This file is indexed.

/usr/include/udunits2.h is in libudunits2-dev 2.1.23-3.

This file is owned by root:root, with mode 0o644.

The actual contents of the file can be viewed below.

   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
 457
 458
 459
 460
 461
 462
 463
 464
 465
 466
 467
 468
 469
 470
 471
 472
 473
 474
 475
 476
 477
 478
 479
 480
 481
 482
 483
 484
 485
 486
 487
 488
 489
 490
 491
 492
 493
 494
 495
 496
 497
 498
 499
 500
 501
 502
 503
 504
 505
 506
 507
 508
 509
 510
 511
 512
 513
 514
 515
 516
 517
 518
 519
 520
 521
 522
 523
 524
 525
 526
 527
 528
 529
 530
 531
 532
 533
 534
 535
 536
 537
 538
 539
 540
 541
 542
 543
 544
 545
 546
 547
 548
 549
 550
 551
 552
 553
 554
 555
 556
 557
 558
 559
 560
 561
 562
 563
 564
 565
 566
 567
 568
 569
 570
 571
 572
 573
 574
 575
 576
 577
 578
 579
 580
 581
 582
 583
 584
 585
 586
 587
 588
 589
 590
 591
 592
 593
 594
 595
 596
 597
 598
 599
 600
 601
 602
 603
 604
 605
 606
 607
 608
 609
 610
 611
 612
 613
 614
 615
 616
 617
 618
 619
 620
 621
 622
 623
 624
 625
 626
 627
 628
 629
 630
 631
 632
 633
 634
 635
 636
 637
 638
 639
 640
 641
 642
 643
 644
 645
 646
 647
 648
 649
 650
 651
 652
 653
 654
 655
 656
 657
 658
 659
 660
 661
 662
 663
 664
 665
 666
 667
 668
 669
 670
 671
 672
 673
 674
 675
 676
 677
 678
 679
 680
 681
 682
 683
 684
 685
 686
 687
 688
 689
 690
 691
 692
 693
 694
 695
 696
 697
 698
 699
 700
 701
 702
 703
 704
 705
 706
 707
 708
 709
 710
 711
 712
 713
 714
 715
 716
 717
 718
 719
 720
 721
 722
 723
 724
 725
 726
 727
 728
 729
 730
 731
 732
 733
 734
 735
 736
 737
 738
 739
 740
 741
 742
 743
 744
 745
 746
 747
 748
 749
 750
 751
 752
 753
 754
 755
 756
 757
 758
 759
 760
 761
 762
 763
 764
 765
 766
 767
 768
 769
 770
 771
 772
 773
 774
 775
 776
 777
 778
 779
 780
 781
 782
 783
 784
 785
 786
 787
 788
 789
 790
 791
 792
 793
 794
 795
 796
 797
 798
 799
 800
 801
 802
 803
 804
 805
 806
 807
 808
 809
 810
 811
 812
 813
 814
 815
 816
 817
 818
 819
 820
 821
 822
 823
 824
 825
 826
 827
 828
 829
 830
 831
 832
 833
 834
 835
 836
 837
 838
 839
 840
 841
 842
 843
 844
 845
 846
 847
 848
 849
 850
 851
 852
 853
 854
 855
 856
 857
 858
 859
 860
 861
 862
 863
 864
 865
 866
 867
 868
 869
 870
 871
 872
 873
 874
 875
 876
 877
 878
 879
 880
 881
 882
 883
 884
 885
 886
 887
 888
 889
 890
 891
 892
 893
 894
 895
 896
 897
 898
 899
 900
 901
 902
 903
 904
 905
 906
 907
 908
 909
 910
 911
 912
 913
 914
 915
 916
 917
 918
 919
 920
 921
 922
 923
 924
 925
 926
 927
 928
 929
 930
 931
 932
 933
 934
 935
 936
 937
 938
 939
 940
 941
 942
 943
 944
 945
 946
 947
 948
 949
 950
 951
 952
 953
 954
 955
 956
 957
 958
 959
 960
 961
 962
 963
 964
 965
 966
 967
 968
 969
 970
 971
 972
 973
 974
 975
 976
 977
 978
 979
 980
 981
 982
 983
 984
 985
 986
 987
 988
 989
 990
 991
 992
 993
 994
 995
 996
 997
 998
 999
1000
1001
1002
1003
1004
1005
1006
1007
1008
1009
1010
1011
1012
1013
1014
1015
1016
1017
1018
1019
1020
1021
1022
1023
1024
1025
1026
1027
1028
1029
1030
1031
1032
1033
1034
1035
1036
1037
1038
1039
1040
1041
1042
1043
1044
1045
1046
1047
1048
1049
1050
1051
1052
1053
1054
1055
1056
1057
1058
1059
1060
1061
1062
1063
1064
1065
1066
1067
1068
1069
1070
1071
1072
1073
1074
1075
1076
1077
1078
1079
1080
1081
1082
1083
1084
1085
1086
1087
1088
1089
1090
1091
1092
1093
1094
1095
1096
1097
1098
1099
1100
1101
1102
1103
1104
1105
1106
1107
1108
1109
1110
1111
1112
1113
1114
1115
1116
1117
1118
1119
1120
1121
1122
1123
1124
1125
1126
1127
1128
1129
1130
1131
1132
1133
1134
1135
1136
1137
1138
1139
1140
1141
1142
1143
1144
1145
1146
1147
1148
1149
1150
1151
1152
1153
1154
1155
1156
1157
1158
1159
1160
1161
1162
1163
1164
1165
1166
1167
1168
1169
1170
1171
1172
1173
1174
1175
1176
1177
1178
1179
1180
1181
1182
1183
1184
1185
1186
1187
1188
1189
1190
1191
1192
1193
1194
1195
1196
1197
1198
1199
1200
1201
1202
1203
1204
1205
1206
1207
1208
1209
1210
1211
1212
1213
1214
1215
1216
1217
1218
1219
1220
1221
1222
1223
1224
1225
1226
1227
1228
1229
1230
1231
1232
1233
1234
1235
1236
1237
1238
1239
1240
1241
1242
1243
1244
1245
1246
1247
1248
1249
1250
1251
1252
1253
1254
1255
1256
1257
1258
1259
1260
1261
1262
1263
1264
1265
1266
1267
1268
1269
1270
1271
1272
1273
1274
1275
1276
1277
1278
1279
1280
1281
1282
1283
1284
1285
1286
1287
1288
1289
1290
/*
 * Copyright 2008, 2009 University Corporation for Atmospheric Research
 *
 * This file is part of the UDUNITS-2 package.  See the file LICENSE
 * in the top-level source-directory of the package for copying and
 * redistribution conditions.
 */
#ifndef UT_UNITS2_H_INCLUDED
#define UT_UNITS2_H_INCLUDED

