aboutsummaryrefslogtreecommitdiff
path: root/src/include/taler_amount_lib.h
blob: 04aa0004513cb20c5d3b2561ab85dec14330511e (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
254
255
256
257
258
259
260
261
262
263
264
265
266
267
268
269
270
271
272
273
274
275
276
277
278
279
280
281
282
283
284
285
286
287
288
289
290
291
292
293
294
295
296
297
298
299
300
301
302
303
304
305
306
307
308
309
310
311
312
313
314
315
316
317
318
319
320
321
322
323
324
325
326
327
328
329
330
331
332
333
334
335
336
337
338
339
340
341
342
343
344
345
346
347
348
349
350
351
352
353
354
355
356
357
358
359
360
361
362
363
364
365
366
367
368
369
370
371
372
373
374
375
376
377
378
379
380
381
382
383
384
385
386
387
388
389
390
391
392
393
394
395
396
397
398
399
400
401
402
403
404
405
406
407
408
409
410
411
412
413
414
415
416
417
418
419
420
421
422
423
424
425
426
427
428
429
430
431
432
433
434
435
436
437
438
439
440
441
442
443
444
445
446
447
448
449
450
451
452
453
454
455
456
/*
  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 <http://www.gnu.org/licenses/>
*/
/**
 * @file include/taler_amount_lib.h
 * @brief amount-representation utility functions
 * @author Sree Harsha Totakura <sreeharsha@totakura.in>
 */
#if ! defined (__TALER_UTIL_LIB_H_INSIDE__)
#error "Only <taler_util.h> can be included directly."
#endif

#ifndef TALER_AMOUNT_LIB_H
#define TALER_AMOUNT_LIB_H

#include <stdint.h>
#include "gnunet/gnunet_common.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

/**
 * Maximum legal 'value' for an amount, based on IEEE double (for JavaScript compatibility).
 */
#define TALER_AMOUNT_MAX_VALUE (1LLU << 52)


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.
 */
enum GNUNET_GenericReturnValue
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.
 */
enum GNUNET_GenericReturnValue
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.
 */
enum GNUNET_GenericReturnValue
TALER_amount_set_zero (const char *cur,
                       struct TALER_Amount *amount);


/**
 * Test if the given @a amount is zero.
 *
 * @param amount amount to compare to zero
 * @return true if the amount is zero,
 *         false if it is non-zero or invalid
 */
bool
TALER_amount_is_zero (const struct TALER_Amount *amount);


/**
 * Test if the given amount is valid.
 *
 * @param amount amount to check
 * @return #GNUNET_OK if @a amount is valid
 */
enum GNUNET_GenericReturnValue
TALER_amount_is_valid (const struct TALER_Amount *amount);


/**
 * Test if the given amount is in the given currency
 *
 * @param amount amount to check
 * @param currency currency to check for
 * @return #GNUNET_OK if @a amount is in @a currency
 */
enum GNUNET_GenericReturnValue
TALER_amount_is_currency (const struct TALER_Amount *amount,
                          const char *currency);


/**
 * 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);


/**
 * 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. NBO variant.
 *
 * @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_nbo (const struct TALER_AmountNBO *a1,
                      const struct TALER_AmountNBO *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
 */
enum GNUNET_GenericReturnValue
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
 */
enum GNUNET_GenericReturnValue
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);

/**
 * Divide one amount by another.  Note that this function
 * may introduce a rounding error. It rounds down.
 *
 * @param dividend amount to divide
 * @param divisor by what to divide, must be positive
 * @return @a dividend / @a divisor, rounded down. -1 on currency mismatch,
 *         INT_MAX for division by zero
 */
int
TALER_amount_divide2 (const struct TALER_Amount *dividend,
                      const struct TALER_Amount *divisor);


/**
 * Multiply an @a amount by a @ factor.
 *
 * @param[out] result where to store @a amount * @a factor
 * @param amount amount to multiply
 * @param factor factor by which to multiply
 */
enum TALER_AmountArithmeticResult
TALER_amount_multiply (struct TALER_Amount *result,
                       const struct TALER_Amount *amount,
                       uint32_t factor);


/**
 * 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
 */
enum GNUNET_GenericReturnValue
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