strace/vsprintf.c

/*
 * Taken from Linux kernel's linux/lib/vsprintf.c
 * and somewhat simplified.
 *
 * Copyright (C) 1991, 1992  Linus Torvalds
 */
/* vsprintf.c -- Lars Wirzenius & Linus Torvalds. */
/*
 * Wirzenius wrote this portably, Torvalds fucked it up :-)
 */

#include "defs.h"

#if USE_CUSTOM_PRINTF

#include <stdarg.h>
#include <limits.h>

#ifndef HAVE_FPUTS_UNLOCKED
# define fputs_unlocked fputs
#endif

#define noinline_for_stack /*nothing*/
#define likely(expr)       (expr)
#define unlikely(expr)     (expr)

#define do_div(n, d)       ({ __typeof(num) t = n % d; n /= d; t; })

#undef isdigit
#define isdigit(a) ((unsigned char)((a) - '0') <= 9)

static inline
int skip_atoi(const char **s)
{
	int i = 0;
	const char *p = *s;

	while (isdigit(*p))
		i = i*10 + *p++ - '0';

	*s = p;
	return i;
}

/* Decimal conversion is by far the most typical, and is used
 * for /proc and /sys data. This directly impacts e.g. top performance
 * with many processes running. We optimize it for speed
 * using ideas described at <http://www.cs.uiowa.edu/~jones/bcd/divide.html>
 * (with permission from the author, Douglas W. Jones).
 */

#if LONG_MAX != 0x7fffffffUL || LLONG_MAX != 0x7fffffffffffffffULL
/* Formats correctly any integer in [0, 999999999] */
static noinline_for_stack
char *put_dec_full9(char *buf, unsigned q)
{
	unsigned r;

	/* Possible ways to approx. divide by 10
	 * (x * 0x1999999a) >> 32 x < 1073741829 (multiply must be 64-bit)
	 * (x * 0xcccd) >> 19     x <      81920 (x < 262149 when 64-bit mul)
	 * (x * 0x6667) >> 18     x <      43699
	 * (x * 0x3334) >> 17     x <      16389
	 * (x * 0x199a) >> 16     x <      16389
	 * (x * 0x0ccd) >> 15     x <      16389
	 * (x * 0x0667) >> 14     x <       2739
	 * (x * 0x0334) >> 13     x <       1029
	 * (x * 0x019a) >> 12     x <       1029
	 * (x * 0x00cd) >> 11     x <       1029 shorter code than * 0x67 (on i386)
	 * (x * 0x0067) >> 10     x <        179
	 * (x * 0x0034) >>  9     x <         69 same
	 * (x * 0x001a) >>  8     x <         69 same
	 * (x * 0x000d) >>  7     x <         69 same, shortest code (on i386)
	 * (x * 0x0007) >>  6     x <         19
	 * See <http://www.cs.uiowa.edu/~jones/bcd/divide.html>
	 */
	r      = (q * (uint64_t)0x1999999a) >> 32;
	*buf++ = (q - 10 * r) + '0'; /* 1 */
	q      = (r * (uint64_t)0x1999999a) >> 32;
	*buf++ = (r - 10 * q) + '0'; /* 2 */
	r      = (q * (uint64_t)0x1999999a) >> 32;
	*buf++ = (q - 10 * r) + '0'; /* 3 */
	q      = (r * (uint64_t)0x1999999a) >> 32;
	*buf++ = (r - 10 * q) + '0'; /* 4 */
	r      = (q * (uint64_t)0x1999999a) >> 32;
	*buf++ = (q - 10 * r) + '0'; /* 5 */
	/* Now value is under 10000, can avoid 64-bit multiply */
	q      = (r * 0x199a) >> 16;
	*buf++ = (r - 10 * q)  + '0'; /* 6 */
	r      = (q * 0xcd) >> 11;
	*buf++ = (q - 10 * r)  + '0'; /* 7 */
	q      = (r * 0xcd) >> 11;
	*buf++ = (r - 10 * q) + '0'; /* 8 */
	*buf++ = q + '0'; /* 9 */
	return buf;
}
#endif

