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1// SPDX-License-Identifier: GPL-2.0-only
2/* -*- linux-c -*- ------------------------------------------------------- *
3 *
4 * Copyright (C) 1991, 1992 Linus Torvalds
5 * Copyright 2007 rPath, Inc. - All Rights Reserved
6 *
7 * ----------------------------------------------------------------------- */
8
9/*
10 * Oh, it's a waste of space, but oh-so-yummy for debugging.
11 */
12
13#include <linux/stdarg.h>
14
15#include <linux/compiler.h>
16#include <linux/ctype.h>
17#include <linux/kernel.h>
18#include <linux/limits.h>
19#include <linux/string.h>
20#include <linux/types.h>
21
22static
23int skip_atoi(const char **s)
24{
25 int i = 0;
26
27 while (isdigit(**s))
28 i = i * 10 + *((*s)++) - '0';
29 return i;
30}
31
32/*
33 * put_dec_full4 handles numbers in the range 0 <= r < 10000.
34 * The multiplier 0xccd is round(2^15/10), and the approximation
35 * r/10 == (r * 0xccd) >> 15 is exact for all r < 16389.
36 */
37static
38void put_dec_full4(char *end, unsigned int r)
39{
40 int i;
41
42 for (i = 0; i < 3; i++) {
43 unsigned int q = (r * 0xccd) >> 15;
44 *--end = '0' + (r - q * 10);
45 r = q;
46 }
47 *--end = '0' + r;
48}
49
50/* put_dec is copied from lib/vsprintf.c with small modifications */
51
52/*
53 * Call put_dec_full4 on x % 10000, return x / 10000.
54 * The approximation x/10000 == (x * 0x346DC5D7) >> 43
55 * holds for all x < 1,128,869,999. The largest value this
56 * helper will ever be asked to convert is 1,125,520,955.
57 * (second call in the put_dec code, assuming n is all-ones).
58 */
59static
60unsigned int put_dec_helper4(char *end, unsigned int x)
61{
62 unsigned int q = (x * 0x346DC5D7ULL) >> 43;
63
64 put_dec_full4(end, x - q * 10000);
65 return q;
66}
67
68/* Based on code by Douglas W. Jones found at
69 * <http://www.cs.uiowa.edu/~jones/bcd/decimal.html#sixtyfour>
70 * (with permission from the author).
71 * Performs no 64-bit division and hence should be fast on 32-bit machines.
72 */
73static
74char *put_dec(char *end, unsigned long long n)
75{
76 unsigned int d3, d2, d1, q, h;
77 char *p = end;
78
79 d1 = ((unsigned int)n >> 16); /* implicit "& 0xffff" */
80 h = (n >> 32);
81 d2 = (h ) & 0xffff;
82 d3 = (h >> 16); /* implicit "& 0xffff" */
83
84 /* n = 2^48 d3 + 2^32 d2 + 2^16 d1 + d0
85 = 281_4749_7671_0656 d3 + 42_9496_7296 d2 + 6_5536 d1 + d0 */
86 q = 656 * d3 + 7296 * d2 + 5536 * d1 + ((unsigned int)n & 0xffff);
87 q = put_dec_helper4(p, q);
88 p -= 4;
89
90 q += 7671 * d3 + 9496 * d2 + 6 * d1;
91 q = put_dec_helper4(p, q);
92 p -= 4;
93
94 q += 4749 * d3 + 42 * d2;
95 q = put_dec_helper4(p, q);
96 p -= 4;
97
98 q += 281 * d3;
99 q = put_dec_helper4(p, q);
100 p -= 4;
101
102 put_dec_full4(p, q);
103 p -= 4;
104
105 /* strip off the extra 0's we printed */
106 while (p < end && *p == '0')
107 ++p;
108
109 return p;
110}
111
112static
113char *number(char *end, unsigned long long num, int base, char locase)
114{
115 /*
116 * locase = 0 or 0x20. ORing digits or letters with 'locase'
