From d36ec905b1d9536198e584915024ed65f0342ab2 Mon Sep 17 00:00:00 2001
From: Yuri Kunde Schlesner <yuriks@yuriks.net>
Date: Sun, 18 Dec 2016 21:48:12 -0800
Subject: [PATCH] Common: Optimize BitSet iterator
---
src/common/bit_set.h | 33 +++++++++++++++++++--------------
1 file changed, 19 insertions(+), 14 deletions(-)
diff --git a/src/common/bit_set.h b/src/common/bit_set.h
index 3059d0cb0..9c2e6b28c 100644
--- a/src/common/bit_set.h
+++ b/src/common/bit_set.h
@@ -121,22 +121,19 @@ public:
class Iterator {
public:
Iterator(const Iterator& other) : m_val(other.m_val), m_bit(other.m_bit) {}
- Iterator(IntTy val, int bit) : m_val(val), m_bit(bit) {}
+ Iterator(IntTy val) : m_val(val), m_bit(0) {}
Iterator& operator=(Iterator other) {
new (this) Iterator(other);
return *this;
}
int operator*() {
- return m_bit;
+ return m_bit + ComputeLsb();
}
Iterator& operator++() {
- if (m_val == 0) {
- m_bit = -1;
- } else {
- int bit = LeastSignificantSetBit(m_val);
- m_val &= ~(1 << bit);
- m_bit = bit;
- }
+ int lsb = ComputeLsb();
+ m_val >>= lsb + 1;
+ m_bit += lsb + 1;
+ m_has_lsb = false;
return *this;
}
Iterator operator++(int _) {
@@ -145,15 +142,24 @@ public:
return other;
}
bool operator==(Iterator other) const {
- return m_bit == other.m_bit;
+ return m_val == other.m_val;
}
bool operator!=(Iterator other) const {
- return m_bit != other.m_bit;
+ return m_val != other.m_val;
}
private:
+ int ComputeLsb() {
+ if (!m_has_lsb) {
+ m_lsb = LeastSignificantSetBit(m_val);
+ m_has_lsb = true;
+ }
+ return m_lsb;
+ }
IntTy m_val;
int m_bit;
+ int m_lsb = -1;
+ bool m_has_lsb = false;
};
BitSet() : m_val(0) {}
@@ -221,11 +227,10 @@ public:
}
Iterator begin() const {
- Iterator it(m_val, 0);
- return ++it;
+ return Iterator(m_val);
}
Iterator end() const {
- return Iterator(m_val, -1);
+ return Iterator(0);
}
IntTy m_val;