wallet: separate datastore access functions for the lightning-downgrade tool to access.

diff --git a/wallet/Makefile b/wallet/Makefile
index 121a2e7..34ea6d4 100644
--- a/wallet/Makefile
+++ b/wallet/Makefile
@@ -2,6 +2,7 @@
 
 WALLET_LIB_SRC :=		\
 	wallet/account_migration.c \
+	wallet/datastore.c 	\
 	wallet/db.c		\
 	wallet/invoices.c	\
 	wallet/migrations.c	\
@@ -34,6 +35,7 @@ WALLET_SQL_FILES := 			\
 	$(DB_SQL_FILES)			\
 	wallet/account_migration.c	\
 	wallet/db.c 			\
+	wallet/datastore.c 		\
 	wallet/invoices.c		\
 	wallet/migrations.c 		\
 	wallet/wallet.c 		\
diff --git a/wallet/datastore.c b/wallet/datastore.c
new file mode 100644
index 0000000..27112a2
--- /dev/null
+++ b/wallet/datastore.c
@@ -0,0 +1,177 @@
+#include "config.h"
+#include <ccan/cast/cast.h>
+#include <ccan/str/str.h>
+#include <ccan/tal/str/str.h>
+#include <db/bindings.h>
+#include <db/common.h>
+#include <db/utils.h>
+#include <wallet/datastore.h>
+#include <wallet/db.h>
+
+/* Does k1 match k2 as far as k2 goes? */
+bool datastore_key_startswith(const char **k1, const char **k2)
+{
+	size_t k1len = tal_count(k1), k2len = tal_count(k2);
+
+	if (k2len > k1len)
+		return false;
+
+	for (size_t i = 0; i < k2len; i++) {
+		if (!streq(k1[i], k2[i]))
+			return false;
+	}
+	return true;
+}
+
+bool datastore_key_eq(const char **k1, const char **k2)
+{
+	return tal_count(k1) == tal_count(k2)
+		&& datastore_key_startswith(k1, k2);
+}
+
+/* We join key parts with nuls for now. */
+void db_bind_datastore_key(struct db_stmt *stmt, const char **key)
+{
+	u8 *joined;
+	size_t len;
+
+	if (tal_count(key) == 1) {
+		db_bind_blob(stmt, (u8 *)key[0], strlen(key[0]));
+		return;
+	}
+
+	len = strlen(key[0]);
+	joined = (u8 *)tal_strdup(tmpctx, key[0]);
+	for (size_t i = 1; i < tal_count(key); i++) {
+		tal_resize(&joined, len + 1 + strlen(key[i]));
+		joined[len] = '\0';
+		memcpy(joined + len + 1, key[i], strlen(key[i]));
+		len += 1 + strlen(key[i]);
+	}
+	db_bind_blob(stmt, joined, len);
+}
+
+u8 *db_datastore_get(const tal_t *ctx,
+		     struct db *db,
+		     const char **key,
+		     u64 *generation)
+{
+	struct db_stmt *stmt;
+	u8 *ret;
+
+	stmt = db_prepare_v2(db,
+			     SQL("SELECT data, generation"
+				 " FROM datastore"
+				 " WHERE key = ?"));
+	db_bind_datastore_key(stmt, key);
+	db_query_prepared(stmt);
+
+	if (!db_step(stmt)) {
+		tal_free(stmt);
+		return NULL;
+	}
+
+	ret = db_col_arr(ctx, stmt, "data", u8);
+	if (generation)
+		*generation = db_col_u64(stmt, "generation");
+	else
+		db_col_ignore(stmt, "generation");
+	tal_free(stmt);
+	return ret;
+}
+
+static const char **db_col_datastore_key(const tal_t *ctx,
+					 struct db_stmt *stmt,
+					 const char *colname)
+{
+	char **key;
+	const u8 *joined = db_col_blob(stmt, colname);
+	size_t len = db_col_bytes(stmt, colname);
+
+	key = tal_arr(ctx, char *, 0);
+	do {
+		size_t partlen;
+		for (partlen = 0; partlen < len; partlen++) {
+			if (joined[partlen] == '\0') {
+				partlen++;
+				break;
+			}
+		}
+		tal_arr_expand(&key, tal_strndup(key, (char *)joined, partlen));
+		len -= partlen;
