Add a FastRandomContext::randrange and use it
(cherry picked from commit 4fd2d2fc97e21efceab849576e544160fd5e3e3d)
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12d8d06c80
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1f41301c97
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@ -685,6 +685,8 @@ AC_CHECK_DECLS([bswap_16, bswap_32, bswap_64],,,
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#include <byteswap.h>
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#endif])
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AC_CHECK_DECLS([__builtin_clz, __builtin_clzl, __builtin_clzll])
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dnl Check for MSG_NOSIGNAL
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AC_MSG_CHECKING(for MSG_NOSIGNAL)
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AC_COMPILE_IFELSE([AC_LANG_PROGRAM([[#include <sys/socket.h>]],
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@ -68,7 +68,7 @@ static void CCheckQueueSpeedPrevectorJob(benchmark::State& state)
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PrevectorJob(){
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}
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PrevectorJob(FastRandomContext& insecure_rand){
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p.resize(insecure_rand.rand32() % (PREVECTOR_SIZE*2));
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p.resize(insecure_rand.randrange(PREVECTOR_SIZE*2));
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}
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bool operator()()
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{
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@ -84,4 +84,25 @@ void static inline WriteBE64(unsigned char* ptr, uint64_t x)
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memcpy(ptr, (char*)&v, 8);
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}
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/** Return the smallest number n such that (x >> n) == 0 (or 64 if the highest bit in x is set. */
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uint64_t static inline CountBits(uint64_t x)
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{
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#ifdef HAVE_DECL___BUILTIN_CLZL
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if (sizeof(unsigned long) >= sizeof(uint64_t)) {
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return x ? 8 * sizeof(unsigned long) - __builtin_clzl(x) : 0;
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}
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#endif
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#ifdef HAVE_DECL___BUILTIN_CLZLL
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if (sizeof(unsigned long long) >= sizeof(uint64_t)) {
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return x ? 8 * sizeof(unsigned long long) - __builtin_clzll(x) : 0;
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}
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#endif
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int ret = 0;
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while (x) {
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x >>= 1;
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++ret;
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}
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return ret;
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}
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#endif // BITCOIN_CRYPTO_COMMON_H
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@ -424,7 +424,7 @@ public:
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// after addresses were pushed.
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if (addr.IsValid() && !addrKnown.contains(addr.GetKey())) {
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if (vAddrToSend.size() >= MAX_ADDR_TO_SEND) {
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vAddrToSend[insecure_rand.rand32() % vAddrToSend.size()] = addr;
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vAddrToSend[insecure_rand.randrange(vAddrToSend.size())] = addr;
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} else {
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vAddrToSend.push_back(addr);
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}
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11
src/random.h
11
src/random.h
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@ -143,6 +143,17 @@ public:
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}
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}
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/** Generate a random integer in the range [0..range). */
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uint64_t randrange(uint64_t range)
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{
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--range;
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int bits = CountBits(range);
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while (true) {
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uint64_t ret = randbits(bits);
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if (ret <= range) return ret;
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}
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}
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/** Generate a random 32-bit integer. */
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uint32_t rand32() { return randbits(32); }
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@ -482,4 +482,26 @@ BOOST_AUTO_TEST_CASE(chacha20_testvector)
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"fab78c9");
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}
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BOOST_AUTO_TEST_CASE(countbits_tests)
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{
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FastRandomContext ctx;
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for (int i = 0; i <= 64; ++i) {
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if (i == 0) {
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// Check handling of zero.
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BOOST_CHECK_EQUAL(CountBits(0), 0);
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} else if (i < 10) {
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for (uint64_t j = 1 << (i - 1); (j >> i) == 0; ++j) {
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// Exhaustively test up to 10 bits
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BOOST_CHECK_EQUAL(CountBits(j), i);
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}
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} else {
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for (int k = 0; k < 1000; k++) {
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// Randomly test 1000 samples of each length above 10 bits.
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uint64_t j = ((uint64_t)1) << (i - 1) | ctx.randbits(i - 1);
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BOOST_CHECK_EQUAL(CountBits(j), i);
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}
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}
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}
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}
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BOOST_AUTO_TEST_SUITE_END()
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@ -30,4 +30,19 @@ BOOST_AUTO_TEST_CASE(fastrandom_tests)
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BOOST_CHECK(ctx3.rand64() != ctx4.rand64()); // extremely unlikely to be equal
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}
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BOOST_AUTO_TEST_CASE(fastrandom_randbits)
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{
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FastRandomContext ctx1;
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FastRandomContext ctx2;
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for (int bits = 0; bits < 63; ++bits) {
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for (int j = 0; j < 1000; ++j) {
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uint64_t rangebits = ctx1.randbits(bits);
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BOOST_CHECK_EQUAL(rangebits >> bits, 0);
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uint64_t range = ((uint64_t)1) << bits | rangebits;
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uint64_t rand = ctx2.randrange(range);
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BOOST_CHECK(rand < range);
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}
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}
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}
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BOOST_AUTO_TEST_SUITE_END()
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