#include <stdarg.h>
#include <stddef.h>

#include "converter.h"

typedef struct ut_system	ut_system;
typedef union ut_unit		ut_unit;

typedef enum {
    UT_SUCCESS = 0,	/* Success */
    UT_BAD_ARG,	        /* An argument violates the function's contract */
    UT_EXISTS,		/* Unit, prefix, or identifier already exists */
    UT_NO_UNIT,		/* No such unit exists */
    UT_OS,		/* Operating-system error.  See "errno". */
    UT_NOT_SAME_SYSTEM,	/* The units belong to different unit-systems */
    UT_MEANINGLESS,	/* The operation on the unit(s) is meaningless */
    UT_NO_SECOND,	/* The unit-system doesn't have a unit named "second" */
    UT_VISIT_ERROR,	/* An error occurred while visiting a unit */
    UT_CANT_FORMAT,	/* A unit can't be formatted in the desired manner */
    UT_SYNTAX,		/* string unit representation contains syntax error */
    UT_UNKNOWN,		/* string unit representation contains unknown word */
    UT_OPEN_ARG,	/* Can't open argument-specified unit database */
    UT_OPEN_ENV,	/* Can't open environment-specified unit database */
    UT_OPEN_DEFAULT,	/* Can't open installed, default, unit database */
    UT_PARSE		/* Error parsing unit specification */
} ut_status;

typedef enum {
    UT_ASCII = 0,
    UT_ISO_8859_1 = 1,
    UT_LATIN1 = UT_ISO_8859_1,
    UT_UTF8 = 2
} ut_encoding;

#define UT_NAMES	4
#define UT_DEFINITION	8


/*
 * Data-structure for a visitor to a unit:
 */
typedef struct {
    /*
     * Visits a basic-unit.  A basic-unit is a base unit like "meter" or a non-
     * dimensional but named unit like "radian".
     *
     * Arguments:
     *	unit		Pointer to the basic-unit.
     *	arg		Client pointer passed to ut_accept_visitor().
     * Returns:
     *	UT_SUCCESS	Success.
     *	else		Failure.
     */
    ut_status	(*visit_basic)(const ut_unit* unit, void* arg); 

    /*
     * Visits a product-unit.  A product-unit is a product of zero or more
     * basic-units, each raised to a non-zero power.
     *
     * Arguments:
     *	unit		Pointer to the product-unit.
     *	count		The number of basic-units in the product.  May be zero.
     *	basicUnits	Pointer to an array of basic-units in the product.
     *	powers		Pointer to an array of powers to which the respective
     *			basic-units are raised.
     *	arg		Client pointer passed to ut_accept_visitor().
     * Returns:
     *	UT_SUCCESS	Success.
     *	else		Failure.
     */
    ut_status	(*visit_product)(const ut_unit* unit, int count,
	const ut_unit* const* basicUnits, const int* powers, void* arg); 

    /*
     * Visits a Galilean-unit.  A Galilean-unit has an underlying unit and a
     * non-unity scale factor or a non-zero offset.
     *
     * Arguments:
     *	unit		Pointer to the Galilean-unit.
     *	scale		The scale factor (e.g., 1000 for a kilometer when the
     *			underlying unit is a meter).
     *	underlyingUnit	Pointer to the underlying unit.
     *	offset		Pointer to the underlying unit.
     *	arg		Client pointer passed to ut_accept_visitor().
     * Returns:
     *	UT_SUCCESS	Success.
     *	else		Failure.
     */
    ut_status	(*visit_galilean)(const ut_unit* unit, double scale,
	const ut_unit* underlyingUnit, double offset, void* arg); 

    /*
     * Visits a timestamp-unit.  A timestamp-unit has an underlying unit of time
     * and an encoded time-origin.
     *
     * Arguments:
     *	unit		Pointer to the timestamp-unit.
     *	timeUnit	Pointer to the underlying unit of time.
     *  origin          Encoded origin of the timestamp-unit.
     *	arg		Client pointer passed to ut_accept_visitor().
     * Returns:
     *	UT_SUCCESS	Success.
     *	else		Failure.
     */
    ut_status	(*visit_timestamp)(const ut_unit* unit,
	const ut_unit* timeUnit, double origin, void* arg); 

    /*
     * Visits a logarithmic-unit.  A logarithmic-unit has a logarithmic base and
     * a unit that specifies the reference level.
     *
     * Arguments:
     *	unit		Pointer to the logarithmic-unit.
     *  base            The logarithmic base (e.g., 2, M_E, 10).
     *	reference	Pointer to the unit that specifies the reference level.
     *	arg		Client pointer passed to ut_accept_visitor().
     * Returns:
     *	UT_SUCCESS	Success.
     *	else		Failure.
     */
    ut_status	(*visit_logarithmic)(const ut_unit* unit, double base,
	const ut_unit* reference, void* arg); 
} ut_visitor;


typedef int (*ut_error_message_handler)(const char* fmt, va_list args);


#ifdef __cplusplus
extern "C" {
#endif


/******************************************************************************
 * Unit System:
 ******************************************************************************/