+		joined += partlen;
+	} while (len != 0);
+
+	return cast_const2(const char **, key);
+}
+
+struct db_stmt *db_datastore_next(const tal_t *ctx,
+				  struct db_stmt *stmt,
+				  const char **startkey,
+				  const char ***key,
+				  const u8 **data,
+				  u64 *generation)
+{
+	if (!db_step(stmt))
+		return tal_free(stmt);
+
+	*key = db_col_datastore_key(ctx, stmt, "key");
+
+	/* We select from startkey onwards, so once we're past it, stop */
+	if (startkey && !datastore_key_startswith(*key, startkey)) {
+		db_col_ignore(stmt, "data");
+		db_col_ignore(stmt, "generation");
+		return tal_free(stmt);
+	}
+
+	if (data)
+		*data = db_col_arr(ctx, stmt, "data", u8);
+	else
+		db_col_ignore(stmt, "data");
+
+	if (generation)
+		*generation = db_col_u64(stmt, "generation");
+	else
+		db_col_ignore(stmt, "generation");
+
+	return stmt;
+}
+
+struct db_stmt *db_datastore_first(const tal_t *ctx,
+				   struct db *db,
+				   const char **startkey,
+				   const char ***key,
+				   const u8 **data,
+				   u64 *generation)
+{
+	struct db_stmt *stmt;
+
+	if (startkey) {
+		stmt = db_prepare_v2(db,
+				     SQL("SELECT key, data, generation"
+					 " FROM datastore"
+					 " WHERE key >= ?"
+					 " ORDER BY key;"));
+		db_bind_datastore_key(stmt, startkey);
+	} else {
+		stmt = db_prepare_v2(db,
+				     SQL("SELECT key, data, generation"
+					 " FROM datastore"
+					 " ORDER BY key;"));
+	}
+	db_query_prepared(stmt);
+
+	return db_datastore_next(ctx, stmt, startkey, key, data, generation);
+}
+
+void db_datastore_update(struct db *db, const char **key, const u8 *data)
+{
+	struct db_stmt *stmt;
+
+	stmt = db_prepare_v2(db,
+			     SQL("UPDATE datastore SET data=?, generation=generation+1 WHERE key=?;"));
+	db_bind_talarr(stmt, data);
+	db_bind_datastore_key(stmt, key);
+	db_exec_prepared_v2(take(stmt));
+}
+
diff --git a/wallet/datastore.h b/wallet/datastore.h
new file mode 100644
index 0000000..3b96f35
--- /dev/null
+++ b/wallet/datastore.h
@@ -0,0 +1,37 @@
+#ifndef LIGHTNING_WALLET_DATASTORE_H
+#define LIGHTNING_WALLET_DATASTORE_H
+/* Access routines for the datastore: here so that tools/lightningd-downgrade
+ * can use them */
+#include "config.h"
+#include <ccan/short_types/short_types.h>
+#include <ccan/tal/tal.h>
+#include <stdbool.h>
+
+struct db;
+struct db_stmt;
+
+/* Does k1 match k2 as far as k2 goes? */
+bool datastore_key_startswith(const char **k1, const char **k2);
+bool datastore_key_eq(const char **k1, const char **k2);
+void db_bind_datastore_key(struct db_stmt *stmt, const char **key);
+u8 *db_datastore_get(const tal_t *ctx,
+		     struct db *db,
+		     const char **key,
+		     u64 *generation);
+struct db_stmt *db_datastore_next(const tal_t *ctx,
+				  struct db_stmt *stmt,
+				  const char **startkey,
+				  const char ***key,
+				  const u8 **data,
+				  u64 *generation);
+
+struct db_stmt *db_datastore_first(const tal_t *ctx,
+				   struct db *db,
+				   const char **startkey,
+				   const char ***key,
+				   const u8 **data,
+				   u64 *generation);
+
+/* Update existing record */
