summaryrefslogtreecommitdiff
path: root/payloads/libpayload/libc/printf.c
blob: 8be713c1ef5bb00748e0a1325668ff7cdd76edfa (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
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
/*
 * This file is part of the libpayload project.
 *
 * It has originally been taken from the HelenOS project
 * (http://www.helenos.eu), and slightly modified for our purposes.
 *
 * Copyright (C) 2001-2004 Jakub Jermar
 * Copyright (C) 2006 Josef Cejka
 * Copyright (C) 2008 Uwe Hermann <uwe@hermann-uwe.de>
 * All rights reserved.
 *
 * Redistribution and use in source and binary forms, with or without
 * modification, are permitted provided that the following conditions
 * are met:
 *
 * - Redistributions of source code must retain the above copyright
 *   notice, this list of conditions and the following disclaimer.
 * - Redistributions in binary form must reproduce the above copyright
 *   notice, this list of conditions and the following disclaimer in the
 *   documentation and/or other materials provided with the distribution.
 * - The name of the author may not be used to endorse or promote products
 *   derived from this software without specific prior written permission.
 *
 * THIS SOFTWARE IS PROVIDED BY THE AUTHOR ``AS IS'' AND ANY EXPRESS OR
 * IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED WARRANTIES
 * OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE DISCLAIMED.
 * IN NO EVENT SHALL THE AUTHOR BE LIABLE FOR ANY DIRECT, INDIRECT,
 * INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT
 * NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
 * DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY
 * THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
 * (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF
 * THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
 */

#include <libpayload.h>
#include <stdarg.h>

/** Structure for specifying output methods for different printf clones. */
struct printf_spec {
	/* Output function, returns count of printed characters or EOF. */
	int (*write) (void *, size_t, void *);
	/* Support data - output stream specification, its state, locks, ... */
	void *data;
};

/** Show prefixes 0x or 0. */
#define __PRINTF_FLAG_PREFIX		0x00000001
/** Signed / unsigned number. */
#define __PRINTF_FLAG_SIGNED		0x00000002
/** Print leading zeroes. */
#define __PRINTF_FLAG_ZEROPADDED	0x00000004
/** Align to left. */
#define __PRINTF_FLAG_LEFTALIGNED	0x00000010
/** Always show + sign. */
#define __PRINTF_FLAG_SHOWPLUS		0x00000020
/** Print space instead of plus. */
#define __PRINTF_FLAG_SPACESIGN		0x00000040
/** Show big characters. */
#define __PRINTF_FLAG_BIGCHARS		0x00000080
/** Number has - sign. */
#define __PRINTF_FLAG_NEGATIVE		0x00000100

/**
 * Buffer big enough for 64-bit number printed in base 2, sign, prefix and 0
 * to terminate string (last one is only for better testing end of buffer by
 * zero-filling subroutine).
 */
#define PRINT_NUMBER_BUFFER_SIZE	(64 + 5)

/** Enumeration of possible arguments types. */
typedef enum {
	PrintfQualifierByte = 0,
	PrintfQualifierShort,
	PrintfQualifierInt,
	PrintfQualifierLong,
	PrintfQualifierLongLong,
	PrintfQualifierPointer,
} qualifier_t;

static char digits_small[] = "0123456789abcdef";
static char digits_big[] = "0123456789ABCDEF";

/**
 * Print one or more characters without adding newline.
 *
 * @param buf	Buffer of >= count bytesi size. NULL pointer is not allowed!
 * @param count	Number of characters to print.
 * @param ps	Output method and its data.
 * @return	Number of characters printed.
 */
static int printf_putnchars(const char *buf, size_t count,
			    struct printf_spec *ps)
{
	return ps->write((void *)buf, count, ps->data);
}

