oxen-core/src/common/pruning.cpp

// Copyright (c) 2019, The Monero Project
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#include "cryptonote_config.h"
#include "misc_log_ex.h"
#include "crypto/crypto.h"
#include "pruning.h"

namespace tools
{

uint32_t make_pruning_seed(uint32_t stripe, uint32_t log_stripes)
{
  CHECK_AND_ASSERT_THROW_MES(log_stripes <= PRUNING_SEED_LOG_STRIPES_MASK, "log_stripes out of range");
  CHECK_AND_ASSERT_THROW_MES(stripe > 0 && stripe <= (1ul << log_stripes), "stripe out of range");
  return (log_stripes << PRUNING_SEED_LOG_STRIPES_SHIFT) | ((stripe - 1) << PRUNING_SEED_STRIPE_SHIFT);
}

bool has_unpruned_block(uint64_t block_height, uint64_t blockchain_height, uint32_t pruning_seed)
{
  const uint32_t stripe = get_pruning_stripe(pruning_seed);
  if (stripe == 0)
    return true;
  const uint32_t log_stripes = get_pruning_log_stripes(pruning_seed);
  uint32_t block_stripe = get_pruning_stripe(block_height, blockchain_height, log_stripes);
  return block_stripe == 0 || block_stripe == stripe;
}

uint32_t get_pruning_stripe(uint64_t block_height, uint64_t blockchain_height, uint32_t log_stripes)
{
  if (block_height + CRYPTONOTE_PRUNING_TIP_BLOCKS >= blockchain_height)
    return 0;
  return ((block_height / CRYPTONOTE_PRUNING_STRIPE_SIZE) & (uint64_t)((1ul << log_stripes) - 1)) + 1;
}

uint32_t get_pruning_seed(uint64_t block_height, uint64_t blockchain_height, uint32_t log_stripes)
{
  const uint32_t stripe = get_pruning_stripe(block_height, blockchain_height, log_stripes);
  if (stripe == 0)
    return 0;
  return make_pruning_seed(stripe, log_stripes);
}

uint64_t get_next_unpruned_block_height(uint64_t block_height, uint64_t blockchain_height, uint32_t pruning_seed)
{
  CHECK_AND_ASSERT_MES(block_height <= CRYPTONOTE_MAX_BLOCK_NUMBER+1, block_height, "block_height too large");
  CHECK_AND_ASSERT_MES(blockchain_height <= CRYPTONOTE_MAX_BLOCK_NUMBER+1, block_height, "blockchain_height too large");
  const uint32_t stripe = get_pruning_stripe(pruning_seed);
  if (stripe == 0)
    return block_height;
  if (block_height + CRYPTONOTE_PRUNING_TIP_BLOCKS >= blockchain_height)
    return block_height;
  const uint32_t seed_log_stripes = get_pruning_log_stripes(pruning_seed);
  const uint64_t log_stripes = seed_log_stripes ? seed_log_stripes : CRYPTONOTE_PRUNING_LOG_STRIPES;
  const uint64_t mask = (1ul << log_stripes) - 1;
  const uint32_t block_pruning_stripe = ((block_height / CRYPTONOTE_PRUNING_STRIPE_SIZE) & mask) + 1;
  if (block_pruning_stripe == stripe)
    return block_height;
  const uint64_t cycles = ((block_height / CRYPTONOTE_PRUNING_STRIPE_SIZE) >> log_stripes);
  const uint64_t cycle_start = cycles + ((stripe > block_pruning_stripe) ? 0 : 1);
  const uint64_t h = cycle_start * (CRYPTONOTE_PRUNING_STRIPE_SIZE << log_stripes) + (stripe - 1) * CRYPTONOTE_PRUNING_STRIPE_SIZE;
  if (h + CRYPTONOTE_PRUNING_TIP_BLOCKS > blockchain_height)
    return blockchain_height < CRYPTONOTE_PRUNING_TIP_BLOCKS ? 0 : blockchain_height - CRYPTONOTE_PRUNING_TIP_BLOCKS;
  CHECK_AND_ASSERT_MES(h >= block_height, block_height, "h < block_height, unexpected");
  return h;
}

uint64_t get_next_pruned_block_height(uint64_t block_height, uint64_t blockchain_height, uint32_t pruning_seed)
{
  const uint32_t stripe = get_pruning_stripe(pruning_seed);
  if (stripe == 0)
    return blockchain_height;
  if (block_height + CRYPTONOTE_PRUNING_TIP_BLOCKS >= blockchain_height)
    return blockchain_height;
  const uint32_t seed_log_stripes = get_pruning_log_stripes(pruning_seed);
  const uint64_t log_stripes = seed_log_stripes ? seed_log_stripes : CRYPTONOTE_PRUNING_LOG_STRIPES;
  const uint64_t mask = (1ul << log_stripes) - 1;
  const uint32_t block_pruning_seed = ((block_height / CRYPTONOTE_PRUNING_STRIPE_SIZE) & mask) + 1;
  if (block_pruning_seed != stripe)
    return block_height;
  const uint32_t next_stripe = 1 + (block_pruning_seed & mask);
  return get_next_unpruned_block_height(block_height, blockchain_height, tools::make_pruning_seed(next_stripe, log_stripes));
}

uint32_t get_random_stripe()
{
  return 1 + crypto::rand<uint8_t>() % (1ul << CRYPTONOTE_PRUNING_LOG_STRIPES);
}

}