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Make merkle_branch() compression optional. #1790

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evoskuil merged 2 commits into from
Mar 1, 2026
Merged

Make merkle_branch() compression optional. #1790

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aca2ca7
Make merkle_branch() compression optional.
evoskuil Mar 1, 2026
5b1b4be
Style.
evoskuil Mar 1, 2026
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3 changes: 2 additions & 1 deletion include/bitcoin/system/chain/block.hpp
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Original file line number Diff line number Diff line change
Expand Up @@ -44,10 +44,11 @@ class BC_API block
struct position { size_t sibling; size_t width; };
using positions = std::vector<position>;

static positions merkle_branch(size_t leaf, size_t leaves) NOEXCEPT;
static bool is_malleable64(const transaction_cptrs& txs) NOEXCEPT;
static uint64_t subsidy(size_t height, uint64_t subsidy_interval,
uint64_t initial_block_subsidy_satoshi, bool bip42) NOEXCEPT;
static positions merkle_branch(size_t leaf, size_t leaves,
bool compress=false) NOEXCEPT;

/// Constructors.
/// -----------------------------------------------------------------------
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10 changes: 6 additions & 4 deletions src/chain/block.cpp
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Expand Up @@ -232,7 +232,7 @@ hashes block::transaction_hashes(bool witness) const NOEXCEPT
// Extra allocation for odd count optimizes for merkle root.
// Vector capacity is never reduced when resizing to smaller size.
const auto count = txs_->size();
const auto size = is_odd(count) && count > one ? add1(count) : count;
const auto size = !is_one(count) && is_odd(count) ? add1(count) : count;
hashes out(size);
out.resize(count);

Expand Down Expand Up @@ -445,23 +445,25 @@ bool block::is_invalid_merkle_root() const NOEXCEPT
}

// public/static (utility)
block::positions block::merkle_branch(size_t leaf, size_t leaves) NOEXCEPT
block::positions block::merkle_branch(size_t leaf, size_t leaves,
bool compress) NOEXCEPT
{
BC_ASSERT(leaves <= power2(sub1(bits<size_t>)));

positions branch{};
if (is_zero(leaves) || leaf >= leaves)
return branch;

// Upper bound, actual count may be less due to duplication.
// Upper bound, actual count may be less given compression.
branch.reserve(ceilinged_log2(leaves));

for (auto width = one, current = leaves; current > one;)
{
const auto sibling = bit_xor(leaf, one);
if (sibling < current++)
if (!compress || sibling < current)
branch.emplace_back(sibling, width);

++current;
shift_left_into(width);
shift_right_into(leaf);
shift_right_into(current);
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156 changes: 114 additions & 42 deletions test/chain/block.cpp
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Expand Up @@ -710,78 +710,136 @@ BOOST_AUTO_TEST_CASE(block__is_invalid_merkle_root__block100k__false)

BOOST_AUTO_TEST_CASE(block__merkle_branch__leaf_zero__empty)
{
BOOST_REQUIRE(block::merkle_branch(0, 0).empty());
BOOST_REQUIRE(block::merkle_branch(0, 0, true).empty());
BOOST_REQUIRE(block::merkle_branch(0, 0, false).empty());
}

BOOST_AUTO_TEST_CASE(block__merkle_branch__one__zero)
{
const auto result = block::merkle_branch(1, 2);
BOOST_REQUIRE_EQUAL(result.size(), 1u);
BOOST_REQUIRE_EQUAL(result[0].sibling, 0u);
BOOST_REQUIRE_EQUAL(result[0].width, 1u);
auto branch = block::merkle_branch(1, 2, true);
BOOST_REQUIRE_EQUAL(branch.size(), 1u);
BOOST_REQUIRE_EQUAL(branch[0].sibling, 0u);
BOOST_REQUIRE_EQUAL(branch[0].width, 1u);

branch = block::merkle_branch(1, 2, false);
BOOST_REQUIRE_EQUAL(branch.size(), 1u);
BOOST_REQUIRE_EQUAL(branch[0].sibling, 0u);
BOOST_REQUIRE_EQUAL(branch[0].width, 1u);
}

