gas utility initial

gas/.gitignore

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+target

gas/Cargo.lock

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+[root]
+name = "gas"
+version = "0.1.0"
+dependencies = [
+ "parity-wasm 0.2.0 (git+https://github.com/nikvolf/parity-wasm)",
+]
+
+[[package]]
+name = "byteorder"
+version = "1.0.0"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+
+[[package]]
+name = "parity-wasm"
+version = "0.2.0"
+source = "git+https://github.com/nikvolf/parity-wasm#cafc5058357f6ea84daaec870057da8455bf74e8"
+dependencies = [
+ "byteorder 1.0.0 (registry+https://github.com/rust-lang/crates.io-index)",
+]
+
+[metadata]
+"checksum byteorder 1.0.0 (registry+https://github.com/rust-lang/crates.io-index)" = "c40977b0ee6b9885c9013cd41d9feffdd22deb3bb4dc3a71d901cc7a77de18c8"
+"checksum parity-wasm 0.2.0 (git+https://github.com/nikvolf/parity-wasm)" = "<none>"

gas/Cargo.toml

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+[package]
+name = "gas"
+version = "0.1.0"
+authors = ["NikVolf <nikvolf@gmail.com>"]
+
+[dependencies]
+parity-wasm = { git="https://github.com/nikvolf/parity-wasm" }

gas/src/main.rs

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+extern crate parity_wasm;
+
+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) => {
+                update_call_index(block, inserted_index)
+            },
+            &mut Call(ref mut call_index) | &mut CallIndirect(ref mut call_index, _) => {
+                if *call_index >= inserted_index { *call_index += 1}
+            },
+            _ => { }
+        }
+    }
+}
+
+fn main() {
+
+    let args = env::args().collect::<Vec<_>>();
+    if args.len() != 3 {
+        println!("Usage: {} input_file.wasm output_file.wasm", args[0]);
+        return;
+    }
+
+    // Loading module
+    let module = parity_wasm::deserialize_file(&args[1]).unwrap();
+
+    // Injecting gas counting external
+    let mut mbuilder = builder::from_module(module);
+    let import_sig = mbuilder.push_signature(
+        builder::signature()
+            .param().i32()
+            .param().i32()
+            .return_type().i32()
+            .build_sig()
+        );
+
+    let gas_func = mbuilder.push_import(
+        builder::import()
+            .module("env")
+            .field("gas")
+            .external().func(import_sig)
+            .build()
+        );
+
+    // Updating calling addresses (all calls to function index >= `gas_func` should be incremented)
+    let mut module = mbuilder.build();
+    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);
+                }
+            },
+            _ => { }
+        }
+    }
+
+    parity_wasm::serialize_to_file(&args[2], module).unwrap();    
+}