psbt: create new_psbt method

Move all psbt creation into single method, new_psbt

note that if a psbt is init'd for a transaction that's
deserialized with scripts etc already attached, then set_global_tx
will fail. instead, we empty all of this out first.

if the tx is being re-init'd from a tx source that had a psbt attached
(e.g. fromwire_) then the script/witness data will get populated
appropriatel from there.

bitcoin/psbt.c

@@ -1,6 +1,7 @@
 #include <assert.h>
 #include <bitcoin/psbt.h>
-#include <ccan/tal/tal.h>
+#include <ccan/cast/cast.h>
+#include <ccan/short_types/short_types.h>
 #include <string.h>
 #include <wally_psbt.h>
 #include <wally_transaction.h>
@@ -13,6 +14,54 @@
 	memmove((arr) + (pos), (arr) + (pos) + 1,		\
 		sizeof(*(arr)) * ((num) - ((pos) + 1)))
 
+void psbt_destroy(struct wally_psbt *psbt)
+{
+	wally_psbt_free(psbt);
+}
+
+struct wally_psbt *new_psbt(const tal_t *ctx, const struct wally_tx *wtx)
+{
+	struct wally_psbt *psbt;
+	int wally_err;
+	u8 **scripts;
+	size_t *script_lens;
+	struct wally_tx_witness_stack **witnesses;
+
+	wally_err = wally_psbt_init_alloc(wtx->num_inputs, wtx->num_outputs, 0, &psbt);
+	assert(wally_err == WALLY_OK);
+	tal_add_destructor(psbt, psbt_destroy);
+
+	/* we can't have scripts on the psbt's global tx,
+	 * so we erase them/stash them until after it's been populated */
+	scripts = tal_arr(NULL, u8 *, wtx->num_inputs);
+	script_lens = tal_arr(NULL, size_t, wtx->num_inputs);
+	witnesses = tal_arr(NULL, struct wally_tx_witness_stack *, wtx->num_inputs);
+	for (size_t i = 0; i < wtx->num_inputs; i++) {
+		scripts[i] = (u8 *)wtx->inputs[i].script;
+		wtx->inputs[i].script = NULL;
+		script_lens[i] = wtx->inputs[i].script_len;
+		wtx->inputs[i].script_len = 0;
+		witnesses[i] = wtx->inputs[i].witness;
+		wtx->inputs[i].witness = NULL;
+	}
+
+	wally_err = wally_psbt_set_global_tx(psbt, cast_const(struct wally_tx *, wtx));
+	assert(wally_err == WALLY_OK);
+
+	/* set the scripts + witnesses back */
+	for (size_t i = 0; i < wtx->num_inputs; i++) {
+		wtx->inputs[i].script = (unsigned char *)scripts[i];
+		wtx->inputs[i].script_len = script_lens[i];
+		wtx->inputs[i].witness = witnesses[i];
+	}
+
+	tal_free(witnesses);
+	tal_free(scripts);
+	tal_free(script_lens);
+
+	return tal_steal(ctx, psbt);
+}
+
 struct wally_psbt_input *psbt_add_input(struct wally_psbt *psbt,
 					struct wally_tx_input *input,
 				       	size_t insert_at)

bitcoin/psbt.h

@@ -1,12 +1,19 @@
 #ifndef LIGHTNING_BITCOIN_PSBT_H
 #define LIGHTNING_BITCOIN_PSBT_H
 #include "config.h"
+#include <ccan/tal/tal.h>
 #include <stddef.h>
 
 struct wally_tx_input;
 struct wally_tx_output;
 struct wally_psbt;
 struct wally_psbt_input;
+struct wally_tx;
+
+void psbt_destroy(struct wally_psbt *psbt);
+
+struct wally_psbt *new_psbt(const tal_t *ctx,
+			    const struct wally_tx *wtx);
 
 struct wally_psbt_input *psbt_add_input(struct wally_psbt *psbt,
 					struct wally_tx_input *input,