BOOST_AUTO_TEST_CASE(block__merkle_branch__two_for_odd_length__zero)
{
const auto result = block::merkle_branch(2, 3);
BOOST_REQUIRE_EQUAL(result.size(), 1u);
BOOST_REQUIRE_EQUAL(result[0].sibling, 0u);
BOOST_REQUIRE_EQUAL(result[0].width, 2u);
auto branch = block::merkle_branch(2, 3, true);
BOOST_REQUIRE_EQUAL(branch.size(), 1u);
BOOST_REQUIRE_EQUAL(branch[0].sibling, 0u);
BOOST_REQUIRE_EQUAL(branch[0].width, 2u);

branch = block::merkle_branch(2, 3, false);
BOOST_REQUIRE_EQUAL(branch.size(), 2u);
BOOST_REQUIRE_EQUAL(branch[0].sibling, 3u);
BOOST_REQUIRE_EQUAL(branch[0].width, 1u);
BOOST_REQUIRE_EQUAL(branch[1].sibling, 0u);
BOOST_REQUIRE_EQUAL(branch[1].width, 2u);
}

BOOST_AUTO_TEST_CASE(block__merkle_branch__three__two_and_zero)
{
const auto result = block::merkle_branch(3, 4);
BOOST_REQUIRE_EQUAL(result.size(), 2u);
BOOST_REQUIRE_EQUAL(result[0].sibling, 2u);
BOOST_REQUIRE_EQUAL(result[0].width, 1u);
BOOST_REQUIRE_EQUAL(result[1].sibling, 0u);
BOOST_REQUIRE_EQUAL(result[1].width, 2u);
auto branch = block::merkle_branch(3, 4, true);
BOOST_REQUIRE_EQUAL(branch.size(), 2u);
BOOST_REQUIRE_EQUAL(branch[0].sibling, 2u);
BOOST_REQUIRE_EQUAL(branch[0].width, 1u);
BOOST_REQUIRE_EQUAL(branch[1].sibling, 0u);
BOOST_REQUIRE_EQUAL(branch[1].width, 2u);

branch = block::merkle_branch(3, 4, false);
BOOST_REQUIRE_EQUAL(branch.size(), 2u);
BOOST_REQUIRE_EQUAL(branch[0].sibling, 2u);
BOOST_REQUIRE_EQUAL(branch[0].width, 1u);
BOOST_REQUIRE_EQUAL(branch[1].sibling, 0u);
BOOST_REQUIRE_EQUAL(branch[1].width, 2u);
}

BOOST_AUTO_TEST_CASE(block__merkle_branch__seven__six_four_and_zero)
{
const auto result = block::merkle_branch(7, 8);
BOOST_REQUIRE_EQUAL(result.size(), 3u);
BOOST_REQUIRE_EQUAL(result[0].sibling, 6u);
BOOST_REQUIRE_EQUAL(result[0].width, 1u);
BOOST_REQUIRE_EQUAL(result[1].sibling, 2u);
BOOST_REQUIRE_EQUAL(result[1].width, 2u);
BOOST_REQUIRE_EQUAL(result[2].sibling, 0u);
BOOST_REQUIRE_EQUAL(result[2].width, 4u);
auto branch = block::merkle_branch(7, 8, true);
BOOST_REQUIRE_EQUAL(branch.size(), 3u);
BOOST_REQUIRE_EQUAL(branch[0].sibling, 6u);
BOOST_REQUIRE_EQUAL(branch[0].width, 1u);
BOOST_REQUIRE_EQUAL(branch[1].sibling, 2u);
BOOST_REQUIRE_EQUAL(branch[1].width, 2u);
BOOST_REQUIRE_EQUAL(branch[2].sibling, 0u);
BOOST_REQUIRE_EQUAL(branch[2].width, 4u);

branch = block::merkle_branch(7, 8, false);
BOOST_REQUIRE_EQUAL(branch.size(), 3u);
BOOST_REQUIRE_EQUAL(branch[0].sibling, 6u);
BOOST_REQUIRE_EQUAL(branch[0].width, 1u);
BOOST_REQUIRE_EQUAL(branch[1].sibling, 2u);
BOOST_REQUIRE_EQUAL(branch[1].width, 2u);
BOOST_REQUIRE_EQUAL(branch[2].sibling, 0u);
BOOST_REQUIRE_EQUAL(branch[2].width, 4u);
}

