Merge branch 'master' of ssh://taler.net:/var/git/exchange

1 files changed, 1445 insertions, 0 deletions

diff --git a/src/include/taler_exchangedb_plugin.h b/src/include/taler_exchangedb_plugin.h
new file mode 100644
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--- /dev/null
+++ b/src/include/taler_exchangedb_plugin.h
@@ -0,0 +1,1445 @@
+/*
+  This file is part of TALER
+  Copyright (C) 2014, 2015, 2016 GNUnet e.V.
+
+  TALER is free software; you can redistribute it and/or modify it under the
+  terms of the GNU General Public License as published by the Free Software
+  Foundation; either version 3, or (at your option) any later version.
+
+  TALER is distributed in the hope that it will be useful, but WITHOUT ANY
+  WARRANTY; without even the implied warranty of MERCHANTABILITY or FITNESS FOR
+  A PARTICULAR PURPOSE.  See the GNU General Public License for more details.
+
+  You should have received a copy of the GNU General Public License along with
+  TALER; see the file COPYING.  If not, If not, see <http://www.gnu.org/licenses/>
+*/
+/**
+ * @file include/taler_exchangedb_plugin.h
+ * @brief Low-level (statement-level) database access for the exchange
+ * @author Florian Dold
+ * @author Christian Grothoff
+ */
+#ifndef TALER_EXCHANGEDB_PLUGIN_H
+#define TALER_EXCHANGEDB_PLUGIN_H
+
+#include <jansson.h>
+#include <gnunet/gnunet_util_lib.h>
+#include "taler_exchangedb_lib.h"
+
+
+/**
+ * @brief Information we keep on bank transfer(s) that established a reserve.
+ */
+struct TALER_EXCHANGEDB_BankTransfer
+{
+
+  /**
+   * Public key of the reserve that was filled.
+   */
+  struct TALER_ReservePublicKeyP reserve_pub;
+
+  /**
+   * Amount that was transferred to the exchange.
+   */
+  struct TALER_Amount amount;
+
+  /**
+   * When did the exchange receive the incoming transaction?
+   * (This is the execution date of the exchange's database,
+   * the execution date of the bank should be in @e wire).
+   */
+  struct GNUNET_TIME_Absolute execution_date;
+
+  /**
+   * Detailed wire information about the transaction.
+   */
+  json_t *wire;
+
+};
+
+
+/**
+ * @brief A summary of a Reserve
+ */
+struct TALER_EXCHANGEDB_Reserve
+{
+  /**
+   * The reserve's public key.  This uniquely identifies the reserve
+   */
+  struct TALER_ReservePublicKeyP pub;
+
+  /**
+   * The balance amount existing in the reserve
+   */
+  struct TALER_Amount balance;
+
+  /**
+   * The expiration date of this reserve
+   */
+  struct GNUNET_TIME_Absolute expiry;
+};
+
+
+/**
+ * @brief Information we keep for a withdrawn coin to reproduce
+ * the /withdraw operation if needed, and to have proof
+ * that a reserve was drained by this amount.
+ */
+struct TALER_EXCHANGEDB_CollectableBlindcoin
+{
+
+  /**
+   * Our signature over the (blinded) coin.
+   */
+  struct TALER_DenominationSignature sig;
+
+  /**
+   * Denomination key (which coin was generated).
+   */
+  struct TALER_DenominationPublicKey denom_pub;
+
+  /**
+   * Value of the coin being exchangeed (matching the denomination key)
+   * plus the transaction fee.  We include this in what is being
+   * signed so that we can verify a reserve's remaining total balance
+   * without needing to access the respective denomination key
+   * information each time.
+   */
+  struct TALER_Amount amount_with_fee;
+
+  /**
+   * Withdrawl fee charged by the exchange.  This must match the Exchange's
+   * denomination key's withdrawl fee.  If the client puts in an
+   * invalid withdrawl fee (too high or too low) that does not match
+   * the Exchange's denomination key, the withdraw operation is invalid
+   * and will be rejected by the exchange.  The @e amount_with_fee minus
+   * the @e withdraw_fee is must match the value of the generated
+   * coin.  We include this in what is being signed so that we can
+   * verify a exchange's accounting without needing to access the
+   * respective denomination key information each time.
+   */
+  struct TALER_Amount withdraw_fee;
+
+  /**
+   * Public key of the reserve that was drained.
+   */
+  struct TALER_ReservePublicKeyP reserve_pub;
+
+  /**
+   * Hash over the blinded message, needed to verify
+   * the @e reserve_sig.
+   */
+  struct GNUNET_HashCode h_coin_envelope;
+
+  /**
+   * Signature confirming the withdrawl, matching @e reserve_pub,
+   * @e denom_pub and @e h_coin_envelope.
+   */
+  struct TALER_ReserveSignatureP reserve_sig;
+};
+
+
+
+/**
+ * @brief Types of operations on a reserved.
+ */
+enum TALER_EXCHANGEDB_ReserveOperation
+{
+  /**
+   * Money was deposited into the reserve via a bank transfer.
+   */
+  TALER_EXCHANGEDB_RO_BANK_TO_EXCHANGE = 0,
+
+  /**
+   * A Coin was withdrawn from the reserve using /withdraw.
+   */
+  TALER_EXCHANGEDB_RO_WITHDRAW_COIN = 1
+};
+
+
+/**
+ * @brief Reserve history as a linked list.  Lists all of the transactions
+ * associated with this reserve (such as the bank transfers that
+ * established the reserve and all /withdraw operations we have done
+ * since).
+ */
+struct TALER_EXCHANGEDB_ReserveHistory
+{
+
+  /**
+   * Next entry in the reserve history.
+   */
+  struct TALER_EXCHANGEDB_ReserveHistory *next;
+
+  /**
+   * Type of the event, determins @e details.
+   */
+  enum TALER_EXCHANGEDB_ReserveOperation type;
+
+  /**
+   * Details of the operation, depending on @e type.
+   */
+  union
+  {
+
+    /**
+     * Details about a bank transfer to the exchange.
+     */
+    struct TALER_EXCHANGEDB_BankTransfer *bank;
+
+    /**
+     * Details about a /withdraw operation.
