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android/platform/bionic/android-9.0.0_r61/./libc/stdio/printf_common.h
blob: 050120e964bed1240d933ac949ed11d8ed69c473 [file]
/*-
* Copyright (c) 1990 The Regents of the University of California.
* All rights reserved.
*
* This code is derived from software contributed to Berkeley by
* Chris Torek.
*
* Redistribution and use in source and binary forms, with or without
* modification, are permitted provided that the following conditions
* are met:
* 1. Redistributions of source code must retain the above copyright
* notice, this list of conditions and the following disclaimer.
* 2. 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.
* 3. Neither the name of the University nor the names of its contributors
* may be used to endorse or promote products derived from this software
* without specific prior written permission.
*
* THIS SOFTWARE IS PROVIDED BY THE REGENTS AND CONTRIBUTORS ``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 REGENTS OR CONTRIBUTORS 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 <sys/mman.h>
#include <sys/types.h>
#include <errno.h>
#include <float.h>
#include <langinfo.h>
#include <limits.h>
#include <locale.h>
#include <math.h>
#include <stdarg.h>
#include <stddef.h>
#include <stdint.h>
#include <stdio.h>
#include <stdlib.h>
#include <string.h>
#include <unistd.h>
#include <wchar.h>
#include "fvwrite.h"
#include "gdtoa.h"
#include "local.h"
union arg {
int intarg;
unsigned int uintarg;
long longarg;
unsigned long ulongarg;
long long longlongarg;
unsigned long long ulonglongarg;
ptrdiff_t ptrdiffarg;
size_t sizearg;
ssize_t ssizearg;
intmax_t intmaxarg;
uintmax_t uintmaxarg;
void* pvoidarg;
char* pchararg;
signed char* pschararg;
short* pshortarg;
int* pintarg;
long* plongarg;
long long* plonglongarg;
ptrdiff_t* pptrdiffarg;
ssize_t* pssizearg;
intmax_t* pintmaxarg;
double doublearg;
long double longdoublearg;
wint_t wintarg;
wchar_t* pwchararg;
};
// Helper function for `fprintf to unbuffered unix file': creates a
// temporary buffer. We only work on write-only files; this avoids
// worries about ungetc buffers and so forth.
static int __sbprintf(FILE* fp, const CHAR_TYPE* fmt, va_list ap) {
FILE fake;
struct __sfileext fakeext;
unsigned char buf[BUFSIZ];
_FILEEXT_SETUP(&fake, &fakeext);
/* copy the important variables */
fake._flags = fp->_flags & ~__SNBF;
fake._file = fp->_file;
fake._cookie = fp->_cookie;
fake._write = fp->_write;
/* set up the buffer */
fake._bf._base = fake._p = buf;
fake._bf._size = fake._w = sizeof(buf);
fake._lbfsize = 0; /* not actually used, but Just In Case */
/* do the work, then copy any error status */
int ret = FUNCTION_NAME(&fake, fmt, ap);
if (ret >= 0 && __sflush(&fake)) ret = EOF;
if (fake._flags & __SERR) fp->_flags |= __SERR;
return ret;
}
static int __find_arguments(const CHAR_TYPE* fmt0, va_list ap, union arg** argtable, size_t* argtablesiz);
static int __grow_type_table(unsigned char** typetable, int* tablesize);
#define DEFPREC 6
#define to_digit(c) ((c) - '0')
#define is_digit(c) ((unsigned)to_digit(c) <= 9)
#define to_char(n) ((CHAR_TYPE)((n) + '0'))
template <typename CharT>
static int exponent(CharT* p0, int exp, int fmtch) {
CharT* p = p0;
*p++ = fmtch;
if (exp < 0) {
exp = -exp;
*p++ = '-';
} else {
*p++ = '+';
}
CharT expbuf[MAXEXPDIG];
CharT* t = expbuf + MAXEXPDIG;
if (exp > 9) {
do {
*--t = to_char(exp % 10);
} while ((exp /= 10) > 9);
*--t = to_char(exp);
for (; t < expbuf + MAXEXPDIG; *p++ = *t++) /* nothing */;
} else {
/*
* Exponents for decimal floating point conversions
* (%[eEgG]) must be at least two characters long,
* whereas exponents for hexadecimal conversions can
* be only one character long.