117 * produces same digits or (maybe lowercased) letters
118 */
119
120 /* we are called with base 8, 10 or 16, only, thus don't need "G..." */
121 static const char digits[16] = "0123456789ABCDEF"; /* "GHIJKLMNOPQRSTUVWXYZ"; */
122
123 switch (base) {
124 case 10:
125 if (num != 0)
126 end = put_dec(end, num);
127 break;
128 case 8:
129 for (; num != 0; num >>= 3)
130 *--end = '0' + (num & 07);
131 break;
132 case 16:
133 for (; num != 0; num >>= 4)
134 *--end = digits[num & 0xf] | locase;
135 break;
136 default:
137 unreachable();
138 }
139
140 return end;
141}
142
143#define ZEROPAD 1 /* pad with zero */
144#define SIGN 2 /* unsigned/signed long */
145#define PLUS 4 /* show plus */
146#define SPACE 8 /* space if plus */
147#define LEFT 16 /* left justified */
148#define SMALL 32 /* Must be 32 == 0x20 */
149#define SPECIAL 64 /* 0x */
150#define WIDE 128 /* UTF-16 string */
151
152static
153int get_flags(const char **fmt)
154{
155 int flags = 0;
156
157 do {
158 switch (**fmt) {
159 case '-':
160 flags |= LEFT;
161 break;
162 case '+':
163 flags |= PLUS;
164 break;
165 case ' ':
166 flags |= SPACE;
167 break;
168 case '#':
169 flags |= SPECIAL;
170 break;
171 case '0':
172 flags |= ZEROPAD;
173 break;
174 default:
175 return flags;
176 }
177 ++(*fmt);
178 } while (1);
179}
180
181static
182int get_int(const char **fmt, va_list *ap)
183{
184 if (isdigit(**fmt))
185 return skip_atoi(fmt);
186 if (**fmt == '*') {
187 ++(*fmt);
188 /* it's the next argument */
189 return va_arg(*ap, int);
190 }
191 return 0;
192}
193
194static
195unsigned long long get_number(int sign, int qualifier, va_list *ap)
196{
197 if (sign) {
198 switch (qualifier) {
199 case 'L':
200 return va_arg(*ap, long long);
201 case 'l':
202 return va_arg(*ap, long);
203 case 'h':
204 return (short)va_arg(*ap, int);
205 case 'H':
206 return (signed char)va_arg(*ap, int);
207 default:
208 return va_arg(*ap, int);
209 };
210 } else {
211 switch (qualifier) {
212 case 'L':
213 return va_arg(*ap, unsigned long long);
214 case 'l':
215 return va_arg(*ap, unsigned long);
216 case 'h':
217 return (unsigned short)va_arg(*ap, int);
218 case 'H':
219 return (unsigned char)va_arg(*ap, int);
220 default:
221 return va_arg(*ap, unsigned int);
222 }
223 }
224}
225
226static
227char get_sign(long long *num, int flags)
228{
229 if (!(flags & SIGN))
230 return 0;
231 if (*num < 0) {
232 *num = -(*num);
233 return '-';
234 }
235 if (flags & PLUS)
236 return '+';
237 if (flags & SPACE)
238 return ' ';
239 return 0;
240}
241
242static
243size_t utf16s_utf8nlen(const u16 *s16, size_t maxlen)
244{
245 size_t len, clen;
246
247 for (len = 0; len < maxlen && *s16; len += clen) {
248 u16 c0 = *s16++;
249
250 /* First, get the length for a BMP character */
251 clen = 1 + (c0 >= 0x80) + (c0 >= 0x800);
252 if (len + clen > maxlen)
253 break;
254 /*
255 * If this is a high surrogate, and we're already at maxlen, we
256 * can't include the character if it's a valid surrogate pair.
257 * Avoid accessing one extra word just to check if it's valid
258 * or not.
