tests/string_test.cpp

/*
 * Copyright (C) 2012 The Android Open Source Project
 *
 * Licensed under the Apache License, Version 2.0 (the "License");
 * you may not use this file except in compliance with the License.
 * You may obtain a copy of the License at
 *
 *      http://www.apache.org/licenses/LICENSE-2.0
 *
 * Unless required by applicable law or agreed to in writing, software
 * distributed under the License is distributed on an "AS IS" BASIS,
 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
 * See the License for the specific language governing permissions and
 * limitations under the License.
 */

#include <gtest/gtest.h>

#include <errno.h>
#include <math.h>
#include <string.h>

#include "buffer_tests.h"

#define KB 1024
#define SMALL 1*KB
#define MEDIUM 4*KB
#define LARGE 64*KB

static int signum(int i) {
  if (i < 0) {
    return -1;
  } else if (i > 0) {
    return 1;
  }
  return 0;
}

TEST(string, strerror) {
  // Valid.
  ASSERT_STREQ("Success", strerror(0));
  ASSERT_STREQ("Operation not permitted", strerror(1));

  // Invalid.
  ASSERT_STREQ("Unknown error -1", strerror(-1));
  ASSERT_STREQ("Unknown error 1234", strerror(1234));
}

#if defined(__BIONIC__)
static void* ConcurrentStrErrorFn(void*) {
  bool equal = (strcmp("Unknown error 2002", strerror(2002)) == 0);
  return reinterpret_cast<void*>(equal);
}
#endif // __BIONIC__

// glibc's strerror isn't thread safe, only its strsignal.
TEST(string, strerror_concurrent) {
#if defined(__BIONIC__)
  const char* strerror1001 = strerror(1001);
  ASSERT_STREQ("Unknown error 1001", strerror1001);

  pthread_t t;
  ASSERT_EQ(0, pthread_create(&t, NULL, ConcurrentStrErrorFn, NULL));
  void* result;
  ASSERT_EQ(0, pthread_join(t, &result));
  ASSERT_TRUE(static_cast<bool>(result));

  ASSERT_STREQ("Unknown error 1001", strerror1001);
#else // __BIONIC__
  GTEST_LOG_(INFO) << "This test does nothing.\n";
#endif // __BIONIC__
}

TEST(string, strerror_r) {
#if defined(__BIONIC__) // glibc's strerror_r doesn't even have the same signature as the POSIX one.
  char buf[256];

  // Valid.
  ASSERT_EQ(0, strerror_r(0, buf, sizeof(buf)));
  ASSERT_STREQ("Success", buf);
  ASSERT_EQ(0, strerror_r(1, buf, sizeof(buf)));
  ASSERT_STREQ("Operation not permitted", buf);

  // Invalid.
  ASSERT_EQ(0, strerror_r(-1, buf, sizeof(buf)));
  ASSERT_STREQ("Unknown error -1", buf);
  ASSERT_EQ(0, strerror_r(1234, buf, sizeof(buf)));
  ASSERT_STREQ("Unknown error 1234", buf);

  // Buffer too small.
  ASSERT_EQ(-1, strerror_r(0, buf, 2));
  ASSERT_EQ(ERANGE, errno);
#else // __BIONIC__
  GTEST_LOG_(INFO) << "This test does nothing.\n";
#endif // __BIONIC__
}

TEST(string, strsignal) {
  // A regular signal.
  ASSERT_STREQ("Hangup", strsignal(1));

  // A real-time signal.
#ifdef __GLIBC__ // glibc reserves real-time signals for internal use, and doesn't count those.
  ASSERT_STREQ("Real-time signal 14", strsignal(48));
#else
  ASSERT_STREQ("Real-time signal 16", strsignal(48));
#endif

  // Errors.
  ASSERT_STREQ("Unknown signal -1", strsignal(-1)); // Too small.
  ASSERT_STREQ("Unknown signal 0", strsignal(0)); // Still too small.
  ASSERT_STREQ("Unknown signal 1234", strsignal(1234)); // Too large.
}

static void* ConcurrentStrSignalFn(void*) {
  bool equal = (strcmp("Unknown signal 2002", strsignal(2002)) == 0);
  return reinterpret_cast<void*>(equal);
}

TEST(string, strsignal_concurrent) {
  const char* strsignal1001 = strsignal(1001);
  ASSERT_STREQ("Unknown signal 1001", strsignal1001);

  pthread_t t;
  ASSERT_EQ(0, pthread_create(&t, NULL, ConcurrentStrSignalFn, NULL));
  void* result;
  ASSERT_EQ(0, pthread_join(t, &result));
  ASSERT_TRUE(static_cast<bool>(result));

  ASSERT_STREQ("Unknown signal 1001", strsignal1001);
}

// TODO: where did these numbers come from?
#define POS_ITER    10
#define ITER        500

// For every length we want to test, vary and change alignment
// of allocated memory, fill it with some values, calculate
// expected result and then run function and compare what we got.
// These tests contributed by Intel Corporation.
// TODO: make these tests more intention-revealing and less random.
template<class Character>
struct StringTestState {
  StringTestState(size_t MAX_LEN) : MAX_LEN(MAX_LEN) {
    int max_alignment = 64;

    // TODO: fix the tests to not sometimes use twice their specified "MAX_LEN".
    glob_ptr = reinterpret_cast<Character*>(valloc(2 * sizeof(Character) * MAX_LEN + max_alignment));
    glob_ptr1 = reinterpret_cast<Character*>(valloc(2 * sizeof(Character) * MAX_LEN + max_alignment));
    glob_ptr2 = reinterpret_cast<Character*>(valloc(2 * sizeof(Character) * MAX_LEN + max_alignment));