+void db_datastore_update(struct db *db, const char **key, const u8 *data);
+#endif /* LIGHTNING_WALLET_DATASTORE_H */
diff --git a/wallet/test/run-chain_moves_duplicate-detect.c b/wallet/test/run-chain_moves_duplicate-detect.c
index 6fecac0..428768d 100644
--- a/wallet/test/run-chain_moves_duplicate-detect.c
+++ b/wallet/test/run-chain_moves_duplicate-detect.c
@@ -21,6 +21,7 @@ static void db_log_(struct logger *log UNUSED, enum log_level level UNUSED, cons
 #include "db/db_sqlite3.c"
 #include "db/exec.c"
 #include "db/utils.c"
+#include "wallet/datastore.c"
 #include "wallet/db.c"
 #include "wallet/migrations.c"
 #include "common/coin_mvt.c"
diff --git a/wallet/test/run-db.c b/wallet/test/run-db.c
index 4a62354..c1b4cb1 100644
--- a/wallet/test/run-db.c
+++ b/wallet/test/run-db.c
@@ -10,6 +10,7 @@ static void db_log_(struct logger *log UNUSED, enum log_level level UNUSED, cons
 #include "db/db_sqlite3.c"
 #include "db/exec.c"
 #include "db/utils.c"
+#include "wallet/datastore.c"
 #include "wallet/db.c"
 #include "wallet/wallet.c"
 #include "wallet/migrations.c"
diff --git a/wallet/test/run-migrate_remove_chain_moves_duplicates.c b/wallet/test/run-migrate_remove_chain_moves_duplicates.c
index 029851a..2bb792e 100644
--- a/wallet/test/run-migrate_remove_chain_moves_duplicates.c
+++ b/wallet/test/run-migrate_remove_chain_moves_duplicates.c
@@ -78,6 +78,34 @@ void connect_htlc_in(struct htlc_in_map *map UNNEEDED, struct htlc_in *hin UNNEE
 /* Generated stub for connect_htlc_out */
 void connect_htlc_out(struct htlc_out_map *map UNNEEDED, struct htlc_out *hout UNNEEDED)
 { fprintf(stderr, "connect_htlc_out called!\n"); abort(); }
+/* Generated stub for db_bind_datastore_key */
+void db_bind_datastore_key(struct db_stmt *stmt UNNEEDED, const char **key UNNEEDED)
+{ fprintf(stderr, "db_bind_datastore_key called!\n"); abort(); }
+/* Generated stub for db_datastore_first */
+struct db_stmt *db_datastore_first(const tal_t *ctx UNNEEDED,
+				   struct db *db UNNEEDED,
+				   const char **startkey UNNEEDED,
+				   const char ***key UNNEEDED,
+				   const u8 **data UNNEEDED,
+				   u64 *generation UNNEEDED)
+{ fprintf(stderr, "db_datastore_first called!\n"); abort(); }
+/* Generated stub for db_datastore_get */
+u8 *db_datastore_get(const tal_t *ctx UNNEEDED,
+		     struct db *db UNNEEDED,
+		     const char **key UNNEEDED,
+		     u64 *generation UNNEEDED)
+{ fprintf(stderr, "db_datastore_get called!\n"); abort(); }
+/* Generated stub for db_datastore_next */
+struct db_stmt *db_datastore_next(const tal_t *ctx UNNEEDED,
+				  struct db_stmt *stmt UNNEEDED,
+				  const char **startkey UNNEEDED,
+				  const char ***key UNNEEDED,
+				  const u8 **data UNNEEDED,
+				  u64 *generation UNNEEDED)
+{ fprintf(stderr, "db_datastore_next called!\n"); abort(); }
+/* Generated stub for db_datastore_update */
+void db_datastore_update(struct db *db UNNEEDED, const char **key UNNEEDED, const u8 *data UNNEEDED)
+{ fprintf(stderr, "db_datastore_update called!\n"); abort(); }
 /* Generated stub for fatal */
 void   fatal(const char *fmt UNNEEDED, ...)
