/*
This file is part of TALER
Copyright (C) 2014, 2015, 2020 Taler Systems SA
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, see
*/
/**
* @file include/taler_amount_lib.h
* @brief amount-representation utility functions
* @author Sree Harsha Totakura
*/
#ifndef TALER_AMOUNT_LIB_H
#define TALER_AMOUNT_LIB_H
#ifdef __cplusplus
extern "C"
{
#if 0 /* keep Emacsens' auto-indent happy */
}
#endif
#endif
/**
* @brief Number of characters (plus 1 for 0-termination) we use to
* represent currency names (i.e. EUR, USD, etc.). We use 8+4 for
* alignment in the `struct TALER_Amount`. The amount is typically an
* ISO 4217 currency code when an alphanumeric 3-digit code is used.
* For regional currencies, the first character should be a "*" followed
* by a region-specific name (i.e. "*BRETAGNEFR").
*/
#define TALER_CURRENCY_LEN 12
/**
* Taler currency length as a string.
*/
#define TALER_CURRENCY_LEN_STR "12"
/**
* @brief The "fraction" value in a `struct TALER_Amount` represents which
* fraction of the "main" value?
*
* Note that we need sub-cent precision here as transaction fees might
* be that low, and as we want to support microdonations.
*
* An actual `struct Amount a` thus represents
* "a.value + (a.fraction / #TALER_AMOUNT_FRAC_BASE)" units of "a.currency".
*/
#define TALER_AMOUNT_FRAC_BASE 100000000
/**
* @brief How many digits behind the comma are required to represent the
* fractional value in human readable decimal format? Must match
* lg(#TALER_AMOUNT_FRAC_BASE).
*/
#define TALER_AMOUNT_FRAC_LEN 8
GNUNET_NETWORK_STRUCT_BEGIN
/**
* @brief Amount, encoded for network transmission.
*/
struct TALER_AmountNBO
{
/**
* Value in the main currency, in NBO.
*/
uint64_t value GNUNET_PACKED;
/**
* Fraction (integer multiples of #TALER_AMOUNT_FRAC_BASE), in NBO.
*/
uint32_t fraction GNUNET_PACKED;
/**
* Type of the currency being represented.
*/
char currency[TALER_CURRENCY_LEN];
};
GNUNET_NETWORK_STRUCT_END
/**
* @brief Representation of monetary value in a given currency.
*/
struct TALER_Amount
{
/**
* Value (numerator of fraction)
*/
uint64_t value;
/**
* Fraction (integer multiples of #TALER_AMOUNT_FRAC_BASE).
*/
uint32_t fraction;
/**
* Currency string, left adjusted and padded with zeros. All zeros
* for "invalid" values.
*/
char currency[TALER_CURRENCY_LEN];
};
/**
* Parse monetary amount, in the format "T:V.F".
*
* @param str amount string
* @param[out] amount amount to write the result to
* @return #GNUNET_OK if the string is a valid monetary amount specification,
* #GNUNET_SYSERR if it is invalid.
*/
int
TALER_string_to_amount (const char *str,
struct TALER_Amount *amount);
/**
* Parse monetary amount, in the format "T:V.F".
* The result is stored in network byte order (NBO).
*
* @param str amount string
* @param[out] amount_nbo amount to write the result to
* @return #GNUNET_OK if the string is a valid amount specification,
* #GNUNET_SYSERR if it is invalid.
*/
int
TALER_string_to_amount_nbo (const char *str,
struct TALER_AmountNBO *amount_nbo);
/**
* Get the value of "zero" in a particular currency.
*
* @param cur currency description
* @param[out] amount amount to write the result to
* @return #GNUNET_OK if @a cur is a valid currency specification,
* #GNUNET_SYSERR if it is invalid.
*/
int
TALER_amount_get_zero (const char *cur,
struct TALER_Amount *amount);
/**
* Test if the given amount is valid.
*
* @param amount amount to check
* @return #GNUNET_OK if @a amount is valid
*/
int
TALER_amount_is_valid (const struct TALER_Amount *amount);
/**
* Convert amount from host to network representation.
*
* @param[out] res where to store amount in network representation
* @param d amount in host representation
*/
void
TALER_amount_hton (struct TALER_AmountNBO *res,
const struct TALER_Amount *d);
/**
* Convert amount from network to host representation.
*
* @param[out] res where to store amount in host representation
* @param dn amount in network representation
*/
void
TALER_amount_ntoh (struct TALER_Amount *res,
const struct TALER_AmountNBO *dn);
/**
* Compare the value/fraction of two amounts. Does not compare the currency.
* Comparing amounts of different currencies will cause the program to abort().
* If unsure, check with #TALER_amount_cmp_currency() first to be sure that
* the currencies of the two amounts are identical.