    InitLenArray();

    srandom(1234);
  }

  ~StringTestState() {
    free(glob_ptr);
    free(glob_ptr1);
    free(glob_ptr2);
  }

  void NewIteration() {
    int alignments[] = { 24, 32, 16, 48, 1, 2, 3, 0, 5, 11 };
    int usable_alignments = 10;
    int align1 = alignments[random() % (usable_alignments - 1)];
    int align2 = alignments[random() % (usable_alignments - 1)];

    ptr = glob_ptr + align1;
    ptr1 = glob_ptr1 + align1;
    ptr2 = glob_ptr2 + align2;
  }

  const size_t MAX_LEN;
  Character *ptr, *ptr1, *ptr2;
  size_t n;
  int len[ITER + 1];

 private:
  Character *glob_ptr, *glob_ptr1, *glob_ptr2;

  // Calculate input lengths and fill state.len with them.
  // Test small lengths with more density than big ones. Manually push
  // smallest (0) and biggest (MAX_LEN) lengths. Avoid repeats.
  // Return number of lengths to test.
  void InitLenArray() {
    n = 0;
    len[n++] = 0;
    for (size_t i = 1; i < ITER; ++i) {
      int l = (int) exp(log((double) MAX_LEN) * i / ITER);
      if (l != len[n - 1]) {
        len[n++] = l;
      }
    }
    len[n++] = MAX_LEN;
  }
};

TEST(string, strcat) {
  StringTestState<char> state(SMALL);
  for (size_t i = 1; i < state.n; i++) {
    for (size_t j = 0; j < POS_ITER; j++) {
      state.NewIteration();

      memset(state.ptr2, '\2', state.MAX_LEN);
      state.ptr2[state.MAX_LEN - 1] = '\0';
      memcpy(state.ptr, state.ptr2, 2 * state.MAX_LEN);

      memset(state.ptr1, random() & 255, state.len[i]);
      state.ptr1[random() % state.len[i]] = '\0';
      state.ptr1[state.len[i] - 1] = '\0';

      strcpy(state.ptr + state.MAX_LEN - 1, state.ptr1);

      EXPECT_TRUE(strcat(state.ptr2, state.ptr1) == state.ptr2);
      EXPECT_TRUE(memcmp(state.ptr, state.ptr2, 2 * state.MAX_LEN) == 0);
    }
  }
}

// one byte target with "\0" source
TEST(string, strcpy2) {
  char buf[1];
  char* orig = strdup("");
  ASSERT_EQ(buf, strcpy(buf, orig));
  ASSERT_EQ('\0', buf[0]);
  free(orig);
}

// multibyte target where we under fill target
TEST(string, strcpy3) {
  char buf[10];
  char* orig = strdup("12345");
  memset(buf, 'A', sizeof(buf));
  ASSERT_EQ(buf, strcpy(buf, orig));
  ASSERT_STREQ("12345", buf);
  ASSERT_EQ('A',  buf[6]);
  ASSERT_EQ('A',  buf[7]);
  ASSERT_EQ('A',  buf[8]);
  ASSERT_EQ('A',  buf[9]);
  free(orig);
}

// multibyte target where we fill target exactly
TEST(string, strcpy4) {
  char buf[10];
  char* orig = strdup("123456789");
  memset(buf, 'A', sizeof(buf));
  ASSERT_EQ(buf, strcpy(buf, orig));
  ASSERT_STREQ("123456789", buf);
  free(orig);
}

// one byte target with "\0" source
TEST(string, stpcpy2) {
  char buf[1];
  char* orig = strdup("");
  ASSERT_EQ(buf, stpcpy(buf, orig));
  ASSERT_EQ('\0', buf[0]);
  free(orig);
}

// multibyte target where we under fill target
TEST(string, stpcpy3) {
  char buf[10];
  char* orig = strdup("12345");
  memset(buf, 'A', sizeof(buf));
  ASSERT_EQ(buf+strlen(orig), stpcpy(buf, orig));
  ASSERT_STREQ("12345", buf);
  ASSERT_EQ('A',  buf[6]);
  ASSERT_EQ('A',  buf[7]);
  ASSERT_EQ('A',  buf[8]);
  ASSERT_EQ('A',  buf[9]);
  free(orig);
}

// multibyte target where we fill target exactly
TEST(string, stpcpy4) {
  char buf[10];
  char* orig = strdup("123456789");
  memset(buf, 'A', sizeof(buf));
  ASSERT_EQ(buf+strlen(orig), stpcpy(buf, orig));
  ASSERT_STREQ("123456789", buf);
  free(orig);
}

TEST(string, strcat2) {
  char buf[10];
  memset(buf, 'A', sizeof(buf));
  buf[0] = 'a';
  buf[1] = '\0';
  char* res = strcat(buf, "01234");
  ASSERT_EQ(buf, res);
  ASSERT_STREQ("a01234", buf);
  ASSERT_EQ('A',  buf[7]);
  ASSERT_EQ('A',  buf[8]);
  ASSERT_EQ('A',  buf[9]);
}

TEST(string, strcat3) {
  char buf[10];
  memset(buf, 'A', sizeof(buf));
  buf[0] = 'a';
  buf[1] = '\0';
  char* res = strcat(buf, "01234567");
  ASSERT_EQ(buf, res);
  ASSERT_STREQ("a01234567", buf);
}

