return -1;
}
+ /// find_prev - Returns the index of the first set bit that precedes the
+ /// the bit at \p PriorTo. Returns -1 if all previous bits are unset.
+ int find_prev(unsigned PriorTo) {
+ if (PriorTo == 0)
+ return -1;
+
+ --PriorTo;
+
+ unsigned WordPos = PriorTo / BITWORD_SIZE;
+ unsigned BitPos = PriorTo % BITWORD_SIZE;
+ BitWord Copy = Bits[WordPos];
+ // Mask off next bits.
+ Copy &= maskTrailingOnes<BitWord>(BitPos + 1);
+
+ if (Copy != 0)
+ return (WordPos + 1) * BITWORD_SIZE - countLeadingZeros(Copy) - 1;
+
+ // Check previous words.
+ for (unsigned i = 1; i <= WordPos; ++i) {
+ unsigned Index = WordPos - i;
+ if (Bits[Index] == 0)
+ continue;
+ return (Index + 1) * BITWORD_SIZE - countLeadingZeros(Bits[Index]) - 1;
+ }
+ return -1;
+ }
+
/// clear - Clear all bits.
void clear() {
Size = 0;
return getPointer()->find_next_unset(Prev);
}
+ /// find_prev - Returns the index of the first set bit that precedes the
+ /// the bit at \p PriorTo. Returns -1 if all previous bits are unset.
+ int find_prev(unsigned PriorTo) const {
+ if (isSmall()) {
+ if (PriorTo == 0)
+ return -1;
+
+ --PriorTo;
+ uintptr_t Bits = getSmallBits();
+ Bits &= maskTrailingOnes<uintptr_t>(PriorTo + 1);
+ if (Bits == 0)
+ return -1;
+
+ return NumBaseBits - countLeadingZeros(Bits) - 1;
+ }
+ return getPointer()->find_prev(PriorTo);
+ }
+
/// Clear all bits.
void clear() {
if (!isSmall())
EXPECT_EQ(75, A.find_next(13));
EXPECT_EQ(-1, A.find_next(75));
+ EXPECT_EQ(-1, A.find_prev(12));
+ EXPECT_EQ(12, A.find_prev(13));
+ EXPECT_EQ(13, A.find_prev(75));
+ EXPECT_EQ(75, A.find_prev(90));
+
EXPECT_EQ(0, A.find_first_unset());
EXPECT_EQ(99, A.find_last_unset());
EXPECT_EQ(14, A.find_next_unset(11));
EXPECT_EQ(16, A.find_next(4));
EXPECT_EQ(-1, A.find_next(16));
+ EXPECT_EQ(-1, A.find_prev(3));
+ EXPECT_EQ(3, A.find_prev(4));
+ EXPECT_EQ(4, A.find_prev(16));
+ EXPECT_EQ(16, A.find_prev(18));
+
EXPECT_EQ(0, A.find_first_unset());
EXPECT_EQ(19, A.find_last_unset());
EXPECT_EQ(5, A.find_next_unset(3));