1 // SPDX-License-Identifier: GPL-2.0-only
2 /* -*- linux-c -*- ------------------------------------------------------- *
4 * Copyright (C) 1991, 1992 Linus Torvalds
5 * Copyright 2007 rPath, Inc. - All Rights Reserved
7 * ----------------------------------------------------------------------- */
10 * Oh, it's a waste of space, but oh-so-yummy for debugging.
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>
23 int skip_atoi(const char **s)
28 i = i * 10 + *((*s)++) - '0';
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.
38 void put_dec_full4(char *end, unsigned int r)
42 for (i = 0; i < 3; i++) {
43 unsigned int q = (r * 0xccd) >> 15;
44 *--end = '0' + (r - q * 10);
50 /* put_dec is copied from lib/vsprintf.c with small modifications */
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).
60 unsigned int put_dec_helper4(char *end, unsigned int x)
62 unsigned int q = (x * 0x346DC5D7ULL) >> 43;
64 put_dec_full4(end, x - q * 10000);
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.
74 char *put_dec(char *end, unsigned long long n)
76 unsigned int d3, d2, d1, q, h;
79 d1 = ((unsigned int)n >> 16); /* implicit "& 0xffff" */
82 d3 = (h >> 16); /* implicit "& 0xffff" */
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);
90 q += 7671 * d3 + 9496 * d2 + 6 * d1;
91 q = put_dec_helper4(p, q);
94 q += 4749 * d3 + 42 * d2;
95 q = put_dec_helper4(p, q);
99 q = put_dec_helper4(p, q);
105 /* strip off the extra 0's we printed */
106 while (p < end && *p == '0')
113 char *number(char *end, unsigned long long num, int base, char locase)
116 * locase = 0 or 0x20. ORing digits or letters with 'locase'
117 * produces same digits or (maybe lowercased) letters
120 /* we are called with base 8, 10 or 16, only, thus don't need "G..." */
121 static const char digits[16] = "0123456789ABCDEF"; /* "GHIJKLMNOPQRSTUVWXYZ"; */
126 end = put_dec(end, num);
129 for (; num != 0; num >>= 3)
130 *--end = '0' + (num & 07);
133 for (; num != 0; num >>= 4)
134 *--end = digits[num & 0xf] | locase;
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 */
152 int get_flags(const char **fmt)
181 int get_int(const char **fmt, va_list *ap)
184 return skip_atoi(fmt);
187 /* it's the next argument */
188 return va_arg(*ap, int);
194 unsigned long long get_number(int sign, int qualifier, va_list *ap)
199 return va_arg(*ap, long long);
201 return va_arg(*ap, long);
203 return (short)va_arg(*ap, int);
205 return (signed char)va_arg(*ap, int);
207 return va_arg(*ap, int);
212 return va_arg(*ap, unsigned long long);
214 return va_arg(*ap, unsigned long);
216 return (unsigned short)va_arg(*ap, int);
218 return (unsigned char)va_arg(*ap, int);
220 return va_arg(*ap, unsigned int);
226 char get_sign(long long *num, int flags)
248 int vsnprintf(char *buf, size_t size, const char *fmt, va_list ap)
250 /* The maximum space required is to print a 64-bit number in octal */
251 char tmp[(sizeof(unsigned long long) * 8 + 2) / 3];
252 char *tmp_end = &tmp[ARRAY_SIZE(tmp)];
259 int flags; /* flags to number() */
261 int field_width; /* width of output field */
262 int precision; /* min. # of digits for integers; max
263 number of chars for from string */
264 int qualifier; /* 'h', 'hh', 'l' or 'll' for integer fields */
269 * We want to pass our input va_list to helper functions by reference,
270 * but there's an annoying edge case. If va_list was originally passed
271 * to us by value, we could just pass &ap down to the helpers. This is
272 * the case on, for example, X86_32.
273 * However, on X86_64 (and possibly others), va_list is actually a
274 * size-1 array containing a structure. Our function parameter ap has
275 * decayed from T[1] to T*, and &ap has type T** rather than T(*)[1],
276 * which is what will be expected by a function taking a va_list *
278 * One standard way to solve this mess is by creating a copy in a local
279 * variable of type va_list and then passing a pointer to that local
280 * copy instead, which is what we do here.
284 for (pos = 0; *fmt; ++fmt) {
285 if (*fmt != '%' || *++fmt == '%') {
291 flags = get_flags(&fmt);
293 /* get field width */
294 field_width = get_int(&fmt, &args);
295 if (field_width < 0) {
296 field_width = -field_width;
303 /* get the precision */
307 precision = get_int(&fmt, &args);
312 /* get the conversion qualifier */
314 if (*fmt == 'h' || *fmt == 'l') {
317 if (qualifier == *fmt) {
318 qualifier -= 'a'-'A';
328 tmp[0] = (unsigned char)va_arg(args, int);
337 s = va_arg(args, char *);
339 s = precision < 6 ? "" : "(null)";
340 precision = len = strnlen(s, precision);
343 /* integer number formats - set up the flags and "break" */
350 precision = 2 * sizeof(void *);
370 * Bail out if the conversion specifier is invalid.
371 * There's probably a typo in the format string and the
372 * remaining specifiers are unlikely to match up with
378 num = (unsigned long)va_arg(args, void *);
380 num = get_number(flags & SIGN, qualifier, &args);
383 sign = get_sign(&num, flags);
387 s = number(tmp_end, num, base, flags & SMALL);
389 /* default precision is 1 */
392 /* precision is minimum number of digits to print */
395 if (flags & SPECIAL) {
397 * For octal, a leading 0 is printed only if necessary,
398 * i.e. if it's not already there because of the
401 if (base == 8 && precision == len)
404 * For hexadecimal, the leading 0x is skipped if the
405 * output is empty, i.e. both the number and the
408 if (base == 16 && precision > 0)
414 * For zero padding, increase the precision to fill the field
417 if ((flags & ZEROPAD) && field_width > precision)
418 precision = field_width;
421 /* Calculate the padding necessary */
422 field_width -= precision;
423 /* Leading padding with ' ' */
425 while (field_width-- > 0)
430 /* 0x/0X for hexadecimal */
431 if (flags & SPECIAL) {
433 PUTC( 'X' | (flags & SMALL));
435 /* Zero padding and excess precision */
436 while (precision-- > len)
441 /* Trailing padding with ' ' */
442 while (field_width-- > 0)
449 buf[min(pos, size-1)] = '\0';
454 int snprintf(char *buf, size_t size, const char *fmt, ...)
460 i = vsnprintf(buf, size, fmt, args);