*/
if (fmtch == 'e' || fmtch == 'E') *p++ = '0';
*p++ = to_char(exp);
}
return (p - p0);
}
#define PAD(howmany, with) \
do { \
if ((n = (howmany)) > 0) { \
while (n > PADSIZE) { \
PRINT(with, PADSIZE); \
n -= PADSIZE; \
} \
PRINT(with, n); \
} \
} while (0)
#define PRINTANDPAD(p, ep, len, with) \
do { \
n2 = (ep) - (p); \
if (n2 > (len)) n2 = (len); \
if (n2 > 0) PRINT((p), n2); \
PAD((len) - (n2 > 0 ? n2 : 0), (with)); \
} while (0)
/*
* The size of the buffer we use as scratch space for integer
* conversions, among other things. Technically, we would need the
* most space for base 10 conversions with thousands' grouping
* characters between each pair of digits. 100 bytes is a
* conservative overestimate even for a 128-bit uintmax_t.
*/
#define BUF 100
#define STATIC_ARG_TBL_SIZE 8 /* Size of static argument table. */
/*
* Flags used during conversion.
*/
#define ALT 0x0001 /* alternate form */
#define LADJUST 0x0004 /* left adjustment */
#define LONGDBL 0x0008 /* long double */
#define LONGINT 0x0010 /* long integer */
#define LLONGINT 0x0020 /* long long integer */
#define SHORTINT 0x0040 /* short integer */
#define ZEROPAD 0x0080 /* zero (as opposed to blank) pad */
#define FPT 0x0100 /* Floating point number */
#define PTRINT 0x0200 /* (unsigned) ptrdiff_t */
#define SIZEINT 0x0400 /* (signed) size_t */
#define CHARINT 0x0800 /* 8 bit integer */
#define MAXINT 0x1000 /* largest integer size (intmax_t) */
/*
* Type ids for argument type table.
*/
#define T_UNUSED 0
#define T_SHORT 1
#define T_U_SHORT 2
#define TP_SHORT 3
#define T_INT 4
#define T_U_INT 5
#define TP_INT 6
#define T_LONG 7
#define T_U_LONG 8
#define TP_LONG 9
#define T_LLONG 10
#define T_U_LLONG 11
#define TP_LLONG 12
#define T_DOUBLE 13
#define T_LONG_DOUBLE 14
#define TP_CHAR 15
#define TP_VOID 16
#define T_PTRINT 17
#define TP_PTRINT 18
#define T_SIZEINT 19
#define T_SSIZEINT 20
#define TP_SSIZEINT 21
#define T_MAXINT 22
#define T_MAXUINT 23
#define TP_MAXINT 24
#define T_CHAR 25
#define T_U_CHAR 26
#define T_WINT 27
#define TP_WCHAR 28
// To extend shorts properly, we need both signed and unsigned
// argument extraction methods.
#define SARG() \
((intmax_t)(flags & MAXINT \
? GETARG(intmax_t) \
: flags & LLONGINT \
? GETARG(long long) \
: flags & LONGINT \
? GETARG(long) \
: flags & PTRINT \
? GETARG(ptrdiff_t) \
: flags & SIZEINT \
? GETARG(ssize_t) \
: flags & SHORTINT \
? (short)GETARG(int) \
: flags & CHARINT ? (signed char)GETARG(int) \
: GETARG(int)))
#define UARG() \
((uintmax_t)(flags & MAXINT \
? GETARG(uintmax_t) \
: flags & LLONGINT \
? GETARG(unsigned long long) \
: flags & LONGINT \
? GETARG(unsigned long) \
: flags & PTRINT ? (uintptr_t)GETARG(ptrdiff_t) : /* XXX */ \
flags & SIZEINT \
? GETARG(size_t) \
: flags & SHORTINT \
? (unsigned short)GETARG(int) \
: flags & CHARINT ? (unsigned char)GETARG(int) \
: GETARG(unsigned int)))
// Append a digit to a value and check for overflow.
#define APPEND_DIGIT(val, dig) \
do { \
if ((val) > INT_MAX / 10) goto overflow; \
(val) *= 10; \
if ((val) > INT_MAX - to_digit((dig))) goto overflow; \
(val) += to_digit((dig)); \
} while (0)
// Get * arguments, including the form *nn$. Preserve the nextarg
// that the argument can be gotten once the type is determined.
