blob: b50dd50169fdb43e1ecf496924cecc6d0f8e6414 [file] [log] [blame]
// 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 "net/http2/tools/random_util.h"
#include <cmath>
#include "base/rand_util.h"
#include "net/http2/tools/http2_random.h"
namespace net {
namespace test {
namespace {
const char kWebsafe64[] =
"0123456789abcdefghijklmnopqrstuvwxyzABCDEFGHIJKLMNOPQRSTUVWXYZ-_";
// Generate two independent standard normal random variables using the polar
// method.
void GenerateRandomSizeSkewedLowHelper(size_t max, size_t* x, size_t* y) {
double a, b, s;
do {
// Draw uniformly on [-1, 1).
a = 2 * base::RandDouble() - 1.0;
b = 2 * base::RandDouble() - 1.0;
s = a * a + b * b;
} while (s >= 1.0);
double t = std::sqrt(-2.0 * std::log(s) / s);
*x = static_cast<size_t>(a * t * max);
*y = static_cast<size_t>(b * t * max);
}
} // anonymous namespace
Http2String RandomString(RandomBase* rng, int len, Http2StringPiece alphabet) {
Http2String random_string;
random_string.reserve(len);
for (int i = 0; i < len; ++i)
random_string.push_back(alphabet[rng->Uniform(alphabet.size())]);
return random_string;
}
size_t GenerateUniformInRange(size_t lo, size_t hi, RandomBase* rng) {
if (lo + 1 >= hi) {
return lo;
}
return lo + rng->Rand64() % (hi - lo);
}
// Here "word" means something that starts with a lower-case letter, and has
// zero or more additional characters that are numbers or lower-case letters.
Http2String GenerateHttp2HeaderName(size_t len, RandomBase* rng) {
Http2StringPiece alpha_lc = "abcdefghijklmnopqrstuvwxyz";
// If the name is short, just make it one word.
if (len < 8) {
return RandomString(rng, len, alpha_lc);
}
// If the name is longer, ensure it starts with a word, and after that may
// have any character in alphanumdash_lc. 4 is arbitrary, could be as low
// as 1.
Http2StringPiece alphanumdash_lc = "abcdefghijklmnopqrstuvwxyz0123456789-";
return RandomString(rng, 4, alpha_lc) +
RandomString(rng, len - 4, alphanumdash_lc);
}
Http2String GenerateWebSafeString(size_t len, RandomBase* rng) {
return RandomString(rng, len, kWebsafe64);
}
Http2String GenerateWebSafeString(size_t lo, size_t hi, RandomBase* rng) {
return GenerateWebSafeString(GenerateUniformInRange(lo, hi, rng), rng);
}
size_t GenerateRandomSizeSkewedLow(size_t max, RandomBase* rng) {
if (max == 0) {
return 0;
}
// Generate a random number with a Gaussian distribution, centered on zero;
// take the absolute, and then keep in range 0 to max.
for (int i = 0; i < 5; i++) {
size_t x, y;
GenerateRandomSizeSkewedLowHelper(max, &x, &y);
if (x <= max)
return x;
if (y <= max)
return y;
}
return rng->Uniform(max + 1);
}
} // namespace test
} // namespace net