generalize the pattern of hash_map<const char*, ...>, use in BuildLog

Refactor the code in StatCache for use in BuildLog.  Now both use
hash tables where the keys are const char*.  Removes another 30ms
from Chrome no-op builds.

1 files changed, 29 insertions, 0 deletions

diff --git a/src/hash_map.h b/src/hash_map.h
index 346a34e..1025f71 100644
--- a/src/hash_map.h
+++ b/src/hash_map.h
@@ -15,6 +15,8 @@
 #ifndef NINJA_MAP_H_
 #define NINJA_MAP_H_
 
+#include <string.h>
+
 #ifdef _MSC_VER
 #include <hash_map>
 
@@ -37,4 +39,31 @@ struct hash<std::string> {
 
 #endif
 
+/// Equality binary predicate for const char*.
+struct ExternalStringEq {
+  bool operator()(const char* a, const char* b) {
+    return strcmp(a, b) == 0;
+  }
+};
+
+/// Hash functor for const char*.
+struct ExternalStringHash {
+  size_t operator()(const char* key) const {
+#ifdef _MSC_VER
+    return stdext::hash<const char*>()(key);
+#else
+    return __gnu_cxx::hash<const char*>()(key);
+#endif
+  }
+};
+
+/// A template for hash_maps keyed by a const char* that is maintained within
+/// the values.  Use like:
+///   ExternalStringHash<Foo*>::Type foos;
+/// to make foos into a hash mapping const char* => Foo*.
+template<typename V>
+struct ExternalStringHashMap {
+  typedef hash_map<const char*, V, ExternalStringHash, ExternalStringEq> Type;
+};
+
 #endif // NINJA_MAP_H_