#define GETASTER(val) \
n2 = 0; \
cp = fmt; \
while (is_digit(*cp)) { \
APPEND_DIGIT(n2, *cp); \
cp++; \
} \
if (*cp == '$') { \
int hold = nextarg; \
if (argtable == NULL) { \
argtable = statargtable; \
if (__find_arguments(fmt0, orgap, &argtable, &argtablesiz) == -1) { \
ret = -1; \
goto error; \
} \
} \
nextarg = n2; \
val = GETARG(int); \
nextarg = hold; \
fmt = ++cp; \
} else { \
val = GETARG(int); \
}
// Get the argument indexed by nextarg. If the argument table is
// built, use it to get the argument. If its not, get the next
// argument (and arguments must be gotten sequentially).
#define GETARG(type) \
((argtable != NULL) ? *((type*)(&argtable[nextarg++])) : (nextarg++, va_arg(ap, type)))
/*
* Find all arguments when a positional parameter is encountered. Returns a
* table, indexed by argument number, of pointers to each arguments. The
* initial argument table should be an array of STATIC_ARG_TBL_SIZE entries.
* It will be replaced with a mmap-ed one if it overflows (malloc cannot be
* used since we are attempting to make snprintf thread safe, and alloca is
* problematic since we have nested functions..)
*/
static int __find_arguments(const CHAR_TYPE* fmt0, va_list ap, union arg** argtable,
size_t* argtablesiz) {
int ch; /* character from fmt */
int n, n2; /* handy integer (short term usage) */
int flags; /* flags as above */
unsigned char* typetable; /* table of types */
unsigned char stattypetable[STATIC_ARG_TBL_SIZE];
int tablesize; /* current size of type table */
int tablemax; /* largest used index in table */
int nextarg; /* 1-based argument index */
int ret = 0; /* return value */
/*
* Add an argument type to the table, expanding if necessary.
*/
#define ADDTYPE(type) \
((nextarg >= tablesize) ? __grow_type_table(&typetable, &tablesize) : 0, \
(nextarg > tablemax) ? tablemax = nextarg : 0, typetable[nextarg++] = type)
#define ADDSARG() \
((flags & MAXINT) \
? ADDTYPE(T_MAXINT) \
: ((flags & PTRINT) ? ADDTYPE(T_PTRINT) \
: ((flags & SIZEINT) \
? ADDTYPE(T_SSIZEINT) \
: ((flags & LLONGINT) \
? ADDTYPE(T_LLONG) \
: ((flags & LONGINT) \
? ADDTYPE(T_LONG) \
: ((flags & SHORTINT) \
? ADDTYPE(T_SHORT) \
: ((flags & CHARINT) ? ADDTYPE(T_CHAR) \
: ADDTYPE(T_INT))))))))
#define ADDUARG() \
((flags & MAXINT) \
? ADDTYPE(T_MAXUINT) \
: ((flags & PTRINT) \
? ADDTYPE(T_PTRINT) \
: ((flags & SIZEINT) \
? ADDTYPE(T_SIZEINT) \
: ((flags & LLONGINT) \
? ADDTYPE(T_U_LLONG) \
: ((flags & LONGINT) \
? ADDTYPE(T_U_LONG) \
: ((flags & SHORTINT) \
? ADDTYPE(T_U_SHORT) \
: ((flags & CHARINT) ? ADDTYPE(T_U_CHAR) \
: ADDTYPE(T_U_INT))))))))
/*
* Add * arguments to the type array.
*/
#define ADDASTER() \
n2 = 0; \
cp = fmt; \
while (is_digit(*cp)) { \
APPEND_DIGIT(n2, *cp); \
cp++; \
} \
if (*cp == '$') { \
int hold = nextarg; \
nextarg = n2; \
ADDTYPE(T_INT); \
nextarg = hold; \
fmt = ++cp; \
} else { \
ADDTYPE(T_INT); \
}
CHAR_TYPE* fmt = const_cast<CHAR_TYPE*>(fmt0);
CHAR_TYPE* cp;
typetable = stattypetable;
tablesize = STATIC_ARG_TBL_SIZE;
tablemax = 0;
nextarg = 1;
memset(typetable, T_UNUSED, STATIC_ARG_TBL_SIZE);
/*
* Scan the format for conversions (`%' character).