TEST(string, strncat2) {
  char buf[10];
  memset(buf, 'A', sizeof(buf));
  buf[0] = 'a';
  buf[1] = '\0';
  char* res = strncat(buf, "01234", sizeof(buf) - strlen(buf) - 1);
  ASSERT_EQ(buf, res);
  ASSERT_STREQ("a01234", buf);
  ASSERT_EQ('A',  buf[7]);
  ASSERT_EQ('A',  buf[8]);
  ASSERT_EQ('A',  buf[9]);
}

TEST(string, strncat3) {
  char buf[10];
  memset(buf, 'A', sizeof(buf));
  buf[0] = 'a';
  buf[1] = '\0';
  char* res = strncat(buf, "0123456789", 5);
  ASSERT_EQ(buf, res);
  ASSERT_STREQ("a01234", buf);
  ASSERT_EQ('A',  buf[7]);
  ASSERT_EQ('A',  buf[8]);
  ASSERT_EQ('A',  buf[9]);
}

TEST(string, strncat4) {
  char buf[10];
  memset(buf, 'A', sizeof(buf));
  buf[0] = 'a';
  buf[1] = '\0';
  char* res = strncat(buf, "01234567", 8);
  ASSERT_EQ(buf, res);
  ASSERT_STREQ("a01234567", buf);
}

TEST(string, strncat5) {
  char buf[10];
  memset(buf, 'A', sizeof(buf));
  buf[0] = 'a';
  buf[1] = '\0';
  char* res = strncat(buf, "01234567", 9);
  ASSERT_EQ(buf, res);
  ASSERT_STREQ("a01234567", buf);
}

TEST(string, strchr_with_0) {
  char buf[10];
  const char* s = "01234";
  memcpy(buf, s, strlen(s) + 1);
  EXPECT_TRUE(strchr(buf, '\0') == (buf + strlen(s)));
}

TEST(string, strchr) {
  int seek_char = random() & 255;

  StringTestState<char> state(SMALL);
  for (size_t i = 1; i < state.n; i++) {
    for (size_t j = 0; j < POS_ITER; j++) {
      state.NewIteration();

      if (~seek_char > 0) {
        memset(state.ptr1, ~seek_char, state.len[i]);
      } else {
        memset(state.ptr1, '\1', state.len[i]);
      }
      state.ptr1[state.len[i] - 1] = '\0';

      int pos = random() % state.MAX_LEN;
      char* expected;
      if (pos >= state.len[i] - 1) {
        if (seek_char == 0) {
          expected = state.ptr1 + state.len[i] - 1;
        } else {
          expected = NULL;
        }
      } else {
        state.ptr1[pos] = seek_char;
        expected = state.ptr1 + pos;
      }

      ASSERT_TRUE(strchr(state.ptr1, seek_char) == expected);
    }
  }
}

TEST(string, strcmp) {
  StringTestState<char> state(SMALL);
  for (size_t i = 1; i < state.n; i++) {
    for (size_t j = 0; j < POS_ITER; j++) {
      state.NewIteration();

      memset(state.ptr1, 'v', state.MAX_LEN);
      memset(state.ptr2, 'n', state.MAX_LEN);
      state.ptr1[state.len[i] - 1] = '\0';
      state.ptr2[state.len[i] - 1] = '\0';

      int pos = 1 + (random() % (state.MAX_LEN - 1));
      int actual;
      int expected;
      if (pos >= state.len[i] - 1) {
        memcpy(state.ptr1, state.ptr2, state.len[i]);
        expected = 0;
        actual = strcmp(state.ptr1, state.ptr2);
      } else {
        memcpy(state.ptr1, state.ptr2, pos);
        if (state.ptr1[pos] > state.ptr2[pos]) {
          expected = 1;
        } else if (state.ptr1[pos] == state.ptr2[pos]) {
          state.ptr1[pos + 1] = '\0';
          state.ptr2[pos + 1] = '\0';
          expected = 0;
        } else {
          expected = -1;
        }
        actual = strcmp(state.ptr1, state.ptr2);
      }

      ASSERT_EQ(expected, signum(actual));
    }
  }
}

TEST(string, stpcpy) {
  StringTestState<char> state(SMALL);
  for (size_t j = 0; j < POS_ITER; j++) {
    state.NewIteration();

    size_t pos = random() % state.MAX_LEN;

    memset(state.ptr1, '\2', pos);
    state.ptr1[pos] = '\0';
    state.ptr1[state.MAX_LEN - 1] = '\0';

    memcpy(state.ptr, state.ptr1, state.MAX_LEN);

    memset(state.ptr2, '\1', state.MAX_LEN);
    state.ptr2[state.MAX_LEN - 1] = '\0';

    memset(state.ptr + state.MAX_LEN, '\1', state.MAX_LEN);
    memcpy(state.ptr + state.MAX_LEN, state.ptr1, pos + 1);
    state.ptr[2 * state.MAX_LEN - 1] = '\0';

    ASSERT_TRUE(stpcpy(state.ptr2, state.ptr1) == state.ptr2 + strlen(state.ptr1));
    ASSERT_FALSE((memcmp(state.ptr1, state.ptr, state.MAX_LEN)) != 0 ||
                 (memcmp(state.ptr2, state.ptr + state.MAX_LEN, state.MAX_LEN) != 0));
  }
}

