From 01a5ea9914b3933e63a88184861900615be76e12 Mon Sep 17 00:00:00 2001
From: Marc Weber <marco-oweber@gmx.de>
Date: Thu, 7 Feb 2013 00:03:46 +0100
Subject: [PATCH] experimental/hash

adding primop function calculating hash of a string

Signed-off-by: Marc Weber <marco-oweber@gmx.de>
---
 src/libexpr/primops.cc        | 26 ++++++++++++++++++++++++++
 tests/lang/eval-okay-hash.exp |  1 +
 tests/lang/eval-okay-hash.nix |  6 ++++++
 3 files changed, 33 insertions(+)
 create mode 100644 tests/lang/eval-okay-hash.exp
 create mode 100644 tests/lang/eval-okay-hash.nix

diff --git a/src/libexpr/primops.cc b/src/libexpr/primops.cc
index f8f893d69..84c4bbb88 100644
--- a/src/libexpr/primops.cc
+++ b/src/libexpr/primops.cc
@@ -1107,6 +1107,30 @@ static void prim_unsafeDiscardOutputDependency(EvalState & state, Value * * args
 }
 
 
+static void prim_hash(EvalState & state, Value * * args, Value & v)
+{
+    PathSet context;
+
+    string type = state.forceStringNoCtx(*args[0]);
+    string s = state.forceStringNoCtx(*args[1]);
+
+    HashType ht;
+    if (type == "md5"){
+      ht = htMD5;
+    } else if (type == "sha256"){
+      ht = htSHA256;
+    } else {
+      throw Error(format("bad hash type `%1%'") % type);
+    }
+
+    Hash h = hashString(ht, s);
+
+    string hash = printHash(h);
+
+    mkString(v, hash, context);
+};
+
+
 /*************************************************************
  * Versions
  *************************************************************/
@@ -1235,6 +1259,8 @@ void EvalState::createBaseEnv()
     addPrimOp("__unsafeDiscardStringContext", 1, prim_unsafeDiscardStringContext);
     addPrimOp("__unsafeDiscardOutputDependency", 1, prim_unsafeDiscardOutputDependency);
 
+    addPrimOp("__hash", 2, prim_hash);
+
     // Versions
     addPrimOp("__parseDrvName", 1, prim_parseDrvName);
     addPrimOp("__compareVersions", 2, prim_compareVersions);
diff --git a/tests/lang/eval-okay-hash.exp b/tests/lang/eval-okay-hash.exp
new file mode 100644
index 000000000..369b983d5
--- /dev/null
+++ b/tests/lang/eval-okay-hash.exp
@@ -0,0 +1 @@
+[ "6c69ee7f211c640419d5366cc076ae46" "bb3438fbabd460ea6dbd27d153e2233b" "900a4469df00ccbfd0c145c6d1e4b7953dd0afafadd7534e3a4019e8d38fc663" "ad0387b3bd8652f730ca46d25f9c170af0fd589f42e7f23f5a9e6412d97d7e56" ]
diff --git a/tests/lang/eval-okay-hash.nix b/tests/lang/eval-okay-hash.nix
new file mode 100644
index 000000000..65cd8afeb
--- /dev/null
+++ b/tests/lang/eval-okay-hash.nix
@@ -0,0 +1,6 @@
+let
+  md5 = builtins.hash "md5";
+  sha256 = builtins.hash "sha256";
+  strings = [ "text 1" "text 2" ];
+in
+  (builtins.map md5 strings) ++ (builtins.map sha256 strings)