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// Copyright (c) 2009-2010 Satoshi Nakamoto
// Copyright (c) 2009-2016 The Bitcoin Core developers
// Distributed under the MIT software license, see the accompanying
// file COPYING or http://www.opensource.org/licenses/mit-license.php.
#ifndef BITCOIN_RANDOM_H
#define BITCOIN_RANDOM_H
#include "crypto/chacha20.h"
#include "crypto/common.h"
#include "uint256.h"
#include <stdint.h>
/* Seed OpenSSL PRNG with additional entropy data */
void RandAddSeed();
/**
* Functions to gather random data via the OpenSSL PRNG
*/
void GetRandBytes(unsigned char* buf, int num);
uint64_t GetRand(uint64_t nMax);
int GetRandInt(int nMax);
uint256 GetRandHash();
/**
* Function to gather random data from multiple sources, failing whenever any
* of those source fail to provide a result.
*/
void GetStrongRandBytes(unsigned char* buf, int num);
/**
* Fast randomness source. This is seeded once with secure random data, but
* is completely deterministic and insecure after that.
* This class is not thread-safe.
*/
class FastRandomContext {
private:
bool requires_seed;
ChaCha20 rng;
unsigned char bytebuf[64];
int bytebuf_size;
uint64_t bitbuf;
int bitbuf_size;
void RandomSeed();
void FillByteBuffer()
{
if (requires_seed) {
RandomSeed();
}
rng.Output(bytebuf, sizeof(bytebuf));
bytebuf_size = sizeof(bytebuf);
}
void FillBitBuffer()
{
bitbuf = rand64();
bitbuf_size = 64;
}
public:
explicit FastRandomContext(bool fDeterministic = false);
/** Initialize with explicit seed (only for testing) */
explicit FastRandomContext(const uint256& seed);
/** Generate a random 64-bit integer. */
uint64_t rand64()
{
if (bytebuf_size < 8) FillByteBuffer();
uint64_t ret = ReadLE64(bytebuf + 64 - bytebuf_size);
bytebuf_size -= 8;
return ret;
}
/** Generate a random (bits)-bit integer. */
uint64_t randbits(int bits) {
if (bits == 0) {
return 0;
} else if (bits > 32) {
return rand64() >> (64 - bits);
} else {
if (bitbuf_size < bits) FillBitBuffer();
uint64_t ret = bitbuf & (~(uint64_t)0 >> (64 - bits));
bitbuf >>= bits;
bitbuf_size -= bits;
return ret;
}
}
/** 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); }
/** Generate a random boolean. */
bool randbool() { return randbits(1); }
};
/* Number of random bytes returned by GetOSRand.
* When changing this constant make sure to change all call sites, and make
* sure that the underlying OS APIs for all platforms support the number.
* (many cap out at 256 bytes).
*/
static const ssize_t NUM_OS_RANDOM_BYTES = 32;
/** Get 32 bytes of system entropy. Do not use this in application code: use
* GetStrongRandBytes instead.
*/
void GetOSRand(unsigned char *ent32);
/** Check that OS randomness is available and returning the requested number
* of bytes.
*/
bool Random_SanityCheck();
#endif // BITCOIN_RANDOM_H