/* Similar to above but do not pad with zeros.
 * Code can be easily arranged to print 9 digits too, but our callers
 * always call put_dec_full9() instead when the number has 9 decimal digits.
 */
static noinline_for_stack
char *put_dec_trunc8(char *buf, unsigned r)
{
	unsigned q;

	/* Copy of previous function's body with added early returns */
	q      = (r * (uint64_t)0x1999999a) >> 32;
	*buf++ = (r - 10 * q) + '0'; /* 2 */
	if (q == 0) return buf;
	r      = (q * (uint64_t)0x1999999a) >> 32;
	*buf++ = (q - 10 * r) + '0'; /* 3 */
	if (r == 0) return buf;
	q      = (r * (uint64_t)0x1999999a) >> 32;
	*buf++ = (r - 10 * q) + '0'; /* 4 */
	if (q == 0) return buf;
	r      = (q * (uint64_t)0x1999999a) >> 32;
	*buf++ = (q - 10 * r) + '0'; /* 5 */
	if (r == 0) return buf;
	q      = (r * 0x199a) >> 16;
	*buf++ = (r - 10 * q)  + '0'; /* 6 */
	if (q == 0) return buf;
	r      = (q * 0xcd) >> 11;
	*buf++ = (q - 10 * r)  + '0'; /* 7 */
	if (r == 0) return buf;
	q      = (r * 0xcd) >> 11;
	*buf++ = (r - 10 * q) + '0'; /* 8 */
	if (q == 0) return buf;
	*buf++ = q + '0'; /* 9 */
	return buf;
}

/* There are two algorithms to print larger numbers.
 * One is generic: divide by 1000000000 and repeatedly print
 * groups of (up to) 9 digits. It's conceptually simple,
 * but requires a (unsigned long long) / 1000000000 division.
 *
 * Second algorithm splits 64-bit unsigned long long into 16-bit chunks,
 * manipulates them cleverly and generates groups of 4 decimal digits.
 * It so happens that it does NOT require long long division.
 *
 * If long is > 32 bits, division of 64-bit values is relatively easy,
 * and we will use the first algorithm.
 * If long long is > 64 bits (strange architecture with VERY large long long),
 * second algorithm can't be used, and we again use the first one.
 *
 * Else (if long is 32 bits and long long is 64 bits) we use second one.
 */

#if LONG_MAX != 0x7fffffffUL || LLONG_MAX != 0x7fffffffffffffffULL

/* First algorithm: generic */

static
char *put_dec(char *buf, unsigned long long n)
{
	if (n >= 100*1000*1000) {
		while (n >= 1000*1000*1000)
			buf = put_dec_full9(buf, do_div(n, 1000*1000*1000));
		if (n >= 100*1000*1000)
			return put_dec_full9(buf, n);
	}
	return put_dec_trunc8(buf, n);
}

#else

/* Second algorithm: valid only for 64-bit long longs */

static noinline_for_stack
char *put_dec_full4(char *buf, unsigned q)
{
	unsigned r;
	r      = (q * 0xcccd) >> 19;
	*buf++ = (q - 10 * r) + '0';
	q      = (r * 0x199a) >> 16;
	*buf++ = (r - 10 * q)  + '0';
	r      = (q * 0xcd) >> 11;
	*buf++ = (q - 10 * r)  + '0';
	*buf++ = r + '0';
	return buf;
}

