[Courgette] Extract qsufsort module and add tests.

courgette/third_party/qsufsort_unittest.cc

+// Copyright 2015 The Chromium Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style license that can be
+// found in the LICENSE file.
+
+#include "courgette/third_party/qsufsort.h"
+
+#include <algorithm>
+#include <cstring>
+#include <string>
+#include <vector>
+
+#include "base/macros.h"
+#include "base/memory/scoped_ptr.h"
+#include "testing/gtest/include/gtest/gtest.h"
+
+TEST(QSufSortTest, Sort) {
+  const char* test_cases[] = {
+    "",
+    "a",
+    "za",
+    "CACAO",
+    "banana",
+    "tobeornottobe",
+    "The quick brown fox jumps over the lazy dog.",
+    "elephantelephantelephantelephantelephant",
+    "-------------------------",
+    "011010011001011010010110011010010",
+    "3141592653589793238462643383279502884197169399375105",
+    "\xFF\xFE\xFF\xFE\xFD\x80\x30\x31\x32\x80\x30\xFF\x01\xAB\xCD",
+  };
+
+  for (size_t idx = 0; idx < arraysize(test_cases); ++idx) {
+    int len = ::strlen(test_cases[idx]);

[Will Harris, 2015/08/11 17:31:36]

strlen returns size_t, should int mostly be replaced by size_t in this function?

[huangs, 2015/08/11 17:46:03]

Done. Gonna try if this causes signed-unsigned compare error in Linux.

[Will Harris, 2015/08/11 17:58:42]

sorry if I wasn't clear; I meant change all the ints to size_t in the function -
it is likely you will get compile warnings otherwise.

+    const unsigned char* s =
+        reinterpret_cast<const unsigned char*>(test_cases[idx]);
+
+    // Generate the suffix array as I.
+    std::vector<int> I(len + 1);
+    std::vector<int> V(len + 1);
+    courgette::qsuf::qsufsort<int*>(&I[0], &V[0], s, len);
+
+    // Expect that I[] is a permutation of [0, len].
+    std::vector<int> I_sorted(I);
+    std::sort(I_sorted.begin(), I_sorted.end());
+    for (int i = 0; i < len + 1; ++i) {
+      EXPECT_EQ(i, I_sorted[i]) << "test_case[" << idx << "]";
+    }
+
+    // First string must be empty string.
+    EXPECT_EQ(len, I[0]) << "test_case[" << idx << "]";
+
+    // Expect that the |len + 1| suffixes are strictly ordered.
+    const unsigned char* end = s + len;
+    for (int i = 0; i < len; ++i) {
+      const unsigned char* suf1 = s + I[i];
+      const unsigned char* suf2 = s + I[i + 1];
+      bool is_less = std::lexicographical_compare(suf1, end, suf2, end);
+      EXPECT_TRUE(is_less) << "test_case[" << idx << "]";
+    }
+  }
+}
+
+TEST(QSufSortTest, Search) {
+  // Initialize main string and the suffix array.
+  // Positions:          00000000001111111111122222222233333333334444
+  //                     01234567890123456789012345678901234567890123
+  const char* old_str = "the quick brown fox jumps over the lazy dog.";
+  int old_size = ::strlen(old_str);

[Will Harris, 2015/08/11 17:31:36]

same as above

[huangs, 2015/08/11 17:46:04]

Done.

+  const unsigned char* old_buf =
+        reinterpret_cast<const unsigned char*>(old_str);
+  std::vector<int> I(old_size + 1);
+  std::vector<int> V(old_size + 1);
+  courgette::qsuf::qsufsort<int*>(&I[0], &V[0], old_buf, old_size);
+
+  // Test queries.
+  const struct {
+    int exp_pos;  // -1 means "don't care".
+    int exp_match_len;
+    const char* query_str;
+  } test_cases[] = {
+    // Entire string.
+    {0, 44, "the quick brown fox jumps over the lazy dog."},
+    // Empty string.
+    {-1, 0, ""},  // Current algorithm does not enforce |pos| == 0.
+    // Exact and unique suffix match.
+    {43, 1, "."},
+    {31, 13, "the lazy dog."},
+    // Exact and unique non-suffix match.
+    {4, 5, "quick"},
+    {0, 9, "the quick"},  // Unique prefix.
+    // Entire word match with mutiple results: take lexicographical first.
+    {31, 3, "the"},  // Non-unique prefix: "the l"... < "the q"...
+    {9, 1, " "},  // " brown"... wins.
+    // Partial and unique match of query prefix.
+    {16, 10, "fox jumps with the hosps"},
+    // Partial and multiple match of query prefix: no guarantees on |pos|.
+    // Take lexicographical first for matching portion *only*, so same results:
+    {-1, 4, "the apple"},  // query      < "the l"... < "the q"...
+    {-1, 4, "the opera"},  // "the l"... < query      < "the q"...
+    {-1, 4, "the zebra"},  // "the l"... < "the q"... < query
+    // Prefix match dominates suffix match.
+    {26, 5, "over quick brown fox"},
+    // No match.
+    {-1, 0, ","},
+    {-1, 0, "1234"},
+    {-1, 0, "THE QUICK BROWN FOX"},
+    {-1, 0, "(the"},
+  };
+
+  for (size_t idx = 0; idx < arraysize(test_cases); ++idx) {
+    const auto& test_case = test_cases[idx];
+    int new_size = ::strlen(test_case.query_str);
+    const unsigned char* new_buf =
+        reinterpret_cast<const unsigned char*>(test_case.query_str);
+
+    // Perform the search.
+    int pos = 0;
+    int match_len = courgette::qsuf::search(
+        &I[0], old_buf, old_size, new_buf, new_size, 0, old_size, &pos);
+
+    // Check basic properties and match with expected values.
+    EXPECT_GE(match_len, 0) << "test_case[" << idx << "]";
+    EXPECT_LE(match_len, new_size) << "test_case[" << idx << "]";
+    if (match_len > 0) {
+      EXPECT_GE(pos, 0) << "test_case[" << idx << "]";
+      EXPECT_LE(pos, old_size - match_len) << "test_case[" << idx << "]";
+      EXPECT_EQ(0, ::memcmp(old_buf + pos, new_buf, match_len))
+           << "test_case[" << idx << "]";
+    }
+    if (test_case.exp_pos >= 0) {
+      EXPECT_EQ(test_case.exp_pos, pos) << "test_case[" << idx << "]";
+    }
+    EXPECT_EQ(test_case.exp_match_len, match_len) << "test_case[" << idx << "]";
+  }
+}