TEST(string, strcpy) {
  StringTestState<char> state(SMALL);
  for (size_t j = 0; j < POS_ITER; j++) {
    state.NewIteration();

    size_t pos = random() % state.MAX_LEN;

    memset(state.ptr1, '\2', pos);
    state.ptr1[pos] = '\0';
    state.ptr1[state.MAX_LEN - 1] = '\0';

    memcpy(state.ptr, state.ptr1, state.MAX_LEN);

    memset(state.ptr2, '\1', state.MAX_LEN);
    state.ptr2[state.MAX_LEN - 1] = '\0';

    memset(state.ptr + state.MAX_LEN, '\1', state.MAX_LEN);
    memcpy(state.ptr + state.MAX_LEN, state.ptr1, pos + 1);
    state.ptr[2 * state.MAX_LEN - 1] = '\0';

    ASSERT_TRUE(strcpy(state.ptr2, state.ptr1) == state.ptr2);
    ASSERT_FALSE((memcmp(state.ptr1, state.ptr, state.MAX_LEN)) != 0 ||
                 (memcmp(state.ptr2, state.ptr + state.MAX_LEN, state.MAX_LEN) != 0));
  }
}

TEST(string, strlcat) {
#if defined(__BIONIC__)
  StringTestState<char> state(SMALL);
  for (size_t i = 0; i < state.n; i++) {
    for (size_t j = 0; j < POS_ITER; j++) {
      state.NewIteration();

      memset(state.ptr2, '\2', state.MAX_LEN + state.len[i]);
      state.ptr2[state.MAX_LEN - 1] = '\0';
      memcpy(state.ptr, state.ptr2, state.MAX_LEN + state.len[i]);

      int pos = random() % state.MAX_LEN;
      memset(state.ptr1, '\3', pos);
      state.ptr1[pos] = '\0';
      if (pos < state.len[i]) {
        memcpy(state.ptr + state.MAX_LEN - 1, state.ptr1, pos + 1);
      } else {
        memcpy(state.ptr + state.MAX_LEN - 1, state.ptr1, state.len[i]);
        state.ptr[state.MAX_LEN + state.len[i] - 1] = '\0';
      }

      strlcat(state.ptr2, state.ptr1, state.MAX_LEN + state.len[i]);

      ASSERT_TRUE(memcmp(state.ptr, state.ptr2, state.MAX_LEN + state.len[i]) == 0);
    }
  }
#else // __BIONIC__
  GTEST_LOG_(INFO) << "This test does nothing.\n";
#endif // __BIONIC__
}

TEST(string, strlcpy) {
#if defined(__BIONIC__)
  StringTestState<char> state(SMALL);
  for (size_t j = 0; j < POS_ITER; j++) {
    state.NewIteration();

    int rand = random() & 255;
    if (rand < 1) {
      rand = 1;
    }
    memset(state.ptr1, rand, state.MAX_LEN);

    size_t pos = random() % state.MAX_LEN;
    if (pos < state.MAX_LEN) {
      state.ptr1[pos] = '\0';
    }
    memcpy(state.ptr, state.ptr1, state.MAX_LEN);

    memset(state.ptr2, random() & 255, state.MAX_LEN);
    memcpy(state.ptr + state.MAX_LEN, state.ptr2, state.MAX_LEN);

    if (pos > state.MAX_LEN - 1) {
      memcpy(state.ptr + state.MAX_LEN, state.ptr1, state.MAX_LEN);
      state.ptr[2 * state.MAX_LEN - 1] = '\0';
    } else {
      memcpy(state.ptr + state.MAX_LEN, state.ptr1, pos + 1);
    }

    ASSERT_EQ(strlcpy(state.ptr2, state.ptr1, state.MAX_LEN), strlen(state.ptr1));
    ASSERT_FALSE((memcmp(state.ptr1, state.ptr, state.MAX_LEN) != 0) ||
                 (memcmp(state.ptr2, state.ptr + state.MAX_LEN, state.MAX_LEN) != 0));
  }
#else // __BIONIC__
  GTEST_LOG_(INFO) << "This test does nothing.\n";
#endif // __BIONIC__
}

TEST(string, strncat) {
  StringTestState<char> state(SMALL);
  for (size_t i = 1; i < state.n; i++) {
    for (size_t j = 0; j < POS_ITER; j++) {
      state.NewIteration();

      memset(state.ptr2, '\2', state.MAX_LEN);
      state.ptr2[state.MAX_LEN - 1] = '\0';
      memcpy(state.ptr, state.ptr2, 2 * state.MAX_LEN);

      memset(state.ptr1, random() & 255, state.len[i]);
      state.ptr1[random() % state.len[i]] = '\0';
      state.ptr1[state.len[i] - 1] = '\0';

      size_t pos = strlen(state.ptr1);

      size_t actual = random() % state.len[i];
      strncpy(state.ptr + state.MAX_LEN - 1, state.ptr1, std::min(actual, pos));
      state.ptr[state.MAX_LEN + std::min(actual, pos) - 1] = '\0';

      ASSERT_TRUE(strncat(state.ptr2, state.ptr1, actual) == state.ptr2);
      ASSERT_EQ(memcmp(state.ptr, state.ptr2, 2 * state.MAX_LEN), 0);
    }
  }
}

