Merge pull request #266 from ethereum/linkViaHash

Support linking via hash.

Author: chriseth

linker.js

@@ -1,3 +1,13 @@
+var keccak = require('keccak');
+
+function keccak256 (input) {
+  return keccak('keccak256').update(input).digest();
+}
+
+function libraryHashPlaceholder (input) {
+  return '$' + keccak256(input).toString('hex').slice(0, 34) + '$';
+}
+
 var linkBytecode = function (bytecode, libraries) {
   // NOTE: for backwards compatibility support old compiler which didn't use file names
   var librariesComplete = {};
@@ -19,11 +29,6 @@ var linkBytecode = function (bytecode, libraries) {
   }
 
   for (libraryName in librariesComplete) {
-    // truncate to 37 characters
-    var internalName = libraryName.slice(0, 36);
-    // prefix and suffix with __
-    var libLabel = '__' + internalName + Array(37 - internalName.length).join('_') + '__';
-
     var hexAddress = librariesComplete[libraryName];
     if (hexAddress.slice(0, 2) !== '0x' || hexAddress.length > 42) {
       throw new Error('Invalid address specified for ' + libraryName);
@@ -32,9 +37,19 @@ var linkBytecode = function (bytecode, libraries) {
     hexAddress = hexAddress.slice(2);
     hexAddress = Array(40 - hexAddress.length + 1).join('0') + hexAddress;
 
-    while (bytecode.indexOf(libLabel) >= 0) {
-      bytecode = bytecode.replace(libLabel, hexAddress);
-    }
+    // Support old (library name) and new (hash of library name)
+    // placeholders.
+    var replace = function (name) {
+      // truncate to 37 characters
+      var truncatedName = name.slice(0, 36);
+      var libLabel = '__' + truncatedName + Array(37 - truncatedName.length).join('_') + '__';
+      while (bytecode.indexOf(libLabel) >= 0) {
+        bytecode = bytecode.replace(libLabel, hexAddress);
+      }
+    };
+
+    replace(libraryName);
+    replace(libraryHashPlaceholder(libraryName));
   }
 
   return bytecode;

package.json

@@ -40,6 +40,7 @@
   "homepage": "https://github.com/ethereum/solc-js#readme",
   "dependencies": {
     "fs-extra": "^0.30.0",
+    "keccak": "^1.0.2",
     "memorystream": "^0.3.1",
     "require-from-string": "^2.0.0",
     "semver": "^5.5.0",

test/linker.js

@@ -139,4 +139,11 @@ tape('Linking', function (t) {
     st.ok(bytecode.indexOf('_') < 0);
     st.end();
   });
+
+  t.test('hashed placeholder', function (st) {
+    var bytecode = '6060604052341561000__$cb901161e812ceb78cfe30ca65050c4337$__66606060606060';
+    bytecode = linker.linkBytecode(bytecode, { 'lib2.sol:L': '0x123456' });
+    st.equal(bytecode, '6060604052341561000000000000000000000000000000000000012345666606060606060');
+    st.end();
+  });
 });