BOOST_AUTO_TEST_CASE(block__merkle_branch__ten_for_odd__eight_and_zero)
{
const auto result = block::merkle_branch(10, 11);
BOOST_REQUIRE_EQUAL(result.size(), 2u);
BOOST_REQUIRE_EQUAL(result[0].sibling, 4u);
BOOST_REQUIRE_EQUAL(result[0].width, 2u);
BOOST_REQUIRE_EQUAL(result[1].sibling, 0u);
BOOST_REQUIRE_EQUAL(result[1].width, 8u);
auto branch = block::merkle_branch(10, 11, true);
BOOST_REQUIRE_EQUAL(branch.size(), 2u);
BOOST_REQUIRE_EQUAL(branch[0].sibling, 4u);
BOOST_REQUIRE_EQUAL(branch[0].width, 2u);
BOOST_REQUIRE_EQUAL(branch[1].sibling, 0u);
BOOST_REQUIRE_EQUAL(branch[1].width, 8u);

branch = block::merkle_branch(10, 11, false);
BOOST_REQUIRE_EQUAL(branch.size(), 4u);
BOOST_REQUIRE_EQUAL(branch[0].sibling, 11u);
BOOST_REQUIRE_EQUAL(branch[0].width, 1u);
BOOST_REQUIRE_EQUAL(branch[1].sibling, 4u);
BOOST_REQUIRE_EQUAL(branch[1].width, 2u);
BOOST_REQUIRE_EQUAL(branch[2].sibling, 3u);
BOOST_REQUIRE_EQUAL(branch[2].width, 4u);
BOOST_REQUIRE_EQUAL(branch[3].sibling, 0u);
BOOST_REQUIRE_EQUAL(branch[3].width, 8u);
}

BOOST_AUTO_TEST_CASE(block__merkle_branch__medium_power_of_two__expected)
{
const block::positions expected{ { 14, 1 }, { 6, 2 }, { 2, 4 }, { 0, 8 } };

const auto result = block::merkle_branch(15, 16);
BOOST_REQUIRE_EQUAL(result.size(), 4u);
BOOST_REQUIRE_EQUAL(result[0].sibling, 14u);
BOOST_REQUIRE_EQUAL(result[0].width, 1u);
BOOST_REQUIRE_EQUAL(result[1].sibling, 6u);
BOOST_REQUIRE_EQUAL(result[1].width, 2u);
BOOST_REQUIRE_EQUAL(result[2].sibling, 2u);
BOOST_REQUIRE_EQUAL(result[2].width, 4u);
BOOST_REQUIRE_EQUAL(result[3].sibling, 0u);
BOOST_REQUIRE_EQUAL(result[3].width, 8u);
auto branch = block::merkle_branch(15, 16, true);
BOOST_REQUIRE_EQUAL(branch.size(), 4u);
BOOST_REQUIRE_EQUAL(branch[0].sibling, 14u);
BOOST_REQUIRE_EQUAL(branch[0].width, 1u);
BOOST_REQUIRE_EQUAL(branch[1].sibling, 6u);
BOOST_REQUIRE_EQUAL(branch[1].width, 2u);
BOOST_REQUIRE_EQUAL(branch[2].sibling, 2u);
BOOST_REQUIRE_EQUAL(branch[2].width, 4u);
BOOST_REQUIRE_EQUAL(branch[3].sibling, 0u);
BOOST_REQUIRE_EQUAL(branch[3].width, 8u);

branch = block::merkle_branch(15, 16, false);
BOOST_REQUIRE_EQUAL(branch.size(), 4u);
BOOST_REQUIRE_EQUAL(branch[0].sibling, 14u);
BOOST_REQUIRE_EQUAL(branch[0].width, 1u);
BOOST_REQUIRE_EQUAL(branch[1].sibling, 6u);
BOOST_REQUIRE_EQUAL(branch[1].width, 2u);
BOOST_REQUIRE_EQUAL(branch[2].sibling, 2u);
BOOST_REQUIRE_EQUAL(branch[2].width, 4u);
BOOST_REQUIRE_EQUAL(branch[3].sibling, 0u);
BOOST_REQUIRE_EQUAL(branch[3].width, 8u);
}

