/util: streaming CityHash

commit_hash:bd4032fbf4c4ece089ad071747194b38df6c5edd

1 files changed, 21 insertions, 0 deletions

diff --git a/util/digest/city_streaming.h b/util/digest/city_streaming.h
new file mode 100644
index 0000000000..f9c5209e0a
--- /dev/null
+++ b/util/digest/city_streaming.h
@@ -0,0 +1,21 @@
+#pragma once
+#include <util/digest/city.h>
+
+/**
+ *   (partially) streaming version of CityHash64 for large data.
+ *   You need to know length and first/last 64 bytes.
+ *   Those bytes should be passed twice: in constructor and thru process().
+ *   Length must be STRICTLY larger than 64 bytes.
+ *   XXX: Dont use CityHash64 if you can use something else and need streaming
+ */
+class TStreamingCityHash64 {
+    ui64 x, y, z;
+    std::pair<ui64, ui64> v, w;
+    char UnalignBuf_[64];
+    size_t UnalignBufSz_, Rest64_;
+
+public:
+    TStreamingCityHash64(size_t len, const char* head64, const char* tail64);
+    void Process(const char* s, size_t avail);
+    ui64 operator()();
+};