Hashing.h - utilities for hashing various data types.

llvm-svn: 150890

1 files changed, 46 insertions, 0 deletions

diff --git a/llvm/lib/Support/Hashing.cpp b/llvm/lib/Support/Hashing.cpp
new file mode 100644
index 00000000000..89b84530afa
--- /dev/null
+++ b/llvm/lib/Support/Hashing.cpp
@@ -0,0 +1,46 @@
+//===-- llvm/ADT/Hashing.cpp - Utilities for hashing ------------*- C++ -*-===//
+//
+//                     The LLVM Compiler Infrastructure
+//
+// This file is distributed under the University of Illinois Open Source
+// License. See LICENSE.TXT for details.
+//
+//===----------------------------------------------------------------------===//
+
+#include "llvm/ADT/Hashing.h"
+
+namespace llvm {
+
+// Add a possibly unaligned sequence of bytes.
+void GeneralHash::addUnaligned(const uint8_t *I, const uint8_t *E) {
+  ptrdiff_t Length = E - I;
+  if (uintptr_t(I) & 3 == 0) {
+    while (Length > 3) {
+      mix(*reinterpret_cast<const uint32_t *>(I));
+      I += 4;
+      Length -= 4;
+    }
+  } else {
+    while (Length > 3) {
+      mix(
+        uint32_t(I[0]) +
+        (uint32_t(I[1]) << 8) +
+        (uint32_t(I[2]) << 16) +
+        (uint32_t(I[3]) << 24));
+      I += 4;
+      Length -= 4;
+    }
+  }
+
+  if (Length & 3) {
+    uint32_t Data = 0;
+    switch (Length & 3) {
+      case 3: Data |= uint32_t(I[2]) << 16;   // fall through
+      case 2: Data |= uint32_t(I[1]) << 8;    // fall through
+      case 1: Data |= uint32_t(I[0]); break;
+    }
+    mix(Data);
+  }
+}
+
+}