/* Based on code by Douglas W. Jones found at
 * <http://www.cs.uiowa.edu/~jones/bcd/decimal.html#sixtyfour>
 * (with permission from the author).
 * Performs no 64-bit division and hence should be fast on 32-bit machines.
 */
static
char *put_dec(char *buf, unsigned long long n)
{
	uint32_t d3, d2, d1, q, h;

	if (n < 100*1000*1000)
		return put_dec_trunc8(buf, n);

	d1  = ((uint32_t)n >> 16); /* implicit "& 0xffff" */
	h   = (n >> 32);
	d2  = (h      ) & 0xffff;
	d3  = (h >> 16); /* implicit "& 0xffff" */

	q   = 656 * d3 + 7296 * d2 + 5536 * d1 + ((uint32_t)n & 0xffff);

	buf = put_dec_full4(buf, q % 10000);
	q   = q / 10000;

	d1  = q + 7671 * d3 + 9496 * d2 + 6 * d1;
	buf = put_dec_full4(buf, d1 % 10000);
	q   = d1 / 10000;

	d2  = q + 4749 * d3 + 42 * d2;
	buf = put_dec_full4(buf, d2 % 10000);
	q   = d2 / 10000;

	d3  = q + 281 * d3;
	if (!d3)
		goto done;
	buf = put_dec_full4(buf, d3 % 10000);
	q   = d3 / 10000;
	if (!q)
		goto done;
	buf = put_dec_full4(buf, q);
 done:
	while (buf[-1] == '0')
		--buf;

	return buf;
}

#endif

/*
 * For strace, the following formats are not supported:
 * %h[h]u, %zu, %tu  - use [unsigned] int/long/long long fmt instead
 * %8.4u  - no precision field for integers allowed (ok for strings)
 * %+d, % d  - no forced sign or force "space positive" sign
 * %-07u  - use %-7u instead
 * %X  - works as %x
 */

#define ZEROPAD	1		/* pad with zero */
#define SIGN	2		/* unsigned/signed long */
//#define PLUS	4		/* show plus */
//#define SPACE	8		/* space if plus */
#define LEFT	16		/* left justified */
//#deefine SMALL	32		/* use lowercase in hex (must be 32 == 0x20) */
#define SPECIAL	64		/* prefix hex with "0x", octal with "0" */

enum format_type {
	FORMAT_TYPE_NONE, /* Just a string part */
	FORMAT_TYPE_WIDTH,
	FORMAT_TYPE_PRECISION,
	FORMAT_TYPE_CHAR,
	FORMAT_TYPE_STR,
	FORMAT_TYPE_PTR,
	FORMAT_TYPE_PERCENT_CHAR,
	FORMAT_TYPE_INVALID,
	FORMAT_TYPE_LONG_LONG,
	FORMAT_TYPE_ULONG,
	FORMAT_TYPE_LONG,
	FORMAT_TYPE_UINT,
	FORMAT_TYPE_INT,
};

struct printf_spec {
	uint8_t	type;		/* format_type enum */
	uint8_t	flags;		/* flags to number() */
	uint8_t	base;		/* number base, 8, 10 or 16 only */
	uint8_t	qualifier;	/* number qualifier, one of 'hHlLtzZ' */
	int	field_width;	/* width of output field */
	int	precision;	/* # of digits/chars */
};

static noinline_for_stack
char *number(char *buf, char *end, unsigned long long num,
	     struct printf_spec spec)
{
	/* we are called with base 8, 10 or 16, only, thus don't need "G..."  */
	static const char digits[16] = "0123456789abcdef"; /* "GHIJKLMNOPQRSTUVWXYZ"; */

	char tmp[sizeof(long long)*3 + 4];
	char sign;
	int need_pfx = ((spec.flags & SPECIAL) && spec.base != 10);
	int i;

	/* We may overflow the buf. Crudely check for it */
	i = sizeof(long long)*3 + 4;
	if (i < spec.field_width)
		i = spec.field_width;
	if ((end - buf) <= i)
		return buf + i;

//we don't use formats like "%-07u"
//	if (spec.flags & LEFT)
//		spec.flags &= ~ZEROPAD;
	sign = 0;
	if (spec.flags & SIGN) {
		if ((signed long long)num < 0) {
			sign = '-';
			num = -(signed long long)num;
			spec.field_width--;
//		} else if (spec.flags & PLUS) {
//			sign = '+';
//			spec.field_width--;
//		} else if (spec.flags & SPACE) {
//			sign = ' ';
//			spec.field_width--;
		}
	}
	if (need_pfx) {
		spec.field_width--;
		if (spec.base == 16)
			spec.field_width--;
	}