 { fprintf(stderr, "fatal called!\n"); abort(); }
diff --git a/wallet/test/run-wallet.c b/wallet/test/run-wallet.c
index 35efcb8..69b1414 100644
--- a/wallet/test/run-wallet.c
+++ b/wallet/test/run-wallet.c
@@ -35,6 +35,7 @@ static void test_error(struct lightningd *ld, bool fatal, const char *fmt, va_li
 #include "db/db_sqlite3.c"
 #include "db/exec.c"
 #include "db/utils.c"
+#include "wallet/datastore.c"
 #include "wallet/db.c"
 #include "wallet/migrations.c"
 
diff --git a/wallet/wallet.c b/wallet/wallet.c
index 2e3421c..c6a272a 100644
--- a/wallet/wallet.c
+++ b/wallet/wallet.c
@@ -24,6 +24,7 @@
 #include <lightningd/peer_htlcs.h>
 #include <lightningd/runes.h>
 #include <onchaind/onchaind_wiregen.h>
+#include <wallet/datastore.h>
 #include <wallet/invoices.h>
 #include <wallet/migrations.h>
 #include <wallet/txfilter.h>
@@ -6333,63 +6334,9 @@ void wallet_invoice_request_mark_used(struct db *db, const struct sha256 *invreq
 	}
 }
 
-/* We join key parts with nuls for now. */
-static void db_bind_datastore_key(struct db_stmt *stmt,
-				  const char **key)
-{
-	u8 *joined;
-	size_t len;
-
-	if (tal_count(key) == 1) {
-		db_bind_blob(stmt, (u8 *)key[0], strlen(key[0]));
-		return;
-	}
-
-	len = strlen(key[0]);
-	joined = (u8 *)tal_strdup(tmpctx, key[0]);
-	for (size_t i = 1; i < tal_count(key); i++) {
-		tal_resize(&joined, len + 1 + strlen(key[i]));
-		joined[len] = '\0';
-		memcpy(joined + len + 1, key[i], strlen(key[i]));
-		len += 1 + strlen(key[i]);
-	}
-	db_bind_blob(stmt, joined, len);
-}
-
-static const char **db_col_datastore_key(const tal_t *ctx,
-					 struct db_stmt *stmt,
-					 const char *colname)
-{
-	char **key;
-	const u8 *joined = db_col_blob(stmt, colname);
-	size_t len = db_col_bytes(stmt, colname);
-
-	key = tal_arr(ctx, char *, 0);
-	do {
-		size_t partlen;
-		for (partlen = 0; partlen < len; partlen++) {
-			if (joined[partlen] == '\0') {
-				partlen++;
-				break;
-			}
-		}
-		tal_arr_expand(&key, tal_strndup(key, (char *)joined, partlen));
-		len -= partlen;
-		joined += partlen;
-	} while (len != 0);
-
-	return cast_const2(const char **, key);
-}
-
 void wallet_datastore_update(struct wallet *w, const char **key, const u8 *data)
 {
-	struct db_stmt *stmt;
-
-	stmt = db_prepare_v2(w->db,
-			     SQL("UPDATE datastore SET data=?, generation=generation+1 WHERE key=?;"));
-	db_bind_talarr(stmt, data);
-	db_bind_datastore_key(stmt, key);
-	db_exec_prepared_v2(take(stmt));
+	db_datastore_update(w->db, key, data);
 }
 
 static void db_datastore_create(struct db *db, const char **key, const u8 *data)
@@ -6458,56 +6405,6 @@ void wallet_datastore_remove(struct wallet *w, const char **key)
 	db_datastore_remove(w->db, key);
 }
 
-/* Does k1 match k2 as far as k2 goes? */