*
* @param a1 first amount
* @param a2 second amount
* @return result of the comparison
* -1 if `a1 < a2`
* 1 if `a1 > a2`
* 0 if `a1 == a2`.
*/
int
TALER_amount_cmp (const struct TALER_Amount *a1,
const struct TALER_Amount *a2);
/**
* Test if @a a1 and @a a2 are the same currency.
*
* @param a1 amount to test
* @param a2 amount to test
* @return #GNUNET_YES if @a a1 and @a a2 are the same currency
* #GNUNET_NO if the currencies are different
* #GNUNET_SYSERR if either amount is invalid
*/
int
TALER_amount_cmp_currency (const struct TALER_Amount *a1,
const struct TALER_Amount *a2);
/**
* Test if @a a1 and @a a2 are the same currency, NBO variant.
*
* @param a1 amount to test
* @param a2 amount to test
* @return #GNUNET_YES if @a a1 and @a a2 are the same currency
* #GNUNET_NO if the currencies are different
* #GNUNET_SYSERR if either amount is invalid
*/
int
TALER_amount_cmp_currency_nbo (const struct TALER_AmountNBO *a1,
const struct TALER_AmountNBO *a2);
/**
* Possible results from calling #TALER_amount_subtract() and
* possibly other arithmetic operations. Negative values
* indicate that the operation did not generate a result.
*/
enum TALER_AmountArithmeticResult
{
/**
* Operation succeeded, result is positive.
*/
TALER_AAR_RESULT_POSITIVE = 1,
/**
* Operation succeeded, result is exactly zero.
*/
TALER_AAR_RESULT_ZERO = 0,
/**
* Operation failed, the result would have been negative.
*/
TALER_AAR_INVALID_NEGATIVE_RESULT = -1,
/**
* Operation failed, result outside of the representable range.
*/
TALER_AAR_INVALID_RESULT_OVERFLOW = -2,
/**
* Operation failed, inputs could not be normalized.
*/
TALER_AAR_INVALID_NORMALIZATION_FAILED = -3,
/**
* Operation failed, input currencies were not identical.
*/
TALER_AAR_INVALID_CURRENCIES_INCOMPATIBLE = -4
};
/**
* Perform saturating subtraction of amounts.
*
* @param[out] diff where to store (@a a1 - @a a2), or invalid if @a a2 > @a a1
* @param a1 amount to subtract from
* @param a2 amount to subtract
* @return operation status, negative on failures
*/
enum TALER_AmountArithmeticResult
TALER_amount_subtract (struct TALER_Amount *diff,
const struct TALER_Amount *a1,
const struct TALER_Amount *a2);
/**
* Perform addition of amounts.
*
* @param[out] sum where to store @a a1 + @a a2, set to "invalid" on overflow
* @param a1 first amount to add
* @param a2 second amount to add
* @return operation status, negative on failures
*/
enum TALER_AmountArithmeticResult
TALER_amount_add (struct TALER_Amount *sum,
const struct TALER_Amount *a1,
const struct TALER_Amount *a2);
/**
* Divide an amount by a @ divisor. Note that this function
* may introduce a rounding error!
*
* @param[out] result where to store @a dividend / @a divisor
* @param dividend amount to divide
* @param divisor by what to divide, must be positive
*/
void
TALER_amount_divide (struct TALER_Amount *result,
const struct TALER_Amount *dividend,
uint32_t divisor);
/**
* Normalize the given amount.
*
* @param[in,out] amount amount to normalize
* @return #GNUNET_OK if normalization worked
* #GNUNET_NO if value was already normalized
* #GNUNET_SYSERR if value was invalid or could not be normalized
*/
int
TALER_amount_normalize (struct TALER_Amount *amount);
/**
* Convert amount to string.
*
* @param amount amount to convert to string
* @return freshly allocated string representation,
* NULL if the @a amount was invalid
*/
char *
TALER_amount_to_string (const struct TALER_Amount *amount);
/**
* Convert amount to string.
*
* @param amount amount to convert to string
* @return statically allocated buffer with string representation,
* NULL if the @a amount was invalid
*/
const char *
TALER_amount2s (const struct TALER_Amount *amount);
/**
* Round the amount to something that can be transferred on the wire.
* The rounding mode is specified via the smallest transferable unit,
* which must only have a fractional part *or* only a value (either
* of the two must be zero!).
*
* @param[in,out] amount amount to round down
* @param[in] round_unit unit that should be rounded down to, and
* either value part or the faction must be zero (but not both)
* @return #GNUNET_OK on success, #GNUNET_NO if rounding was unnecessary,
* #GNUNET_SYSERR if the amount or currency or @a round_unit was invalid
*/
int
TALER_amount_round_down (struct TALER_Amount *amount,
const struct TALER_Amount *round_unit);
#if 0 /* keep Emacsens' auto-indent happy */
{
#endif
#ifdef __cplusplus
}
#endif
#endif