size_t N = Str.size();
if (N > Length)
return npos;
- for (size_t e = Length - N + 1, i = min(From, e); i != e; ++i)
- if (substr(i, N).equals(Str))
- return i;
+
+ // For short haystacks or unsupported needles fall back to the naive algorithm
+ if (Length < 16 || N > 255 || N == 0) {
+ for (size_t e = Length - N + 1, i = min(From, e); i != e; ++i)
+ if (substr(i, N).equals(Str))
+ return i;
+ return npos;
+ }
+
+ // Build the bad char heuristic table, with uint8_t to reduce cache thrashing.
+ uint8_t BadCharSkip[256];
+ std::memset(BadCharSkip, N, 256);
+ for (unsigned i = 0; i != N-1; ++i)
+ BadCharSkip[(uint8_t)Str[i]] = N-1-i;
+
+ unsigned Len = Length, Pos = min(From, Length);
+ while (Len >= N) {
+ if (substr(Pos, N).equals(Str)) // See if this is the correct substring.
+ return Pos;
+
+ // Otherwise skip the appropriate number of bytes.
+ uint8_t Skip = BadCharSkip[(uint8_t)Data[Pos+N-1]];
+ Len -= Skip;
+ Pos += Skip;
+ }
+
return npos;
}
EXPECT_EQ(StringRef::npos, Str.find("zz"));
EXPECT_EQ(2U, Str.find("ll", 2));
EXPECT_EQ(StringRef::npos, Str.find("ll", 3));
+ EXPECT_EQ(0U, Str.find(""));
+ StringRef LongStr("hellx xello hell ello world foo bar hello");
+ EXPECT_EQ(36U, LongStr.find("hello"));
+ EXPECT_EQ(28U, LongStr.find("foo"));
+ EXPECT_EQ(12U, LongStr.find("hell", 2));
+ EXPECT_EQ(0U, LongStr.find(""));
EXPECT_EQ(3U, Str.rfind('l'));
EXPECT_EQ(StringRef::npos, Str.rfind('z'));