/**
 * Print a string without adding a newline.
 *
 * @param str	String to print.
 * @param ps	Write function specification and support data.
 * @return	Number of characters printed.
 */
static int printf_putstr(const char *str, struct printf_spec *ps)
{
	size_t count;

	if (str == NULL) {
		char *nullstr = "(NULL)";
		return printf_putnchars(nullstr, strlen(nullstr), ps);
	}

	count = strlen(str);

	return ps->write((void *)str, count, ps->data);
}

/**
 * Print one character.
 *
 * @param c	Character to be printed.
 * @param ps	Output method.
 * @return	Number of characters printed.
 */
static int printf_putchar(int c, struct printf_spec *ps)
{
	unsigned char ch = c;

	return ps->write((void *)&ch, 1, ps->data);
}

/**
 * Print one formatted character.
 *
 * @param c	Character to print.
 * @param width	Width modifier.
 * @param flags	Flags that change the way the character is printed.
 * @return	Number of characters printed, negative value on failure.
 */
static int print_char(char c, int width, uint64_t flags, struct printf_spec *ps)
{
	int counter = 0;

	if (!(flags & __PRINTF_FLAG_LEFTALIGNED)) {
		while (--width > 0) {
			if (printf_putchar(' ', ps) > 0)
				++counter;
		}
	}

	if (printf_putchar(c, ps) > 0)
		counter++;

	while (--width > 0) {
		if (printf_putchar(' ', ps) > 0)
			++counter;
	}

	return ++counter;
}

/**
 * Print string.
 *
 * @param s		String to be printed.
 * @param width		Width modifier.
 * @param precision	Precision modifier.
 * @param flags		Flags that modify the way the string is printed.
 * @return		Number of characters printed, negative value on	failure.
 */
static int print_string(char *s, int width, unsigned int precision,
			uint64_t flags, struct printf_spec *ps)
{
	int counter = 0, retval;
	size_t size;

	if (s == NULL)
		return printf_putstr("(NULL)", ps);
	size = strlen(s);
	/* Print leading spaces. */
	if (precision == 0)
		precision = size;
	width -= precision;

	if (!(flags & __PRINTF_FLAG_LEFTALIGNED)) {
		while (width-- > 0) {
			if (printf_putchar(' ', ps) == 1)
				counter++;
		}
	}

	if ((retval = printf_putnchars(s, MIN(size, precision), ps)) < 0)
		return -counter;
	counter += retval;

	while (width-- > 0) {
		if (printf_putchar(' ', ps) == 1)
			++counter;
	}

	return counter;
}

/**
 * Print a number in a given base.
 *
 * Print significant digits of a number in given base.
 *
 * @param num		Number to print.
 * @param widt		Width modifier.h
 * @param precision	Precision modifier.
 * @param base		Base to print the number in (must be between 2 and 16).
 * @param flags		Flags that modify the way the number is printed.
 * @return		Number of characters printed.
 */
static int print_number(uint64_t num, int width, int precision, int base,
			uint64_t flags, struct printf_spec *ps)
{
	char *digits = digits_small;
	char d[PRINT_NUMBER_BUFFER_SIZE];
	char *ptr = &d[PRINT_NUMBER_BUFFER_SIZE - 1];
	int size = 0;		/* Size of number with all prefixes and signs. */
	int number_size;	/* Size of plain number. */
	char sgn;
	int retval;
	int counter = 0;

	if (flags & __PRINTF_FLAG_BIGCHARS)
		digits = digits_big;

	*ptr-- = 0;		/* Put zero at end of string. */

	if (num == 0) {
		*ptr-- = '0';
		size++;
	} else {
		do {
			*ptr-- = digits[num % base];
			size++;
		} while (num /= base);
	}

	number_size = size;