TEST(string, strncmp) {
  StringTestState<char> state(SMALL);
  for (size_t i = 1; i < state.n; i++) {
    for (size_t j = 0; j < POS_ITER; j++) {
      state.NewIteration();

      memset(state.ptr1, 'v', state.MAX_LEN);
      memset(state.ptr2, 'n', state.MAX_LEN);
      state.ptr1[state.len[i] - 1] = '\0';
      state.ptr2[state.len[i] - 1] = '\0';

      int pos = 1 + (random() % (state.MAX_LEN - 1));
      int actual;
      int expected;
      if (pos >= state.len[i] - 1) {
        memcpy(state.ptr1, state.ptr2, state.len[i]);
        expected = 0;
        actual = strncmp(state.ptr1, state.ptr2, state.len[i]);
      } else {
        memcpy(state.ptr1, state.ptr2, pos);
        if (state.ptr1[pos] > state.ptr2[pos]) {
          expected = 1;
        } else if (state.ptr1[pos] == state.ptr2[pos]) {
          state.ptr1[pos + 1] = '\0';
          state.ptr2[pos + 1] = '\0';
          expected = 0;
        } else {
          expected = -1;
        }
        actual = strncmp(state.ptr1, state.ptr2, state.len[i]);
      }

      ASSERT_EQ(expected, signum(actual));
    }
  }
}

TEST(string, stpncpy) {
  StringTestState<char> state(SMALL);
  for (size_t j = 0; j < ITER; j++) {
    state.NewIteration();

    // Choose a random value to fill the string, except \0 (string terminator),
    // or \1 (guarantees it's different from anything in ptr2).
    memset(state.ptr1, (random() % 254) + 2, state.MAX_LEN);
    // Choose a random size for our src buffer.
    size_t ptr1_len = random() % state.MAX_LEN;
    state.ptr1[ptr1_len] = '\0';
    // Copy ptr1 into ptr, used to verify that ptr1 does not get modified.
    memcpy(state.ptr, state.ptr1, state.MAX_LEN);
    // Init ptr2 to a set value.
    memset(state.ptr2, '\1', state.MAX_LEN);

    // Choose a random amount of data to copy.
    size_t copy_len = random() % state.MAX_LEN;

    // Set the second half of ptr to the expected pattern in ptr2.
    memset(state.ptr + state.MAX_LEN, '\1', state.MAX_LEN);
    memcpy(state.ptr + state.MAX_LEN, state.ptr1, copy_len);
    size_t expected_end;
    if (copy_len > ptr1_len) {
      memset(state.ptr + state.MAX_LEN + ptr1_len, '\0', copy_len - ptr1_len);
      expected_end = ptr1_len;
    } else {
      expected_end = copy_len;
    }

    ASSERT_EQ(state.ptr2 + expected_end, stpncpy(state.ptr2, state.ptr1, copy_len));

    // Verify ptr1 was not modified.
    ASSERT_EQ(0, memcmp(state.ptr1, state.ptr, state.MAX_LEN));
    // Verify ptr2 contains the expected data.
    ASSERT_EQ(0, memcmp(state.ptr2, state.ptr + state.MAX_LEN, state.MAX_LEN));
  }
}

TEST(string, strncpy) {
  StringTestState<char> state(SMALL);
  for (size_t j = 0; j < ITER; j++) {
    state.NewIteration();

    // Choose a random value to fill the string, except \0 (string terminator),
    // or \1 (guarantees it's different from anything in ptr2).
    memset(state.ptr1, (random() % 254) + 2, state.MAX_LEN);
    // Choose a random size for our src buffer.
    size_t ptr1_len = random() % state.MAX_LEN;
    state.ptr1[ptr1_len] = '\0';
    // Copy ptr1 into ptr, used to verify that ptr1 does not get modified.
    memcpy(state.ptr, state.ptr1, state.MAX_LEN);
    // Init ptr2 to a set value.
    memset(state.ptr2, '\1', state.MAX_LEN);

    // Choose a random amount of data to copy.
    size_t copy_len = random() % state.MAX_LEN;

    // Set the second half of ptr to the expected pattern in ptr2.
    memset(state.ptr + state.MAX_LEN, '\1', state.MAX_LEN);
    memcpy(state.ptr + state.MAX_LEN, state.ptr1, copy_len);
    size_t expected_end;
    if (copy_len > ptr1_len) {
      memset(state.ptr + state.MAX_LEN + ptr1_len, '\0', copy_len - ptr1_len);
      expected_end = ptr1_len;
    } else {
      expected_end = copy_len;
    }

    ASSERT_EQ(state.ptr2 + expected_end, stpncpy(state.ptr2, state.ptr1, copy_len));

    // Verify ptr1 was not modified.
    ASSERT_EQ(0, memcmp(state.ptr1, state.ptr, state.MAX_LEN));
    // Verify ptr2 contains the expected data.
    ASSERT_EQ(0, memcmp(state.ptr2, state.ptr + state.MAX_LEN, state.MAX_LEN));
  }
}

TEST(string, strrchr) {
  int seek_char = random() & 255;
  StringTestState<char> state(SMALL);
  for (size_t i = 1; i < state.n; i++) {
    for (size_t j = 0; j < POS_ITER; j++) {
      state.NewIteration();

      if (~seek_char > 0) {
        memset(state.ptr1, ~seek_char, state.len[i]);
      } else {
        memset(state.ptr1, '\1', state.len[i]);
      }
      state.ptr1[state.len[i] - 1] = '\0';

      int pos = random() % state.MAX_LEN;
      char* expected;
      if (pos >= state.len[i] - 1) {
        if (seek_char == 0) {
          expected = state.ptr1 + state.len[i] - 1;
        } else {
          expected = NULL;
        }
      } else {
        state.ptr1[pos] = seek_char;
        expected = state.ptr1 + pos;
      }

