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txprepare: use excess_as_change flag to simplify withdraw/txprepare logic.

Browse Source 
This was added to fundpsbt/utxopsbt in v0.10, but the txprepare plugin
didn't take advantage of it, instead calculating its own change amount
and output.

Signed-off-by: Rusty Russell <rusty@rustcorp.com.au>
This commit is contained in:
Rusty Russell
2023-06-29 09:44:09 +09:30
parent e20ceba9e0
commit 37005b93d3
1 changed files with 4 additions and 69 deletions
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73
plugins/txprepare.c
View File

@@ -30,9 +30,6 @@ struct txprepare {
struct wally_psbt *psbt;
u32 feerate;
/* Once we have reserved all the inputs, this is set. */
struct amount_sat change_amount;
/* For withdraw, we actually send immediately. */
bool is_withdraw;
@@ -238,48 +235,6 @@ static struct command_result *finish_txprepare(struct command *cmd,
return command_finished(cmd, js);
}
/* newaddr has given us a change address. */
static struct command_result *newaddr_done(struct command *cmd,
const char *buf,
const jsmntok_t *result,
struct txprepare *txp)
{
size_t num = tal_count(txp->outputs), pos;
const jsmntok_t *addr = json_get_member(buf, result, "bech32");
/* Insert change in random position in outputs */
tal_resize(&txp->outputs, num+1);
pos = pseudorand(num+1);
memmove(txp->outputs + pos + 1,
txp->outputs + pos,
sizeof(txp->outputs[0]) * (num - pos));
txp->outputs[pos].amount = txp->change_amount;
txp->outputs[pos].is_to_external = false;
if (json_to_address_scriptpubkey(txp, chainparams, buf, addr,
&txp->outputs[pos].script)
!= ADDRESS_PARSE_SUCCESS) {
return command_fail(cmd, LIGHTNINGD,
"Change address '%.*s' unparsable?",
addr->end - addr->start,
buf + addr->start);
}
return finish_txprepare(cmd, txp);
}
static bool resolve_all_output_amount(struct txprepare *txp,
struct amount_sat excess)
{
if (!amount_sat_greater_eq(excess, chainparams->dust_limit))
return false;
assert(amount_sat_eq(txp->outputs[txp->all_output_idx].amount,
AMOUNT_SAT(-1ULL)));
txp->outputs[txp->all_output_idx].amount = excess;
return true;
}
/* fundpsbt/utxopsbt gets a viable PSBT for us. */
static struct command_result *psbt_created(struct command *cmd,
const char *buf,
@@ -287,7 +242,6 @@ static struct command_result *psbt_created(struct command *cmd,
struct txprepare *txp)
{
const jsmntok_t *psbttok;
struct out_req *req;
struct amount_msat excess_msat;
struct amount_sat excess;
u32 weight;
@@ -328,32 +282,12 @@ static struct command_result *psbt_created(struct command *cmd,
result->end - result->start,
buf + result->start);
/* If we have an "all" output, now we can derive its value: excess
* in this case will be total value after inputs paid for themselves. */
/* If we have an "all" output, we now know its value ("excess_msat") */
if (txp->all_output_idx != -1) {
if (!resolve_all_output_amount(txp, excess))
return command_fail(cmd, FUND_CANNOT_AFFORD,
"Insufficient funds to make"
" 'all' output");
/* Never produce change if they asked for all */
excess = AMOUNT_SAT(0);
txp->outputs[txp->all_output_idx].amount = excess;
}
/* So, do we need change? */
txp->change_amount = change_amount(excess, txp->feerate, weight);
if (amount_sat_eq(txp->change_amount, AMOUNT_SAT(0)))
return finish_txprepare(cmd, txp);
/* Ask for a change address */
req = jsonrpc_request_start(cmd->plugin, cmd,
"newaddr",
newaddr_done,
/* It would be nice to unreserve inputs,
* but probably won't happen. */
forward_error,
txp);
return send_outreq(cmd->plugin, req);
return finish_txprepare(cmd, txp);
}
/* Common point for txprepare and withdraw */
@@ -399,6 +333,7 @@ static struct command_result *txprepare_continue(struct command *cmd,
json_add_string(req->js, "satoshi", "all");
json_add_u32(req->js, "startweight", txp->weight);
json_add_bool(req->js, "excess_as_change", true);
json_add_string(req->js, "feerate", feerate);
return send_outreq(cmd->plugin, req);