*/
for (;;) {
for (cp = fmt; (ch = *fmt) != '\0' && ch != '%'; fmt++) continue;
if (ch == '\0') goto done;
fmt++; /* skip over '%' */
flags = 0;
rflag:
ch = *fmt++;
reswitch:
switch (ch) {
case ' ':
case '#':
case '\'':
goto rflag;
case '*':
ADDASTER();
goto rflag;
case '-':
case '+':
goto rflag;
case '.':
if ((ch = *fmt++) == '*') {
ADDASTER();
goto rflag;
}
while (is_digit(ch)) {
ch = *fmt++;
}
goto reswitch;
case '0':
goto rflag;
case '1':
case '2':
case '3':
case '4':
case '5':
case '6':
case '7':
case '8':
case '9':
n = 0;
do {
APPEND_DIGIT(n, ch);
ch = *fmt++;
} while (is_digit(ch));
if (ch == '$') {
nextarg = n;
goto rflag;
}
goto reswitch;
case 'L':
flags |= LONGDBL;
goto rflag;
case 'h':
if (*fmt == 'h') {
fmt++;
flags |= CHARINT;
} else {
flags |= SHORTINT;
}
goto rflag;
case 'j':
flags |= MAXINT;
goto rflag;
case 'l':
if (*fmt == 'l') {
fmt++;
flags |= LLONGINT;
} else {
flags |= LONGINT;
}
goto rflag;
case 'q':
flags |= LLONGINT;
goto rflag;
case 't':
flags |= PTRINT;
goto rflag;
case 'z':
flags |= SIZEINT;
goto rflag;
case 'C':
flags |= LONGINT;
/*FALLTHROUGH*/
case 'c':
if (flags & LONGINT)
ADDTYPE(T_WINT);
else
ADDTYPE(T_INT);
break;
case 'D':
flags |= LONGINT;
/*FALLTHROUGH*/
case 'd':
case 'i':
ADDSARG();
break;
case 'a':
case 'A':
case 'e':
case 'E':
case 'f':
case 'F':
case 'g':
case 'G':
if (flags & LONGDBL)
ADDTYPE(T_LONG_DOUBLE);
else
ADDTYPE(T_DOUBLE);
break;
#ifndef NO_PRINTF_PERCENT_N
case 'n':
if (flags & LLONGINT)
ADDTYPE(TP_LLONG);
else if (flags & LONGINT)
ADDTYPE(TP_LONG);
else if (flags & SHORTINT)
ADDTYPE(TP_SHORT);
else if (flags & PTRINT)
ADDTYPE(TP_PTRINT);
else if (flags & SIZEINT)
ADDTYPE(TP_SSIZEINT);
else if (flags & MAXINT)
ADDTYPE(TP_MAXINT);
else
ADDTYPE(TP_INT);
continue; /* no output */
#endif /* NO_PRINTF_PERCENT_N */
case 'O':
flags |= LONGINT;
/*FALLTHROUGH*/
case 'o':
ADDUARG();
break;
case 'p':
ADDTYPE(TP_VOID);
break;
case 'S':
flags |= LONGINT;
/*FALLTHROUGH*/
case 's':
ADDTYPE((flags & LONGINT) ? TP_WCHAR : TP_CHAR);
break;
case 'U':
flags |= LONGINT;
/*FALLTHROUGH*/
case 'u':
case 'X':
case 'x':
ADDUARG();
break;
default: /* "%?" prints ?, unless ? is NUL */
if (ch == '\0') goto done;
break;
}
}
done:
/*
* Build the argument table.