259 */
260 if ((c0 & 0xfc00) == 0xd800) {
261 if (len + clen == maxlen)
262 break;
263 if ((*s16 & 0xfc00) == 0xdc00) {
264 ++s16;
265 ++clen;
266 }
267 }
268 }
269
270 return len;
271}
272
273static
274u32 utf16_to_utf32(const u16 **s16)
275{
276 u16 c0, c1;
277
278 c0 = *(*s16)++;
279 /* not a surrogate */
280 if ((c0 & 0xf800) != 0xd800)
281 return c0;
282 /* invalid: low surrogate instead of high */
283 if (c0 & 0x0400)
284 return 0xfffd;
285 c1 = **s16;
286 /* invalid: missing low surrogate */
287 if ((c1 & 0xfc00) != 0xdc00)
288 return 0xfffd;
289 /* valid surrogate pair */
290 ++(*s16);
291 return (0x10000 - (0xd800 << 10) - 0xdc00) + (c0 << 10) + c1;
292}
293
294#define PUTC(c) \
295do { \
296 if (pos < size) \
297 buf[pos] = (c); \
298 ++pos; \
299} while (0);
300
301int vsnprintf(char *buf, size_t size, const char *fmt, va_list ap)
302{
303 /* The maximum space required is to print a 64-bit number in octal */
304 char tmp[(sizeof(unsigned long long) * 8 + 2) / 3];
305 char *tmp_end = &tmp[ARRAY_SIZE(tmp)];
306 long long num;
307 int base;
308 const char *s;
309 size_t len, pos;
310 char sign;
311
312 int flags; /* flags to number() */
313
314 int field_width; /* width of output field */
315 int precision; /* min. # of digits for integers; max
316 number of chars for from string */
317 int qualifier; /* 'h', 'hh', 'l' or 'll' for integer fields */
318
319 va_list args;
320
321 /*
322 * We want to pass our input va_list to helper functions by reference,
323 * but there's an annoying edge case. If va_list was originally passed
324 * to us by value, we could just pass &ap down to the helpers. This is
325 * the case on, for example, X86_32.
326 * However, on X86_64 (and possibly others), va_list is actually a
327 * size-1 array containing a structure. Our function parameter ap has
328 * decayed from T[1] to T*, and &ap has type T** rather than T(*)[1],
329 * which is what will be expected by a function taking a va_list *
330 * parameter.
331 * One standard way to solve this mess is by creating a copy in a local
332 * variable of type va_list and then passing a pointer to that local
333 * copy instead, which is what we do here.
334 */
335 va_copy(args, ap);
336
337 for (pos = 0; *fmt; ++fmt) {
338 if (*fmt != '%' || *++fmt == '%') {
339 PUTC(*fmt);
340 continue;
341 }
342
343 /* process flags */
344 flags = get_flags(&fmt);
345
346 /* get field width */
347 field_width = get_int(&fmt, &args);
348 if (field_width < 0) {
349 field_width = -field_width;
350 flags |= LEFT;
351 }
352
353 if (flags & LEFT)
354 flags &= ~ZEROPAD;
355
356 /* get the precision */
357 precision = -1;
358 if (*fmt == '.') {
359 ++fmt;
360 precision = get_int(&fmt, &args);
361 if (precision >= 0)
362 flags &= ~ZEROPAD;
363 }
364
365 /* get the conversion qualifier */
366 qualifier = -1;
367 if (*fmt == 'h' || *fmt == 'l') {
368 qualifier = *fmt;
369 ++fmt;
370 if (qualifier == *fmt) {
371 qualifier -= 'a'-'A';
372 ++fmt;
373 }
374 }
375
376 sign = 0;
377
378 switch (*fmt) {
379 case 'c':
380 flags &= LEFT;
381 s = tmp;
382 if (qualifier == 'l') {
383 ((u16 *)tmp)[0] = (u16)va_arg(args, unsigned int);
384 ((u16 *)tmp)[1] = L'\0';
385 precision = INT_MAX;
386 goto wstring;
387 } else {
388 tmp[0] = (unsigned char)va_arg(args, int);
389 precision = len = 1;
390 }
391 goto output;
392
393 case 's':
394 flags &= LEFT;
395 if (precision < 0)
396 precision = INT_MAX;
397 s = va_arg(args, void *);
398 if (!s)
399 s = precision < 6 ? "" : "(null)";
400 else if (qualifier == 'l') {
401 wstring:
402 flags |= WIDE;
403 precision = len = utf16s_utf8nlen((const u16 *)s, precision);
404 goto output;
405 }
406 precision = len = strnlen(s, precision);
407 goto output;
408
409 /* integer number formats - set up the flags and "break" */
410 case 'o':
411 base = 8;
412 break;
413
414 case 'p':
415 if (precision < 0)
416 precision = 2 * sizeof(void *);
417 fallthrough;
418 case 'x':
419 flags |= SMALL;
420 fallthrough;
421 case 'X':
422 base = 16;
423 break;
424
425 case 'd':
426 case 'i':
427 flags |= SIGN;
428 fallthrough;
429 case 'u':
430 flags &= ~SPECIAL;
431 base = 10;
432 break;
433
434 default:
435 /*
436 * Bail out if the conversion specifier is invalid.
