438 lines
12 KiB
C
438 lines
12 KiB
C
/*
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This file is part of TALER
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Copyright (C) 2014, 2015, 2020 Taler Systems SA
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TALER is free software; you can redistribute it and/or modify it under the
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terms of the GNU General Public License as published by the Free Software
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Foundation; either version 3, or (at your option) any later version.
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TALER is distributed in the hope that it will be useful, but WITHOUT ANY
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WARRANTY; without even the implied warranty of MERCHANTABILITY or FITNESS FOR
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A PARTICULAR PURPOSE. See the GNU General Public License for more details.
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You should have received a copy of the GNU General Public License along with
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TALER; see the file COPYING. If not, see <http://www.gnu.org/licenses/>
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*/
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/**
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* @file include/taler_amount_lib.h
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* @brief amount-representation utility functions
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* @author Sree Harsha Totakura <sreeharsha@totakura.in>
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*/
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#ifndef TALER_AMOUNT_LIB_H
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#define TALER_AMOUNT_LIB_H
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#ifdef __cplusplus
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extern "C"
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{
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#if 0 /* keep Emacsens' auto-indent happy */
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}
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#endif
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#endif
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/**
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* @brief Number of characters (plus 1 for 0-termination) we use to
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* represent currency names (i.e. EUR, USD, etc.). We use 8+4 for
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* alignment in the `struct TALER_Amount`. The amount is typically an
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* ISO 4217 currency code when an alphanumeric 3-digit code is used.
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* For regional currencies, the first character should be a "*" followed
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* by a region-specific name (i.e. "*BRETAGNEFR").
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*/
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#define TALER_CURRENCY_LEN 12
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/**
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* Taler currency length as a string.
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*/
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#define TALER_CURRENCY_LEN_STR "12"
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/**
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* @brief The "fraction" value in a `struct TALER_Amount` represents which
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* fraction of the "main" value?
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*
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* Note that we need sub-cent precision here as transaction fees might
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* be that low, and as we want to support microdonations.
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*
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* An actual `struct Amount a` thus represents
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* "a.value + (a.fraction / #TALER_AMOUNT_FRAC_BASE)" units of "a.currency".
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*/
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#define TALER_AMOUNT_FRAC_BASE 100000000
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/**
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* @brief How many digits behind the comma are required to represent the
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* fractional value in human readable decimal format? Must match
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* lg(#TALER_AMOUNT_FRAC_BASE).
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*/
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#define TALER_AMOUNT_FRAC_LEN 8
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/**
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* Maximum legal 'value' for an amount, based on IEEE double (for JavaScript compatibility).
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*/
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#define TALER_AMOUNT_MAX_VALUE (1LLU << 52)
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GNUNET_NETWORK_STRUCT_BEGIN
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/**
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* @brief Amount, encoded for network transmission.
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*/
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struct TALER_AmountNBO
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{
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/**
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* Value in the main currency, in NBO.
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*/
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uint64_t value GNUNET_PACKED;
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/**
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* Fraction (integer multiples of #TALER_AMOUNT_FRAC_BASE), in NBO.
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*/
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uint32_t fraction GNUNET_PACKED;
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/**
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* Type of the currency being represented.
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*/
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char currency[TALER_CURRENCY_LEN];
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};
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GNUNET_NETWORK_STRUCT_END
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/**
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* @brief Representation of monetary value in a given currency.
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*/
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struct TALER_Amount
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{
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/**
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* Value (numerator of fraction)
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*/
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uint64_t value;
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/**
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* Fraction (integer multiples of #TALER_AMOUNT_FRAC_BASE).
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*/
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uint32_t fraction;
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/**
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* Currency string, left adjusted and padded with zeros. All zeros
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* for "invalid" values.
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*/
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char currency[TALER_CURRENCY_LEN];
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};
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/**
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* Parse monetary amount, in the format "T:V.F".
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*
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* @param str amount string
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* @param[out] amount amount to write the result to
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* @return #GNUNET_OK if the string is a valid monetary amount specification,
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* #GNUNET_SYSERR if it is invalid.
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*/
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enum GNUNET_GenericReturnValue
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TALER_string_to_amount (const char *str,
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struct TALER_Amount *amount);
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/**
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* Parse monetary amount, in the format "T:V.F".
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* The result is stored in network byte order (NBO).
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*
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* @param str amount string
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* @param[out] amount_nbo amount to write the result to
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* @return #GNUNET_OK if the string is a valid amount specification,
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* #GNUNET_SYSERR if it is invalid.
