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doxygen documentation for difficulty functions

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Thomas Winget 2015-10-07 22:28:43 -04:00
parent 37fa7b44d6
commit f2cc3a9eaf
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2 changed files with 42 additions and 3 deletions
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8
src/cryptonote_core/difficulty.cpp
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@ -116,8 +116,8 @@ namespace cryptonote {
return !carry; return !carry;
} }
difficulty_type next_difficulty(vector<uint64_t> timestamps, vector<difficulty_type> cumulative_difficulties, size_t target_seconds) { difficulty_type next_difficulty(std::vector<std::uint64_t> timestamps, std::vector<difficulty_type> cumulative_difficulties, size_t target_seconds) {
//cutoff DIFFICULTY_LAG
if(timestamps.size() > DIFFICULTY_WINDOW) if(timestamps.size() > DIFFICULTY_WINDOW)
{ {
timestamps.resize(DIFFICULTY_WINDOW); timestamps.resize(DIFFICULTY_WINDOW);
@ -151,13 +151,15 @@ namespace cryptonote {
assert(total_work > 0); assert(total_work > 0);
uint64_t low, high; uint64_t low, high;
mul(total_work, target_seconds, low, high); mul(total_work, target_seconds, low, high);
// blockchain errors "difficulty overhead" if this function returns zero.
// TODO: consider throwing an exception instead
if (high != 0 || low + time_span - 1 < low) { if (high != 0 || low + time_span - 1 < low) {
return 0; return 0;
} }
return (low + time_span - 1) / time_span; return (low + time_span - 1) / time_span;
} }
difficulty_type next_difficulty(vector<uint64_t> timestamps, vector<difficulty_type> cumulative_difficulties) difficulty_type next_difficulty(std::vector<std::uint64_t> timestamps, std::vector<difficulty_type> cumulative_difficulties)
{ {
return next_difficulty(std::move(timestamps), std::move(cumulative_difficulties), DIFFICULTY_TARGET); return next_difficulty(std::move(timestamps), std::move(cumulative_difficulties), DIFFICULTY_TARGET);
} }

37
src/cryptonote_core/difficulty.h
View File

@ -39,7 +39,44 @@ namespace cryptonote
{ {
typedef std::uint64_t difficulty_type; typedef std::uint64_t difficulty_type;
/**
* @brief checks if a hash fits the given difficulty
*
* The hash passes if (hash * difficulty) < 2^192.
* Phrased differently, if (hash * difficulty) fits without overflow into
* the least significant 192 bits of the 256 bit multiplication result.
*
* @param hash the hash to check
* @param difficulty the difficulty to check against
*
* @return true if valid, else false
*/
bool check_hash(const crypto::hash &hash, difficulty_type difficulty); bool check_hash(const crypto::hash &hash, difficulty_type difficulty);
/**
* @brief gets the required difficulty for the next block
*
* This function calculates the required difficulty for the block that
* follows the blocks to which the passed timestamps and difficulties
* belong.
*
* The current difficulty algorithm is as follows:
* - take the total time and cumulative difficulty ("total work")
* - let m = the total work multiplied by the target block time
* - if (m + total time) > 2^64, give 0 for the next difficulty,
* the blockchain class treats this as an error "difficulty overhead"
*
* - the next difficulty = (m + the total time - 1) / the total time
*
* @param timestamps the most recent timestamps
* @param cumulative_difficulties the most recent difficulties
*
* @return the required difficulty for the next block
*/
difficulty_type next_difficulty(std::vector<std::uint64_t> timestamps, std::vector<difficulty_type> cumulative_difficulties); difficulty_type next_difficulty(std::vector<std::uint64_t> timestamps, std::vector<difficulty_type> cumulative_difficulties);
/**
* @overload
*/
difficulty_type next_difficulty(std::vector<std::uint64_t> timestamps, std::vector<difficulty_type> cumulative_difficulties, size_t target_seconds); difficulty_type next_difficulty(std::vector<std::uint64_t> timestamps, std::vector<difficulty_type> cumulative_difficulties, size_t target_seconds);
} }