	/* generate full string in tmp[], in reverse order */
	i = 0;
	if (num < spec.base)
		tmp[i++] = digits[num];
	/* Generic code, for any base:
	else do {
		tmp[i++] = (digits[do_div(num,base)]);
	} while (num != 0);
	*/
	else if (spec.base != 10) { /* 8 or 16 */
		int mask = spec.base - 1;
		int shift = 3;

		if (spec.base == 16)
			shift = 4;
		do {
			tmp[i++] = digits[((unsigned char)num) & mask];
			num >>= shift;
		} while (num);
	} else { /* base 10 */
		i = put_dec(tmp, num) - tmp;
	}

//spec.precision is assumed 0 ("not specified")
//	/* printing 100 using %2d gives "100", not "00" */
//	if (i > spec.precision)
//		spec.precision = i;
//	/* leading space padding */
//	spec.field_width -= spec.precision;
	spec.field_width -= i;
	if (!(spec.flags & (ZEROPAD+LEFT))) {
		while (--spec.field_width >= 0) {
			///if (buf < end)
				*buf = ' ';
			++buf;
		}
	}
	/* sign */
	if (sign) {
		///if (buf < end)
			*buf = sign;
		++buf;
	}
	/* "0x" / "0" prefix */
	if (need_pfx) {
		///if (buf < end)
			*buf = '0';
		++buf;
		if (spec.base == 16) {
			///if (buf < end)
				*buf = 'x';
			++buf;
		}
	}
	/* zero or space padding */
	if (!(spec.flags & LEFT)) {
		char c = (spec.flags & ZEROPAD) ? '0' : ' ';
		while (--spec.field_width >= 0) {
			///if (buf < end)
				*buf = c;
			++buf;
		}
	}
//	/* hmm even more zero padding? */
//	while (i <= --spec.precision) {
//		///if (buf < end)
//			*buf = '0';
//		++buf;
//	}
	/* actual digits of result */
	while (--i >= 0) {
		///if (buf < end)
			*buf = tmp[i];
		++buf;
	}
	/* trailing space padding */
	while (--spec.field_width >= 0) {
		///if (buf < end)
			*buf = ' ';
		++buf;
	}

	return buf;
}

static noinline_for_stack
char *string(char *buf, char *end, const char *s, struct printf_spec spec)
{
	int len, i;

	if (!s)
		s = "(null)";

	len = strnlen(s, spec.precision);

	/* We may overflow the buf. Crudely check for it */
	i = len;
	if (i < spec.field_width)
		i = spec.field_width;
	if ((end - buf) <= i)
		return buf + i;

	if (!(spec.flags & LEFT)) {
		while (len < spec.field_width--) {
			///if (buf < end)
				*buf = ' ';
			++buf;
		}
	}
	for (i = 0; i < len; ++i) {
		///if (buf < end)
			*buf = *s;
		++buf; ++s;
	}
	while (len < spec.field_width--) {
		///if (buf < end)
			*buf = ' ';
		++buf;
	}

	return buf;
}

static noinline_for_stack
char *pointer(const char *fmt, char *buf, char *end, void *ptr,
	      struct printf_spec spec)
{
//	spec.flags |= SMALL;
	if (spec.field_width == -1) {
		spec.field_width = 2 * sizeof(void *);
		spec.flags |= ZEROPAD;
	}
	spec.base = 16;

	return number(buf, end, (unsigned long) ptr, spec);
}

/*
 * Helper function to decode printf style format.
 * Each call decode a token from the format and return the
 * number of characters read (or likely the delta where it wants
 * to go on the next call).
 * The decoded token is returned through the parameters
 *
 * 'h', 'l', or 'L' for integer fields
 * 'z' support added 23/7/1999 S.H.
 * 'z' changed to 'Z' --davidm 1/25/99
 * 't' added for ptrdiff_t
 *
 * @fmt: the format string
 * @type of the token returned
 * @flags: various flags such as +, -, # tokens..
 * @field_width: overwritten width
 * @base: base of the number (octal, hex, ...)
 * @precision: precision of a number
 * @qualifier: qualifier of a number (long, size_t, ...)
 */
static noinline_for_stack
int format_decode(const char *fmt, struct printf_spec *spec)
{
	const char *start = fmt;

