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shibing624
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//..
// Finally, we observe that we obtain different numbers:
//..
ASSERT(unseededR1 != rand());
ASSERT(unseededR2 != rand());
//..
} break;
case 2: {
// --------------------------------------------------------------------
// 'int getRandomBytesNonBlocking(buf, numB)' TEST
//
// Concerns:
//: 1 If a number is passed, that many bytes are set.
//: 2 The random bytes are distributed uniformly (probabilistic).
//
// Plan:
//: 1 Request a large pool and random bytes from non-blocking random
//: number generator. Verify that each is unique. Verify that the
//: numbers approximate a uniform distribution.
//
// Testing:
// static int getRandomBytesNonBlocking(buf, numB);
// --------------------------------------------------------------------
const int NUM_ITERATIONS = 25;
const int NUM_TRIALS = 10;
int cnt = 0;
unsigned char buffer[NUM_ITERATIONS * 4] = { };
unsigned char or_buffer[NUM_ITERATIONS * 4] = { };
unsigned char and_buffer[NUM_ITERATIONS * 4] = { };
const unsigned NUM_BYTES = sizeof buffer;
if (verbose)
cout << endl
<< "'int getRandomBytesNonBlocking(buf, numB)' TEST" << endl
<< "===============================================" << endl;
// 1) If a number is passed, that many bytes are set.
if (veryVerbose) {
cout << "\nTesting the number of bytes set." << endl;
}
for (unsigned i = 0; i < 5; ++i) {
memset(buffer, 0, NUM_BYTES);
memset(or_buffer, 0, NUM_BYTES);
memset(and_buffer, 0xf, NUM_BYTES);
// Repeat the accession of random bytes 'NUM_TRIALS' times to
// prevent false negatives
for (int j = 0; j < NUM_TRIALS; ++j) {
if (veryVerbose) { P(j) }
ASSERT(0 == Util::getRandomBytesNonBlocking(buffer, i));
// '|' and '&' the bytes
for (unsigned k = 0; k < i; ++k) {
or_buffer[k] |= buffer[k];
and_buffer[k] &= buffer[k];
}
}
// Check that the bytes set are non-zero and non-0xf. Since
// 'NUM_TRIALS > 4', the is less than a 2^(-32) chance of these
// tests failing due to randomness. They are much more likely to
// fail on '1 == i' than later.
if (0 < i) {
int or_sum = 0, and_sum = 0;
for (unsigned j = 0; j < i; ++j) {
or_sum += or_buffer[j];
and_sum += ~and_buffer[j];
}
LOOP2_ASSERT(i, or_sum, 0 != or_sum);
LOOP2_ASSERT(i, and_sum, 0 != and_sum);
}
// check that remaining bytes are still unset.
for (unsigned j = i; j < NUM_BYTES; ++j) {
LOOP3_ASSERT(i, j, int(buffer[j]), 0 == buffer[j]);
}
}
if (veryVerbose) {
cout << "\nTesting the distribution of rand." << endl;
}
// 3) The random bytes are uniformly distributed (probabilistic)
int numbers[NUM_ITERATIONS] = { };
for (int i = 0; i< NUM_ITERATIONS; ++i) {
int rand;
if (veryVerbose) { P(i) }
ASSERT(0 == Util::getRandomBytesNonBlocking(
reinterpret_cast<unsigned char *>(&rand),
sizeof rand));
numbers[i] = rand;
if (veryVerbose) { P_(i) P(rand) }
for (int j = 0; j < i; ++j) {
ASSERT(numbers[j] != rand);
if (veryVerbose) { P_(j) P(numbers[j]) }
}
for (int b = 0; b < 15; ++b) {
cnt += rand & 1;
rand >>= 1;
if (veryVerbose) { P(cnt) }
}
}
double expected = (NUM_ITERATIONS * 15) / 2;