/*
 * Returns the unit-system corresponding to an XML file.  This is the usual way
 * that a client will obtain a unit-system.
 *
 * Arguments:
 *	path	The pathname of the XML file or NULL.  If NULL, then the
 *		pathname specified by the environment variable UDUNITS2_XML_PATH
 *		is used if set; otherwise, the compile-time pathname of the
 *		installed, default, unit database is used.
 * Returns:
 *	NULL	Failure.  "ut_get_status()" will be
 *		    UT_OPEN_ARG		"path" is non-NULL but file couldn't be
 *					opened.  See "errno" for reason.
 *		    UT_OPEN_ENV		"path" is NULL and environment variable
 *					UDUNITS2_XML_PATH is set but file
 *					couldn't be opened.  See "errno" for
 *					reason.
 *		    UT_OPEN_DEFAULT	"path" is NULL, environment variable
 *					UDUNITS2_XML_PATH is unset, and the
 *					installed, default, unit database
 *					couldn't be opened.  See "errno" for
 *					reason.
 *		    UT_PARSE		Couldn't parse unit database.
 *		    UT_OS		Operating-system error.  See "errno".
 *	else	Pointer to the unit-system defined by "path".
 */
ut_system*
ut_read_xml(
    const char*	path);


/*
 * Returns a new unit-system.  On success, the unit-system will only contain
 * the dimensionless unit one.  See "ut_get_dimensionless_unit_one()".
 *
 * Returns:
 *	NULL	Failure.  "ut_get_status()" will be:
 *		    UT_OS	Operating-system error.  See "errno".
 *	else	Pointer to a new unit system.
 */
ut_system*
ut_new_system(void);


/*
 * Frees a unit-system.  All unit-to-identifier and identifier-to-unit mappings
 * will be removed.
 *
 * Arguments:
 *	system		Pointer to the unit-system to be freed.  Use of "system"
 *			upon return results in undefined behavior.
 */
void
ut_free_system(
    ut_system*	system);


/*
 * Returns the unit-system to which a unit belongs.
 *
 * Arguments:
 *	unit	Pointer to the unit in question.
 * Returns:
 *	NULL	Failure.  "ut_get_status()" will be
 *		    UT_BAD_ARG	"unit" is NULL.
 *	else	Pointer to the unit-system to which "unit" belongs.
 */
ut_system*
ut_get_system(
    const ut_unit* const	unit);


/*
 * Returns the dimensionless-unit one of a unit-system.
 *
 * Arguments:
 *	system	Pointer to the unit-system for which the dimensionless-unit one
 *		will be returned.
 * Returns:
 *	NULL	Failure.  "ut_get_status()" will be:
 *		    UT_BAD_ARG	"system" is NULL.
 *	else	Pointer to the dimensionless-unit one associated with "system".
 *		While not necessary, the pointer may be passed to ut_free()
 *		when the unit is no longer needed by the client.
 */
ut_unit*
ut_get_dimensionless_unit_one(
    const ut_system* const	system);


/*
 * Returns the unit with a given name from a unit-system.  Name comparisons
 * are case-insensitive.
 *
 * Arguments:
 *	system	Pointer to the unit-system.
 *	name	Pointer to the name of the unit to be returned.
 * Returns:
 *	NULL	Failure.  "ut_get_status()" will be
 *		    UT_SUCCESS		"name" doesn't map to a unit of
 *					"system".
 *		    UT_BAD_ARG		"system" or "name" is NULL.
 *	else	Pointer to the unit of the unit-system with the given name.
 *		The pointer should be passed to ut_free() when the unit is
 *		no longer needed.
 */
ut_unit*
ut_get_unit_by_name(
    const ut_system* const	system,
    const char* const		name);


/*
 * Returns the unit with a given symbol from a unit-system.  Symbol 
 * comparisons are case-sensitive.
 *
 * Arguments:
 *	system		Pointer to the unit-system.
 *	symbol		Pointer to the symbol associated with the unit to be
 *			returned.
 * Returns:
 *	NULL	Failure.  "ut_get_status()" will be
 *		    UT_SUCCESS		"symbol" doesn't map to a unit of
 *					"system".
 *		    UT_BAD_ARG		"system" or "symbol" is NULL.
 *	else	Pointer to the unit in the unit-system with the given symbol.
 *		The pointer should be passed to ut_free() when the unit is no
 *		longer needed.
 */
ut_unit*
ut_get_unit_by_symbol(
    const ut_system* const	system,
    const char* const		symbol);


/*
 * Sets the "second" unit of a unit-system.  This function must be called before
 * the first call to "ut_offset_by_time()". ut_read_xml() calls this function if the
 * resulting unit-system contains a unit named "second".
 *
 * Arguments:
 *	second		Pointer to the "second" unit.
 * Returns:
 *	UT_BAD_ARG	"second" is NULL.
 *	UT_EXISTS	The second unit of the unit-system to which "second"
 *			belongs is set to a different unit.
 *	UT_SUCCESS	Success.
 */
ut_status
ut_set_second(
    const ut_unit* const	second);


/******************************************************************************
 * Defining Unit Prefixes:
 ******************************************************************************/


/*
 * Adds a name-prefix to a unit-system.  A name-prefix is something like "mega"
 * or "milli".  Comparisons between name-prefixes are case-insensitive.
 *
 * Arguments:
 *	system		Pointer to the unit-system.
 *	name		Pointer to the name-prefix (e.g., "mega").  May be freed
 *			upon return.
 *	value		The value of the prefix (e.g., 1e6).
 * Returns:
 *	UT_SUCCESS	Success.
 *	UT_BAD_ARG	"system" or "name" is NULL, or "value" is 0.
 *	UT_EXISTS	"name" already maps to a different value.
 *	UT_OS		Operating-system failure.  See "errno".
 */
ut_status
ut_add_name_prefix(
    ut_system* const	system,
    const char* const	name,
    const double	value);


