Coinselection Functions

int wally_coinselect_assets(const uint64_t *values, size_t num_values, uint64_t target, uint64_t attempts, uint32_t io_ratio, uint32_t *indices_out, size_t indices_out_len, size_t *written)

Select input asset values to meet a given payment target.

Parameters:

  • values – The UTXO asset values to select from. Must be ordered from largest to smallest.

  • num_values – The number of asset values in values.

  • target – The desired payment value target.

  • attempts – The maximum number of permutations to check. Must be at least num_values + 1.

  • io_ratio – The approximate expected ratio of input to output sizes in the resulting transaction. Larger values will result in more input permutations being searched for exact matches. Must be non-zero, a good default value is 5.

  • indices_out – Destination for the zero-based indices into values making up the chosen solution. Must be at least the smaller of num_values and WALLY_CS_MAX_ASSETS.

  • indices_out_len – Size of indices_out. Passing WALLY_CS_MAX_ASSETS will ensure the buffer is large enough.

  • written – Destination for the the number of indices written to indices_out.

This function always finds a solution if one is available. If the given values are insufficient to reach the target then zero elements will be returned. If the sum of the values returned is not equal to target then a change output for the remainder will be required.

Returns:

See Error Codes

Coinselection Constants

WALLY_CS_MAX_ASSETS

The maximum number of asset values that can be returned in a coin selection