	/*
	 * Collect the sum of all prefixes/signs/... to calculate padding and
	 * leading zeroes.
	 */
	if (flags & __PRINTF_FLAG_PREFIX) {
		switch (base) {
		case 2:	/* Binary formating is not standard, but useful. */
			size += 2;
			break;
		case 8:
			size++;
			break;
		case 16:
			size += 2;
			break;
		}
	}

	sgn = 0;
	if (flags & __PRINTF_FLAG_SIGNED) {
		if (flags & __PRINTF_FLAG_NEGATIVE) {
			sgn = '-';
			size++;
		} else if (flags & __PRINTF_FLAG_SHOWPLUS) {
			sgn = '+';
			size++;
		} else if (flags & __PRINTF_FLAG_SPACESIGN) {
			sgn = ' ';
			size++;
		}
	}

	if (flags & __PRINTF_FLAG_LEFTALIGNED)
		flags &= ~__PRINTF_FLAG_ZEROPADDED;

	/*
	 * If the number is leftaligned or precision is specified then
	 * zeropadding is ignored.
	 */
	if (flags & __PRINTF_FLAG_ZEROPADDED) {
		if ((precision == 0) && (width > size))
			precision = width - size + number_size;
	}

	/* Print leading spaces. */
	if (number_size > precision) {
		/* Print the whole number not only a part. */
		precision = number_size;
	}

	width -= precision + size - number_size;

	if (!(flags & __PRINTF_FLAG_LEFTALIGNED)) {
		while (width-- > 0) {
			if (printf_putchar(' ', ps) == 1)
				counter++;
		}
	}

	/* Print sign. */
	if (sgn) {
		if (printf_putchar(sgn, ps) == 1)
			counter++;
	}

	/* Print prefix. */
	if (flags & __PRINTF_FLAG_PREFIX) {
		switch (base) {
		case 2:	/* Binary formating is not standard, but useful. */
			if (printf_putchar('0', ps) == 1)
				counter++;
			if (flags & __PRINTF_FLAG_BIGCHARS) {
				if (printf_putchar('B', ps) == 1)
					counter++;
			} else {
				if (printf_putchar('b', ps) == 1)
					counter++;
			}
			break;
		case 8:
			if (printf_putchar('o', ps) == 1)
				counter++;
			break;
		case 16:
			if (printf_putchar('0', ps) == 1)
				counter++;
			if (flags & __PRINTF_FLAG_BIGCHARS) {
				if (printf_putchar('X', ps) == 1)
					counter++;
			} else {
				if (printf_putchar('x', ps) == 1)
					counter++;
			}
			break;
		}
	}

	/* Print leading zeroes. */
	precision -= number_size;
	while (precision-- > 0) {
		if (printf_putchar('0', ps) == 1)
			counter++;
	}

	/* Print number itself. */
	if ((retval = printf_putstr(++ptr, ps)) > 0)
		counter += retval;

	/* Print ending spaces. */
	while (width-- > 0) {
		if (printf_putchar(' ', ps) == 1)
			counter++;
	}