/*
 * Adds a symbol-prefix to a unit-system.  A symbol-prefix is something like
 * "M" or "y".  Comparisons between symbol-prefixes are case-sensitive.
 *
 * Arguments:
 *	system		Pointer to the unit-system.
 *	symbol		Pointer to the symbol-prefix (e.g., "M").  May be freed
 *			upon return.
 *	value		The value of the prefix (e.g., 1e6).
 * Returns:
 *	UT_SUCCESS	Success.
 *	UT_BADSYSTEM	"system" or "symbol" is NULL.
 *	UT_BAD_ARG	"value" is 0.
 *	UT_EXISTS	"symbol" already maps to a different value.
 *	UT_OS		Operating-system failure.  See "errno".
 */
ut_status
ut_add_symbol_prefix(
    ut_system* const	system,
    const char* const	symbol,
    const double	value);


/******************************************************************************
 * Defining and Deleting Units:
 ******************************************************************************/


/*
 * Adds a base-unit to a unit-system.  Clients that use ut_read_xml() should not
 * normally need to call this function.
 *
 * Arguments:
 *	system	Pointer to the unit-system to which to add the new base-unit.
 * Returns:
 *	NULL	Failure.  "ut_get_status()" will be
 *		    UT_BAD_ARG		"system" or "name" is NULL.
 *		    UT_OS		Operating-system error.  See "errno".
 *	else	Pointer to the new base-unit.  The pointer should be passed to
 *		ut_free() when the unit is no longer needed by the client (the
 *		unit will remain in the unit-system).
 */
ut_unit*
ut_new_base_unit(
    ut_system* const	system);


/*
 * Adds a dimensionless-unit to a unit-system.  In the SI system of units, the
 * derived-unit radian is a dimensionless-unit.  Clients that use ut_read_xml()
 * should not normally need to call this function.
 *
 * Arguments:
 *	system	Pointer to the unit-system to which to add the new
 *		dimensionless-unit.
 * Returns:
 *	NULL	Failure.  "ut_get_status()" will be
 *		    UT_BAD_ARG		"system" is NULL.
 *		    UT_OS		Operating-system error.  See "errno".
 *	else	Pointer to the new dimensionless-unit.  The pointer should be
 *		passed to ut_free() when the unit is no longer needed by the
 *		client (the unit will remain in the unit-system).
 */
ut_unit*
ut_new_dimensionless_unit(
    ut_system* const	system);


/*
 * Returns a clone of a unit.
 *
 * Arguments:
 *	unit	Pointer to the unit to be cloned.
 * Returns:
 *	NULL	Failure.  ut_get_status() will be
 *		    UT_OS	Operating-system failure.  See "errno".
 *		    UT_BAD_ARG	"unit" is NULL.
 *	else	Pointer to the clone of "unit".  The pointer should be
 *		passed to ut_free() when the unit is no longer needed by the
 *		client.
 */
ut_unit*
ut_clone(
    const ut_unit*	unit);


/*
 * Frees resources associated with a unit.  This function should be invoked on
 * all units that are no longer needed by the client.  Use of the unit upon
 * return from this function will result in undefined behavior.
 *
 * Arguments:
 *	unit	Pointer to the unit to have its resources freed or NULL.
 */
void
ut_free(
    ut_unit* const	unit);


/******************************************************************************
 * Mapping between Units and Names:
 ******************************************************************************/


/*
 * Returns the name in a given encoding to which a unit maps.
 *
 * Arguments:
 *	unit		Pointer to the unit whose name should be returned.
 *	encoding	The desired encoding of the name.
 * Returns:
 *	NULL		Failure.  "ut_get_status()" will be
 *			    UT_BAD_ARG		"unit" is NULL.
 *			    UT_SUCCESS		"unit" doesn't map to a name in
 *						in the given encoding.
 *	else		Pointer to the name in the given encoding to which
 *			"unit" maps.
 */
const char*
ut_get_name(
    const ut_unit* const	unit,
    const ut_encoding		encoding);


/*
 * Adds a mapping from a name to a unit.
 *
 * Arguments:
 *	name		Pointer to the name to be mapped to "unit".  May be
 *			freed upon return.
 *      encoding        The character encoding of "name".
 *	unit		Pointer to the unit to be mapped-to by "name".  May be
 *			freed upon return.
 * Returns:
 *	UT_BAD_ARG	"name" or "unit" is NULL.
 *	UT_OS		Operating-system error.  See "errno".
 *	UT_EXISTS	"name" already maps to a different unit.
 *	UT_SUCCESS	Success.
 */
ut_status
ut_map_name_to_unit(
    const char* const		name,
    const ut_encoding		encoding,
    const ut_unit* const	unit);


/*
 * Removes a mapping from a name to a unit.  After this function,
 * ut_get_unit_by_name(system,name) will no longer return a unit.
 *
 * Arguments:
 *	system		The unit-system to which the unit belongs.
 *	name		The name of the unit.
 *      encoding        The character encoding of "name".
 * Returns:
 *	UT_SUCCESS	Success.
 *	UT_BAD_ARG	"system" or "name" is NULL.
 */
ut_status
ut_unmap_name_to_unit(
    ut_system*		system,
    const char* const	name,
    const ut_encoding   encoding);


/*
 * Adds a mapping from a unit to a name.
 *
 * Arguments:
 *	unit		Pointer to the unit to be mapped to "name".  May be
 *			freed upon return.
 *	name		Pointer to the name to be mapped-to by "unit".  May be
 *			freed upon return.
 *	encoding	The encoding of "name".
 * Returns:
 *	UT_SUCCESS	Success.
 *	UT_BAD_ARG	"unit" or "name" is NULL, or "name" is not in the
 *                      specified encoding.
 *	UT_OS		Operating-system error.  See "errno".
 *	UT_EXISTS	"unit" already maps to a name.
 */
ut_status
ut_map_unit_to_name(
    const ut_unit* const	unit,
    const char* const		name,
    ut_encoding			encoding);


