psbt: methods to mutate psbt in place

add the missing psbt helpers for adding and removing an input and output

bitcoin/Makefile

@@ -7,6 +7,7 @@ BITCOIN_SRC :=					\
 	bitcoin/locktime.c			\
 	bitcoin/preimage.c			\
 	bitcoin/privkey.c			\
+	bitcoin/psbt.c				\
 	bitcoin/pubkey.c			\
 	bitcoin/pullpush.c			\
 	bitcoin/script.c			\
@@ -26,6 +27,7 @@ BITCOIN_HEADERS := bitcoin/address.h		\
 	bitcoin/locktime.h			\
 	bitcoin/preimage.h			\
 	bitcoin/privkey.h			\
+	bitcoin/psbt.h				\
 	bitcoin/pubkey.h			\
 	bitcoin/pullpush.h			\
 	bitcoin/script.h			\

bitcoin/psbt.c

@@ -0,0 +1,90 @@
+#include <assert.h>
+#include <bitcoin/psbt.h>
+#include <ccan/tal/tal.h>
+#include <string.h>
+#include <wally_psbt.h>
+#include <wally_transaction.h>
+
+#define MAKE_ROOM(arr, pos, num)				\
+	memmove((arr) + (pos) + 1, (arr) + (pos),		\
+		sizeof(*(arr)) * ((num) - ((pos) + 1)))
+
+#define REMOVE_ELEM(arr, pos, num)				\
+	memmove((arr) + (pos), (arr) + (pos) + 1,		\
+		sizeof(*(arr)) * ((num) - ((pos) + 1)))
+
+struct wally_psbt_input *psbt_add_input(struct wally_psbt *psbt,
+					struct wally_tx_input *input,
+				       	size_t insert_at)
+{
+	struct wally_tx *tx;
+	struct wally_tx_input tmp_in;
+
+	tx = psbt->tx;
+	assert(insert_at <= tx->num_inputs);
+	wally_tx_add_input(tx, input);
+	tmp_in = tx->inputs[tx->num_inputs - 1];
+	MAKE_ROOM(tx->inputs, insert_at, tx->num_inputs);
+	tx->inputs[insert_at] = tmp_in;
+
+    	if (psbt->inputs_allocation_len < tx->num_inputs) {
+		struct wally_psbt_input *p = tal_arr(psbt, struct wally_psbt_input, tx->num_inputs);
+		memcpy(p, psbt->inputs, sizeof(*psbt->inputs) * psbt->inputs_allocation_len);
+		tal_free(psbt->inputs);
+
+		psbt->inputs = p;
+		psbt->inputs_allocation_len = tx->num_inputs;
+	}
+
+	psbt->num_inputs += 1;
+	MAKE_ROOM(psbt->inputs, insert_at, psbt->num_inputs);
+	memset(&psbt->inputs[insert_at], 0, sizeof(psbt->inputs[insert_at]));
+	return &psbt->inputs[insert_at];
+}
+
+void psbt_rm_input(struct wally_psbt *psbt,
+		   size_t remove_at)
+{
+	assert(remove_at < psbt->tx->num_inputs);
+	wally_tx_remove_input(psbt->tx, remove_at);
+	REMOVE_ELEM(psbt->inputs, remove_at, psbt->num_inputs);
+	psbt->num_inputs -= 1;
+}
+
+struct wally_psbt_output *psbt_add_output(struct wally_psbt *psbt,
+					  struct wally_tx_output *output,
+					  size_t insert_at)
+{
+	struct wally_tx *tx;
+	struct wally_tx_output tmp_out;
+
+	tx = psbt->tx;
+	assert(insert_at <= tx->num_outputs);
+	wally_tx_add_output(tx, output);
+	tmp_out = tx->outputs[tx->num_outputs - 1];
+	MAKE_ROOM(tx->outputs, insert_at, tx->num_outputs);
+	tx->outputs[insert_at] = tmp_out;
+
+    	if (psbt->outputs_allocation_len < tx->num_outputs) {
+		struct wally_psbt_output *p = tal_arr(psbt, struct wally_psbt_output, tx->num_outputs);
+		memcpy(p, psbt->outputs, sizeof(*psbt->outputs) * psbt->outputs_allocation_len);
+		tal_free(psbt->outputs);
+
+		psbt->outputs = p;
+		psbt->outputs_allocation_len = tx->num_outputs;
+	}
+
+	psbt->num_outputs += 1;
+	MAKE_ROOM(psbt->outputs, insert_at, psbt->num_outputs);
+	memset(&psbt->outputs[insert_at], 0, sizeof(psbt->outputs[insert_at]));
+	return &psbt->outputs[insert_at];
+}
+
+void psbt_rm_output(struct wally_psbt *psbt,
+		    size_t remove_at)
+{
+	assert(remove_at < psbt->tx->num_outputs);
+	wally_tx_remove_output(psbt->tx, remove_at);
+	REMOVE_ELEM(psbt->outputs, remove_at, psbt->num_outputs);
+	psbt->num_outputs -= 1;
+}

bitcoin/psbt.h

@@ -0,0 +1,25 @@
+#ifndef LIGHTNING_BITCOIN_PSBT_H
+#define LIGHTNING_BITCOIN_PSBT_H
+#include "config.h"
+#include <stddef.h>
+
+struct wally_tx_input;
+struct wally_tx_output;
+struct wally_psbt;
+struct wally_psbt_input;
+
+struct wally_psbt_input *psbt_add_input(struct wally_psbt *psbt,
+					struct wally_tx_input *input,
+					size_t insert_at);
+
+void psbt_rm_input(struct wally_psbt *psbt,
+		   size_t remove_at);
+
+struct wally_psbt_output *psbt_add_output(struct wally_psbt *psbt,
+					  struct wally_tx_output *output,
+					  size_t insert_at);
+
+void psbt_rm_output(struct wally_psbt *psbt,
+		    size_t remove_at);
+
+#endif /* LIGHTNING_BITCOIN_PSBT_H */

plugins/Makefile

@@ -20,6 +20,7 @@ PLUGIN_LIB_OBJS := $(PLUGIN_LIB_SRC:.c=.o)
 PLUGIN_COMMON_OBJS :=				\
 	bitcoin/base58.o			\
 	bitcoin/privkey.o			\
+	bitcoin/psbt.o				\
 	bitcoin/pubkey.o			\
 	bitcoin/pullpush.o			\
 	bitcoin/script.o			\