437 * There's probably a typo in the format string and the
438 * remaining specifiers are unlikely to match up with
439 * the arguments.
440 */
441 goto fail;
442 }
443 if (*fmt == 'p') {
444 num = (unsigned long)va_arg(args, void *);
445 } else {
446 num = get_number(flags & SIGN, qualifier, &args);
447 }
448
449 sign = get_sign(&num, flags);
450 if (sign)
451 --field_width;
452
453 s = number(tmp_end, num, base, flags & SMALL);
454 len = tmp_end - s;
455 /* default precision is 1 */
456 if (precision < 0)
457 precision = 1;
458 /* precision is minimum number of digits to print */
459 if (precision < len)
460 precision = len;
461 if (flags & SPECIAL) {
462 /*
463 * For octal, a leading 0 is printed only if necessary,
464 * i.e. if it's not already there because of the
465 * precision.
466 */
467 if (base == 8 && precision == len)
468 ++precision;
469 /*
470 * For hexadecimal, the leading 0x is skipped if the
471 * output is empty, i.e. both the number and the
472 * precision are 0.
473 */
474 if (base == 16 && precision > 0)
475 field_width -= 2;
476 else
477 flags &= ~SPECIAL;
478 }
479 /*
480 * For zero padding, increase the precision to fill the field
481 * width.
482 */
483 if ((flags & ZEROPAD) && field_width > precision)
484 precision = field_width;
485
486output:
487 /* Calculate the padding necessary */
488 field_width -= precision;
489 /* Leading padding with ' ' */
490 if (!(flags & LEFT))
491 while (field_width-- > 0)
492 PUTC(' ');
493 /* sign */
494 if (sign)
495 PUTC(sign);
496 /* 0x/0X for hexadecimal */
497 if (flags & SPECIAL) {
498 PUTC('0');
499 PUTC( 'X' | (flags & SMALL));
500 }
501 /* Zero padding and excess precision */
502 while (precision-- > len)
503 PUTC('0');
504 /* Actual output */
505 if (flags & WIDE) {
506 const u16 *ws = (const u16 *)s;
507
508 while (len-- > 0) {
509 u32 c32 = utf16_to_utf32(&ws);
510 u8 *s8;
511 size_t clen;
512
513 if (c32 < 0x80) {
514 PUTC(c32);
515 continue;
516 }
517
518 /* Number of trailing octets */
519 clen = 1 + (c32 >= 0x800) + (c32 >= 0x10000);
520
521 len -= clen;
522 s8 = (u8 *)&buf[pos];
523
524 /* Avoid writing partial character */
525 PUTC('\0');
526 pos += clen;
527 if (pos >= size)
528 continue;
529
530 /* Set high bits of leading octet */
531 *s8 = (0xf00 >> 1) >> clen;
532 /* Write trailing octets in reverse order */
533 for (s8 += clen; clen; --clen, c32 >>= 6)
534 *s8-- = 0x80 | (c32 & 0x3f);
535 /* Set low bits of leading octet */
536 *s8 |= c32;
537 }
538 } else {
539 while (len-- > 0)
540 PUTC(*s++);
541 }
542 /* Trailing padding with ' ' */
543 while (field_width-- > 0)
544 PUTC(' ');
545 }
546fail:
547 va_end(args);
548
549 if (size)
550 buf[min(pos, size-1)] = '\0';
551
552 return pos;
553}
554
555int snprintf(char *buf, size_t size, const char *fmt, ...)
556{
557 va_list args;
558 int i;
559
560 va_start(args, fmt);
561 i = vsnprintf(buf, size, fmt, args);
562 va_end(args);
563 return i;
564}