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*/
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enum GNUNET_GenericReturnValue
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TALER_string_to_amount_nbo (const char *str,
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struct TALER_AmountNBO *amount_nbo);
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/**
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* Get the value of "zero" in a particular currency.
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*
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* @param cur currency description
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* @param[out] amount amount to write the result to
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* @return #GNUNET_OK if @a cur is a valid currency specification,
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* #GNUNET_SYSERR if it is invalid.
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*/
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enum GNUNET_GenericReturnValue
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TALER_amount_set_zero (const char *cur,
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struct TALER_Amount *amount);
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/**
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* Test if the given @a amount is zero.
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*
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* @param amount amount to compare to zero
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* @return true if the amount is zero,
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* false if it is non-zero or invalid
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*/
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bool
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TALER_amount_is_zero (const struct TALER_Amount *amount);
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/**
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* Test if the given amount is valid.
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*
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* @param amount amount to check
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* @return #GNUNET_OK if @a amount is valid
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*/
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enum GNUNET_GenericReturnValue
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TALER_amount_is_valid (const struct TALER_Amount *amount);
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/**
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* Convert amount from host to network representation.
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*
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* @param[out] res where to store amount in network representation
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* @param d amount in host representation
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*/
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void
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TALER_amount_hton (struct TALER_AmountNBO *res,
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const struct TALER_Amount *d);
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/**
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* Convert amount from network to host representation.
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*
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* @param[out] res where to store amount in host representation
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* @param dn amount in network representation
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*/
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void
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TALER_amount_ntoh (struct TALER_Amount *res,
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const struct TALER_AmountNBO *dn);
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/**
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* Compare the value/fraction of two amounts. Does not compare the currency.
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* Comparing amounts of different currencies will cause the program to abort().
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* If unsure, check with #TALER_amount_cmp_currency() first to be sure that
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* the currencies of the two amounts are identical.
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*
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* @param a1 first amount
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* @param a2 second amount
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* @return result of the comparison
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* -1 if `a1 < a2`
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* 1 if `a1 > a2`
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* 0 if `a1 == a2`.
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*/
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int
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TALER_amount_cmp (const struct TALER_Amount *a1,
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const struct TALER_Amount *a2);
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/**
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* Compare the value/fraction of two amounts. Does not compare the currency.
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* Comparing amounts of different currencies will cause the program to abort().
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* If unsure, check with #TALER_amount_cmp_currency() first to be sure that
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* the currencies of the two amounts are identical. NBO variant.
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*
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* @param a1 first amount
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* @param a2 second amount
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* @return result of the comparison
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* -1 if `a1 < a2`
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* 1 if `a1 > a2`
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* 0 if `a1 == a2`.
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*/
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int
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TALER_amount_cmp_nbo (const struct TALER_AmountNBO *a1,
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const struct TALER_AmountNBO *a2);
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/**
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* Test if @a a1 and @a a2 are the same currency.
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*
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* @param a1 amount to test
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* @param a2 amount to test
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* @return #GNUNET_YES if @a a1 and @a a2 are the same currency
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* #GNUNET_NO if the currencies are different
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* #GNUNET_SYSERR if either amount is invalid
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*/
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enum GNUNET_GenericReturnValue
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TALER_amount_cmp_currency (const struct TALER_Amount *a1,
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const struct TALER_Amount *a2);
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/**
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* Test if @a a1 and @a a2 are the same currency, NBO variant.
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*
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* @param a1 amount to test
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* @param a2 amount to test
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* @return #GNUNET_YES if @a a1 and @a a2 are the same currency
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* #GNUNET_NO if the currencies are different
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* #GNUNET_SYSERR if either amount is invalid
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*/
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enum GNUNET_GenericReturnValue
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TALER_amount_cmp_currency_nbo (const struct TALER_AmountNBO *a1,
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const struct TALER_AmountNBO *a2);
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/**
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* Possible results from calling #TALER_amount_subtract() and
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* possibly other arithmetic operations. Negative values
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* indicate that the operation did not generate a result.
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*/
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enum TALER_AmountArithmeticResult
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{
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/**
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* Operation succeeded, result is positive.
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*/
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TALER_AAR_RESULT_POSITIVE = 1,
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/**
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* Operation succeeded, result is exactly zero.