+     */
+    struct TALER_EXCHANGEDB_CollectableBlindcoin *withdraw;
+
+  } details;
+
+};
+
+
+/**
+ * @brief Specification for a /deposit operation.  The combination of
+ * the coin's public key, the merchant's public key and the
+ * transaction ID must be unique.  While a coin can (theoretically) be
+ * deposited at the same merchant twice (with partial spending), the
+ * merchant must either use a different public key or a different
+ * transaction ID for the two transactions.  The same coin must not
+ * be used twice at the same merchant for the same transaction
+ * (as determined by transaction ID).  (Note: we might want to
+ * fix #3819 and include at least h_contract as well.)
+ */
+struct TALER_EXCHANGEDB_Deposit
+{
+  /**
+   * Information about the coin that is being deposited.
+   */
+  struct TALER_CoinPublicInfo coin;
+
+  /**
+   * ECDSA signature affirming that the customer intends
+   * this coin to be deposited at the merchant identified
+   * by @e h_wire in relation to the contract identified
+   * by @e h_contract.
+   */
+  struct TALER_CoinSpendSignatureP csig;
+
+  /**
+   * Public key of the merchant.  Enables later identification
+   * of the merchant in case of a need to rollback transactions.
+   */
+  struct TALER_MerchantPublicKeyP merchant_pub;
+
+  /**
+   * Hash over the contract between merchant and customer
+   * (remains unknown to the Exchange).
+   */
+  struct GNUNET_HashCode h_contract;
+
+  /**
+   * Hash of the (canonical) representation of @e wire, used
+   * to check the signature on the request.  Generated by
+   * the exchange from the detailed wire data provided by the
+   * merchant.
+   */
+  struct GNUNET_HashCode h_wire;
+
+  /**
+   * Detailed wire information for executing the transaction.
+   */
+  json_t *wire;
+
+  /**
+   * Merchant-generated transaction ID to detect duplicate
+   * transactions.
+   */
+  uint64_t transaction_id;
+
+  /**
+   * Time when this request was generated.  Used, for example, to
+   * assess when (roughly) the income was achieved for tax purposes.
+   * Note that the Exchange will only check that the timestamp is not "too
+   * far" into the future (i.e. several days).  The fact that the
+   * timestamp falls within the validity period of the coin's
+   * denomination key is irrelevant for the validity of the deposit
+   * request, as obviously the customer and merchant could conspire to
+   * set any timestamp.  Also, the Exchange must accept very old deposit
+   * requests, as the merchant might have been unable to transmit the
+   * deposit request in a timely fashion (so back-dating is not
+   * prevented).
+   */
+  struct GNUNET_TIME_Absolute timestamp;
+
+  /**
+   * How much time does the merchant have to issue a refund request?
+   * Zero if refunds are not allowed.  After this time, the coin
+   * cannot be refunded.
+   */
+  struct GNUNET_TIME_Absolute refund_deadline;
+
+  /**
+   * How much time does the merchant have to execute the wire transfer?
+   * This time is advisory for aggregating transactions, not a hard
+   * constraint (as the merchant can theoretically pick any time,
+   * including one in the past).
+   */
+  struct GNUNET_TIME_Absolute wire_deadline;
+
+  /**
+   * Fraction of the coin's remaining value to be deposited, including
+   * depositing fee (if any).  The coin is identified by @e coin_pub.
+   */
+  struct TALER_Amount amount_with_fee;
+
+  /**
+   * Depositing fee.
+   */
+  struct TALER_Amount deposit_fee;
+
+};
+
+
+/**
+ * @brief Global information for a refreshing session.  Includes
+ * dimensions of the operation, security parameters and
+ * client signatures from "/refresh/melt" and "/refresh/commit".
+ */
+struct TALER_EXCHANGEDB_RefreshSession
+{
+
+  /**
+   * Number of coins we are melting.
+   */
+  uint16_t num_oldcoins;
+
+  /**
+   * Number of new coins we are creating.
+   */
+  uint16_t num_newcoins;
+
+  /**
+   * Index (smaller #TALER_CNC_KAPPA) which the exchange has chosen to not
+   * have revealed during cut and choose.
+   */
+  uint16_t noreveal_index;
+
+};
+
+
+/**
+ * @brief Specification for coin in a /refresh/melt operation.
+ */
+struct TALER_EXCHANGEDB_RefreshMelt
+{
+  /**
+   * Information about the coin that is being melted.
+   */
+  struct TALER_CoinPublicInfo coin;
+
+  /**
+   * Signature over the melting operation.
+   */
+  struct TALER_CoinSpendSignatureP coin_sig;
+
+  /**
+   * Hash of the refresh session this coin is melted into.
+   */
+  struct GNUNET_HashCode session_hash;
+
+  /**
+   * How much value is being melted?  This amount includes the fees,
+   * so the final amount contributed to the melt is this value minus
+   * the fee for melting the coin.  We include the fee in what is
+   * being signed so that we can verify a reserve's remaining total
+   * balance without needing to access the respective denomination key
+   * information each time.
+   */
+  struct TALER_Amount amount_with_fee;
+
+  /**
+   * Melting fee charged by the exchange.  This must match the Exchange's
+   * denomination key's melting fee.  If the client puts in an invalid
+   * melting fee (too high or too low) that does not match the Exchange's
+   * denomination key, the melting operation is invalid and will be
+   * rejected by the exchange.  The @e amount_with_fee minus the @e
+   * melt_fee is the amount that will be credited to the melting
+   * session.
+   */
+  struct TALER_Amount melt_fee;
+
+};
+
+
+/**
+ * @brief We have as many `struct TALER_EXCHANGEDB_RefreshCommitCoin` as there are new
+ * coins being created by the refresh (for each of the #TALER_CNC_KAPPA
+ * sets).  These are the coins we ask the exchange to sign if the
+ * respective set is selected.
+ */
+struct TALER_EXCHANGEDB_RefreshCommitCoin
+{
+
+  /**
+   * Encrypted data allowing those able to decrypt it to derive
+   * the private keys of the new coins created by the refresh.
+   */
+  struct TALER_RefreshLinkEncrypted *refresh_link;
+
+  /**
+   * Blinded message to be signed (in envelope), with @e coin_env_size bytes.
+   */
+  char *coin_ev;
+
+  /**
+   * Number of bytes in @e coin_ev.
+   */
+  size_t coin_ev_size;
+
+};
+
+
+/**
+ * @brief Linked list of refresh information linked to a coin.
+ */
+struct TALER_EXCHANGEDB_LinkDataList
+{
+  /**
+   * Information is stored in a NULL-terminated linked list.
