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94 lines
2.8 KiB
C++
94 lines
2.8 KiB
C++
// Copyright 2016 The Chromium Authors. All rights reserved.
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// Use of this source code is governed by a BSD-style license that can be
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// found in the LICENSE file.
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#include "net/http2/tools/random_util.h"
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#include <cmath>
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#include "base/rand_util.h"
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#include "net/http2/tools/http2_random.h"
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namespace net {
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namespace test {
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namespace {
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const char kWebsafe64[] =
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"0123456789abcdefghijklmnopqrstuvwxyzABCDEFGHIJKLMNOPQRSTUVWXYZ-_";
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// Generate two independent standard normal random variables using the polar
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// method.
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void GenerateRandomSizeSkewedLowHelper(size_t max, size_t* x, size_t* y) {
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double a, b, s;
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do {
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// Draw uniformly on [-1, 1).
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a = 2 * base::RandDouble() - 1.0;
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b = 2 * base::RandDouble() - 1.0;
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s = a * a + b * b;
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} while (s >= 1.0);
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double t = std::sqrt(-2.0 * std::log(s) / s);
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*x = static_cast<size_t>(a * t * max);
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*y = static_cast<size_t>(b * t * max);
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}
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} // anonymous namespace
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Http2String RandomString(RandomBase* rng, int len, Http2StringPiece alphabet) {
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Http2String random_string;
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random_string.reserve(len);
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for (int i = 0; i < len; ++i)
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random_string.push_back(alphabet[rng->Uniform(alphabet.size())]);
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return random_string;
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}
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size_t GenerateUniformInRange(size_t lo, size_t hi, RandomBase* rng) {
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if (lo + 1 >= hi) {
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return lo;
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}
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return lo + rng->Rand64() % (hi - lo);
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}
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// Here "word" means something that starts with a lower-case letter, and has
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// zero or more additional characters that are numbers or lower-case letters.
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Http2String GenerateHttp2HeaderName(size_t len, RandomBase* rng) {
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Http2StringPiece alpha_lc = "abcdefghijklmnopqrstuvwxyz";
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// If the name is short, just make it one word.
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if (len < 8) {
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return RandomString(rng, len, alpha_lc);
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}
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// If the name is longer, ensure it starts with a word, and after that may
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// have any character in alphanumdash_lc. 4 is arbitrary, could be as low
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// as 1.
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Http2StringPiece alphanumdash_lc = "abcdefghijklmnopqrstuvwxyz0123456789-";
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return RandomString(rng, 4, alpha_lc) +
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RandomString(rng, len - 4, alphanumdash_lc);
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}
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Http2String GenerateWebSafeString(size_t len, RandomBase* rng) {
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return RandomString(rng, len, kWebsafe64);
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}
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Http2String GenerateWebSafeString(size_t lo, size_t hi, RandomBase* rng) {
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return GenerateWebSafeString(GenerateUniformInRange(lo, hi, rng), rng);
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}
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size_t GenerateRandomSizeSkewedLow(size_t max, RandomBase* rng) {
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if (max == 0) {
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return 0;
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}
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// Generate a random number with a Gaussian distribution, centered on zero;
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// take the absolute, and then keep in range 0 to max.
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for (int i = 0; i < 5; i++) {
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size_t x, y;
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GenerateRandomSizeSkewedLowHelper(max, &x, &y);
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if (x <= max)
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return x;
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if (y <= max)
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return y;
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}
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return rng->Uniform(max + 1);
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}
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} // namespace test
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} // namespace net
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