Added V8_COMPILE_CACHE_CACHE_DIR option

Closes #23

README.md

@@ -26,9 +26,11 @@ The ability to tap into V8 to produce/consume this cache was introduced in [Node
 
 Set the environment variable `DISABLE_V8_COMPILE_CACHE=1` to disable the cache.
 
+Cache directory is defined by environment variable `V8_COMPILE_CACHE_CACHE_DIR` or defaults to `<os.tmpdir()>/v8-compile-cache-<V8_VERSION>`.
+
 ## Internals
 
-The caches are stored in `$TMP/v8-compile-cache/V8_VERSION`, where there are `.BLOB` and `.MAP` files corresponding to the entry module that required `v8-compile-cache`. The cache is _entry module specific_ because it is faster to load the entire code cache into memory at once, than it is to read it from disk on a file-by-file basis.
+Cache files are suffixed `.BLOB` and `.MAP` corresponding to the entry module that required `v8-compile-cache`. The cache is _entry module specific_ because it is faster to load the entire code cache into memory at once, than it is to read it from disk on a file-by-file basis.
 
 ## Benchmarks
 

bench/run.sh

@@ -1,8 +1,10 @@
 #!/bin/bash
 
-# for i in {1..5}; do node bench/require-yarn.js; done
+set -eo pipefail
 
-# rm -rf "$TMPDIR/v8-compile-cache"
+V8_COMPILE_CACHE_CACHE_DIR=$(mktemp -d)
+export V8_COMPILE_CACHE_CACHE_DIR=$V8_COMPILE_CACHE_CACHE_DIR
+trap 'rm -r "$V8_COMPILE_CACHE_CACHE_DIR"' EXIT
 
 THIS_DIR="$(cd "$(dirname "${BASH_SOURCE[0]}")" && pwd)"
 : "${NODE_BIN:=node}"

test/getCacheDir-test.js

@@ -26,6 +26,7 @@ tap.test('getCacheDir (chakracore)', t => {
       process: {
         getuid: process.getuid,
         versions: {chakracore: '1.2.3'},
+        env: {},
       },
       path,
       os,
@@ -49,6 +50,7 @@ tap.test('getCacheDir (unknown)', t => {
         getuid: process.getuid,
         version: '1.2.3',
         versions: {},
+        env: {},
       },
       path,
       os,
@@ -62,3 +64,24 @@ tap.test('getCacheDir (unknown)', t => {
 
   t.done();
 });
+
+tap.test('getCacheDir (env)', t => {
+  const cacheDir = vm.runInNewContext(
+    '(' + getCacheDir.toString() + ')();',
+    {
+      process: {
+        getuid: process.getuid,
+        versions: {},
+        env: {
+          V8_COMPILE_CACHE_CACHE_DIR: 'from env',
+        },
+      },
+      path,
+      os,
+    }
+  );
+
+  t.equal(cacheDir, 'from env');
+
+  t.done();
+});

v8-compile-cache.js

@@ -310,6 +310,11 @@ function supportsCachedData() {
 }
 
 function getCacheDir() {
+  const v8_compile_cache_cache_dir = process.env.V8_COMPILE_CACHE_CACHE_DIR;
+  if (v8_compile_cache_cache_dir) {
+    return v8_compile_cache_cache_dir;
+  }
+
   // Avoid cache ownership issues on POSIX systems.
   const dirname = typeof process.getuid === 'function'
     ? 'v8-compile-cache-' + process.getuid()