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*/
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TALER_AAR_RESULT_ZERO = 0,
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/**
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* Operation failed, the result would have been negative.
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*/
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TALER_AAR_INVALID_NEGATIVE_RESULT = -1,
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/**
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* Operation failed, result outside of the representable range.
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*/
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TALER_AAR_INVALID_RESULT_OVERFLOW = -2,
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/**
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* Operation failed, inputs could not be normalized.
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*/
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TALER_AAR_INVALID_NORMALIZATION_FAILED = -3,
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/**
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* Operation failed, input currencies were not identical.
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*/
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TALER_AAR_INVALID_CURRENCIES_INCOMPATIBLE = -4
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};
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/**
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* Perform saturating subtraction of amounts.
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*
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* @param[out] diff where to store (@a a1 - @a a2), or invalid if @a a2 > @a a1
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* @param a1 amount to subtract from
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* @param a2 amount to subtract
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* @return operation status, negative on failures
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*/
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enum TALER_AmountArithmeticResult
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TALER_amount_subtract (struct TALER_Amount *diff,
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const struct TALER_Amount *a1,
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const struct TALER_Amount *a2);
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/**
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* Perform addition of amounts.
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*
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* @param[out] sum where to store @a a1 + @a a2, set to "invalid" on overflow
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* @param a1 first amount to add
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* @param a2 second amount to add
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* @return operation status, negative on failures
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*/
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enum TALER_AmountArithmeticResult
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TALER_amount_add (struct TALER_Amount *sum,
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const struct TALER_Amount *a1,
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const struct TALER_Amount *a2);
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/**
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* Divide an amount by a @ divisor. Note that this function
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* may introduce a rounding error!
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*
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* @param[out] result where to store @a dividend / @a divisor
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* @param dividend amount to divide
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* @param divisor by what to divide, must be positive
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*/
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void
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TALER_amount_divide (struct TALER_Amount *result,
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const struct TALER_Amount *dividend,
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uint32_t divisor);
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/**
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* Divide one amount by another. Note that this function
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* may introduce a rounding error. It rounds down.
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*
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* @param dividend amount to divide
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* @param divisor by what to divide, must be positive
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* @return @a dividend / @a divisor, rounded down. -1 on currency mismatch,
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* INT_MAX for division by zero
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*/
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int
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TALER_amount_divide2 (const struct TALER_Amount *dividend,
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const struct TALER_Amount *divisor);
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/**
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* Multiply an @a amount by a @ factor.
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*
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* @param[out] result where to store @a amount * @a factor
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* @param amount amount to multiply
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* @param factor factor by which to multiply
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*/
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enum TALER_AmountArithmeticResult
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TALER_amount_multiply (struct TALER_Amount *result,
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const struct TALER_Amount *amount,
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uint32_t factor);
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/**
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* Normalize the given amount.
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*
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* @param[in,out] amount amount to normalize
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* @return #GNUNET_OK if normalization worked
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* #GNUNET_NO if value was already normalized
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* #GNUNET_SYSERR if value was invalid or could not be normalized
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*/
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int
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TALER_amount_normalize (struct TALER_Amount *amount);
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/**
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* Convert amount to string.
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*
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* @param amount amount to convert to string
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* @return freshly allocated string representation,
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* NULL if the @a amount was invalid
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*/
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char *
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TALER_amount_to_string (const struct TALER_Amount *amount);
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/**
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* Convert amount to string.
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*
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* @param amount amount to convert to string
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* @return statically allocated buffer with string representation,
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* NULL if the @a amount was invalid
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*/
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const char *
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TALER_amount2s (const struct TALER_Amount *amount);
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/**
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* Round the amount to something that can be transferred on the wire.
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* The rounding mode is specified via the smallest transferable unit,
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* which must only have a fractional part *or* only a value (either
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* of the two must be zero!).
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*
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* @param[in,out] amount amount to round down
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* @param[in] round_unit unit that should be rounded down to, and
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* either value part or the faction must be zero (but not both)
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* @return #GNUNET_OK on success, #GNUNET_NO if rounding was unnecessary,
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* #GNUNET_SYSERR if the amount or currency or @a round_unit was invalid
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*/
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enum GNUNET_GenericReturnValue
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TALER_amount_round_down (struct TALER_Amount *amount,
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const struct TALER_Amount *round_unit);
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#if 0 /* keep Emacsens' auto-indent happy */
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{
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#endif
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#ifdef __cplusplus
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}
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#endif
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#endif
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