bitcoin/test/run-bitcoin_block_from_hex.c

@@ -1,4 +1,5 @@
 #include "../block.c"
+#include "../psbt.c"
 #include "../pullpush.c"
 #include "../shadouble.c"
 #include "../tx.c"
@@ -42,16 +43,6 @@ u8 *fromwire_tal_arrn(const tal_t *ctx UNNEEDED,
 /* Generated stub for fromwire_u16 */
 u16 fromwire_u16(const u8 **cursor UNNEEDED, size_t *max UNNEEDED)
 { fprintf(stderr, "fromwire_u16 called!\n"); abort(); }
-/* Generated stub for psbt_add_input */
-struct wally_psbt_input *psbt_add_input(struct wally_psbt *psbt UNNEEDED,
-					struct wally_tx_input *input UNNEEDED,
-					size_t insert_at UNNEEDED)
-{ fprintf(stderr, "psbt_add_input called!\n"); abort(); }
-/* Generated stub for psbt_add_output */
-struct wally_psbt_output *psbt_add_output(struct wally_psbt *psbt UNNEEDED,
-					  struct wally_tx_output *output UNNEEDED,
-					  size_t insert_at UNNEEDED)
-{ fprintf(stderr, "psbt_add_output called!\n"); abort(); }
 /* Generated stub for towire_amount_sat */
 void towire_amount_sat(u8 **pptr UNNEEDED, const struct amount_sat sat UNNEEDED)
 { fprintf(stderr, "towire_amount_sat called!\n"); abort(); }

bitcoin/test/run-tx-encode.c

@@ -1,4 +1,5 @@
 #include <assert.h>
+#include <bitcoin/psbt.c>
 #include <bitcoin/pullpush.c>
 #include <bitcoin/shadouble.c>
 #include <bitcoin/tx.c>
@@ -43,16 +44,6 @@ u8 *fromwire_tal_arrn(const tal_t *ctx UNNEEDED,
 /* Generated stub for fromwire_u16 */
 u16 fromwire_u16(const u8 **cursor UNNEEDED, size_t *max UNNEEDED)
 { fprintf(stderr, "fromwire_u16 called!\n"); abort(); }
-/* Generated stub for psbt_add_input */
-struct wally_psbt_input *psbt_add_input(struct wally_psbt *psbt UNNEEDED,
-					struct wally_tx_input *input UNNEEDED,
-					size_t insert_at UNNEEDED)
-{ fprintf(stderr, "psbt_add_input called!\n"); abort(); }
-/* Generated stub for psbt_add_output */
-struct wally_psbt_output *psbt_add_output(struct wally_psbt *psbt UNNEEDED,
-					  struct wally_tx_output *output UNNEEDED,
-					  size_t insert_at UNNEEDED)
-{ fprintf(stderr, "psbt_add_output called!\n"); abort(); }
 /* Generated stub for towire_amount_sat */
 void towire_amount_sat(u8 **pptr UNNEEDED, const struct amount_sat sat UNNEEDED)
 { fprintf(stderr, "towire_amount_sat called!\n"); abort(); }

bitcoin/tx.c

@@ -478,7 +478,6 @@ struct bitcoin_tx *bitcoin_tx(const tal_t *ctx,
 			      varint_t input_count, varint_t output_count,
 			      u32 nlocktime)
 {
-	int ret;
 	struct bitcoin_tx *tx = tal(ctx, struct bitcoin_tx);
 	assert(chainparams);
 
@@ -496,11 +495,7 @@ struct bitcoin_tx *bitcoin_tx(const tal_t *ctx,
 	tx->wtx->locktime = nlocktime;
 	tx->wtx->version = 2;
 	tx->chainparams = chainparams;
-
-	ret = wally_psbt_init_alloc(input_count, output_count,
-				    0, &tx->psbt);
-	assert(ret == WALLY_OK);
-	ret = wally_psbt_set_global_tx(tx->psbt, tx->wtx);
+	tx->psbt = new_psbt(tx, tx->wtx);
 
 	return tx;
 }
@@ -519,7 +514,7 @@ struct bitcoin_tx *pull_bitcoin_tx(const tal_t *ctx, const u8 **cursor,
 				   size_t *max)
 {
 	size_t wsize;
-	int flags = WALLY_TX_FLAG_USE_WITNESS, ret;
+	int flags = WALLY_TX_FLAG_USE_WITNESS;
 	struct bitcoin_tx *tx = tal(ctx, struct bitcoin_tx);
 
 	if (chainparams->is_elements)
@@ -546,11 +541,7 @@ struct bitcoin_tx *pull_bitcoin_tx(const tal_t *ctx, const u8 **cursor,
 	    tal_arrz(tx, struct amount_sat *, tx->wtx->inputs_allocation_len);
 	tx->chainparams = chainparams;
 
-	ret = wally_psbt_init_alloc(tx->wtx->num_inputs, tx->wtx->num_outputs,
-				    0, &tx->psbt);
-	assert(ret == WALLY_OK);
-	ret = wally_psbt_set_global_tx(tx->psbt, tx->wtx);
-
+	tx->psbt = new_psbt(tx, tx->wtx);
 
 	*cursor += wsize;
 	*max -= wsize;