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wallet: Return change satoshis when selecting coins

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We'd be computing them later most of the time anyway.
This commit is contained in:
Christian Decker
2017-06-20 16:54:53 +02:00
committed by Rusty Russell
parent 3f594172b2
commit a775b52941
3 changed files with 11 additions and 10 deletions
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9
lightningd/build_utxos.c
View File

@@ -172,22 +172,17 @@ const struct utxo **build_utxos(const tal_t *ctx,
u32 feerate_per_kw, u64 dust_limit,
u64 *change_satoshis, u32 *change_keyindex)
{
u64 satoshi_in = 0;
u64 fee_estimate = 0;
u64 bip32_max_index = db_get_intvar(ld->wallet->db, "bip32_max_index", 0);
const struct utxo **utxos =
wallet_select_coins(ctx, ld->wallet, satoshi_out, feerate_per_kw, &fee_estimate);
wallet_select_coins(ctx, ld->wallet, satoshi_out, feerate_per_kw,
&fee_estimate, change_satoshis);
/* Oops, didn't have enough coins available */
if (!utxos)
return NULL;
/* How much are we actually claiming? */
for (size_t i=0; i<tal_count(utxos); i++)
satoshi_in += utxos[i]->amount;
/* Do we need a change output? */
*change_satoshis = satoshi_in - (fee_estimate + satoshi_out);
if (*change_satoshis < dust_limit) {
*change_satoshis = 0;
*change_keyindex = 0;

9
wallet/wallet.c
View File

@@ -129,17 +129,20 @@ void wallet_confirm_utxos(struct wallet *w, const struct utxo **utxos)
const struct utxo **wallet_select_coins(const tal_t *ctx, struct wallet *w,
const u64 value,
const u32 feerate_per_kw,
u64 *fee_estimate)
u64 *fee_estimate, u64 *changesatoshi)
{
size_t i = 0;
struct utxo **available;
const struct utxo **utxos = tal_arr(ctx, const struct utxo *, 0);
*fee_estimate = 0;
/* We assume two outputs for the weight. */
u64 satoshi_in = 0, weight = (4 + (8 + 22) * 2 + 4) * 4;
tal_add_destructor2(utxos, destroy_utxos, w);
db_begin_transaction(w->db);
if (!db_begin_transaction(w->db)) {
fatal("Unable to begin transaction: %s", w->db->err);
}
available = wallet_get_utxos(ctx, w, output_state_available);
for (i = 0; i < tal_count(available); i++) {
@@ -171,6 +174,8 @@ const struct utxo **wallet_select_coins(const tal_t *ctx, struct wallet *w,
} else {
/* Commit the db transaction to persist markings */
db_commit_transaction(w->db);
*changesatoshi = satoshi_in - value - *fee_estimate;
}
return utxos;
}

3
wallet/wallet.h
View File

@@ -77,7 +77,8 @@ struct utxo **wallet_get_utxos(const tal_t *ctx, struct wallet *w,
const struct utxo **wallet_select_coins(const tal_t *ctx, struct wallet *w,
const u64 value,
const u32 feerate_per_kw,
u64 *fee_estimate);
u64 *fee_estimate,
u64 *change_satoshi);
/**
* wallet_confirm_utxos - Once we've spent a set of utxos, mark them confirmed.