+   */
+  struct TALER_EXCHANGEDB_LinkDataList *next;
+
+  /**
+   * Link data, used to recover the private key of the coin
+   * by the owner of the old coin.
+   */
+  struct TALER_RefreshLinkEncrypted *link_data_enc;
+
+  /**
+   * Denomination public key, determines the value of the coin.
+   */
+  struct TALER_DenominationPublicKey denom_pub;
+
+  /**
+   * Signature over the blinded envelope.
+   */
+  struct TALER_DenominationSignature ev_sig;
+};
+
+
+/**
+ * @brief Enumeration to classify the different types of transactions
+ * that can be done with a coin.
+ */
+enum TALER_EXCHANGEDB_TransactionType
+{
+  /**
+   * /deposit operation.
+   */
+  TALER_EXCHANGEDB_TT_DEPOSIT = 0,
+
+  /**
+   * /refresh/melt operation.
+   */
+  TALER_EXCHANGEDB_TT_REFRESH_MELT = 1
+
+};
+
+
+/**
+ * @brief List of transactions we performed for a particular coin.
+ */
+struct TALER_EXCHANGEDB_TransactionList
+{
+
+  /**
+   * Next pointer in the NULL-terminated linked list.
+   */
+  struct TALER_EXCHANGEDB_TransactionList *next;
+
+  /**
+   * Type of the transaction, determines what is stored in @e details.
+   */
+  enum TALER_EXCHANGEDB_TransactionType type;
+
+  /**
+   * Details about the transaction, depending on @e type.
+   */
+  union
+  {
+
+    /**
+     * Details if transaction was a /deposit operation.
+     */
+    struct TALER_EXCHANGEDB_Deposit *deposit;
+
+    /**
+     * Details if transaction was a /refresh/melt operation.
+     */
+    struct TALER_EXCHANGEDB_RefreshMelt *melt;
+
+  } details;
+
+};
+
+
+/**
+ * @brief All of the information from a /refresh/melt commitment.
+ */
+struct TALER_EXCHANGEDB_MeltCommitment
+{
+
+  /**
+   * Number of coins we are melting.
+   */
+  uint16_t num_oldcoins;
+
+  /**
+   * Number of new coins we are creating.
+   */
+  uint16_t num_newcoins;
+
+  /**
+   * Array of @e num_oldcoins melt operation details.
+   */
+  struct TALER_EXCHANGEDB_RefreshMelt *melts;
+
+  /**
+   * Array of @e num_newcoins denomination keys
+   */
+  struct TALER_DenominationPublicKey *denom_pubs;
+
+  /**
+   * 2D-Array of #TALER_CNC_KAPPA and @e num_newcoins commitments.
+   */
+  struct TALER_EXCHANGEDB_RefreshCommitCoin *commit_coins[TALER_CNC_KAPPA];
+
+  /**
+   * 2D-Array of #TALER_CNC_KAPPA and @e new_oldcoins links.
+   */
+  struct TALER_RefreshCommitLinkP *commit_links[TALER_CNC_KAPPA];
+};
+
+
+/**
+ * @brief Handle for a database session (per-thread, for transactions).
+ */
+struct TALER_EXCHANGEDB_Session;
+
+
+/**
+ * Function called with details about deposits that
+ * have been made, with the goal of executing the
+ * corresponding wire transaction.
+ *
+ * @param cls closure
+ * @param rowid unique ID for the deposit in our DB, used for marking
+ *              it as 'tiny' or 'done'
+ * @param merchant_pub public key of the merchant
+ * @param coin_pub public key of the coin
+ * @param amount_with_fee amount that was deposited including fee
+ * @param deposit_fee amount the exchange gets to keep as transaction fees
+ * @param transaction_id unique transaction ID chosen by the merchant
+ * @param h_contract hash of the contract between merchant and customer
+ * @param wire_deadline by which the merchant adviced that he would like the
+ *        wire transfer to be executed
+ * @param wire wire details for the merchant, NULL from iterate_matching_deposits()
+ * @return #GNUNET_OK to continue to iterate, #GNUNET_SYSERR to stop
+ */
+typedef int
+(*TALER_EXCHANGEDB_DepositIterator)(void *cls,
+                                    unsigned long long rowid,
+                                    const struct TALER_MerchantPublicKeyP *merchant_pub,
+                                    const struct TALER_CoinSpendPublicKeyP *coin_pub,
+                                    const struct TALER_Amount *amount_with_fee,
+                                    const struct TALER_Amount *deposit_fee,
+                                    uint64_t transaction_id,
+                                    const struct GNUNET_HashCode *h_contract,
+                                    struct GNUNET_TIME_Absolute wire_deadline,
+                                    const json_t *wire);
+
+
+/**
+ * Function called with the session hashes and transfer secret
+ * information for a given coin.
+ *
+ * @param cls closure
+ * @param session_hash a session the coin was melted in
+ * @param transfer_pub public transfer key for the session
+ * @param shared_secret_enc set to shared secret for the session
+ */
+typedef void
+(*TALER_EXCHANGEDB_TransferDataCallback)(void *cls,
+                                         const struct GNUNET_HashCode *session_hash,
+                                         const struct TALER_TransferPublicKeyP *transfer_pub,
+                                         const struct TALER_EncryptedLinkSecretP *shared_secret_enc);
+
+
+/**
+ * Function called with the results of the lookup of the
+ * wire transfer identifier information.  Only called if
+ * we are at least aware of the transaction existing.
+ *
+ * @param cls closure
+ * @param wtid wire transfer identifier, NULL
+ *         if the transaction was not yet done
+ * @param coin_contribution how much did the coin we asked about
+ *        contribute to the total transfer value? (deposit value including fee)
+ * @param coin_fee how much did the exchange charge for the deposit fee
+ * @param execution_time when was the transaction done, or
+ *         when we expect it to be done (if @a wtid was NULL)
+ */
+typedef void
+(*TALER_EXCHANGEDB_DepositWtidCallback)(void *cls,
+                                        const struct TALER_WireTransferIdentifierRawP *wtid,
+                                        const struct TALER_Amount *coin_contribution,
+                                        const struct TALER_Amount *coin_fee,
+                                        struct GNUNET_TIME_Absolute execution_time);
+
+
+/**
+ * Function called with the results of the lookup of the
+ * transaction data associated with a wire transfer identifier.