-bool datastore_key_startswith(const char **k1, const char **k2)
-{
-	size_t k1len = tal_count(k1), k2len = tal_count(k2);
-
-	if (k2len > k1len)
-		return false;
-
-	for (size_t i = 0; i < k2len; i++) {
-		if (!streq(k1[i], k2[i]))
-			return false;
-	}
-	return true;
-}
-
-bool datastore_key_eq(const char **k1, const char **k2)
-{
-	return tal_count(k1) == tal_count(k2)
-		&& datastore_key_startswith(k1, k2);
-}
-
-static u8 *db_datastore_get(const tal_t *ctx,
-			    struct db *db,
-			    const char **key,
-			    u64 *generation)
-{
-	struct db_stmt *stmt;
-	u8 *ret;
-
-	stmt = db_prepare_v2(db,
-			     SQL("SELECT data, generation"
-				 " FROM datastore"
-				 " WHERE key = ?"));
-	db_bind_datastore_key(stmt, key);
-	db_query_prepared(stmt);
-
-	if (!db_step(stmt)) {
-		tal_free(stmt);
-		return NULL;
-	}
-
-	ret = db_col_arr(ctx, stmt, "data", u8);
-	if (generation)
-		*generation = db_col_u64(stmt, "generation");
-	else
-		db_col_ignore(stmt, "generation");
-	tal_free(stmt);
-	return ret;
-}
-
 u8 *wallet_datastore_get(const tal_t *ctx,
 			 struct wallet *w,
 			 const char **key,
@@ -6516,65 +6413,6 @@ u8 *wallet_datastore_get(const tal_t *ctx,
 	return db_datastore_get(ctx, w->db, key, generation);
 }
 
-static struct db_stmt *db_datastore_next(const tal_t *ctx,
-					 struct db_stmt *stmt,
-					 const char **startkey,
-					 const char ***key,
-					 const u8 **data,
-					 u64 *generation)
-{
-	if (!db_step(stmt))
-		return tal_free(stmt);
-
-	*key = db_col_datastore_key(ctx, stmt, "key");
-
-	/* We select from startkey onwards, so once we're past it, stop */
-	if (startkey && !datastore_key_startswith(*key, startkey)) {
-		db_col_ignore(stmt, "data");
-		db_col_ignore(stmt, "generation");
-		return tal_free(stmt);
-	}
-
-	if (data)
-		*data = db_col_arr(ctx, stmt, "data", u8);
-	else
-		db_col_ignore(stmt, "data");
-
-	if (generation)
-		*generation = db_col_u64(stmt, "generation");
-	else
-		db_col_ignore(stmt, "generation");
-
-	return stmt;
-}
-
-static struct db_stmt *db_datastore_first(const tal_t *ctx,
-					  struct db *db,
-					  const char **startkey,
-					  const char ***key,
-					  const u8 **data,
-					  u64 *generation)
-{
-	struct db_stmt *stmt;
-
-	if (startkey) {
-		stmt = db_prepare_v2(db,
-				     SQL("SELECT key, data, generation"
-					 " FROM datastore"
-					 " WHERE key >= ?"
-					 " ORDER BY key;"));
-		db_bind_datastore_key(stmt, startkey);
-	} else {
-		stmt = db_prepare_v2(db,
-				     SQL("SELECT key, data, generation"
-					 " FROM datastore"
-					 " ORDER BY key;"));
-	}
-	db_query_prepared(stmt);
-
-	return db_datastore_next(ctx, stmt, startkey, key, data, generation);
-}
-
 struct db_stmt *wallet_datastore_first(const tal_t *ctx,
 				       struct wallet *w,
 				       const char **startkey,