mirrors/linux
2
0
Fork 0
mirror of https://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git synced 2026-05-16 11:21:26 -04:00
Code Issues Packages Projects Releases Wiki Activity

tools/nolibc/printf: Use bit-masks to hold requested flag, length and conversion chars

Browse Source 
Use flags bits (1u << (ch & 31)) for the flags, length modifiers, and
conversion specifiers.
This makes it easy to test for multiple values at once.

Detect the conversion flags " #+-0" although they are currently all ignored.

Unconditionally generate the signed values (for %d) to remove a second
set of checks for the size.

Separate out the formatting of single characters from numbers.
Output the sign for negative values then negate and treat as unsigned.

Signed-off-by: David Laight <david.laight.linux@gmail.com>
Acked-by: Willy Tarreau <w@1wt.eu>
Link: https://patch.msgid.link/20260308113742.12649-9-david.laight.linux@gmail.com
Signed-off-by: Thomas Weißschuh <linux@weissschuh.net>
This commit is contained in:
David Laight
2026-03-08 11:37:33 +00:00
committed by Thomas Weißschuh
parent c5b9173ce9
commit 85f1152778
1 changed files with 106 additions and 48 deletions
Download Patch File Download Diff File Expand all files Collapse all files

154
tools/include/nolibc/stdio.h
View File

@@ -291,10 +291,14 @@ int fseek(FILE *stream, long offset, int whence)
}
/* minimal printf(). It supports the following formats:
* - %[l*]{d,u,c,x,p}
* - %s
* - unknown modifiers are ignored.
/* printf(). Supports the following integer and string formats.
* - %[#-+ 0][width][{l,ll,j}]{c,d,u,x,p,s,m,%}
* - %% generates a single %
* - %m outputs strerror(errno).
* - The modifiers [#-+ 0] are currently ignored.
* - No support for precision or variable widths.
* - No support for floating point or wide characters.
* - Invalid formats are copied to the output buffer.
*
* Called by vfprintf() and snprintf() to do the actual formatting.
* The callers provide a callback function to save the formatted data.
@@ -305,15 +309,43 @@ int fseek(FILE *stream, long offset, int whence)
* - with (NULL, 0) at the end of the __nolibc_printf.
* If the callback returns non-zero __nolibc_printf() immediately returns -1.
*/
typedef int (*__nolibc_printf_cb)(void *state, const char *buf, size_t size);
/* This code uses 'flag' variables that are indexed by the low 6 bits
* of characters to optimise checks for multiple characters.
*
* _NOLIBC_PF_FLAGS_CONTAIN(flags, 'a', 'b'. ...)
* returns non-zero if the bit for any of the specified characters is set.
*
* _NOLIBC_PF_CHAR_IS_ONE_OF(ch, 'a', 'b'. ...)
* returns the flag bit for ch if it is one of the specified characters.
* All the characters must be in the same 32 character block (non-alphabetic,
* upper case, or lower case) of the ASCII character set.
*/
#define _NOLIBC_PF_FLAG(ch) (1u << ((ch) & 0x1f))
#define _NOLIBC_PF_FLAG_NZ(ch) ((ch) ? _NOLIBC_PF_FLAG(ch) : 0)
#define _NOLIBC_PF_FLAG8(cmp_1, cmp_2, cmp_3, cmp_4, cmp_5, cmp_6, cmp_7, cmp_8, ...) \
(_NOLIBC_PF_FLAG_NZ(cmp_1) | _NOLIBC_PF_FLAG_NZ(cmp_2) | \
_NOLIBC_PF_FLAG_NZ(cmp_3) | _NOLIBC_PF_FLAG_NZ(cmp_4) | \
_NOLIBC_PF_FLAG_NZ(cmp_5) | _NOLIBC_PF_FLAG_NZ(cmp_6) | \
_NOLIBC_PF_FLAG_NZ(cmp_7) | _NOLIBC_PF_FLAG_NZ(cmp_8))
#define _NOLIBC_PF_FLAGS_CONTAIN(flags, ...) \
((flags) & _NOLIBC_PF_FLAG8(__VA_ARGS__, 0, 0, 0, 0, 0, 0, 0))
#define _NOLIBC_PF_CHAR_IS_ONE_OF(ch, cmp_1, ...) \
((unsigned int)(ch) - (cmp_1 & 0xe0) > 0x1f ? 0 : \
_NOLIBC_PF_FLAGS_CONTAIN(_NOLIBC_PF_FLAG(ch), cmp_1, __VA_ARGS__))
static __attribute__((unused, format(printf, 3, 0)))
int __nolibc_printf(__nolibc_printf_cb cb, void *state, const char *fmt, va_list args)