+ *
+ * @param cls closure
+ * @param merchant_pub public key of the merchant (should be same for all callbacks with the same @e cls)
+ * @param h_wire hash of wire transfer details of the merchant (should be same for all callbacks with the same @e cls)
+ * @param h_contract which contract was this payment about
+ * @param transaction_id merchant's transaction ID for the payment
+ * @param coin_pub which public key was this payment about
+ * @param coin_value amount contributed by this coin in total (with fee)
+ * @param coin_fee applicable fee for this coin
+ */
+typedef void
+(*TALER_EXCHANGEDB_WireTransferDataCallback)(void *cls,
+                                             const struct TALER_MerchantPublicKeyP *merchant_pub,
+                                             const struct GNUNET_HashCode *h_wire,
+                                             const struct GNUNET_HashCode *h_contract,
+                                             uint64_t transaction_id,
+                                             const struct TALER_CoinSpendPublicKeyP *coin_pub,
+                                             const struct TALER_Amount *coin_value,
+                                             const struct TALER_Amount *coin_fee);
+
+
+/**
+ * Callback with data about a prepared transaction.
+ *
+ * @param cls closure
+ * @param rowid row identifier used to mark prepared transaction as done
+ * @param buf transaction data that was persisted, NULL on error
+ * @param buf_size number of bytes in @a buf, 0 on error
+ */
+typedef void
+(*TALER_EXCHANGEDB_WirePreparationCallback) (void *cls,
+                                             unsigned long long rowid,
+                                             const char *buf,
+                                             size_t buf_size);
+
+
+/**
+ * @brief The plugin API, returned from the plugin's "init" function.
+ * The argument given to "init" is simply a configuration handle.
+ */
+struct TALER_EXCHANGEDB_Plugin
+{
+
+  /**
+   * Closure for all callbacks.
+   */
+  void *cls;
+
+  /**
+   * Name of the library which generated this plugin.  Set by the
+   * plugin loader.
+   */
+  char *library_name;
+
+  /**
+   * Get the thread-local database-handle.
+   * Connect to the db if the connection does not exist yet.
+   *
+   * @param cls the @e cls of this struct with the plugin-specific state
+   * @param temporary #GNUNET_YES to use a temporary schema; #GNUNET_NO to use the
+   *        database default one
+   * @param the database connection, or NULL on error
+   */
+  struct TALER_EXCHANGEDB_Session *
+  (*get_session) (void *cls,
+                  int temporary);
+
+
+  /**
+   * Drop the temporary taler schema.  This is only useful for testcases.
+   *
+   * @param cls the @e cls of this struct with the plugin-specific state
+   * @return #GNUNET_OK upon success; #GNUNET_SYSERR upon failure
+   */
+  int
+  (*drop_temporary) (void *cls,
+                     struct TALER_EXCHANGEDB_Session *db);
+
+
+  /**
+   * Create the necessary tables if they are not present
+   *
+   * @param cls the @e cls of this struct with the plugin-specific state
+   * @param temporary should we use a temporary schema
+   * @return #GNUNET_OK upon success; #GNUNET_SYSERR upon failure
+   */
+  int
+  (*create_tables) (void *cls,
+                    int temporary);
+
+
+  /**
+   * Start a transaction.
+   *
+   * @param cls the @e cls of this struct with the plugin-specific state
+   * @param session connection to use
+   * @return #GNUNET_OK on success
+   */
+  int
+  (*start) (void *cls,
+            struct TALER_EXCHANGEDB_Session *session);
+
+
+  /**
+   * Commit a transaction.
+   *
+   * @param cls the @e cls of this struct with the plugin-specific state
+   * @param session connection to use
+   * @return #GNUNET_OK on success, #GNUNET_NO if the transaction
+   *         can be retried, #GNUNET_SYSERR on hard failures
+   */
+  int
+  (*commit) (void *cls,
+             struct TALER_EXCHANGEDB_Session *session);
+
+
+  /**
+   * Abort/rollback a transaction.
+   *
+   * @param cls the @e cls of this struct with the plugin-specific state
+   * @param session connection to use
+   */
+  void
+  (*rollback) (void *cls,
+               struct TALER_EXCHANGEDB_Session *session);
+
+
+  /**
+   * Insert information about a denomination key and in particular
+   * the properties (value, fees, expiration times) the coins signed
+   * with this key have.
+   *
+   * @param cls the @e cls of this struct with the plugin-specific state
+   * @param session connection to use
+   * @param denom_pub the public key used for signing coins of this denomination
+   * @param issue issuing information with value, fees and other info about the coin
+   * @return #GNUNET_OK on success; #GNUNET_SYSERR on failure
+   */
+  int
+  (*insert_denomination_info) (void *cls,
+                               struct TALER_EXCHANGEDB_Session *session,
+                               const struct TALER_DenominationPublicKey *denom_pub,
+                               const struct TALER_EXCHANGEDB_DenominationKeyInformationP *issue);
+
+
+  /**
+   * Fetch information about a denomination key.
+   *
+   * @param cls the @e cls of this struct with the plugin-specific state
+   * @param session connection to use
+   * @param denom_pub the public key used for signing coins of this denomination
+   * @param[out] issue set to issue information with value, fees and other info about the coin, can be NULL
+   * @return #GNUNET_OK on success; #GNUNET_NO if no record was found, #GNUNET_SYSERR on failure
+   */
+  int
+  (*get_denomination_info) (void *cls,
+                            struct TALER_EXCHANGEDB_Session *session,
+                            const struct TALER_DenominationPublicKey *denom_pub,
+                            struct TALER_EXCHANGEDB_DenominationKeyInformationP *issue);
+
+
+  /**
+   * Get the summary of a reserve.
+   *
+   * @param cls the @e cls of this struct with the plugin-specific state
+   * @param db the database connection handle
+   * @param[in,out] reserve the reserve data.  The public key of the reserve should be set
+   *          in this structure; it is used to query the database.  The balance
+   *          and expiration are then filled accordingly.
+   * @return #GNUNET_OK upon success; #GNUNET_SYSERR upon failure
+   */
+  int
+  (*reserve_get) (void *cls,
+                  struct TALER_EXCHANGEDB_Session *db,
+                  struct TALER_EXCHANGEDB_Reserve *reserve);
+
+
+  /**
+   * Insert a incoming transaction into reserves.  New reserves are
+   * also created through this function.  Note that this API call
+   * starts (and stops) its own transaction scope (so the application
+   * must not do so).