	return counter;
}

/** Print formatted string.
 *
 * Print string formatted according to the fmt parameter and variadic arguments.
 * Each formatting directive must have the following form:
 * 
 * 	\% [ FLAGS ] [ WIDTH ] [ .PRECISION ] [ TYPE ] CONVERSION
 *
 * FLAGS:@n
 * 	- "#"	Force to print prefix.For \%o conversion, the prefix is 0, for
 *		\%x and \%X prefixes are 0x and	0X and for conversion \%b the
 *		prefix is 0b.
 *
 * 	- "-"	Align to left.
 *
 * 	- "+"	Print positive sign just as negative.
 *
 * 	- " "	If the printed number is positive and "+" flag is not set,
 *		print space in place of sign.
 *
 * 	- "0"	Print 0 as padding instead of spaces. Zeroes are placed between
 *		sign and the rest of the number. This flag is ignored if "-"
 *		flag is specified.
 * 
 * WIDTH:@n
 * 	- Specify the minimal width of a printed argument. If it is bigger,
 *	width is ignored. If width is specified with a "*" character instead of
 *	number, width is taken from parameter list. And integer parameter is
 *	expected before parameter for processed conversion specification. If
 *	this value is negative its absolute value is taken and the "-" flag is
 *	set.
 *
 * PRECISION:@n
 * 	- Value precision. For numbers it specifies minimum valid numbers.
 *	Smaller numbers are printed with leading zeroes. Bigger numbers are not
 *	affected. Strings with more than precision characters are cut off. Just
 *	as with width, an "*" can be used used instead of a number. An integer
 *	value is then expected in parameters. When both width and precision are
 *	specified using "*", the first parameter is used for width and the
 *	second one for precision.
 * 
 * TYPE:@n
 * 	- "hh"	Signed or unsigned char.@n
 * 	- "h"	Signed or unsigned short.@n
 * 	- ""	Signed or unsigned int (default value).@n
 * 	- "l"	Signed or unsigned long int.@n
 * 	- "ll"	Signed or unsigned long long int.@n
 * 
 * 
 * CONVERSION:@n
 * 	- %	Print percentile character itself.
 *
 * 	- c	Print single character.
 *
 * 	- s	Print zero terminated string. If a NULL value is passed as
 *		value, "(NULL)" is printed instead.
 * 
 * 	- P, p	Print value of a pointer. Void * value is expected and it is
 *		printed in hexadecimal notation with prefix (as with \%#X / \%#x
 *		for 32-bit or \%#X / \%#x for 64-bit long pointers).
 *
 * 	- b	Print value as unsigned binary number. Prefix is not printed by
 *		default. (Nonstandard extension.)
 * 
 * 	- o	Print value as unsigned octal number. Prefix is not printed by
 *		default. 
 *
 * 	- d, i	Print signed decimal number. There is no difference between d
 *		and i conversion.
 *
 * 	- u	Print unsigned decimal number.
 *
 * 	- X, x	Print hexadecimal number with upper- or lower-case. Prefix is
 *		not printed by default.
 * 
 * All other characters from fmt except the formatting directives are printed in
 * verbatim.
 *
 * @param fmt	Formatting NULL terminated string.
 * @param ps	TODO.
 * @param ap	TODO.
 * @return	Number of characters printed, negative value on failure.
 */
static int printf_core(const char *fmt, struct printf_spec *ps, va_list ap)
{
	int i = 0;		/* Index of the currently processed char from fmt */
	int j = 0;		/* Index to the first not printed nonformating character */
	int end;
	int counter;		/* Counter of printed characters */
	int retval;		/* Used to store return values from called functions */
	char c;
	qualifier_t qualifier;	/* Type of argument */
	int base;		/* Base in which a numeric parameter will be printed */
	uint64_t number;	/* Argument value */
	size_t size;		/* Byte size of integer parameter */
	int width, precision;
	uint64_t flags;

	counter = 0;

	while ((c = fmt[i])) {
		/* Control character. */
		if (c == '%') {
			/* Print common characters if any processed. */
			if (i > j) {
				if ((retval = printf_putnchars(&fmt[j],
				    (size_t) (i - j), ps)) < 0) {
					counter = -counter;
					goto out;	/* Error */
				}
				counter += retval;
			}

			j = i;
			/* Parse modifiers. */
			flags = 0;
			end = 0;

			do {
				++i;
				switch (c = fmt[i]) {
				case '#':
					flags |= __PRINTF_FLAG_PREFIX;
					break;
				case '-':
					flags |= __PRINTF_FLAG_LEFTALIGNED;
					break;
				case '+':
					flags |= __PRINTF_FLAG_SHOWPLUS;
					break;
				case ' ':
					flags |= __PRINTF_FLAG_SPACESIGN;
					break;
				case '0':
					flags |= __PRINTF_FLAG_ZEROPADDED;
					break;
				default:
					end = 1;
				};

			} while (end == 0);

