Bug 998507 - add BinarySearch (r=sunfish)

--HG--
extra : rebase_source : 6ba04575a5dd8a886235e6799bc790c7a3afc64f

js/src/jit/AsmJSSignalHandlers.cpp

@@ -6,6 +6,8 @@
 
 #include "jit/AsmJSSignalHandlers.h"
 
+#include "mozilla/BinarySearch.h"
+
 #include "assembler/assembler/MacroAssembler.h"
 #include "jit/AsmJSModule.h"
 
@@ -207,35 +209,29 @@ SetXMMRegToNaN(bool isFloat32, T *xmm_reg)
     }
 }
 
+struct GetHeapAccessOffset
+{
+    const AsmJSModule &module;
+    explicit GetHeapAccessOffset(const AsmJSModule &module) : module(module) {}
+    uintptr_t operator[](size_t index) const {
+        return module.heapAccess(index).offset();
+    }
+};
+
 // Perform a binary search on the projected offsets of the known heap accesses
 // in the module.
 static const AsmJSHeapAccess *
 LookupHeapAccess(const AsmJSModule &module, uint8_t *pc)
 {
     JS_ASSERT(module.containsPC(pc));
-    size_t targetOffset = pc - module.codeBase();
 
-    if (module.numHeapAccesses() == 0)
+    uintptr_t pcOff = pc - module.codeBase();
+
+    size_t match;
+    if (!BinarySearch(GetHeapAccessOffset(module), 0, module.numHeapAccesses(), pcOff, &match))
         return nullptr;
 
-    size_t low = 0;
-    size_t high = module.numHeapAccesses() - 1;
-    while (high - low >= 2) {
-        size_t mid = low + (high - low) / 2;
-        uint32_t midOffset = module.heapAccess(mid).offset();
-        if (targetOffset == midOffset)
-            return &module.heapAccess(mid);
-        if (targetOffset < midOffset)
-            high = mid;
-        else
-            low = mid;
-    }
-    if (targetOffset == module.heapAccess(low).offset())
-        return &module.heapAccess(low);
-    if (targetOffset == module.heapAccess(high).offset())
-        return &module.heapAccess(high);
-
-    return nullptr;
+    return &module.heapAccess(match);
 }
 #endif
 

mfbt/BinarySearch.h

@@ -0,0 +1,62 @@
+/* -*- Mode: C++; tab-width: 8; indent-tabs-mode: nil; c-basic-offset: 2 -*- */
+/* vim: set ts=8 sts=2 et sw=2 tw=80: */
+/* This Source Code Form is subject to the terms of the Mozilla Public
+ * License, v. 2.0. If a copy of the MPL was not distributed with this
+ * file, You can obtain one at http://mozilla.org/MPL/2.0/. */
+
+#ifndef mozilla_BinarySearch_h
+#define mozilla_BinarySearch_h
+
+#include "mozilla/Assertions.h"
+
+#include <stddef.h>
+
+namespace mozilla {
+
+/*
+ * The algorithm searches the given container 'c' over the sorted index range
+ * [begin, end) for an index 'i' where 'c[i] == target'. If such an index 'i' is
+ * found, BinarySearch returns 'true' and the index is returned via the outparam
+ * 'matchOrInsertionPoint'. If no index is found, BinarySearch returns 'false'
+ * and the outparam returns the first index in [begin, end] where 'target' can
+ * be inserted to maintain sorted order.
+ *
+ * Example:
+ *
+ *   Vector<int> sortedInts = ...
+ *
+ *   size_t match;
+ *   if (BinarySearch(sortedInts, 0, sortedInts.length(), 13, &match))
+ *     printf("found 13 at %lu\n", match);
+ */
+
+template <typename Container, typename T>
+bool
+BinarySearch(const Container &c, size_t begin, size_t end, T target, size_t *matchOrInsertionPoint)
+{
+  MOZ_ASSERT(begin <= end);
+
+  size_t low = begin;
+  size_t high = end;
+  while (low != high) {
+    size_t middle = low + (high - low) / 2;
+    const T &middleValue = c[middle];
+
+    if (target == middleValue) {
+      *matchOrInsertionPoint = middle;
+      return true;
+    }
+
+    if (target < middleValue)
+      high = middle;
+    else
+      low = middle + 1;
+  }
+
+  *matchOrInsertionPoint = low;
+  return false;
+}
+
+} // namespace mozilla
+
+#endif // mozilla_BinarySearch_h

mfbt/moz.build

@@ -16,6 +16,7 @@ EXPORTS.mozilla = [
     'Assertions.h',
     'Atomics.h',
     'Attributes.h',
+    'BinarySearch.h',
     'BloomFilter.h',
     'Casting.h',
     'ChaosMode.h',