{
char lpref, ch;
char ch;
unsigned long long v;
long long signed_v;
int written, width, len;
unsigned int flags, ch_flag;
char outbuf[21];
char *out;
const char *outstr;
written = 0;
@@ -324,6 +356,7 @@ int __nolibc_printf(__nolibc_printf_cb cb, void *state, const char *fmt, va_list
break;
width = 0;
flags = 0;
if (ch != '%') {
while (*fmt && *fmt != '%')
fmt++;
@@ -334,7 +367,14 @@ int __nolibc_printf(__nolibc_printf_cb cb, void *state, const char *fmt, va_list
/* we're in a format sequence */
ch = *fmt++;
/* Conversion flag characters */
while (1) {
ch = *fmt++;
ch_flag = _NOLIBC_PF_CHAR_IS_ONE_OF(ch, ' ', '#', '+', '-', '0');
if (!ch_flag)
break;
flags |= ch_flag;
}
/* width */
while (ch >= '0' && ch <= '9') {
@@ -344,63 +384,78 @@ int __nolibc_printf(__nolibc_printf_cb cb, void *state, const char *fmt, va_list
ch = *fmt++;
}
/* Length modifiers */
if (ch == 'l') {
lpref = 1;
ch = *fmt++;
if (ch == 'l') {
lpref = 2;
ch = *fmt++;
/* Length modifier.
* They miss the conversion flags characters " #+-0" so can go into flags.
* Change ll to j (both always 64bits).
*/
ch_flag = _NOLIBC_PF_CHAR_IS_ONE_OF(ch, 'l', 'j');
if (ch_flag != 0) {
if (ch == 'l' && fmt[0] == 'l') {
fmt++;
ch_flag = _NOLIBC_PF_FLAG('j');
}
} else if (ch == 'j') {
/* intmax_t is long long */
lpref = 2;
flags |= ch_flag;
ch = *fmt++;
} else {
lpref = 0;
}
if (ch == 'c' || ch == 'd' || ch == 'u' || ch == 'x' || ch == 'p') {
char *out = outbuf;
/* Conversion specifiers. */
if (ch == 'p') {
/* Numeric and pointer conversion specifiers.
*
* Use an explicit bound check (rather than _NOLIBC_PF_CHAR_IS_ONE_OF())
* so ch_flag can be used later.
*/
ch_flag = _NOLIBC_PF_FLAG(ch);
if ((ch >= 'a' && ch <= 'z') &&
_NOLIBC_PF_FLAGS_CONTAIN(ch_flag, 'c', 'd', 'u', 'x', 'p')) {
/* 'long' is needed for pointer conversions and ltz lengths.
* A single test can be used provided 'p' (the same bit as '0')
* is masked from flags.
*/
if (_NOLIBC_PF_FLAGS_CONTAIN(ch_flag | (flags & ~_NOLIBC_PF_FLAG('p')),
'p', 'l')) {
v = va_arg(args, unsigned long);
} else if (lpref) {
if (lpref > 1)
v = va_arg(args, unsigned long long);
else
v = va_arg(args, unsigned long);
signed_v = (long)v;
} else if (_NOLIBC_PF_FLAGS_CONTAIN(flags, 'j')) {
v = va_arg(args, unsigned long long);
signed_v = v;
} else {
v = va_arg(args, unsigned int);
signed_v = (int)v;
}
if (ch == 'd') {
/* sign-extend the value */
if (lpref == 0)
v = (long long)(int)v;
else if (lpref == 1)
v = (long long)(long)v;
if (ch == 'c') {
/* "%c" - single character. */
outbuf[0] = v;
len = 1;
outstr = outbuf;
goto do_output;
}
switch (ch) {
case 'c':
out[0] = v;
out[1] = 0;
break;
case 'd':
i64toa_r(v, out);
break;
case 'u':
out = outbuf;
if (_NOLIBC_PF_FLAGS_CONTAIN(ch_flag, 'd')) {
/* "%d" and "%i" - signed decimal numbers. */
if (signed_v < 0) {
*out++ = '-';
v = -(signed_v + 1);
v++;
}
}
/* Convert the number to ascii in the required base. */
if (_NOLIBC_PF_FLAGS_CONTAIN(ch_flag, 'd', 'u')) {
/* Base 10 */
u64toa_r(v, out);
break;
case 'p':
*(out++) = '0';
*(out++) = 'x';
__nolibc_fallthrough;
default: /* 'x' and 'p' above */
} else {
/* Base 16 */
if (_NOLIBC_PF_FLAGS_CONTAIN(ch_flag, 'p')) {
*(out++) = '0';
*(out++) = 'x';
}
u64toh_r(v, out);
break;
}
outstr = outbuf;
goto do_strlen_output;
}
@@ -443,6 +498,9 @@ int __nolibc_printf(__nolibc_printf_cb cb, void *state, const char *fmt, va_list
do_output:
written += len;
/* Stop gcc back-merging this code into one of the conditionals above. */
_NOLIBC_OPTIMIZER_HIDE_VAR(len);
width -= len;
while (width > 0) {
/* Output pad in 16 byte blocks with the small block first. */