	/* we finished early by reading the field width */
	if (spec->type == FORMAT_TYPE_WIDTH) {
		if (spec->field_width < 0) {
			spec->field_width = -spec->field_width;
			spec->flags |= LEFT;
		}
		spec->type = FORMAT_TYPE_NONE;
		goto precision;
	}

	/* we finished early by reading the precision */
	if (spec->type == FORMAT_TYPE_PRECISION) {
		if (spec->precision < 0)
			spec->precision = 0;

		spec->type = FORMAT_TYPE_NONE;
		goto qualifier;
	}

	/* By default */
	spec->type = FORMAT_TYPE_NONE;

	for (;;) {
		if (*fmt == '\0')
			return fmt - start;
		if (*fmt == '%')
			break;
		++fmt;
	}

	/* Return the current non-format string */
	if (fmt != start)
		return fmt - start;

	/* Process flags */
	spec->flags = 0;

	while (1) { /* this also skips first '%' */
		bool found = true;

		++fmt;

		switch (*fmt) {
		case '-': spec->flags |= LEFT;    break;
//		case '+': spec->flags |= PLUS;    break;
//		case ' ': spec->flags |= SPACE;   break;
		case '#': spec->flags |= SPECIAL; break;
		case '0': spec->flags |= ZEROPAD; break;
		default:  found = false;
		}

		if (!found)
			break;
	}

	/* get field width */
	spec->field_width = -1;

	if (isdigit(*fmt))
		spec->field_width = skip_atoi(&fmt);
	else if (*fmt == '*') {
		/* it's the next argument */
		spec->type = FORMAT_TYPE_WIDTH;
		return ++fmt - start;
	}

precision:
	/* get the precision */
	spec->precision = -1;
	if (*fmt == '.') {
		++fmt;
		if (isdigit(*fmt)) {
			spec->precision = skip_atoi(&fmt);
//			if (spec->precision < 0)
//				spec->precision = 0;
		} else if (*fmt == '*') {
			/* it's the next argument */
			spec->type = FORMAT_TYPE_PRECISION;
			return ++fmt - start;
		}
	}

qualifier:
	/* get the conversion qualifier */
	spec->qualifier = -1;
	if (*fmt == 'l') {
		spec->qualifier = *fmt++;
		if (unlikely(spec->qualifier == *fmt)) {
			spec->qualifier = 'L';
			++fmt;
		}
	}

	/* default base */
	spec->base = 10;
	switch (*fmt) {
	case 'c':
		spec->type = FORMAT_TYPE_CHAR;
		return ++fmt - start;

	case 's':
		spec->type = FORMAT_TYPE_STR;
		return ++fmt - start;

	case 'p':
		spec->type = FORMAT_TYPE_PTR;
		return ++fmt - start;

	case '%':
		spec->type = FORMAT_TYPE_PERCENT_CHAR;
		return ++fmt - start;

	/* integer number formats - set up the flags and "break" */
	case 'o':
		spec->base = 8;
		break;

	case 'x':
//		spec->flags |= SMALL;

	case 'X':
		spec->base = 16;
		break;

	case 'd':
	case 'i':
		spec->flags |= SIGN;
	case 'u':
		break;

	default:
		spec->type = FORMAT_TYPE_INVALID;
		return fmt - start;
	}

	if (spec->qualifier == 'L')
		spec->type = FORMAT_TYPE_LONG_LONG;
	else if (spec->qualifier == 'l') {
		if (spec->flags & SIGN)
			spec->type = FORMAT_TYPE_LONG;
		else
			spec->type = FORMAT_TYPE_ULONG;
	} else {
		if (spec->flags & SIGN)
			spec->type = FORMAT_TYPE_INT;
		else
			spec->type = FORMAT_TYPE_UINT;
	}