mfbt/tests/TestBinarySearch.cpp

@@ -0,0 +1,75 @@
+/* -*- Mode: C++; tab-width: 2; indent-tabs-mode: nil; c-basic-offset: 2 -*- */
+/* This Source Code Form is subject to the terms of the Mozilla Public
+ * License, v. 2.0. If a copy of the MPL was not distributed with this file,
+ * You can obtain one at http://mozilla.org/MPL/2.0/. */
+
+#include "mozilla/Assertions.h"
+#include "mozilla/BinarySearch.h"
+#include "mozilla/Vector.h"
+
+using mozilla::Vector;
+using mozilla::BinarySearch;
+
+struct Person
+{
+  int age;
+  int id;
+  Person(int age, int id) : age(age), id(id) {}
+};
+
+struct GetAge
+{
+  Vector<Person> &v;
+  GetAge(Vector<Person> &v) : v(v) {}
+  int operator[](size_t index) const { return v[index].age; }
+};
+
+int main()
+{
+  size_t m;
+
+  Vector<int> v1;
+  v1.append(2);
+  v1.append(4);
+  v1.append(6);
+  v1.append(8);
+
+  MOZ_ASSERT(!BinarySearch(v1, 0, v1.length(), 1, &m) && m == 0);
+  MOZ_ASSERT( BinarySearch(v1, 0, v1.length(), 2, &m) && m == 0);
+  MOZ_ASSERT(!BinarySearch(v1, 0, v1.length(), 3, &m) && m == 1);
+  MOZ_ASSERT( BinarySearch(v1, 0, v1.length(), 4, &m) && m == 1);
+  MOZ_ASSERT(!BinarySearch(v1, 0, v1.length(), 5, &m) && m == 2);
+  MOZ_ASSERT( BinarySearch(v1, 0, v1.length(), 6, &m) && m == 2);
+  MOZ_ASSERT(!BinarySearch(v1, 0, v1.length(), 7, &m) && m == 3);
+  MOZ_ASSERT( BinarySearch(v1, 0, v1.length(), 8, &m) && m == 3);
+  MOZ_ASSERT(!BinarySearch(v1, 0, v1.length(), 9, &m) && m == 4);
+
+  MOZ_ASSERT(!BinarySearch(v1, 1, 3, 1, &m) && m == 1);
+  MOZ_ASSERT(!BinarySearch(v1, 1, 3, 2, &m) && m == 1);
+  MOZ_ASSERT(!BinarySearch(v1, 1, 3, 3, &m) && m == 1);
+  MOZ_ASSERT( BinarySearch(v1, 1, 3, 4, &m) && m == 1);
+  MOZ_ASSERT(!BinarySearch(v1, 1, 3, 5, &m) && m == 2);
+  MOZ_ASSERT( BinarySearch(v1, 1, 3, 6, &m) && m == 2);
+  MOZ_ASSERT(!BinarySearch(v1, 1, 3, 7, &m) && m == 3);
+  MOZ_ASSERT(!BinarySearch(v1, 1, 3, 8, &m) && m == 3);
+  MOZ_ASSERT(!BinarySearch(v1, 1, 3, 9, &m) && m == 3);
+
+  MOZ_ASSERT(!BinarySearch(v1, 0, 0, 0, &m) && m == 0);
+  MOZ_ASSERT(!BinarySearch(v1, 0, 0, 9, &m) && m == 0);
+
+  Vector<int> v2;
+  MOZ_ASSERT(!BinarySearch(v2, 0, 0, 0, &m) && m == 0);
+  MOZ_ASSERT(!BinarySearch(v2, 0, 0, 9, &m) && m == 0);
+
+  Vector<Person> v3;
+  v3.append(Person(2, 42));
+  v3.append(Person(4, 13));
+  v3.append(Person(6, 360));
+  MOZ_ASSERT(!BinarySearch(GetAge(v3), 0, v3.length(), 1, &m) && m == 0);
+  MOZ_ASSERT( BinarySearch(GetAge(v3), 0, v3.length(), 2, &m) && m == 0);
+  MOZ_ASSERT(!BinarySearch(GetAge(v3), 0, v3.length(), 3, &m) && m == 1);
+  MOZ_ASSERT( BinarySearch(GetAge(v3), 0, v3.length(), 4, &m) && m == 1);
+  MOZ_ASSERT(!BinarySearch(GetAge(v3), 0, v3.length(), 5, &m) && m == 2);
+  MOZ_ASSERT( BinarySearch(GetAge(v3), 0, v3.length(), 6, &m) && m == 2);
+  MOZ_ASSERT(!BinarySearch(GetAge(v3), 0, v3.length(), 7, &m) && m == 3);
+}

mfbt/tests/moz.build

@@ -6,6 +6,7 @@
 
 CPP_UNIT_TESTS += [
     'TestAtomics.cpp',
+    'TestBinarySearch.cpp',
     'TestBloomFilter.cpp',
     'TestCasting.cpp',
     'TestCeilingFloor.cpp',