/*
 * Removes a mapping from a unit to a name.
 *
 * Arguments:
 *	unit		Pointer to the unit.  May be freed upon return.
 *	encoding	The encoding to be removed.  No other encodings will be
 *			removed.
 * Returns:
 *	UT_BAD_ARG	"unit" is NULL.
 *	UT_SUCCESS	Success.
 */
ut_status
ut_unmap_unit_to_name(
    const ut_unit* const	unit,
    ut_encoding			encoding);


/******************************************************************************
 * Mapping between Units and Symbols:
 ******************************************************************************/


/*
 * Returns the symbol in a given encoding to which a unit maps.
 *
 * Arguments:
 *	unit		Pointer to the unit whose symbol should be returned.
 *	encoding	The desired encoding of the symbol.
 * Returns:
 *	NULL		Failure.  "ut_get_status()" will be
 *			    UT_BAD_ARG		"unit" is NULL.
 *			    UT_SUCCESS		"unit" doesn't map to a symbol
 *						in the given encoding.
 *	else		Pointer to the symbol in the given encoding to which
 *			"unit" maps.
 */
const char*
ut_get_symbol(
    const ut_unit* const	unit,
    const ut_encoding	encoding);


/*
 * Adds a mapping from a symbol to a unit.
 *
 * Arguments:
 *	symbol		Pointer to the symbol to be mapped to "unit".  May be
 *			freed upon return.
 *      ut_encoding     The character encoding of "symbol".
 *	unit		Pointer to the unit to be mapped-to by "symbol".  May
 *			be freed upon return.
 * Returns:
 *	UT_BAD_ARG	"symbol" or "unit" is NULL.
 *	UT_OS		Operating-system error.  See "errno".
 *	UT_EXISTS	"symbol" already maps to a different unit.
 *	UT_SUCCESS	Success.
 */
ut_status
ut_map_symbol_to_unit(
    const char* const		symbol,
    const ut_encoding		encoding,
    const ut_unit* const	unit);


/*
 * Removes a mapping from a symbol to a unit.  After this function,
 * ut_get_unit_by_symbol(system,symbol) will no longer return a unit.
 *
 * Arguments:
 *	system		The unit-system to which the unit belongs.
 *	symbol		The symbol of the unit.
 *      encoding        The character encoding of "symbol".
 * Returns:
 *	UT_SUCCESS	Success.
 *	UT_BAD_ARG	"system" or "symbol" is NULL.
 */
ut_status
ut_unmap_symbol_to_unit(
    ut_system*		system,
    const char* const	symbol,
    const ut_encoding   encoding);


/*
 * Adds a mapping from a unit to a symbol.
 *
 * Arguments:
 *	unit		Pointer to the unit to be mapped to "symbol".  May be
 *			freed upon return.
 *	symbol		Pointer to the symbol to be mapped-to by "unit".  May
 *			be freed upon return.
 *	encoding	The encoding of "symbol".
 * Returns:
 *	UT_SUCCESS	Success.
 *	UT_BAD_ARG	"unit" or "symbol" is NULL.
 *	UT_OS		Operating-system error.  See "errno".
 *	UT_EXISTS	"unit" already maps to a symbol.
 */
ut_status
ut_map_unit_to_symbol(
    const ut_unit*		unit,
    const char* const		symbol,
    ut_encoding			encoding);


/*
 * Removes a mapping from a unit to a symbol.
 *
 * Arguments:
 *	unit		Pointer to the unit to be unmapped to a symbol.  May be
 *			freed upon return.
 *	encoding	The encoding to be removed.  The mappings for "unit" in
 *			other encodings will not be removed.
 * Returns:
 *	UT_SUCCESS	Success.
 *	UT_BAD_ARG	"unit" is NULL.
 */
ut_status
ut_unmap_unit_to_symbol(
    const ut_unit* const	unit,
    ut_encoding			encoding);


/******************************************************************************
 * Getting Information about a Unit:
 ******************************************************************************/


/*
 * Indicates if a given unit is dimensionless or not.  Note that logarithmic
 * units are dimensionless by definition.
 *
 * Arguments:
 *	unit	Pointer to the unit in question.
 * Returns:
 *	0	"unit" is dimensionfull or an error occurred.  "ut_get_status()"
 *		 will be
 *		    UT_BAD_ARG		"unit" is NULL.
 *		    UT_SUCCESS		"unit" is dimensionfull.
 *	else	"unit" is dimensionless.
 */
int
ut_is_dimensionless(
    const ut_unit* const	unit);


/*
 * Indicates if two units belong to the same unit-system.
 *
 * Arguments:
 *	unit1		Pointer to a unit.
 *	unit2		Pointer to another unit.
 * Returns:
 *	0		Failure or the units belong to different unit-systems.
 *			"ut_get_status()" will be
 *	    		    UT_BAD_ARG		"unit1" or "unit2" is NULL.
 *	    		    UT_SUCCESS		The units belong to different
 *						unit-systems.
 *	else		The units belong to the same unit-system.
 */
int
ut_same_system(
    const ut_unit* const	unit1,
    const ut_unit* const	unit2);


/*
 * Compares two units.  Returns a value less than, equal to, or greater than
 * zero as the first unit is considered less than, equal to, or greater than
 * the second unit, respectively.  Units from different unit-systems never
 * compare equal.
 *
 * Arguments:
 *	unit1		Pointer to a unit or NULL.
 *	unit2		Pointer to another unit or NULL.
 * Returns:
 *	<0	The first unit is less than the second unit.
 *	 0	The first and second units are equal or both units are NULL.
 *	>0	The first unit is greater than the second unit.
 */
int
ut_compare(
    const ut_unit* const	unit1,
    const ut_unit* const	unit2);


