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Add a FastRandomContext::randrange and use it

pull/1/head
Pieter Wuille 5 years ago
parent
commit
4fd2d2fc97
  1. 2
      configure.ac
  2. 2
      src/bench/checkqueue.cpp
  3. 21
      src/crypto/common.h
  4. 2
      src/net.h
  5. 12
      src/random.h
  6. 23
      src/test/crypto_tests.cpp
  7. 15
      src/test/random_tests.cpp

2
configure.ac

@ -550,6 +550,8 @@ AC_CHECK_DECLS([bswap_16, bswap_32, bswap_64],,, @@ -550,6 +550,8 @@ AC_CHECK_DECLS([bswap_16, bswap_32, bswap_64],,,
#include <byteswap.h>
#endif])
AC_CHECK_DECLS([__builtin_clz, __builtin_clzl, __builtin_clzll])
dnl Check for MSG_NOSIGNAL
AC_MSG_CHECKING(for MSG_NOSIGNAL)
AC_COMPILE_IFELSE([AC_LANG_PROGRAM([[#include <sys/socket.h>]],

2
src/bench/checkqueue.cpp

@ -68,7 +68,7 @@ static void CCheckQueueSpeedPrevectorJob(benchmark::State& state) @@ -68,7 +68,7 @@ static void CCheckQueueSpeedPrevectorJob(benchmark::State& state)
PrevectorJob(){
}
PrevectorJob(FastRandomContext& insecure_rand){
p.resize(insecure_rand.rand32() % (PREVECTOR_SIZE*2));
p.resize(insecure_rand.randrange(PREVECTOR_SIZE*2));
}
bool operator()()
{

21
src/crypto/common.h

@ -79,4 +79,25 @@ void static inline WriteBE64(unsigned char* ptr, uint64_t x) @@ -79,4 +79,25 @@ void static inline WriteBE64(unsigned char* ptr, uint64_t x)
memcpy(ptr, (char*)&v, 8);
}
/** Return the smallest number n such that (x >> n) == 0 (or 64 if the highest bit in x is set. */
uint64_t static inline CountBits(uint64_t x)
{
#ifdef HAVE_DECL___BUILTIN_CLZL
if (sizeof(unsigned long) >= sizeof(uint64_t)) {
return x ? 8 * sizeof(unsigned long) - __builtin_clzl(x) : 0;
}
#endif
#ifdef HAVE_DECL___BUILTIN_CLZLL
if (sizeof(unsigned long long) >= sizeof(uint64_t)) {
return x ? 8 * sizeof(unsigned long long) - __builtin_clzll(x) : 0;
}
#endif
int ret = 0;
while (x) {
x >>= 1;
++ret;
}
return ret;
}
#endif // BITCOIN_CRYPTO_COMMON_H

2
src/net.h

@ -760,7 +760,7 @@ public: @@ -760,7 +760,7 @@ public:
// after addresses were pushed.
if (_addr.IsValid() && !addrKnown.contains(_addr.GetKey())) {
if (vAddrToSend.size() >= MAX_ADDR_TO_SEND) {
vAddrToSend[insecure_rand.rand32() % vAddrToSend.size()] = _addr;
vAddrToSend[insecure_rand.randrange(vAddrToSend.size())] = _addr;
} else {
vAddrToSend.push_back(_addr);
}

12
src/random.h

@ -7,6 +7,7 @@ @@ -7,6 +7,7 @@
#define BITCOIN_RANDOM_H
#include "crypto/chacha20.h"
#include "crypto/common.h"
#include "uint256.h"
#include <stdint.h>
@ -91,6 +92,17 @@ public: @@ -91,6 +92,17 @@ public:
}
}
/** Generate a random integer in the range [0..range). */
uint64_t randrange(uint64_t range)
{
--range;
int bits = CountBits(range);
while (true) {
uint64_t ret = randbits(bits);
if (ret <= range) return ret;
}
}
/** Generate a random 32-bit integer. */
uint32_t rand32() { return randbits(32); }

23
src/test/crypto_tests.cpp

@ -10,6 +10,7 @@ @@ -10,6 +10,7 @@
#include "crypto/sha512.h"
#include "crypto/hmac_sha256.h"
#include "crypto/hmac_sha512.h"
#include "random.h"
#include "utilstrencodings.h"
#include "test/test_bitcoin.h"
#include "test/test_random.h"
@ -484,4 +485,26 @@ BOOST_AUTO_TEST_CASE(chacha20_testvector) @@ -484,4 +485,26 @@ BOOST_AUTO_TEST_CASE(chacha20_testvector)
"fab78c9");
}
BOOST_AUTO_TEST_CASE(countbits_tests)
{
FastRandomContext ctx;
for (int i = 0; i <= 64; ++i) {
if (i == 0) {
// Check handling of zero.
BOOST_CHECK_EQUAL(CountBits(0), 0);
} else if (i < 10) {
for (uint64_t j = 1 << (i - 1); (j >> i) == 0; ++j) {
// Exhaustively test up to 10 bits
BOOST_CHECK_EQUAL(CountBits(j), i);
}
} else {
for (int k = 0; k < 1000; k++) {
// Randomly test 1000 samples of each length above 10 bits.
uint64_t j = ((uint64_t)1) << (i - 1) | ctx.randbits(i - 1);
BOOST_CHECK_EQUAL(CountBits(j), i);
}
}
}
}
BOOST_AUTO_TEST_SUITE_END()

15
src/test/random_tests.cpp

@ -35,4 +35,19 @@ BOOST_AUTO_TEST_CASE(fastrandom_tests) @@ -35,4 +35,19 @@ BOOST_AUTO_TEST_CASE(fastrandom_tests)
BOOST_CHECK(ctx3.rand64() != ctx4.rand64()); // extremely unlikely to be equal
}
BOOST_AUTO_TEST_CASE(fastrandom_randbits)
{
FastRandomContext ctx1;
FastRandomContext ctx2;
for (int bits = 0; bits < 63; ++bits) {
for (int j = 0; j < 1000; ++j) {
uint64_t rangebits = ctx1.randbits(bits);
BOOST_CHECK_EQUAL(rangebits >> bits, 0);
uint64_t range = ((uint64_t)1) << bits | rangebits;
uint64_t rand = ctx2.randrange(range);
BOOST_CHECK(rand < range);
}
}
}
BOOST_AUTO_TEST_SUITE_END()

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