	return ++fmt - start;
}

/**
 * vsnprintf - Format a string and place it in a buffer
 * @buf: The buffer to place the result into
 * @size: The size of the buffer, including the trailing null space
 * @fmt: The format string to use
 * @args: Arguments for the format string
 *
 * The return value is the number of characters which would
 * be generated for the given input, excluding the trailing
 * '\0', as per ISO C99. If you want to have the exact
 * number of characters written into @buf as return value
 * (not including the trailing '\0'), use vscnprintf(). If the
 * return is greater than or equal to @size, the resulting
 * string is truncated.
 *
 * If you're not already dealing with a va_list consider using snprintf().
 */
static
int kernel_vsnprintf(char *buf, size_t size, const char *fmt, va_list args)
{
	unsigned long long num;
	char *str, *end;
	struct printf_spec spec = {0};

	str = buf;
	end = buf + size;

	while (*fmt) {
		const char *old_fmt = fmt;
		int read = format_decode(fmt, &spec);

		fmt += read;

		switch (spec.type) {
		case FORMAT_TYPE_NONE: {
			int copy = read;
			if (str < end) {
				if (copy > end - str)
					copy = end - str;
				memcpy(str, old_fmt, copy);
			}
			str += read;
			break;
		}

		case FORMAT_TYPE_WIDTH:
			spec.field_width = va_arg(args, int);
			break;

		case FORMAT_TYPE_PRECISION:
			spec.precision = va_arg(args, int);
			break;

		case FORMAT_TYPE_CHAR: {
			char c;

			if (!(spec.flags & LEFT)) {
				while (--spec.field_width > 0) {
					if (str < end)
						*str = ' ';
					++str;

				}
			}
			c = (unsigned char) va_arg(args, int);
			if (str < end)
				*str = c;
			++str;
			while (--spec.field_width > 0) {
				if (str < end)
					*str = ' ';
				++str;
			}
			break;
		}

		case FORMAT_TYPE_STR:
			str = string(str, end, va_arg(args, char *), spec);
			break;

		case FORMAT_TYPE_PTR:
			str = pointer(fmt+1, str, end, va_arg(args, void *),
				      spec);
//			while (isalnum(*fmt))
//				fmt++;
			break;

		case FORMAT_TYPE_PERCENT_CHAR:
			if (str < end)
				*str = '%';
			++str;
			break;

		case FORMAT_TYPE_INVALID:
			if (str < end)
				*str = '%';
			++str;
			break;

		default:
			switch (spec.type) {
			case FORMAT_TYPE_LONG_LONG:
				num = va_arg(args, long long);
				break;
			case FORMAT_TYPE_ULONG:
				num = va_arg(args, unsigned long);
				break;
			case FORMAT_TYPE_LONG:
				num = va_arg(args, long);
				break;
			case FORMAT_TYPE_INT:
				num = (int) va_arg(args, int);
				break;
			default:
				num = va_arg(args, unsigned int);
			}

			str = number(str, end, num, spec);
		}
	}

//	if (size > 0) {
		if (str < end)
			*str = '\0';
//		else
//			end[-1] = '\0';
//	}

	/* the trailing null byte doesn't count towards the total */
	return str-buf;

}

int strace_vfprintf(FILE *fp, const char *fmt, va_list args)
{
	static char *buf = NULL;
	static unsigned buflen = 0;

	int r;
	va_list a1;

	va_copy(a1, args);
	unsigned len = kernel_vsnprintf(buf, buflen, fmt, a1);
	va_end(a1);

	if (len >= buflen) {
		buflen = len + 256;
		free(buf);
		buf = malloc(buflen);
		if (!buf)
			die_out_of_memory();
		/*len =*/ kernel_vsnprintf(buf, buflen, fmt, args);
	}

	r = fputs_unlocked(buf, fp);
	if (r < 0) return r;
	return len;
}

#endif /* USE_CUSTOM_PRINTF */