+   *
+   * @param cls the @e cls of this struct with the plugin-specific state
+   * @param db the database connection handle
+   * @param reserve_pub public key of the reserve
+   * @param balance the amount that has to be added to the reserve
+   * @param execution_time when was the amount added
+   * @param details bank transaction details justifying the increment,
+   *        must be unique for each incoming transaction
+   * @return #GNUNET_OK upon success; #GNUNET_NO if the given
+   *         @a details are already known for this @a reserve_pub,
+   *         #GNUNET_SYSERR upon failures (DB error, incompatible currency)
+   */
+  int
+  (*reserves_in_insert) (void *cls,
+                         struct TALER_EXCHANGEDB_Session *db,
+                         const struct TALER_ReservePublicKeyP *reserve_pub,
+                         const struct TALER_Amount *balance,
+                         struct GNUNET_TIME_Absolute execution_time,
+                         const json_t *details);
+
+
+  /**
+   * Locate the response for a /withdraw request under the
+   * key of the hash of the blinded message.
+   *
+   * @param cls the @e cls of this struct with the plugin-specific state
+   * @param session database connection to use
+   * @param h_blind hash of the blinded coin to be signed (will match
+   *                `h_coin_envelope` in the @a collectable to be returned)
+   * @param collectable corresponding collectable coin (blind signature)
+   *                    if a coin is found
+   * @return #GNUNET_SYSERR on internal error
+   *         #GNUNET_NO if the collectable was not found
+   *         #GNUNET_YES on success
+   */
+  int
+  (*get_withdraw_info) (void *cls,
+                        struct TALER_EXCHANGEDB_Session *session,
+                        const struct GNUNET_HashCode *h_blind,
+                        struct TALER_EXCHANGEDB_CollectableBlindcoin *collectable);
+
+
+  /**
+   * Store collectable bit coin under the corresponding
+   * hash of the blinded message.
+   *
+   * @param cls the @e cls of this struct with the plugin-specific state
+   * @param session database connection to use
+   * @param collectable corresponding collectable coin (blind signature)
+   *                    if a coin is found
+   * @return #GNUNET_SYSERR on internal error
+   *         #GNUNET_NO if the collectable was not found
+   *         #GNUNET_YES on success
+   */
+  int
+  (*insert_withdraw_info) (void *cls,
+                           struct TALER_EXCHANGEDB_Session *session,
+                           const struct TALER_EXCHANGEDB_CollectableBlindcoin *collectable);
+
+
+  /**
+   * Get all of the transaction history associated with the specified
+   * reserve.
+   *
+   * @param cls the @e cls of this struct with the plugin-specific state
+   * @param session connection to use
+   * @param reserve_pub public key of the reserve
+   * @return known transaction history (NULL if reserve is unknown)
+   */
+  struct TALER_EXCHANGEDB_ReserveHistory *
+  (*get_reserve_history) (void *cls,
+                          struct TALER_EXCHANGEDB_Session *session,
+                          const struct TALER_ReservePublicKeyP *reserve_pub);
+
+
+  /**
+   * Free memory associated with the given reserve history.
+   *
+   * @param cls the @e cls of this struct with the plugin-specific state
+   * @param rh history to free.
+   */
+  void
+  (*free_reserve_history) (void *cls,
+                           struct TALER_EXCHANGEDB_ReserveHistory *rh);
+
+
+  /**
+   * Check if we have the specified deposit already in the database.
+   *
+   * @param cls the @e cls of this struct with the plugin-specific state
+   * @param session database connection
+   * @param deposit deposit to search for
+   * @return #GNUNET_YES if we know this operation,
+   *         #GNUNET_NO if this exact deposit is unknown to us,
+   *         #GNUNET_SYSERR on DB error
+   */
+  int
+  (*have_deposit) (void *cls,
+                   struct TALER_EXCHANGEDB_Session *session,
+                   const struct TALER_EXCHANGEDB_Deposit *deposit);
+
+
+  /**
+   * Insert information about deposited coin into the database.
+   *
+   * @param cls the @e cls of this struct with the plugin-specific state
+   * @param session connection to the database
+   * @param deposit deposit information to store
+   * @return #GNUNET_OK on success, #GNUNET_SYSERR on error
+   */
+  int
+  (*insert_deposit) (void *cls,
+                     struct TALER_EXCHANGEDB_Session *session,
+                     const struct TALER_EXCHANGEDB_Deposit *deposit);
+
+
+  /**
+   * Mark a deposit as tiny, thereby declaring that it cannot be
+   * executed by itself and should no longer be returned by
+   * @e iterate_ready_deposits()
+   *
+   * @param cls the @e cls of this struct with the plugin-specific state
+   * @param session connection to the database
+   * @param deposit_rowid identifies the deposit row to modify
+   * @return #GNUNET_OK on success, #GNUNET_SYSERR on error
+   */
+  int
+  (*mark_deposit_tiny) (void *cls,
+                        struct TALER_EXCHANGEDB_Session *session,
+                        unsigned long long rowid);
+
+
+  /**
+   * Mark a deposit as done, thereby declaring that it cannot be
+   * executed at all anymore, and should no longer be returned by
+   * @e iterate_ready_deposits() or @e iterate_matching_deposits().
+   *
+   * @param cls the @e cls of this struct with the plugin-specific state
+   * @param session connection to the database
+   * @param deposit_rowid identifies the deposit row to modify
+   * @return #GNUNET_OK on success, #GNUNET_SYSERR on error
+   */
+  int
+  (*mark_deposit_done) (void *cls,
+                        struct TALER_EXCHANGEDB_Session *session,
+                        unsigned long long rowid);
+
+
+  /**
+   * Obtain information about deposits that are ready to be executed.
+   * Such deposits must not be marked as "tiny" or "done", and the
+   * execution time must be in the past.
+   *
+   * @param cls the @e cls of this struct with the plugin-specific state
+   * @param session connection to the database
+   * @param deposit_cb function to call for ONE such deposit
+   * @param deposit_cb_cls closure for @a deposit_cb
+   * @return number of rows processed, 0 if none exist,
+   *         #GNUNET_SYSERR on error
+   */
+  int
+  (*get_ready_deposit) (void *cls,
+                        struct TALER_EXCHANGEDB_Session *session,
+                        TALER_EXCHANGEDB_DepositIterator deposit_cb,
+                        void *deposit_cb_cls);
+
+
+/**
+ * Maximum number of results we return from iterate_matching_deposits().
+ *
+ * Limit on the number of transactions we aggregate at once.  Note
+ * that the limit must be big enough to ensure that when transactions
+ * of the smallest possible unit are aggregated, they do surpass the
+ * "tiny" threshold beyond which we never trigger a wire transaction!
