From 52925684387496e83425c79f74b29a91943466a7 Mon Sep 17 00:00:00 2001
From: Boris Kolpackov <boris@codesynthesis.com>
Date: Tue, 24 Feb 2015 06:27:57 +0200
Subject: Make empty key to always be prefix in prefix_map

---
 build/algorithm.cxx               |  7 ++-----
 build/prefix-map                  | 10 ++++++++--
 tests/build/prefix-map/driver.cxx | 12 +++++-------
 3 files changed, 15 insertions(+), 14 deletions(-)

diff --git a/build/algorithm.cxx b/build/algorithm.cxx
index ddf0071..d418cda 100644
--- a/build/algorithm.cxx
+++ b/build/algorithm.cxx
@@ -44,13 +44,10 @@ namespace build
       if (i == rules.end ()) // No rules registered for this target type.
         continue;
 
-      const auto& rules (i->second); // Name map.
+      const auto& rules (i->second); // Hint map.
 
       string hint; // @@ TODO
-
-      auto rs (hint.empty ()
-               ? make_pair (rules.begin (), rules.end ())
-               : rules.find (hint));
+      auto rs (rules.find (hint));
 
       for (auto i (rs.first); i != rs.second; ++i)
       {
diff --git a/build/prefix-map b/build/prefix-map
index d2ca9be..a385ca8 100644
--- a/build/prefix-map
+++ b/build/prefix-map
@@ -39,8 +39,9 @@ namespace build
     prefix (const K& p, const K& k) const
     {
       size_type pn (p.size ());
-      return compare (
-        p.c_str (), pn, k.c_str (), pn == k.size () ? pn : pn + 1) == 0;
+      return pn == 0 || // Empty key is always a prefix.
+        compare (
+          p.c_str (), pn, k.c_str (), pn == k.size () ? pn : pn + 1) == 0;
     }
 
     int
@@ -76,6 +77,11 @@ namespace build
   // the ability to retrieve a range of entries that have a specific
   // prefix. The '.' and '/' above are the delimiter characters.
   //
+  // Note that as a special rule, the default implementation of
+  // compare_prefix treats empty key as everyone's prefix even if
+  // the paths don't start with the delimiter (useful to represent
+  // a "root path").
+  //
   // Implementation-wise, the idea is to pretend that each key ends
   // with the delimiter. This way we automatically avoid matching
   // 'foobar' as having a prefix 'foo'.
diff --git a/tests/build/prefix-map/driver.cxx b/tests/build/prefix-map/driver.cxx
index fb5269c..77edb6c 100644
--- a/tests/build/prefix-map/driver.cxx
+++ b/tests/build/prefix-map/driver.cxx
@@ -35,7 +35,8 @@ main ()
 
     {
       auto r (m.find (""));
-      assert (r.first == r.second);
+      assert (r.first != r.second && r.first->second == 1 &&
+              ++r.first == r.second);
     }
 
     {
@@ -70,7 +71,9 @@ main ()
 
     {
       auto r (m.find (""));
-      assert (r.first == r.second);
+      assert (r.first != r.second && r.first->second == 2 &&
+              ++r.first != r.second && r.first->second == 1 &&
+              ++r.first == r.second);
     }
 
     {
@@ -114,11 +117,6 @@ main ()
       '.');
 
     {
-      auto r (m.find (""));
-      assert (r.first == r.second);
-    }
-
-    {
       auto r (m.find ("fo"));
       assert (r.first == r.second);
     }
-- 
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