			/* Width & '*' operator. */
			width = 0;
			if (isdigit(fmt[i])) {
				while (isdigit(fmt[i])) {
					width *= 10;
					width += fmt[i++] - '0';
				}
			} else if (fmt[i] == '*') {
				/* Get width value from argument list. */
				i++;
				width = (int)va_arg(ap, int);
				if (width < 0) {
					/* Negative width sets '-' flag. */
					width *= -1;
					flags |= __PRINTF_FLAG_LEFTALIGNED;
				}
			}

			/* Precision and '*' operator. */
			precision = 0;
			if (fmt[i] == '.') {
				++i;
				if (isdigit(fmt[i])) {
					while (isdigit(fmt[i])) {
						precision *= 10;
						precision += fmt[i++] - '0';
					}
				} else if (fmt[i] == '*') {
					/* Get precision from argument list. */
					i++;
					precision = (int)va_arg(ap, int);
					/* Ignore negative precision. */
					if (precision < 0)
						precision = 0;
				}
			}

			switch (fmt[i++]) {
			/** @todo unimplemented qualifiers:
			 * t ptrdiff_t - ISO C 99
			 */
			case 'h':	/* char or short */
				qualifier = PrintfQualifierShort;
				if (fmt[i] == 'h') {
					i++;
					qualifier = PrintfQualifierByte;
				}
				break;
			case 'l':	/* long or long long */
				qualifier = PrintfQualifierLong;
				if (fmt[i] == 'l') {
					i++;
					qualifier = PrintfQualifierLongLong;
				}
				break;
			default:
				/* default type */
				qualifier = PrintfQualifierInt;
				--i;
			}

			base = 10;

			switch (c = fmt[i]) {
			/* String and character conversions */
			case 's':
				if ((retval = print_string(va_arg(ap, char *),
				    width, precision, flags, ps)) < 0) {
					counter = -counter;
					goto out;
				};
				counter += retval;
				j = i + 1;
				goto next_char;
			case 'c':
				c = va_arg(ap, unsigned int);
				retval = print_char(c, width, flags, ps);
				if (retval < 0) {
					counter = -counter;
					goto out;
				};
				counter += retval;
				j = i + 1;
				goto next_char;

			/* Integer values */
			case 'P':	/* pointer */
				flags |= __PRINTF_FLAG_BIGCHARS;
			case 'p':
				flags |= __PRINTF_FLAG_PREFIX;
				base = 16;
				qualifier = PrintfQualifierPointer;
				break;
			case 'b':
				base = 2;
				break;
			case 'o':
				base = 8;
				break;
			case 'd':
			case 'i':
				flags |= __PRINTF_FLAG_SIGNED;
			case 'u':
				break;
			case 'X':
				flags |= __PRINTF_FLAG_BIGCHARS;
			case 'x':
				base = 16;
				break;
			case '%': /* percentile itself */
				j = i;
				goto next_char;
			default: /* Bad formatting */
				/*
				 * Unknown format. Now, j is the index of '%'
				 * so we will print whole bad format sequence.
				 */
				goto next_char;
			}

			/* Print integers. */
			/* Print number. */
			switch (qualifier) {
			case PrintfQualifierByte:
				size = sizeof(unsigned char);
				number = (uint64_t) va_arg(ap, unsigned int);
				break;
			case PrintfQualifierShort:
				size = sizeof(unsigned short);
				number = (uint64_t) va_arg(ap, unsigned int);
				break;
			case PrintfQualifierInt:
				size = sizeof(unsigned int);
				number = (uint64_t) va_arg(ap, unsigned int);
				break;
			case PrintfQualifierLong:
				size = sizeof(unsigned long);
				number = (uint64_t) va_arg(ap, unsigned long);
				break;
			case PrintfQualifierLongLong:
				size = sizeof(unsigned long long);
				number = (uint64_t) va_arg(ap, unsigned long long);
				break;
			case PrintfQualifierPointer:
				size = sizeof(void *);
				number = (uint64_t) (unsigned long)va_arg(ap, void *);
				break;
			default:	/* Unknown qualifier */
				counter = -counter;
				goto out;
			}