+ */
+#define TALER_EXCHANGEDB_MATCHING_DEPOSITS_LIMIT 10000
+#define TALER_EXCHANGEDB_MATCHING_DEPOSITS_LIMIT_STR "10000"
+
+  /**
+   * Obtain information about other pending deposits for the same
+   * destination.  Those deposits must not already be "done".
+   *
+   * @param cls the @e cls of this struct with the plugin-specific state
+   * @param session connection to the database
+   * @param h_wire destination of the wire transfer
+   * @param merchant_pub public key of the merchant
+   * @param deposit_cb function to call for each deposit
+   * @param deposit_cb_cls closure for @a deposit_cb
+   * @param limit maximum number of matching deposits to return; should
+   *        be #TALER_EXCHANGEDB_MATCHING_DEPOSITS_LIMIT, larger values
+   *        are not supported, smaller values would be inefficient.
+   * @return number of rows processed, 0 if none exist,
+   *         #GNUNET_SYSERR on error
+   */
+  int
+  (*iterate_matching_deposits) (void *cls,
+                                struct TALER_EXCHANGEDB_Session *session,
+                                const struct GNUNET_HashCode *h_wire,
+                                const struct TALER_MerchantPublicKeyP *merchant_pub,
+                                TALER_EXCHANGEDB_DepositIterator deposit_cb,
+                                void *deposit_cb_cls,
+                                uint32_t limit);
+
+
+  /**
+   * Lookup refresh session data under the given @a session_hash.
+   *
+   * @param cls the @e cls of this struct with the plugin-specific state
+   * @param session database handle to use
+   * @param session_hash hash over the melt to use for the lookup
+   * @param[out] refresh_session where to store the result
+   * @return #GNUNET_YES on success,
+   *         #GNUNET_NO if not found,
+   *         #GNUNET_SYSERR on DB failure
+   */
+  int
+  (*get_refresh_session) (void *cls,
+                          struct TALER_EXCHANGEDB_Session *session,
+                          const struct GNUNET_HashCode *session_hash,
+                          struct TALER_EXCHANGEDB_RefreshSession *refresh_session);
+
+
+  /**
+   * Store new refresh session data under the given @a session_hash.
+   *
+   * @param cls the @e cls of this struct with the plugin-specific state
+   * @param session database handle to use
+   * @param session_hash hash over the melt to use to locate the session
+   * @param refresh_session session data to store
+   * @return #GNUNET_YES on success,
+   *         #GNUNET_SYSERR on DB failure
+   */
+  int
+  (*create_refresh_session) (void *cls,
+                             struct TALER_EXCHANGEDB_Session *session,
+                             const struct GNUNET_HashCode *session_hash,
+                             const struct TALER_EXCHANGEDB_RefreshSession *refresh_session);
+
+
+  /**
+   * Store the given /refresh/melt request in the database.
+   *
+   * @param cls the @e cls of this struct with the plugin-specific state
+   * @param session database connection
+   * @param oldcoin_index index of the coin to store
+   * @param melt coin melt operation details to store; includes
+   *             the session hash of the melt
+   * @return #GNUNET_OK on success
+   *         #GNUNET_SYSERR on internal error
+   */
+  int
+  (*insert_refresh_melt) (void *cls,
+                          struct TALER_EXCHANGEDB_Session *session,
+                          uint16_t oldcoin_index,
+                          const struct TALER_EXCHANGEDB_RefreshMelt *melt);
+
+
+  /**
+   * Get information about melted coin details from the database.
+   *
+   * @param cls the @e cls of this struct with the plugin-specific state
+   * @param session database connection
+   * @param session_hash hash to identify refresh session
+   * @param oldcoin_index index of the coin to retrieve
+   * @param melt melt data to fill in, can be NULL
+   * @return #GNUNET_OK on success
+   *         #GNUNET_SYSERR on internal error
+   */
+  int
+  (*get_refresh_melt) (void *cls,
+                       struct TALER_EXCHANGEDB_Session *session,
+                       const struct GNUNET_HashCode *session_hash,
+                       uint16_t oldcoin_index,
+                       struct TALER_EXCHANGEDB_RefreshMelt *melt);
+
+
+  /**
+   * Store in the database which coin(s) we want to create
+   * in a given refresh operation.
+   *
+   * @param cls the @e cls of this struct with the plugin-specific state
+   * @param session database connection
+   * @param session_hash hash to identify refresh session
+   * @param num_newcoins number of coins to generate, size of the @a denom_pubs array
+   * @param denom_pubs array denominations of the coins to create
+   * @return #GNUNET_OK on success
+   *         #GNUNET_SYSERR on internal error
+   */
+  int
+  (*insert_refresh_order) (void *cls,
+                           struct TALER_EXCHANGEDB_Session *session,
+                           const struct GNUNET_HashCode *session_hash,
+                           uint16_t num_newcoins,
+                           const struct TALER_DenominationPublicKey *denom_pubs);
+
+
+  /**
+   * Lookup in the database for the @a num_newcoins coins that we want to
+   * create in the given refresh operation.
+   *
+   * @param cls the @e cls of this struct with the plugin-specific state
+   * @param session database connection
+   * @param session_hash hash to identify refresh session
+   * @param num_newcoins size of the @a denom_pubs array
+   * @param[out] denom_pubs where to write @a num_newcoins denomination keys
+   * @return #GNUNET_OK on success
+   *         #GNUNET_SYSERR on internal error
+   */
+  int
+  (*get_refresh_order) (void *cls,
+                        struct TALER_EXCHANGEDB_Session *session,
+                        const struct GNUNET_HashCode *session_hash,
+                        uint16_t num_newcoins,
+                        struct TALER_DenominationPublicKey *denom_pubs);
+
+
+  /**
+   * Store information about the commitments of the given index @a i
+   * for the given refresh session in the database.
+   *
+   * @param cls the @e cls of this struct with the plugin-specific state
+   * @param session database connection to use
+   * @param session_hash hash to identify refresh session
+   * @param cnc_index cut and choose index (1st dimension), relating to #TALER_CNC_KAPPA
+   * @param num_newcoins coin index size of the @a commit_coins array
+   * @param commit_coin array of coin commitments to store
+   * @return #GNUNET_OK on success
+   *         #GNUNET_SYSERR on error
+   */
+  int
+  (*insert_refresh_commit_coins) (void *cls,
+                                  struct TALER_EXCHANGEDB_Session *session,
+                                  const struct GNUNET_HashCode *session_hash,
+                                  uint16_t cnc_index,
+                                  uint16_t num_newcoins,
+                                  const struct TALER_EXCHANGEDB_RefreshCommitCoin *commit_coins);
+
+
+  /**
+   * Obtain information about the commitment of the
+   * given coin of the given refresh session from the database.