      ASSERT_TRUE(strrchr(state.ptr1, seek_char) == expected);
    }
  }
}

TEST(string, memchr) {
  int seek_char = random() & 255;
  StringTestState<char> state(SMALL);
  for (size_t i = 0; i < state.n; i++) {
    for (size_t j = 0; j < POS_ITER; j++) {
      state.NewIteration();

      memset(state.ptr1, ~seek_char, state.len[i]);

      int pos = random() % state.MAX_LEN;
      char* expected;
      if (pos >= state.len[i]) {
        expected = NULL;
      } else {
        state.ptr1[pos] = seek_char;
        expected = state.ptr1 + pos;
      }

      ASSERT_TRUE(memchr(state.ptr1, seek_char, state.len[i]) == expected);
    }
  }
}

TEST(string, memrchr) {
  int seek_char = random() & 255;
  StringTestState<char> state(SMALL);
  for (size_t i = 0; i < state.n; i++) {
    for (size_t j = 0; j < POS_ITER; j++) {
      state.NewIteration();

      memset(state.ptr1, ~seek_char, state.len[i]);

      int pos = random() % state.MAX_LEN;
      char* expected;
      if (pos >= state.len[i]) {
        expected = NULL;
      } else {
        state.ptr1[pos] = seek_char;
        expected = state.ptr1 + pos;
      }

      ASSERT_TRUE(memrchr(state.ptr1, seek_char, state.len[i]) == expected);
    }
  }
}

TEST(string, memcmp) {
  StringTestState<char> state(SMALL);
  for (size_t i = 0; i < state.n; i++) {
    for (size_t j = 0; j < POS_ITER; j++) {
      state.NewIteration();

      int c1 = random() & 0xff;
      int c2 = random() & 0xff;
      memset(state.ptr1, c1, state.MAX_LEN);
      memset(state.ptr2, c1, state.MAX_LEN);

      int pos = (state.len[i] == 0) ? 0 : (random() % state.len[i]);
      state.ptr2[pos] = c2;

      int expected = (static_cast<int>(c1) - static_cast<int>(c2));
      int actual = memcmp(state.ptr1, state.ptr2, state.MAX_LEN);

      ASSERT_EQ(signum(expected), signum(actual));
    }
  }
}

extern "C" int __memcmp16(const unsigned short *ptr1, const unsigned short *ptr2, size_t n);

TEST(string, __memcmp16) {
#if defined(__BIONIC__)
  StringTestState<unsigned short> state(SMALL);

  for (size_t i = 0; i < state.n; i++) {
    for (size_t j = 0; j < POS_ITER; j++) {
      state.NewIteration();

      unsigned short mask = 0xffff;
      unsigned short c1 = rand() & mask;
      unsigned short c2 = rand() & mask;

      std::fill(state.ptr1, state.ptr1 + state.MAX_LEN, c1);
      std::fill(state.ptr2, state.ptr2 + state.MAX_LEN, c1);

      int pos = (state.len[i] == 0) ? 0 : (random() % state.len[i]);
      state.ptr2[pos] = c2;

      int expected = (static_cast<unsigned short>(c1) - static_cast<unsigned short>(c2));
      int actual = __memcmp16(state.ptr1, state.ptr2, (size_t) state.MAX_LEN);

      ASSERT_EQ(expected, actual);
    }
  }
#else // __BIONIC__
  GTEST_LOG_(INFO) << "This test does nothing.\n";
#endif // __BIONIC__
}

TEST(string, wmemcmp) {
  StringTestState<wchar_t> state(SMALL);

  for (size_t i = 0; i < state.n; i++) {
    for (size_t j = 0; j < POS_ITER; j++) {
      state.NewIteration();

      long long mask = ((long long) 1 << 8 * sizeof(wchar_t)) - 1;
      int c1 = rand() & mask;
      int c2 = rand() & mask;
      wmemset(state.ptr1, c1, state.MAX_LEN);
      wmemset(state.ptr2, c1, state.MAX_LEN);

      int pos = (state.len[i] == 0) ? 0 : (random() % state.len[i]);
      state.ptr2[pos] = c2;

      int expected = (static_cast<int>(c1) - static_cast<int>(c2));
      int actual = wmemcmp(state.ptr1, state.ptr2, (size_t) state.MAX_LEN);

      ASSERT_EQ(signum(expected), signum(actual));
    }
  }
}

TEST(string, memcpy) {
  StringTestState<char> state(LARGE);
  int rand = random() & 255;
  for (size_t i = 0; i < state.n - 1; i++) {
    for (size_t j = 0; j < POS_ITER; j++) {
      state.NewIteration();

      size_t pos = random() % (state.MAX_LEN - state.len[i]);

      memset(state.ptr1, rand, state.len[i]);
      memset(state.ptr1 + state.len[i], ~rand, state.MAX_LEN - state.len[i]);

      memset(state.ptr2, rand, state.len[i]);
      memset(state.ptr2 + state.len[i], ~rand, state.MAX_LEN - state.len[i]);
      memset(state.ptr2 + pos, '\0', state.len[i]);

      ASSERT_FALSE(memcpy(state.ptr2 + pos, state.ptr1 + pos, state.len[i]) != state.ptr2 + pos);
      ASSERT_EQ(0, memcmp(state.ptr1, state.ptr2, state.MAX_LEN));
    }
  }
}

TEST(string, memset) {
  StringTestState<char> state(LARGE);
  char ch = random () & 255;
  for (size_t i = 0; i < state.n - 1; i++) {
    for (size_t j = 0; j < POS_ITER; j++) {
      state.NewIteration();

      memset(state.ptr1, ~ch, state.MAX_LEN);
      memcpy(state.ptr2, state.ptr1, state.MAX_LEN);

      size_t pos = random () % (state.MAX_LEN - state.len[i]);
      for (size_t k = pos; k < pos + state.len[i]; k++) {
        state.ptr1[k] = ch;
      }