/*
 * Indicates if numeric values in one unit are convertible to numeric values in
 * another unit via "ut_get_converter()".  In making this determination, 
 * dimensionless units are ignored.
 *
 * Arguments:
 *	unit1		Pointer to a unit.
 *	unit2		Pointer to another unit.
 * Returns:
 *	0		Failure.  "ut_get_status()" will be
 *	    		    UT_BAD_ARG		"unit1" or "unit2" is NULL.
 *			    UT_NOT_SAME_SYSTEM	"unit1" and "unit2" belong to
 *						different unit-sytems.
 *			    UT_SUCCESS		Conversion between the units is
 *						not possible (e.g., "unit1" is
 *						"meter" and "unit2" is
 *						"kilogram").
 *	else	Numeric values can be converted between the units.
 */
int
ut_are_convertible(
    const ut_unit* const	unit1,
    const ut_unit* const	unit2);


/*
 * Returns a converter of numeric values in one unit to numeric values in
 * another unit.  The returned converter should be passed to cv_free() when it is
 * no longer needed by the client.
 *
 * NOTE:  Leap seconds are not taken into account when converting between
 * timestamp units.
 *
 * Arguments:
 *	from		Pointer to the unit from which to convert values.
 *	to		Pointer to the unit to which to convert values.
 * Returns:
 *	NULL		Failure.  "ut_get_status()" will be:
 *			    UT_BAD_ARG		"from" or "to" is NULL.
 *			    UT_NOT_SAME_SYSTEM	"from" and "to" belong to
 *						different unit-systems.
 *			    UT_MEANINGLESS	Conversion between the units is
 *						not possible.  See
 *						"ut_are_convertible()".
 *	else		Pointer to the appropriate converter.  The pointer
 *			should be passed to cv_free() when no longer needed by
 *			the client.
 */
cv_converter*
ut_get_converter(
    ut_unit* const	from,
    ut_unit* const	to);


/******************************************************************************
 * Arithmetic Unit Manipulation:
 ******************************************************************************/


/*
 * Returns a unit equivalent to another unit scaled by a numeric factor,
 * e.g.,
 *	const ut_unit*	meter = ...
 *	const ut_unit*	kilometer = ut_scale(1000, meter);
 *
 * Arguments:
 *	factor		The numeric scale factor.
 *	unit		Pointer to the unit to be scaled.
 * Returns:
 *	NULL		Failure.  "ut_get_status()" will be
 *			    UT_BAD_ARG  	"factor" is 0 or "unit" is NULL.
 *			    UT_OS		Operating-system error.  See
 *						"errno".
 *	else		Pointer to the resulting unit.  The pointer should be
 *			passed to ut_free() when the unit is no longer needed by
 *			the client.
 */
ut_unit*
ut_scale(
    const double		factor,
    const ut_unit* const	unit);


/*
 * Returns a unit equivalent to another unit offset by a numeric amount,
 * e.g.,
 *	const ut_unit*	kelvin = ...
 *	const ut_unit*	celsius = ut_offset(kelvin, 273.15);
 *
 * Arguments:
 *	unit		Pointer to the unit to be offset.
 *	offset		The numeric offset.
 * Returns:
 *	NULL		Failure.  "ut_get_status()" will be
 *			    UT_BAD_ARG		"unit" is NULL.
 *			    UT_OS		Operating-system error.  See
 *						"errno".
 *	else		Pointer to the resulting unit.  The pointer should be
 *			passed to ut_free() when the unit is no longer needed by
 *			the client.
 */
ut_unit*
ut_offset(
    const ut_unit* const	unit,
    const double	offset);


/*
 * Returns a unit equivalent to another unit relative to a particular time.
 * e.g.,
 *	const ut_unit*	second = ...
 *	const ut_unit*	secondsSinceTheEpoch =
 *              ut_offset_by_time(second, ut_encode_time(1970, 1, 1, 0, 0, 0.0));
 *
 * Arguments:
 *	unit	Pointer to the time-unit to be made relative to a time-origin.
 *	origin	The origin as returned by ut_encode_time().
 * Returns:
 *	NULL	Failure.  "ut_get_status()" will be
 *		    UT_BAD_ARG		"unit" is NULL.
 *		    UT_OS		Operating-system error.  See "errno".
 *		    UT_MEANINGLESS	Creation of a timestamp unit based on
 *					"unit" is not meaningful.
 *		    UT_NO_SECOND	The associated unit-system doesn't
 *					contain a "second" unit.  See
 *					ut_set_second().
 *	else	Pointer to the resulting unit.  The pointer should be passed
 *		to ut_free() when the unit is no longer needed by the client.
 */
ut_unit*
ut_offset_by_time(
    const ut_unit* const	unit,
    const double	origin);


/*
 * Returns the result of multiplying one unit by another unit.
 *
 * Arguments:
 *	unit1	Pointer to a unit.
 *	unit2	Pointer to another unit.
 * Returns:
 *	NULL	Failure.  "ut_get_status()" will be:
 *		    UT_BAD_ARG		"unit1" or "unit2" is NULL.
 *		    UT_NOT_SAME_SYSTEM	"unit1" and "unit2" belong to
 *					different unit-systems.
 *		    UT_OS		Operating-system error. See "errno".
 *	else	Pointer to the resulting unit.  The pointer should be passed
 *		to ut_free() when the unit is no longer needed by the client.
 */
ut_unit*
ut_multiply(
    const ut_unit* const	unit1,
    const ut_unit* const	unit2);


/*
 * Returns the inverse (i.e., reciprocal) of a unit.  This convenience function
 * is equal to "ut_raise(unit, -1)".
 *
 * Arguments:
 *	unit	Pointer to the unit.
 * Returns:
 *	NULL	Failure.  "ut_get_status()" will be:
 *		    UT_BAD_ARG		"unit" is NULL.
 *		    UT_OS		Operating-system error. See "errno".
 *	else	Pointer to the resulting unit.  The pointer should be passed to
 *		ut_free() when the unit is no longer needed by the client.
 */
ut_unit*
ut_invert(
    const ut_unit* const	unit);