+   *
+   * @param cls the @e cls of this struct with the plugin-specific state
+   * @param session database connection to use
+   * @param session_hash hash to identify refresh session
+   * @param cnc_index cut and choose set index (1st dimension)
+   * @param num_coins size of the @a commit_coins array
+   * @param[out] commit_coins array of coin commitments to return
+   * @return #GNUNET_OK on success
+   *         #GNUNET_NO if not found
+   *         #GNUNET_SYSERR on error
+   */
+  int
+  (*get_refresh_commit_coins) (void *cls,
+                               struct TALER_EXCHANGEDB_Session *session,
+                               const struct GNUNET_HashCode *session_hash,
+                               uint16_t cnc_index,
+                               uint16_t num_coins,
+                               struct TALER_EXCHANGEDB_RefreshCommitCoin *commit_coins);
+
+
+  /**
+   * Store the commitment to the given (encrypted) refresh link data
+   * for the given refresh session.
+   *
+   * @param cls the @e cls of this struct with the plugin-specific state
+   * @param session database connection to use
+   * @param session_hash hash to identify refresh session
+   * @param cnc_index cut and choose index (1st dimension), relating to #TALER_CNC_KAPPA
+   * @param num_links size of the @a commit_link array
+   * @param commit_links array of link information to store
+   * @return #GNUNET_SYSERR on internal error, #GNUNET_OK on success
+   */
+  int
+  (*insert_refresh_commit_links) (void *cls,
+                                  struct TALER_EXCHANGEDB_Session *session,
+                                  const struct GNUNET_HashCode *session_hash,
+                                  uint16_t cnc_index,
+                                  uint16_t num_links,
+                                  const struct TALER_RefreshCommitLinkP *commit_links);
+
+  /**
+   * Obtain the commited (encrypted) refresh link data
+   * for the given refresh session.
+   *
+   * @param cls the @e cls of this struct with the plugin-specific state
+   * @param session database connection to use
+   * @param session_hash hash to identify refresh session
+   * @param cnc_index cut and choose index (1st dimension)
+   * @param num_links size of the @a links array to return
+   * @param[out] links array link information to return
+   * @return #GNUNET_SYSERR on internal error,
+   *         #GNUNET_NO if commitment was not found
+   *         #GNUNET_OK on success
+   */
+  int
+  (*get_refresh_commit_links) (void *cls,
+                               struct TALER_EXCHANGEDB_Session *session,
+                               const struct GNUNET_HashCode *session_hash,
+                               uint16_t cnc_index,
+                               uint16_t num_links,
+                               struct TALER_RefreshCommitLinkP *links);
+
+
+  /**
+   * Get all of the information from the given melt commit operation.
+   *
+   * @param cls the @e cls of this struct with the plugin-specific state
+   * @param session database connection to use
+   * @param session_hash hash to identify refresh session
+   * @return NULL if the @a session_hash does not correspond to any known melt
+   *         operation
+   */
+  struct TALER_EXCHANGEDB_MeltCommitment *
+  (*get_melt_commitment) (void *cls,
+                          struct TALER_EXCHANGEDB_Session *session,
+                          const struct GNUNET_HashCode *session_hash);
+
+
+  /**
+   * Free information about a melt commitment.
+   *
+   * @param cls the @e cls of this struct with the plugin-specific state
+   * @param mc melt commitment data to free
+   */
+  void
+  (*free_melt_commitment) (void *cls,
+                           struct TALER_EXCHANGEDB_MeltCommitment *mc);
+
+
+  /**
+   * Insert signature of a new coin generated during refresh into
+   * the database indexed by the refresh session and the index
+   * of the coin.  This data is later used should an old coin
+   * be used to try to obtain the private keys during "/refresh/link".
+   *
+   * @param cls the @e cls of this struct with the plugin-specific state
+   * @param session database connection
+   * @param session_hash hash to identify refresh session
+   * @param newcoin_index coin index
+   * @param ev_sig coin signature
+   * @return #GNUNET_OK on success
+   */
+  int
+  (*insert_refresh_out) (void *cls,
+                         struct TALER_EXCHANGEDB_Session *session,
+                         const struct GNUNET_HashCode *session_hash,
+                         uint16_t newcoin_index,
+                         const struct TALER_DenominationSignature *ev_sig);
+
+
+  /**
+   * Obtain the link data of a coin, that is the encrypted link
+   * information, the denomination keys and the signatures.
+   *
+   * @param cls the @e cls of this struct with the plugin-specific state
+   * @param session database connection
+   * @param session_hash session to get linkage data for
+   * @return all known link data for the session
+   */
+  struct TALER_EXCHANGEDB_LinkDataList *
+  (*get_link_data_list) (void *cls,
+                         struct TALER_EXCHANGEDB_Session *session,
+                         const struct GNUNET_HashCode *session_hash);
+
+
+  /**
+   * Free memory of the link data list.
+   *
+   * @param cls the @e cls of this struct with the plugin-specific state
+   * @param ldl link data list to release
+   */
+  void
+  (*free_link_data_list) (void *cls,
+                          struct TALER_EXCHANGEDB_LinkDataList *ldl);
+
+
+  /**
+   * Obtain shared secret and transfer public key from the public key of
+   * the coin.  This information and the link information returned by
+   * @e get_link_data_list() enable the owner of an old coin to determine
+   * the private keys of the new coins after the melt.
+   *
+   *
+   * @param cls the @e cls of this struct with the plugin-specific state
+   * @param session database connection
+   * @param coin_pub public key of the coin
+   * @param tdc function to call for each session the coin was melted into
+   * @param tdc_cls closure for @a tdc
+   * @return #GNUNET_OK on success,
+   *         #GNUNET_NO on failure (not found)
+   *         #GNUNET_SYSERR on internal failure (database issue)
+   */
+  int
+  (*get_transfer) (void *cls,
+                   struct TALER_EXCHANGEDB_Session *session,
+                   const struct TALER_CoinSpendPublicKeyP *coin_pub,
+                   TALER_EXCHANGEDB_TransferDataCallback tdc,
+                   void *tdc_cls);
+
+
+  /**
+   * Compile a list of all (historic) transactions performed
+   * with the given coin (/refresh/melt and /deposit operations).