      ASSERT_TRUE(memset(state.ptr2 + pos, ch, state.len[i]) == state.ptr2 + pos);

      ASSERT_EQ(0, memcmp(state.ptr1, state.ptr2, state.MAX_LEN));
    }
  }
}

TEST(string, memmove) {
  StringTestState<char> state(LARGE);
  for (size_t i = 0; i < state.n - 1; i++) {
    for (size_t j = 0; j < POS_ITER; j++) {
      state.NewIteration();

      memset(state.ptr1, random() & 255, 2 * state.MAX_LEN);

      size_t pos = random() % (state.MAX_LEN - state.len[i]);

      memset(state.ptr1, random() & 255, state.len[i]);
      memcpy(state.ptr2, state.ptr1, 2 * state.MAX_LEN);
      memcpy(state.ptr, state.ptr1, state.len[i]);
      memcpy(state.ptr1 + pos, state.ptr, state.len[i]);

      ASSERT_TRUE(memmove(state.ptr2 + pos, state.ptr2, state.len[i]) == state.ptr2 + pos);
      ASSERT_EQ(0, memcmp(state.ptr2, state.ptr1, 2 * state.MAX_LEN));
    }
  }
}

TEST(string, bcopy) {
  StringTestState<char> state(LARGE);
  for (size_t i = 0; i < state.n; i++) {
    for (size_t j = 0; j < POS_ITER; j++) {
      state.NewIteration();

      memset(state.ptr1, random() & 255, state.MAX_LEN);
      memset(state.ptr1 + state.MAX_LEN, random() & 255, state.MAX_LEN);
      memcpy(state.ptr2, state.ptr1, 2 * state.MAX_LEN);

      size_t start = random() % (2 * state.MAX_LEN - state.len[i]);
      memcpy(state.ptr2 + start, state.ptr1, state.len[i]);

      bcopy(state.ptr1, state.ptr1 + start, state.len[i]);
      ASSERT_EQ(0, memcmp(state.ptr1, state.ptr2, 2 * state.MAX_LEN));
    }
  }
}

TEST(string, bzero) {
  StringTestState<char> state(LARGE);
  for (size_t j = 0; j < ITER; j++) {
    state.NewIteration();

    memset(state.ptr1, random() & 255, state.MAX_LEN);

    size_t start = random() % state.MAX_LEN;
    size_t end = start + random() % (state.MAX_LEN - start);

    memcpy(state.ptr2, state.ptr1, start);
    memset(state.ptr2 + start, '\0', end - start);
    memcpy(state.ptr2 + end, state.ptr1 + end, state.MAX_LEN - end);

    bzero(state.ptr1 + start, end - start);

    ASSERT_EQ(0, memcmp(state.ptr1, state.ptr2, state.MAX_LEN));
  }
}

static void DoMemcpyTest(uint8_t* src, uint8_t* dst, size_t len) {
  memset(src, (len % 255) + 1, len);
  memset(dst, 0, len);

  ASSERT_EQ(dst, memcpy(dst, src, len));
  ASSERT_TRUE(memcmp(src, dst, len) == 0);
}

TEST(string, memcpy_align) {
  RunSrcDstBufferAlignTest(LARGE, DoMemcpyTest);
}

TEST(string, memcpy_overread) {
  RunSrcDstBufferOverreadTest(DoMemcpyTest);
}

static void DoMemsetTest(uint8_t* buf, size_t len) {
  for (size_t i = 0; i < len; i++) {
    buf[i] = 0;
  }
  int value = (len % 255) + 1;
  ASSERT_EQ(buf, memset(buf, value, len));
  for (size_t i = 0; i < len; i++) {
    ASSERT_EQ(value, buf[i]);
  }
}

TEST(string, memset_align) {
  RunSingleBufferAlignTest(LARGE, DoMemsetTest);
}

static void DoStrlenTest(uint8_t* buf, size_t len) {
  if (len >= 1) {
    memset(buf, (32 + (len % 96)), len - 1);
    buf[len-1] = '\0';
    ASSERT_EQ(len-1, strlen(reinterpret_cast<char*>(buf)));
  }
}

TEST(string, strlen_align) {
  RunSingleBufferAlignTest(LARGE, DoStrlenTest);
}

TEST(string, strlen_overread) {
  RunSingleBufferOverreadTest(DoStrlenTest);
}

static void DoStrcpyTest(uint8_t* src, uint8_t* dst, size_t len) {
  if (len >= 1) {
    memset(src, (32 + (len % 96)), len - 1);
    src[len-1] = '\0';
    memset(dst, 0, len);
    ASSERT_EQ(dst, reinterpret_cast<uint8_t*>(strcpy(reinterpret_cast<char*>(dst),
                                                     reinterpret_cast<char*>(src))));
    ASSERT_TRUE(memcmp(src, dst, len) == 0);
  }
}

TEST(string, strcpy_align) {
  RunSrcDstBufferAlignTest(LARGE, DoStrcpyTest);
}

TEST(string, strcpy_overread) {
  RunSrcDstBufferOverreadTest(DoStrcpyTest);
}

static void DoStpcpyTest(uint8_t* src, uint8_t* dst, size_t len) {
  if (len >= 1) {
    memset(src, (32 + (len % 96)), len - 1);
    src[len-1] = '\0';
    memset(dst, 0, len);
    ASSERT_EQ(dst+len-1, reinterpret_cast<uint8_t*>(stpcpy(reinterpret_cast<char*>(dst),
                                                           reinterpret_cast<char*>(src))));
    ASSERT_TRUE(memcmp(src, dst, len) == 0);
  }
}

