235 lines
6.3 KiB
C
235 lines
6.3 KiB
C
/*
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This file is part of TALER
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Copyright (C) 2014, 2015 Christian Grothoff (and other contributing authors)
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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, 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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/**
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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 alpha-numeric 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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* @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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#define TALER_AMOUNT_FRAC_BASE 1000000
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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 6
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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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* Additinal fractional value, 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 (denominator of fraction)
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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 denomination description, in the format "T:V.F".
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*
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* @param str denomination description
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* @param denom denomination to write the result to
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* @return #GNUNET_OK if the string is a valid denomination specification,
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* #GNUNET_SYSERR if it is invalid.
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*/
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int
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TALER_string_to_amount (const char *str,
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struct TALER_Amount *denom);
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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 denom denomination 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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int
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TALER_amount_get_zero (const char *cur,
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struct TALER_Amount *denom);
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/**
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* Convert amount from host to network representation.
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*
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* @param 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 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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*/
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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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* 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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int
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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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* Perform saturating subtraction of amounts.
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*
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* @param 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 #GNUNET_OK if the subtraction worked,
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* #GNUNET_NO if @a a1 = @a a2
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* #GNUNET_SYSERR if @a a2 > @a a1 or currencies are incompatible;
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* @a diff is set to invalid
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*/
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int
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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 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 #GNUNET_OK if the addition worked,
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* #GNUNET_SYSERR on overflow
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*/
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int
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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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* Normalize the given amount.
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*
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* @param 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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#endif
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