Support binary downloads (#316)

Co-authored-by: Bert Belder <bertbelder@gmail.com>

Cargo.toml

@@ -47,6 +47,11 @@ exclude = [
  "!v8/tools/testrunner/utils/dump_build_config.py",
 ]
 
+[features]
+# Enable this feature to download and prebuilt V8 binaries from
+# https://github.com/denoland/rusty_v8/releases
+binary = []
+
 [dependencies]
 lazy_static = "1.4.0"
 libc = "0.2.67"

README.md

@@ -29,7 +29,7 @@ V8 Version: 8.2.308, 2020-03-12
    Due to the complexity and size of V8's build, this is nontrivial. For example
    the crate size must be kept under 10 MiB in order to publish.
 
-## Build
+## Build V8 from Source
 
 Use `cargo build -vv` to build the crate.
 
@@ -56,6 +56,20 @@ environmental variable.
 
 Env vars used in build.rs: `SCCACHE`, `GN`, `NINJA`, `CLANG_BASE_PATH`, `GN_ARGS`
 
+## Binary Build
+
+V8 is very large and take a long time to compile. Many users may prefer to use
+a prebuilt version of V8. We publish static libs for every version of rusty v8
+on [Github](https://github.com/denoland/rusty_v8/releases).
+
+To use these prebuilt binaries use the `binary` feature:
+
+```
+cargo build --features="binary"
+```
+
+This will cause rusty v8 to download the binaries during the build process.
+
 ## FAQ
 
 **Building V8 takes over 30 minutes, this is too slow for me to use this crate.

build.rs

@@ -23,9 +23,12 @@ fn main() {
     .map(|s| s.starts_with("rls"))
     .unwrap_or(false);
 
-  if !(is_trybuild || is_cargo_doc | is_rls) {
+  if cfg!(feature = "binary") {
+    download_static_lib_binaries();
+  } else if !(is_trybuild || is_cargo_doc | is_rls) {
     build_v8()
   }
+
   if !(is_cargo_doc || is_rls) {
     print_link_flags()
   }
@@ -166,6 +169,70 @@ fn download_ninja_gn_binaries() {
   env::set_var("NINJA", ninja);
 }
 
+fn static_lib_url() -> (String, String) {
+  let base = "https://github.com/denoland/rusty_v8/releases/download";
+  let version = env::var("CARGO_PKG_VERSION").unwrap();
+  let target = env::var("TARGET").unwrap();
+  if cfg!(target_os = "windows") {
+    // Note: we always use the release build on windows.
+    let url = format!("{}/v{}/rusty_v8_release_{}.lib", base, version, target);
+    let static_lib_name = "rusty_v8.lib".to_string();
+    (url, static_lib_name)
+  } else {
+    let profile = env::var("PROFILE").unwrap();
+    assert!(profile == "release" || profile == "debug");
+    let url =
+      format!("{}/v{}/librusty_v8_{}_{}.a", base, version, profile, target);
+    let static_lib_name = "librusty_v8.a".to_string();
+    (url, static_lib_name)
+  }
+}
+
+fn download_static_lib_binaries() {
+  let (url, static_lib_name) = static_lib_url();
+  println!("static lib URL: {}", url);
+
+  let root = env::current_dir().unwrap();
+
+  // target/debug//build/rusty_v8-d9e5a424d4f96994/out/
+  let out_dir = env::var_os("OUT_DIR").unwrap();
+  let out_dir_abs = root.join(out_dir);
+
+  // This would be target/debug or target/release
+  let target_dir = out_dir_abs
+    .parent()
+    .unwrap()
+    .parent()
+    .unwrap()
+    .parent()
+    .unwrap();
+  let obj_dir = target_dir.join("gn_out").join("obj");
+  std::fs::create_dir_all(&obj_dir).unwrap();
+
+  println!("cargo:rustc-link-search={}", obj_dir.display());
+
+  let filename = obj_dir.join(static_lib_name);
+
+  if filename.exists() {
+    println!("static lib already exists {}", filename.display());
+    println!("To re-download this file, it must be manually deleted.");
+  } else {
+    // Using python to do the HTTP download because it's already a dependency
+    // and so we don't have to add a Rust HTTP client dependency.
+    println!("Downloading {}", url);
+    let status = Command::new("python")
+      .arg("./tools/download_file.py")
+      .arg("--url")
+      .arg(url)
+      .arg("--filename")
+      .arg(&filename)
+      .status()
+      .unwrap();
+    assert!(status.success());
+    assert!(filename.exists());
+  }
+}
+
 fn print_link_flags() {
   println!("cargo:rustc-link-lib=static=rusty_v8");
 

tools/download_file.py

@@ -0,0 +1,62 @@
+#!/usr/bin/env python
+# Copyright (c) 2012 The Chromium Authors. All rights reserved.
+# Use of this source code is governed by a BSD-style license that can be
+# found in the LICENSE file.
+
+from __future__ import print_function
+import argparse
+import os
+import sys
+
+try:
+    from urllib2 import HTTPError, URLError, urlopen
+except ImportError:  # For Py3 compatibility
+    from urllib.error import HTTPError, URLError
+    from urllib.request import urlopen
+
+def DownloadUrl(url, output_file):
+    """Download url into output_file."""
+    CHUNK_SIZE = 4096
+    num_retries = 3
+    retry_wait_s = 5  # Doubled at each retry.
+
+    while True:
+        try:
+            sys.stdout.write('Downloading %s...' % url)
+            sys.stdout.flush()
+            response = urlopen(url)
+            bytes_done = 0
+            while True:
+                chunk = response.read(CHUNK_SIZE)
+                if not chunk:
+                    break
+                output_file.write(chunk)
+                bytes_done += len(chunk)
+            if bytes_done == 0:
+                raise URLError("empty response")
+            print(' Done.')
+            return
+        except URLError as e:
+            sys.stdout.write('\n')
+            print(e)
+            if num_retries == 0 or isinstance(e, HTTPError) and e.code == 404:
+                raise e
+            num_retries -= 1
+            print('Retrying in %d s ...' % retry_wait_s)
+            sys.stdout.flush()
+            time.sleep(retry_wait_s)
+            retry_wait_s *= 2
+
+
+def main():
+    parser = argparse.ArgumentParser(description='Download a file')
+    parser.add_argument('--filename', help='where to put the file')
+    parser.add_argument('--url', help='what url to download')
+    args = parser.parse_args()
+    with open(args.filename, "wb") as f:
+        DownloadUrl(args.url, f)
+    return 0
+
+
+if __name__ == '__main__':
+    sys.exit(main())

tools/ninja_gn_binaries.py

@@ -25,7 +25,6 @@ DIR = None
 def DownloadUrl(url, output_file):
     """Download url into output_file."""
     CHUNK_SIZE = 4096
-    TOTAL_DOTS = 10
     num_retries = 3
     retry_wait_s = 5  # Doubled at each retry.