/*
 * Returns the result of dividing one unit by another unit.  This convenience
 * function is equivalent to the following sequence:
 *     {
 *         ut_unit* inverse = ut_invert(denom);
 *         ut_multiply(numer, inverse);
 *         ut_free(inverse);
 *     }
 *
 * Arguments:
 *	numer	Pointer to the numerator (top, dividend) unit.
 *	denom	Pointer to the denominator (bottom, divisor) unit.
 * Returns:
 *	NULL	Failure.  "ut_get_status()" will be:
 *		    UT_BAD_ARG		"numer" or "denom" is NULL.
 *		    UT_NOT_SAME_SYSTEM	"unit1" and "unit2" belong to
 *					different unit-systems.
 *		    UT_OS		Operating-system error. See "errno".
 *	else	Pointer to the resulting unit.  The pointer should be passed to
 *		ut_free() when the unit is no longer needed by the client.
 */
ut_unit*
ut_divide(
    const ut_unit* const	numer,
    const ut_unit* const	denom);


/*
 * Returns the result of raising a unit to a power.
 *
 * Arguments:
 *	unit	Pointer to the unit.
 *	power	The power by which to raise "unit".  Must be greater than or 
 *		equal to -255 and less than or equal to 255.
 * Returns:
 *	NULL	Failure.  "ut_get_status()" will be:
 *		    UT_BAD_ARG		"unit" is NULL or "power" is invalid.
 *		    UT_OS		Operating-system error. See "errno".
 *	else	Pointer to the resulting unit.  The pointer should be passed to
 *		ut_free() when the unit is no longer needed by the client.
 */
ut_unit*
ut_raise(
    const ut_unit* const	unit,
    const int			power);


/*
 * Returns the result of taking the root of a unit.
 *
 * Arguments:
 *	unit	Pointer to the unit.
 *	root	The root to take of "unit".  Must be greater than or 
 *		equal to 1 and less than or equal to 255.
 * Returns:
 *	NULL	Failure.  "ut_get_status()" will be:
 *		    UT_BAD_ARG		"unit" is NULL, or "root" is invalid.
 *		                        In particular, all powers of base units
 *		                        in "unit" must be integral multiples of
 *		                        "root".
 *		    UT_OS		Operating-system error. See "errno".
 *	else	Pointer to the resulting unit.  The pointer should be passed to
 *		ut_free() when the unit is no longer needed by the client.
 */
ut_unit*
ut_root(
    const ut_unit* const	unit,
    const int			root);


/*
 * Returns the logarithmic unit corresponding to a logarithmic base and a
 * reference level.  For example, the following creates a decibel unit with a
 * one milliwatt reference level:
 *
 *     const ut_unit* watt = ...;
 *     const ut_unit* milliWatt = ut_scale(0.001, watt);
 *
 *     if (milliWatt != NULL) {
 *         const ut_unit* bel_1_mW = ut_log(10.0, milliWatt);
 *
 *         if (bel_1_mW != NULL) {
 *             const ut_unit* decibel_1_mW = ut_scale(0.1, bel_1_mW);
 *
 *             if (decibel_1_mW != NULL) {
 *                 ...
 *                 ut_free(decibel_1_mW);
 *             }			// "decibel_1_mW" allocated
 *
 *             ut_free(bel_1_mW);
 *         }				// "bel_1_mW" allocated
 *
 *         ut_free(milliWatt);
 *     }				// "milliWatt" allocated
 *
 * Arguments:
 *	base		The logarithmic base (e.g., 2, M_E, 10).  Must be
 *                      greater than one.  "M_E" is defined in <math.h>.
 *	reference	Pointer to the reference value as a unit.
 * Returns:
 *	NULL		Failure.  "ut_get_status()" will be:
 *			    UT_BAD_ARG	        "base" is invalid or "reference"
 *                                              is NULL.
 *			    UT_OS		Operating-system error. See
 *						"errno".
 *	else		Pointer to the resulting unit.  The pointer should be
 *			passed to ut_free() when the unit is no longer needed by
 *			the client.
 */
ut_unit*
ut_log(
    const double		base,
    const ut_unit* const	reference);


/******************************************************************************
 * Parsing and Formatting Units:
 ******************************************************************************/


/*
 * Returns the binary representation of a unit corresponding to a string
 * representation.
 *
 * Arguments:
 *	system		Pointer to the unit-system in which the parsing will
 *			occur.
 *	string		The string to be parsed (e.g., "millimeters").  There
 *			should be no leading or trailing whitespace in the
 *			string.  See ut_trim().
 *	encoding	The encoding of "string".
 * Returns:
 *	NULL		Failure.  "ut_get_status()" will be one of
 *			    UT_BAD_ARG		"system" or "string" is NULL.
 *			    UT_SYNTAX		"string" contained a syntax
 *						error.
 *			    UT_UNKNOWN		"string" contained an unknown
 *						identifier.
 *			    UT_OS		Operating-system failure.  See
 *						"errno".
 *	else		Pointer to the unit corresponding to "string".
 */
ut_unit*
ut_parse(
    const ut_system* const	system,
    const char* const		string,
    const ut_encoding		encoding);


/*
 * Removes leading and trailing whitespace from a string.
 *
 * Arguments:
 *	string		NUL-terminated string.  Will be modified if it contains
 *                      whitespace..
 *	encoding	The character-encoding of "string".
 * Returns:
 *      "string", with all leading and trailing whitespace removed.
 */
char*
ut_trim(
    char* const	        string,
    const ut_encoding	encoding);