BOOST_AUTO_TEST_CASE(block__merkle_branch__power_of_two_minus_one__expected)
{
constexpr auto leaf = 1023u;
constexpr auto size = ceilinged_log2(add1(leaf));
const auto branch = block::merkle_branch(leaf, add1(leaf));
auto branch = block::merkle_branch(leaf, add1(leaf), true);
BOOST_REQUIRE_EQUAL(branch.size(), size);
BOOST_REQUIRE_EQUAL(branch.front().sibling, 1022u);
BOOST_REQUIRE_EQUAL(branch.front().width, 1u);
BOOST_REQUIRE_EQUAL(branch.back().sibling, 0u);
BOOST_REQUIRE_EQUAL(branch.back().width, power2(sub1(size)));

branch = block::merkle_branch(leaf, add1(leaf), false);
BOOST_REQUIRE_EQUAL(branch.size(), size);
BOOST_REQUIRE_EQUAL(branch.front().sibling, 1022u);
BOOST_REQUIRE_EQUAL(branch.front().width, 1u);
Expand All @@ -793,7 +851,14 @@ BOOST_AUTO_TEST_CASE(block__merkle_branch__odd_large_leaf_with_duplication__expe
{
constexpr auto leaf = 2047u;
constexpr auto size = ceilinged_log2(add1(leaf));
const auto branch = block::merkle_branch(leaf, add1(leaf));
auto branch = block::merkle_branch(leaf, add1(leaf), true);
BOOST_REQUIRE_EQUAL(branch.size(), size);
BOOST_REQUIRE_EQUAL(branch.front().sibling, 2046u);
BOOST_REQUIRE_EQUAL(branch.front().width, 1u);
BOOST_REQUIRE_EQUAL(branch.back().sibling, 0u);
BOOST_REQUIRE_EQUAL(branch.back().width, power2(sub1(size)));

branch = block::merkle_branch(leaf, add1(leaf), false);
BOOST_REQUIRE_EQUAL(branch.size(), size);
BOOST_REQUIRE_EQUAL(branch.front().sibling, 2046u);
BOOST_REQUIRE_EQUAL(branch.front().width, 1u);
Expand All @@ -804,7 +869,14 @@ BOOST_AUTO_TEST_CASE(block__merkle_branch__odd_large_leaf_with_duplication__expe
BOOST_AUTO_TEST_CASE(block__merkle_branch__maximum_non_overflow__expected)
{
constexpr auto maximum = sub1(power2(sub1(bits<size_t>)));
const auto branch = block::merkle_branch(maximum, add1(maximum));
auto branch = block::merkle_branch(maximum, add1(maximum), true);
BOOST_REQUIRE_EQUAL(branch.size(), sub1(bits<size_t>));
BOOST_REQUIRE_EQUAL(branch.front().sibling, sub1(maximum));
BOOST_REQUIRE_EQUAL(branch.front().width, 1u);
BOOST_REQUIRE_EQUAL(branch.back().sibling, 0u);
BOOST_REQUIRE_EQUAL(branch.back().width, power2(sub1(sub1(bits<size_t>))));

branch = block::merkle_branch(maximum, add1(maximum), false);
BOOST_REQUIRE_EQUAL(branch.size(), sub1(bits<size_t>));
BOOST_REQUIRE_EQUAL(branch.front().sibling, sub1(maximum));
BOOST_REQUIRE_EQUAL(branch.front().width, 1u);
Expand Down
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