			if (flags & __PRINTF_FLAG_SIGNED) {
				if (number & (0x1 << (size * 8 - 1))) {
					flags |= __PRINTF_FLAG_NEGATIVE;

					if (size == sizeof(uint64_t)) {
						number = -((int64_t) number);
					} else {
						number = ~number;
						number &= ~(0xFFFFFFFFFFFFFFFFll << (size * 8));
						number++;
					}
				}
			}

			if ((retval = print_number(number, width, precision,
						   base, flags, ps)) < 0) {
				counter = -counter;
				goto out;
			}

			counter += retval;
			j = i + 1;
		}
next_char:
		++i;
	}

	if (i > j) {
		if ((retval = printf_putnchars(&fmt[j],
		    (u64) (i - j), ps)) < 0) {
			counter = -counter;
			goto out;	/* Error */

		}
		counter += retval;
	}

out:
	return counter;
}

int sprintf(char *str, const char *fmt, ...)
{
	int ret;
	va_list args;

	va_start(args, fmt);
	ret = vsprintf(str, fmt, args);
	va_end(args);

	return ret;
}

struct vsnprintf_data {
	size_t size;		/* Total space for string */
	size_t len;		/* Count of currently used characters */
	char *string;		/* Destination string */
};

/**
 * Write string to given buffer.
 *
 * Write at most data->size characters including trailing zero. According to
 * C99, snprintf() has to return number of characters that would have been
 * written if enough space had been available. Hence the return value is not
 * number of really printed characters but size of the input string.
 * Number of really used characters is stored in data->len.
 *
 * @param str	Source string to print.
 * @param count	Size of source string.
 * @param data	Structure with destination string, counter of used space
 *              and total string size.
 * @return Number of characters to print (not characters really printed!).
 */
static int vsnprintf_write(const char *str, size_t count,
			   struct vsnprintf_data *data)
{
	size_t i;

	i = data->size - data->len;
	if (i == 0)
		return count;

	/* We have only one free byte left in buffer => write trailing zero. */
	if (i == 1) {
		data->string[data->size - 1] = 0;
		data->len = data->size;
		return count;
	}

	/*
	 * We have not enough space for whole string with the trailing
	 * zero => print only a part of string.
	 */
	if (i <= count) {
		memcpy((void *)(data->string + data->len), (void *)str, i - 1);
		data->string[data->size - 1] = 0;
		data->len = data->size;
		return count;
	}

	/* Buffer is big enough to print whole string. */
	memcpy((void *)(data->string + data->len), (void *)str, count);
	data->len += count;
	/*
	 * Put trailing zero at end, but not count it into data->len so
	 * it could be rewritten next time.
	 */
	data->string[data->len] = 0;

	return count;
}

int vsnprintf(char *str, size_t size, const char *fmt, va_list ap)
{
	struct vsnprintf_data data = { size, 0, str };
	struct printf_spec ps =
	    { (int (*)(void *, size_t, void *))vsnprintf_write, &data };

	/* Print 0 at end of string - fix case that nothing will be printed. */
	if (size > 0)
		str[0] = 0;

	/* vsnprintf_write() ensures that str will be terminated by zero. */
	return printf_core(fmt, &ps, ap);
}

int vsprintf(char *str, const char *fmt, va_list ap)
{
	return vsnprintf(str, (size_t) - 1, fmt, ap);
}

int printf(const char *fmt, ...)
{
	int ret;
	va_list args;

	va_start(args, fmt);
	ret = vprintf(fmt, args);
	va_end(args);

	return ret;
}

static int vprintf_write(const char *str, size_t count, void *unused)
{
	size_t i;

	for (i = 0; i < count; i++)
		putchar(str[i]);

	return i;
}

int vprintf(const char *fmt, va_list ap)
{
	struct printf_spec ps =
	    { (int (*)(void *, size_t, void *))vprintf_write, NULL };

	return printf_core(fmt, &ps, ap);
}