/*
 * Formats a unit.
 *
 * Arguments:
 *	unit		Pointer to the unit to be formatted.
 *	buf		Pointer to the buffer into which to format "unit".
 *	size		Size of the buffer in bytes.
 *	opts		Formatting options: bitwise-OR of zero or more of the
 *			following:
 *			    UT_NAMES		Use unit names instead of
 *						symbols
 *                          UT_DEFINITION       The formatted string should be
 *                                              the definition of "unit" in
 *                                              terms of basic-units instead of
 *						stopping any expansion at the
 *						highest level possible.
 *			    UT_ASCII		The string should be formatted
 *						using the ASCII character set
 *						(default).
 *			    UT_LATIN1		The string should be formatted
 *						using the ISO Latin-1 (alias
 *						ISO-8859-1) character set.
 *			    UT_UTF8		The string should be formatted
 *						using the UTF-8 character set.
 *			UT_LATIN1 and UT_UTF8 are mutually exclusive: they may
 *			not both be specified.
 * Returns:
 *	-1		Failure:  "ut_get_status()" will be
 *			    UT_BAD_ARG		"unit" or "buf" is NULL, or both
 *                                              UT_LATIN1 and UT_UTF8 specified.
 *			    UT_CANT_FORMAT	"unit" can't be formatted in
 *						the desired manner.
 *      else		Success.  Number of characters printed in "buf".  If
 *			the number is equal to the size of the buffer, then the
 *			buffer is too small to have a terminating NUL character.
 */
int
ut_format(
    const ut_unit* const	unit,
    char*		buf,
    size_t		size,
    unsigned		opts);


/*
 * Accepts a visitor to a unit.
 *
 * Arguments:
 *	unit		Pointer to the unit to accept the visitor.
 *	visitor		Pointer to the visitor of "unit".
 *	arg		An arbitrary pointer that will be passed to "visitor".
 * Returns:
 *	UT_BAD_ARG	"unit" or "visitor" is NULL.
 *	UT_VISIT_ERROR	A error occurred in "visitor" while visiting "unit".
 *	UT_SUCCESS	Success.
 */
ut_status
ut_accept_visitor(
    const ut_unit* const		unit,
    const ut_visitor* const	visitor,
    void* const			arg);


/******************************************************************************
 * Time Handling:
 ******************************************************************************/


/*
 * Encodes a date as a double-precision value.
 *
 * Arguments:
 *	year		The year.
 *	month		The month.
 *	day		The day (1 = the first of the month).
 * Returns:
 *	The date encoded as a scalar value.
 */
double
ut_encode_date(
    int		year,
    int		month,
    int		day);


/*
 * Encodes a time as a double-precision value.
 *
 * Arguments:
 *	hours		The number of hours (0 = midnight).
 *	minutes		The number of minutes.
 *	seconds		The number of seconds.
 * Returns:
 *	The clock-time encoded as a scalar value.
 */
double
ut_encode_clock(
    int		hours,
    int		minutes,
    double	seconds);


/*
 * Encodes a time as a double-precision value.  The convenience function is
 * equivalent to "ut_encode_date(year,month,day) + 
 * ut_encode_clock(hour,minute,second)"
 *
 * Arguments:
 *	year	The year.
 *	month	The month.
 *	day	The day.
 *	hour	The hour.
 *	minute	The minute.
 *	second	The second.
 * Returns:
 *	The time encoded as a scalar value.
 */
double
ut_encode_time(
    const int		year,
    const int		month,
    const int		day,
    const int		hour,
    const int		minute,
    const double	second);


/*
 * Decodes a time from a double-precision value.
 *
 * Arguments:
 *      value           The value to be decoded.
 *      year            Pointer to the variable to be set to the year.
 *      month           Pointer to the variable to be set to the month.
 *      day             Pointer to the variable to be set to the day.
 *      hour            Pointer to the variable to be set to the hour.
 *      minute          Pointer to the variable to be set to the minute.
 *      second          Pointer to the variable to be set to the second.
 *      resolution      Pointer to the variable to be set to the resolution
 *                      of the decoded time in seconds.
 */
void
ut_decode_time(
    double	value,
    int		*year,
    int		*month,
    int		*day,
    int		*hour,
    int		*minute,
    double	*second,
    double	*resolution);


/******************************************************************************
 * Error Handling:
 ******************************************************************************/


/*
 * Returns the status of the last operation by the units module.  This function
 * will not change the status.
 */
ut_status
ut_get_status(void);


/*
 * Sets the status of the units module.  This function would not normally be
 * called by the user unless they were doing their own parsing or formatting.
 *
 * Arguments:
 *	status	The status of the units module.
 */
void
ut_set_status(
    ut_status	status);


/*
 * Handles an error-message.
 *
 * Arguments:
 *	fmt	The format for the error-message.
 *	...	The arguments for "fmt".
 * Returns:
 *	<0	An output error was encountered.
 *	else	The number of bytes of "fmt" and "arg" written excluding any
 *		terminating NUL.
 */
int
ut_handle_error_message(
    const char* const	fmt,
    ...);


/*
 * Returns the previously-installed error-message handler and optionally
 * installs a new handler.  The initial handler is "ut_write_to_stderr()".
 *
 * Arguments:
 *      handler		NULL or pointer to the error-message handler.  If NULL,
 *			then the handler is not changed.  The 
 *			currently-installed handler can be obtained this way.
 * Returns:
 *	Pointer to the previously-installed error-message handler.
 */
ut_error_message_handler
ut_set_error_message_handler(
    ut_error_message_handler	handler);


/*
 * Writes an error-message to the standard-error stream when received and
 * appends a newline.  This is the initial error-message handler.
 *
 * Arguments:
 *	fmt	The format for the error-message.
 *	args	The arguments of "fmt".
 * Returns:
 *	<0	A output error was encountered.  See "errno".
 *	else	The number of bytes of "fmt" and "arg" written excluding any
 *		terminating NUL.
 */
int
ut_write_to_stderr(
    const char* const	fmt,
    va_list		args);


/*
 * Does nothing with an error-message.
 *
 * Arguments:
 *	fmt	The format for the error-message.
 *	args	The arguments of "fmt".
 * Returns:
 *	0	Always.
 */
int
ut_ignore(
    const char* const	fmt,
    va_list		args);


#ifdef __cplusplus
}
#endif

#endif