Auto protobuf build

.travis.yml

@@ -1,5 +1,9 @@
 language: rust
-cache: cargo # https://docs.travis-ci.com/user/caching/#Rust-Cargo-cache
+cache:
+  directories:
+    - $HOME/protobuf
+    - $HOME/.cargo
+    - $TRAVIS_BUILD_DIR/target
 
 rust:
   - stable
@@ -12,6 +16,7 @@ matrix:
   allow_failures:
     - env: NAME='nightly'
     - env: NAME='kcov'
+    - env: NAME='rustfmt' # temporarily allow rustfmt to fail until it can recognise conditional cfgs properly
   include:
     - env: NAME='nightly'
       rust: nightly
@@ -20,7 +25,7 @@ matrix:
       before_script:
         - rustup component add rustfmt-preview
       script:
-        - cargo fmt --all -- --write-mode=diff
+        - cargo fmt --all -- --check
     - env: NAME='kcov'
       sudo: required # travis-ci/travis-ci#9061
       before_script:
@@ -57,3 +62,7 @@ script:
   - cargo build --verbose --all-features
   - cargo test --verbose --all-features
   - cargo doc --verbose --all-features --no-deps
+
+before_install:
+  - export PATH=$PATH:$HOME/protobuf/bin
+  - bash install_protobuf.sh

Cargo.toml

@@ -19,10 +19,13 @@ categories    = ["data-structures", "cryptography"]
 
 [dependencies]
 ring = "^0.12.0"
-protobuf = { version = "^1.6.0", optional = true }
+protobuf = { version = "1.7.1", optional = true }
 serde = { version = "^1.0.55", optional = true }
 serde_derive = { version = "^1.0.55", optional = true }
 
+[build-dependencies]
+protoc-rust = "1.7.1"
+
 [dev-dependencies]
 serde_json = "1.0.17"
 

build.rs

@@ -0,0 +1,15 @@
+extern crate protoc_rust;
+
+fn build_protobuf<'a>(out_dir: &'a str, input: &'a [&'a str], includes: &'a [&'a str]) {
+    use self::protoc_rust::{run, Args};
+    run(Args {
+        out_dir,
+        input,
+        includes,
+    }).expect("protoc");
+}
+
+fn main() {
+    #[cfg(feature = "serialization-protobuf")]
+    build_protobuf("src/proto", &["protobuf/proof.proto"], &[]);
+}

install_protobuf.sh

@@ -0,0 +1,22 @@
+#!/usr/bin/bash
+set -e
+
+check_protoc_version () {
+    version="libprotoc $1"
+    PROTOC="$HOME/protobuf/bin/protoc"
+    if [ -f $PROTOC ]; then
+        this_version=`$PROTOC --version`
+        return `[ "$version" = "$this_version" ]`
+    else
+        return 1
+    fi
+}
+
+if check_protoc_version '3.5.1'; then
+    echo protoc version 3.5.1 detected.
+    exit
+fi
+
+wget https://github.com/google/protobuf/archive/v3.5.1.tar.gz
+tar -xzvf v3.5.1.tar.gz
+cd protobuf-3.5.1 && ./autogen.sh && ./configure --prefix=$HOME/protobuf && make && make install