*/
if (tablemax >= STATIC_ARG_TBL_SIZE) {
*argtablesiz = sizeof(union arg) * (tablemax + 1);
*argtable = static_cast<arg*>(mmap(NULL, *argtablesiz,
PROT_WRITE | PROT_READ,
MAP_ANON | MAP_PRIVATE, -1, 0));
if (*argtable == MAP_FAILED) return -1;
}
for (n = 1; n <= tablemax; n++) {
switch (typetable[n]) {
case T_UNUSED:
case T_CHAR:
case T_U_CHAR:
case T_SHORT:
case T_U_SHORT:
case T_INT:
(*argtable)[n].intarg = va_arg(ap, int);
break;
case TP_SHORT:
(*argtable)[n].pshortarg = va_arg(ap, short*);
break;
case T_U_INT:
(*argtable)[n].uintarg = va_arg(ap, unsigned int);
break;
case TP_INT:
(*argtable)[n].pintarg = va_arg(ap, int*);
break;
case T_LONG:
(*argtable)[n].longarg = va_arg(ap, long);
break;
case T_U_LONG:
(*argtable)[n].ulongarg = va_arg(ap, unsigned long);
break;
case TP_LONG:
(*argtable)[n].plongarg = va_arg(ap, long*);
break;
case T_LLONG:
(*argtable)[n].longlongarg = va_arg(ap, long long);
break;
case T_U_LLONG:
(*argtable)[n].ulonglongarg = va_arg(ap, unsigned long long);
break;
case TP_LLONG:
(*argtable)[n].plonglongarg = va_arg(ap, long long*);
break;
case T_DOUBLE:
(*argtable)[n].doublearg = va_arg(ap, double);
break;
case T_LONG_DOUBLE:
(*argtable)[n].longdoublearg = va_arg(ap, long double);
break;
case TP_CHAR:
(*argtable)[n].pchararg = va_arg(ap, char*);
break;
case TP_VOID:
(*argtable)[n].pvoidarg = va_arg(ap, void*);
break;
case T_PTRINT:
(*argtable)[n].ptrdiffarg = va_arg(ap, ptrdiff_t);
break;
case TP_PTRINT:
(*argtable)[n].pptrdiffarg = va_arg(ap, ptrdiff_t*);
break;
case T_SIZEINT:
(*argtable)[n].sizearg = va_arg(ap, size_t);
break;
case T_SSIZEINT:
(*argtable)[n].ssizearg = va_arg(ap, ssize_t);
break;
case TP_SSIZEINT:
(*argtable)[n].pssizearg = va_arg(ap, ssize_t*);
break;
case T_MAXINT:
(*argtable)[n].intmaxarg = va_arg(ap, intmax_t);
break;
case T_MAXUINT:
(*argtable)[n].uintmaxarg = va_arg(ap, uintmax_t);
break;
case TP_MAXINT:
(*argtable)[n].pintmaxarg = va_arg(ap, intmax_t*);
break;
case T_WINT:
(*argtable)[n].wintarg = va_arg(ap, wint_t);
break;
case TP_WCHAR:
(*argtable)[n].pwchararg = va_arg(ap, wchar_t*);
break;
}
}
goto finish;
overflow:
errno = ENOMEM;
ret = -1;
finish:
if (typetable != NULL && typetable != stattypetable) {
munmap(typetable, *argtablesiz);
typetable = NULL;
}
return (ret);
}
/*
* Increase the size of the type table.
*/
static int __grow_type_table(unsigned char** typetable, int* tablesize) {
unsigned char* old_table = *typetable;
int new_size = *tablesize * 2;
if (new_size < getpagesize()) new_size = getpagesize();
if (*tablesize == STATIC_ARG_TBL_SIZE) {
*typetable = static_cast<unsigned char*>(mmap(NULL, new_size,
PROT_WRITE | PROT_READ,
MAP_ANON | MAP_PRIVATE, -1, 0));
if (*typetable == MAP_FAILED) return -1;
bcopy(old_table, *typetable, *tablesize);
} else {
unsigned char* new_table = static_cast<unsigned char*>(mmap(NULL, new_size,
PROT_WRITE | PROT_READ,
MAP_ANON | MAP_PRIVATE, -1, 0));
if (new_table == MAP_FAILED) return -1;
memmove(new_table, *typetable, *tablesize);
munmap(*typetable, *tablesize);
*typetable = new_table;
}
memset(*typetable + *tablesize, T_UNUSED, (new_size - *tablesize));
*tablesize = new_size;
return 0;
}
struct helpers {
// Flush out all the vectors defined by the given uio,
// then reset it so that it can be reused.
static int sprint(FILE* fp, struct __suio* uio) {
if (uio->uio_resid == 0) {
uio->uio_iovcnt = 0;
return 0;
}
int result = __sfvwrite(fp, uio);
uio->uio_resid = 0;
uio->uio_iovcnt = 0;
return result;
}
// Convert a wide character string argument for the %ls format to a multibyte
// string representation. If not -1, prec specifies the maximum number of
// bytes to output, and also means that we can't assume that the wide char
// string is null-terminated.
