[Courgette] Make BSDiff search() use lexicographical_compare().

courgette/third_party/bsdiff/bsdiff_search_unittest.cc

+// Copyright 2016 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/bsdiff/bsdiff_search.h"
+
+#include <cstring>
+#include <vector>
+
+#include "base/macros.h"
+#include "courgette/third_party/bsdiff/qsufsort.h"
+#include "testing/gtest/include/gtest/gtest.h"
+
+TEST(BSDiffSearchTest, Search) {
+  // Initialize main string and the suffix array.
+  // Positions:      000000000011111111111222222222333333333344444
+  //                 012345678901234567890123456789012345678901234
+  const char* str = "the quick brown fox jumps over the lazy dog.";
+  int size = static_cast<int>(::strlen(str));
+  const unsigned char* buf = reinterpret_cast<const unsigned char*>(str);
+  std::vector<int> I(size + 1);
+  std::vector<int> V(size + 1);
+  courgette::qsuf::qsufsort<int*>(&I[0], &V[0], buf, size);
+
+  // Specific queries.
+  const struct {
+    int exp_pos;  // -1 means "don't care".
+    int exp_match_size;
+    const char* query_str;
+  } test_cases[] = {
+      // Entire string: exact and unique.
+      {0, 44, "the quick brown fox jumps over the lazy dog."},
+      // Empty string: exact and non-unique.
+      {-1, 0, ""},
+      // Exact and unique suffix matches.
+      {43, 1, "."},
+      {31, 13, "the lazy dog."},
+      // Exact and unique non-suffix matches.
+      {4, 5, "quick"},
+      {0, 9, "the quick"},  // Unique prefix.
+      // Partial and unique matches.
+      {16, 10, "fox jumps with the hosps"},  // Unique prefix.
+      {18, 1, "xyz"},
+      // Exact and non-unique match: take lexicographical first.
+      {-1, 3, "the"},  // Non-unique prefix.
+      {-1, 1, " "},
+      // Partial and non-unique match: no guarantees on |pos|!
+      {-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 (unique).
+      {26, 5, "over quick brown fox"},
+      // Empty matchs.
+      {-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 query_size = static_cast<int>(::strlen(test_case.query_str));
+    const unsigned char* query_buf =
+        reinterpret_cast<const unsigned char*>(test_case.query_str);
+
+    // Perform the search.
+    int pos = 0;
+    int match_size =
+        courgette::search(&I[0], buf, size, query_buf, query_size, &pos);
+
+    // Check basic properties and match with expected values.
+    EXPECT_GE(match_size, 0);
+    EXPECT_LE(match_size, query_size);
+    if (match_size > 0) {
+      EXPECT_GE(pos, 0);
+      EXPECT_LE(pos, size - match_size);
+      EXPECT_EQ(0, ::memcmp(buf + pos, query_buf, match_size));
+    }
+    if (test_case.exp_pos >= 0) {
+      EXPECT_EQ(test_case.exp_pos, pos);
+    }
+    EXPECT_EQ(test_case.exp_match_size, match_size);
+  }
+}
+
+TEST(BSDiffSearchTest, SearchExact) {
+  const char* test_cases[] = {
+      "a",
+      "aa",
+      "az",
+      "za",
+      "aaaaa",
+      "CACAO",
+      "banana",
+      "tobeornottobe",
+      "the quick brown fox jumps over the lazy dog.",
+      "elephantelephantelephantelephantelephant",
+      "011010011001011010010110011010010",
+  };
+  for (size_t idx = 0; idx < arraysize(test_cases); ++idx) {
+    int size = static_cast<int>(::strlen(test_cases[idx]));
+    const unsigned char* buf =
+        reinterpret_cast<const unsigned char*>(test_cases[idx]);
+    std::vector<int> I(size + 1);
+    std::vector<int> V(size + 1);
+    courgette::qsuf::qsufsort<int*>(&I[0], &V[0], buf, size);
+
+    // Test exact matches for every non-empty substring.
+    for (int lo = 0; lo < size; ++lo) {
+      for (int hi = lo + 1; hi <= size; ++hi) {
+        std::string query(buf + lo, buf + hi);
+        int query_size = static_cast<int>(query.length());
+        ASSERT_EQ(query_size, hi - lo);
+        const unsigned char* query_buf =
+            reinterpret_cast<const unsigned char*>(query.c_str());
+        int pos = 0;
+        int match_size =
+            courgette::search(&I[0], buf, size, query_buf, query_size, &pos);
+
+        EXPECT_EQ(query_size, match_size);
+        EXPECT_GE(pos, 0);
+        EXPECT_LE(pos, size - match_size);
+        std::string suffix(buf + pos, buf + size);
+        EXPECT_EQ(suffix.substr(0, query_size), query);
+      }
+    }
+  }
+}