculate actual function index of the imported definition
+    //    (substract all imports that are NOT functions)
+
+    for import_entry in module.import_section().expect("Builder should have insert the import section").entries() {
+        match *import_entry.external() {
+            elements::External::Function(_) => {},
+            _ => { gas_func -= 1; }
+        }
+    }
+
+    // Updating calling addresses (all calls to function index >= `gas_func` should be incremented)
+    for section in module.sections_mut() {
+        match section {
+            &mut elements::Section::Code(ref mut code_section) => {
+                for ref mut func_body in code_section.bodies_mut() {
+                    update_call_index(func_body.code_mut(), gas_func);
+                    inject_counter(func_body.code_mut(), gas_func);
+                }
+            },
+            &mut elements::Section::Export(ref mut export_section) => {
+                for ref mut export in export_section.entries_mut() {
+                    match export.internal_mut() {
+                        &mut elements::Internal::Function(ref mut func_index) => {
+                            if *func_index >= gas_func { *func_index += 1}
+                        },
+                        _ => {}
+                    } 
+                }
+            },
+            &mut elements::Section::Element(ref mut elements_section) => {
+                for ref mut segment in elements_section.entries_mut() {
+                    // update all indirect call addresses initial values
+                    for func_index in segment.members_mut() {
+                        if *func_index >= gas_func { *func_index += 1}
+                    }
+                }
+            },
+            _ => { }
+        }
+    }
+
+    module    
+}
\ No newline at end of file
diff --git a/src/lib.rs b/src/lib.rs
index 8d4d9bd..926cc32 100644
--- a/src/lib.rs
+++ b/src/lib.rs
@@ -1,6 +1,8 @@
 extern crate parity_wasm;
 
 mod optimizer;
-pub mod symbols;
+mod gas;
+mod symbols;
 
-pub use optimizer::optimize;
\ No newline at end of file
+pub use optimizer::optimize;
+pub use gas::inject_gas_counter;
\ No newline at end of file