aboutsummaryrefslogtreecommitdiff
path: root/src/include/taler_amount_lib.h
blob: 06549bac1ad594035c096d8ae66d85335e6095c2 (plain)
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
61
62
63
64
65
66
67
68
69
70
71
72
73
74
75
76
77
78
79
80
81
82
83
84
85
86
87
88
89
90
91
92
93
94
95
96
97
98
99
100
101
102
103
104
105
106
107
108
109
110
111
112
113
114
115
116
117
118
119
120
121
122
123
124
125
126
127
128
129
130
131
132
133
134
135
136
137
138
139
140
141
142
143
144
145
146
147
148
149
150
151
152
153
154
155
156
157
158
159
160
161
162
163
164
165
166
167
168
169
170
171
172
173
174
175
176
177
178
179
180
181
182
183
184
185
186
187
188
189
190
191
192
193
194
195
196
197
198
199
200
201
202
203
204
205
206
207
208
209
210
211
212
213
214
215
216
217
218
219
220
221
222
223
224
225
226
227
228
229
230
231
232
233
234
235
236
237
238
239
240
241
242
243
244
245
246
247
248
249
250
251
252
253
/*
  This file is part of TALER
  Copyright (C) 2014, 2015 Christian Grothoff (and other contributing authors)

  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_amount_lib.h
 * @brief amount-representation utility functions
 * @author Sree Harsha Totakura <sreeharsha@totakura.in>
 */
#ifndef TALER_AMOUNT_LIB_H
#define TALER_AMOUNT_LIB_H


/**
 * @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 alpha-numeric 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.
 */
#define TALER_AMOUNT_FRAC_BASE 1000000

/**
 * @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 6


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;

  /**
   * Additinal fractional value, 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 (denominator of fraction)
   */
  uint32_t fraction;

  /**
   * Currency string, left adjusted and padded with zeros.  All zeros
   * for "invalid" values.
   */
  char currency[TALER_CURRENCY_LEN];
};


/**
 * Parse denomination description, in the format "T:V.F".
 *
 * @param str denomination description
 * @param denom denomination to write the result to
 * @return #GNUNET_OK if the string is a valid denomination specification,
 *         #GNUNET_SYSERR if it is invalid.
 */
int
TALER_string_to_amount (const char *str,
                        struct TALER_Amount *denom);


/**
 * Get the value of "zero" in a particular currency.
 *
 * @param cur currency description
 * @param denom denomination 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 *denom);


/**
 * Convert amount from host to network representation.
 *
 * @param 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 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
 */
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);


/**
 * Perform saturating subtraction of amounts.
 *
 * @param 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 #GNUNET_OK if the subtraction worked,
 *         #GNUNET_NO if @a a1 = @a a2
 *         #GNUNET_SYSERR if @a a2 > @a a1 or currencies are incompatible;
 *                        @a diff is set to invalid
 */
int
TALER_amount_subtract (struct TALER_Amount *diff,
                       const struct TALER_Amount *a1,
                       const struct TALER_Amount *a2);


/**
 * Perform addition of amounts.
 *
 * @param 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 #GNUNET_OK if the addition worked,
 *         #GNUNET_SYSERR on overflow
 */
int
TALER_amount_add (struct TALER_Amount *sum,
                  const struct TALER_Amount *a1,
                  const struct TALER_Amount *a2);


/**
 * Normalize the given amount.
 *
 * @param 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);


#endif