static char* wcsconv(wchar_t* wcsarg, int prec) {
mbstate_t mbs;
char buf[MB_LEN_MAX];
wchar_t* p;
char* convbuf;
size_t clen, nbytes;
// Allocate space for the maximum number of bytes we could output.
if (prec < 0) {
memset(&mbs, 0, sizeof(mbs));
p = wcsarg;
nbytes = wcsrtombs(NULL, (const wchar_t**)&p, 0, &mbs);
if (nbytes == (size_t)-1) return NULL;
} else {
// Optimisation: if the output precision is small enough,
// just allocate enough memory for the maximum instead of
// scanning the string.
if (prec < 128) {
nbytes = prec;
} else {
nbytes = 0;
p = wcsarg;
memset(&mbs, 0, sizeof(mbs));
for (;;) {
clen = wcrtomb(buf, *p++, &mbs);
if (clen == 0 || clen == (size_t)-1 || nbytes + clen > (size_t)prec) break;
nbytes += clen;
}
if (clen == (size_t)-1) return NULL;
}
}
if ((convbuf = static_cast<char*>(malloc(nbytes + 1))) == NULL) return NULL;
// Fill the output buffer.
p = wcsarg;
memset(&mbs, 0, sizeof(mbs));
if ((nbytes = wcsrtombs(convbuf, (const wchar_t**)&p, nbytes, &mbs)) == (size_t)-1) {
free(convbuf);
return NULL;
}
convbuf[nbytes] = '\0';
return convbuf;
}
// Like __fputwc_unlock, but handles fake string (__SSTR) files properly.
// File must already be locked.
static wint_t xfputwc(wchar_t wc, FILE* fp) {
if ((fp->_flags & __SSTR) == 0) return __fputwc_unlock(wc, fp);
char buf[MB_LEN_MAX];
mbstate_t mbs = {};
size_t len = wcrtomb(buf, wc, &mbs);
if (len == (size_t)-1) {
fp->_flags |= __SERR;
errno = EILSEQ;
return WEOF;
}
struct __siov iov;
iov.iov_base = buf;
iov.iov_len = len;
struct __suio uio;
uio.uio_iov = &iov;
uio.uio_resid = len;
uio.uio_iovcnt = 1;
return (__sfvwrite(fp, &uio) != EOF ? (wint_t)wc : WEOF);
}
// Convert a multibyte character string argument for the %s format to a wide
// string representation. ``prec'' specifies the maximum number of bytes
// to output. If ``prec'' is greater than or equal to zero, we can't assume
// that the multibyte character string ends in a null character.
//
// Returns NULL on failure.
// To find out what happened check errno for ENOMEM, EILSEQ and EINVAL.
static wchar_t* mbsconv(char* mbsarg, int prec) {
mbstate_t mbs;
const char* p;
size_t insize, nchars, nconv;
if (mbsarg == NULL) return NULL;
// Supplied argument is a multibyte string; convert it to wide characters first.
if (prec >= 0) {
// String is not guaranteed to be NUL-terminated. Find the number of characters to print.
p = mbsarg;
insize = nchars = nconv = 0;
bzero(&mbs, sizeof(mbs));
while (nchars != (size_t)prec) {
nconv = mbrlen(p, MB_CUR_MAX, &mbs);
if (nconv == (size_t)0 || nconv == (size_t)-1 || nconv == (size_t)-2) break;
p += nconv;
nchars++;
insize += nconv;
}
if (nconv == (size_t)-1 || nconv == (size_t)-2) return (NULL);
} else {
insize = strlen(mbsarg);
}
// Allocate buffer for the result and perform the conversion,
// converting at most `size' bytes of the input multibyte string to
// wide characters for printing.
wchar_t* convbuf = static_cast<wchar_t*>(calloc(insize + 1, sizeof(*convbuf)));
if (convbuf == NULL) return NULL;
wchar_t* wcp = convbuf;
p = mbsarg;
bzero(&mbs, sizeof(mbs));
nconv = 0;
while (insize != 0) {
nconv = mbrtowc(wcp, p, insize, &mbs);
if (nconv == 0 || nconv == (size_t)-1 || nconv == (size_t)-2) break;
wcp++;
p += nconv;
insize -= nconv;
}
if (nconv == (size_t)-1 || nconv == (size_t)-2) {
free(convbuf);
return NULL;
}
*wcp = '\0';
return convbuf;
}
};