TEST(string, stpcpy_align) {
  RunSrcDstBufferAlignTest(LARGE, DoStpcpyTest);
}

TEST(string, stpcpy_overread) {
  RunSrcDstBufferOverreadTest(DoStpcpyTest);
}

// Use our own incrementer to cut down on the total number of calls.
static size_t LargeSetIncrement(size_t len) {
  if (len >= 4096) {
    return 4096;
  } else if (len >= 1024) {
    return 1024;
  } else if (len >= 256) {
    return 256;
  }
  return 1;
}

#define STRCAT_DST_LEN  128

static void DoStrcatTest(uint8_t* src, uint8_t* dst, size_t len) {
  if (len >= 1) {
    int value = 32 + (len % 96);
    memset(src, value, len - 1);
    src[len-1] = '\0';

    if (len >= STRCAT_DST_LEN) {
      // Create a small buffer for doing quick compares in each loop.
      uint8_t cmp_buf[STRCAT_DST_LEN];
      // Make sure dst string contains a different value then the src string.
      int value2 = 32 + (value + 2) % 96;
      memset(cmp_buf, value2, sizeof(cmp_buf));

      for (size_t i = 1; i <= STRCAT_DST_LEN; i++) {
        memset(dst, value2, i-1);
        memset(dst+i-1, 0, len-i);
        src[len-i] = '\0';
        ASSERT_EQ(dst, reinterpret_cast<uint8_t*>(strcat(reinterpret_cast<char*>(dst),
                                                         reinterpret_cast<char*>(src))));
        ASSERT_TRUE(memcmp(dst, cmp_buf, i-1) == 0);
        ASSERT_TRUE(memcmp(src, dst+i-1, len-i+1) == 0);
      }
    } else {
      dst[0] = '\0';
      ASSERT_EQ(dst, reinterpret_cast<uint8_t*>(strcat(reinterpret_cast<char*>(dst),
                                                       reinterpret_cast<char*>(src))));
      ASSERT_TRUE(memcmp(src, dst, len) == 0);
    }
  }
}

TEST(string, strcat_align) {
  RunSrcDstBufferAlignTest(MEDIUM, DoStrcatTest, LargeSetIncrement);
}

TEST(string, strcat_overread) {
  RunSrcDstBufferOverreadTest(DoStrcatTest);
}

static void DoStrcmpTest(uint8_t* buf1, uint8_t* buf2, size_t len) {
  if (len >= 1) {
    memset(buf1, (32 + (len % 96)), len - 1);
    buf1[len-1] = '\0';
    memset(buf2, (32 + (len % 96)), len - 1);
    buf2[len-1] = '\0';
    ASSERT_EQ(0, strcmp(reinterpret_cast<char*>(buf1),
                        reinterpret_cast<char*>(buf2)));
  }
}

static void DoStrcmpFailTest(uint8_t* buf1, uint8_t* buf2, size_t len1, size_t len2) {
  // Do string length differences.
  int c = (32 + (len1 % 96));
  memset(buf1, c, len1 - 1);
  buf1[len1-1] = '\0';
  memset(buf2, c, len2 - 1);
  buf2[len2-1] = '\0';
  ASSERT_NE(0, strcmp(reinterpret_cast<char*>(buf1),
                      reinterpret_cast<char*>(buf2)));

  // Do single character differences.
  size_t len;
  if (len1 > len2) {
    len = len2;
  } else {
    len = len1;
  }
  // Need at least a two character buffer to do this test.
  if (len > 1) {
    buf1[len-1] = '\0';
    buf2[len-1] = '\0';
    int diff_c = (c + 1) % 96;

    buf1[len-2] = diff_c;
    ASSERT_NE(0, strcmp(reinterpret_cast<char*>(buf1),
                        reinterpret_cast<char*>(buf2)));

    buf1[len-2] = c;
    buf2[len-2] = diff_c;
    ASSERT_NE(0, strcmp(reinterpret_cast<char*>(buf1),
                        reinterpret_cast<char*>(buf2)));
  }
}

TEST(string, strcmp_align) {
  RunCmpBufferAlignTest(MEDIUM, DoStrcmpTest, DoStrcmpFailTest, LargeSetIncrement);
}

TEST(string, strcmp_overread) {
  RunCmpBufferOverreadTest(DoStrcmpTest, DoStrcmpFailTest);
}

static void DoMemcmpTest(uint8_t* buf1, uint8_t* buf2, size_t len) {
  memset(buf1, len+1, len);
  memset(buf2, len+1, len);
  ASSERT_EQ(0, memcmp(buf1, buf2, len));
}

static void DoMemcmpFailTest(uint8_t* buf1, uint8_t* buf2, size_t len1, size_t len2) {
  size_t len;
  if (len1 > len2) {
    len = len2;
  } else {
    len = len1;
  }

  memset(buf1, len2+1, len);
  buf1[len-1] = len2;
  memset(buf2, len2+1, len);
  ASSERT_NE(0, memcmp(buf1, buf2, len));

  buf1[len-1] = len2+1;
  buf2[len-1] = len2;
  ASSERT_NE(0, memcmp(buf1, buf2, len));
}

TEST(string, memcmp_align) {
  RunCmpBufferAlignTest(MEDIUM, DoMemcmpTest, DoMemcmpFailTest, LargeSetIncrement);
}

TEST(string, memcmp_overread) {
  RunCmpBufferOverreadTest(DoMemcmpTest, DoMemcmpFailTest);
}