+   *
+   * @param cls the @e cls of this struct with the plugin-specific state
+   * @param session database connection
+   * @param coin_pub coin to investigate
+   * @return list of transactions, NULL if coin is fresh
+   */
+  struct TALER_EXCHANGEDB_TransactionList *
+  (*get_coin_transactions) (void *cls,
+                            struct TALER_EXCHANGEDB_Session *session,
+                            const struct TALER_CoinSpendPublicKeyP *coin_pub);
+
+
+  /**
+   * Free linked list of transactions.
+   *
+   * @param cls the @e cls of this struct with the plugin-specific state
+   * @param list list to free
+   */
+  void
+  (*free_coin_transaction_list) (void *cls,
+                                 struct TALER_EXCHANGEDB_TransactionList *list);
+
+
+  /**
+   * Lookup the list of Taler transactions that was aggregated
+   * into a wire transfer by the respective @a raw_wtid.
+   *
+   * @param cls the @e cls of this struct with the plugin-specific state
+   * @param session database connection
+   * @param wtid the raw wire transfer identifier we used
+   * @param cb function to call on each transaction found
+   * @param cb_cls closure for @a cb
+   * @return #GNUNET_OK on success, #GNUNET_SYSERR on database errors,
+   *         #GNUNET_NO if we found no results
+   */
+  int
+  (*lookup_wire_transfer) (void *cls,
+                           struct TALER_EXCHANGEDB_Session *session,
+                           const struct TALER_WireTransferIdentifierRawP *wtid,
+                           TALER_EXCHANGEDB_WireTransferDataCallback cb,
+                           void *cb_cls);
+
+
+  /**
+   * Try to find the wire transfer details for a deposit operation.
+   * If we did not execute the deposit yet, return when it is supposed
+   * to be executed.
+   *
+   * @param cls closure
+   * @param session database connection
+   * @param h_contract hash of the contract
+   * @param h_wire hash of merchant wire details
+   * @param coin_pub public key of deposited coin
+   * @param merchant_pub merchant public key
+   * @param transaction_id transaction identifier
+   * @param cb function to call with the result
+   * @param cb_cls closure to pass to @a cb
+   * @return #GNUNET_OK on success, #GNUNET_SYSERR on DB errors,
+   *         #GNUNET_NO if nothing was found
+   */
+  int
+  (*wire_lookup_deposit_wtid)(void *cls,
+                              struct TALER_EXCHANGEDB_Session *session,
+			      const struct GNUNET_HashCode *h_contract,
+			      const struct GNUNET_HashCode *h_wire,
+			      const struct TALER_CoinSpendPublicKeyP *coin_pub,
+			      const struct TALER_MerchantPublicKeyP *merchant_pub,
+			      uint64_t transaction_id,
+			      TALER_EXCHANGEDB_DepositWtidCallback cb,
+			      void *cb_cls);
+
+
+  /**
+   * Function called to insert aggregation information into the DB.
+   *
+   * @param cls closure
+   * @param session database connection
+   * @param wtid the raw wire transfer identifier we used
+   * @param merchant_pub public key of the merchant (should be same for all callbacks with the same @e cls)
+   * @param h_wire hash of wire transfer details of the merchant (should be same for all callbacks with the same @e cls)
+   * @param h_contract which contract was this payment about
+   * @param transaction_id merchant's transaction ID for the payment
+   * @param execution_time when did we execute the transaction
+   * @param coin_pub which public key was this payment about
+   * @param coin_value amount contributed by this coin in total
+   * @param coin_fee deposit fee charged by exchange for this coin
+   * @return #GNUNET_OK on success, #GNUNET_SYSERR on DB errors
+   */
+  int
+  (*insert_aggregation_tracking)(void *cls,
+                                 struct TALER_EXCHANGEDB_Session *session,
+                                 const struct TALER_WireTransferIdentifierRawP *wtid,
+                                 const struct TALER_MerchantPublicKeyP *merchant_pub,
+                                 const struct GNUNET_HashCode *h_wire,
+                                 const struct GNUNET_HashCode *h_contract,
+                                 uint64_t transaction_id,
+                                 struct GNUNET_TIME_Absolute execution_time,
+                                 const struct TALER_CoinSpendPublicKeyP *coin_pub,
+                                 const struct TALER_Amount *coin_value,
+                                 const struct TALER_Amount *coin_fee);
+
+
+  /**
+   * Function called to insert wire transfer commit data into the DB.
+   *
+   * @param cls closure
+   * @param session database connection
+   * @param type type of the wire transfer (i.e. "sepa")
+   * @param buf buffer with wire transfer preparation data
+   * @param buf_size number of bytes in @a buf
+   * @return #GNUNET_OK on success, #GNUNET_SYSERR on DB errors
+   */
+  int
+  (*wire_prepare_data_insert)(void *cls,
+                              struct TALER_EXCHANGEDB_Session *session,
+                              const char *type,
+                              const char *buf,
+                              size_t buf_size);
+
+
+  /**
+   * Function called to mark wire transfer commit data as finished.
+   *
+   * @param cls closure
+   * @param session database connection
+   * @param rowid which entry to mark as finished
+   * @return #GNUNET_OK on success, #GNUNET_SYSERR on DB errors
+   */
+  int
+  (*wire_prepare_data_mark_finished)(void *cls,
+                                     struct TALER_EXCHANGEDB_Session *session,
+                                     unsigned long long rowid);
+
+
+  /**
+   * Function called to get an unfinished wire transfer
+   * preparation data. Fetches at most one item.
+   *
+   * @param cls closure
+   * @param session database connection
+   * @param type type fo the wire transfer (i.e. "sepa")
+   * @param cb function to call for ONE unfinished item
+   * @param cb_cls closure for @a cb
+   * @return #GNUNET_OK on success,
+   *         #GNUNET_NO if there are no entries,
+   *         #GNUNET_SYSERR on DB errors
+   */
+  int
+  (*wire_prepare_data_get)(void *cls,
+                           struct TALER_EXCHANGEDB_Session *session,
+                           const char *type,
+                           TALER_EXCHANGEDB_WirePreparationCallback cb,
+                           void *cb_cls);
+
+
+};
+
+
+#endif /* _TALER_EXCHANGE_DB_H */