trampoline/lib/lib9/fmt/fmt.c

/* Copyright (c) 2002-2006 Lucent Technologies; see LICENSE */
#include <stdarg.h>
#include <string.h>

/*
 * As of 2020, older systems like RHEL 6 and AIX still do not have C11 atomics.
 * On those systems, make the code use volatile int accesses and hope for the best.
 * (Most uses of fmtinstall are not actually racing with calls to print that lookup
 * formats. The code used volatile here for years without too many problems,
 * even though that's technically racy. A mutex is not OK, because we want to
 * be able to call print from signal handlers.)
 *
 * RHEL is using an old GCC (atomics were added in GCC 4.9).
 * AIX is using its own IBM compiler (XL C).
 */
#if __IBMC__ || !__clang__ && __GNUC__ && (__GNUC__ < 4 || (__GNUC__==4 && __GNUC_MINOR__<9))
#warning not using C11 stdatomic on legacy system
#define _Atomic volatile
#define atomic_load(x) (*(x))
#define atomic_store(x, y) (*(x)=(y))
#define ATOMIC_VAR_INIT(x) (x)
#else
#include <stdatomic.h>
#endif

#include "plan9.h"
#include "fmt.h"
#include "fmtdef.h"

enum
{
	Maxfmt = 128
};

typedef struct Convfmt Convfmt;
struct Convfmt
{
	int	c;
	Fmts	fmt;
};

static struct
{
	/*
	 * lock updates to fmt by calling __fmtlock, __fmtunlock.
	 * reads can start at nfmt and work backward without
	 * further locking. later fmtinstalls take priority over earlier
	 * ones because of the backwards loop.
	 * once installed, a format is never overwritten.
	 */
	_Atomic int	nfmt;
	Convfmt	fmt[Maxfmt];
} fmtalloc = {
	27,
	{
		{' ',	__flagfmt},
		{'#',	__flagfmt},
		{'%',	__percentfmt},
		{'\'',	__flagfmt},
		{'+',	__flagfmt},
		{',',	__flagfmt},
		{'-',	__flagfmt},
		{'C',	__runefmt},	/* Plan 9 addition */
		{'E',	__efgfmt},
	#ifndef PLAN9PORT
		{'F',	__efgfmt},	/* ANSI only */
	#endif
		{'G',	__efgfmt},
	#ifndef PLAN9PORT
		{'L',	__flagfmt},	/* ANSI only */
	#endif
		{'S',	__runesfmt},	/* Plan 9 addition */
		{'X',	__ifmt},
		{'b',	__ifmt},		/* Plan 9 addition */
		{'c',	__charfmt},
		{'d',	__ifmt},
		{'e',	__efgfmt},
		{'f',	__efgfmt},
		{'g',	__efgfmt},
		{'h',	__flagfmt},
	#ifndef PLAN9PORT
		{'i',	__ifmt},		/* ANSI only */
	#endif
		{'l',	__flagfmt},
		{'n',	__countfmt},
		{'o',	__ifmt},
		{'p',	__ifmt},
		{'r',	__errfmt},
		{'s',	__strfmt},
	#ifdef PLAN9PORT
		{'u',	__flagfmt},
	#else
		{'u',	__ifmt},
	#endif
		{'x',	__ifmt},
	}
};

int	(*fmtdoquote)(int);

/*
 * __fmtlock() must be set
 */
static int
__fmtinstall(int c, Fmts f)
{
	Convfmt *p;
	int i;

	if(c<=0 || c>=65536)
		return -1;
	if(!f)
		f = __badfmt;

	i = atomic_load(&fmtalloc.nfmt);
	if(i == Maxfmt)
		return -1;
	p = &fmtalloc.fmt[i];
	p->c = c;
	p->fmt = f;
	atomic_store(&fmtalloc.nfmt, i+1);

	return 0;
}

int
fmtinstall(int c, int (*f)(Fmt*))
{
	int ret;

	__fmtlock();
	ret = __fmtinstall(c, f);
	__fmtunlock();
	return ret;
}

static Fmts
fmtfmt(int c)
{
	Convfmt *p, *ep;

	ep = &fmtalloc.fmt[atomic_load(&fmtalloc.nfmt)];
	for(p=ep; p-- > fmtalloc.fmt; )
		if(p->c == c)
			return p->fmt;

	return __badfmt;
}

void*
__fmtdispatch(Fmt *f, void *fmt, int isrunes)
{
	Rune rune, r;
	int i, n;

	f->flags = 0;
	f->width = f->prec = 0;

	for(;;){
		if(isrunes){
			r = *(Rune*)fmt;
			fmt = (Rune*)fmt + 1;
		}else{
			fmt = (char*)fmt + chartorune(&rune, (char*)fmt);
			r = rune;
		}
		f->r = r;
		switch(r){
		case '\0':
			return nil;
		case '.':
			f->flags |= FmtWidth|FmtPrec;
			continue;
		case '0':
			if(!(f->flags & FmtWidth)){
				f->flags |= FmtZero;
				continue;
			}
			/* fall through */
		case '1': case '2': case '3': case '4':
		case '5': case '6': case '7': case '8': case '9':
			i = 0;
			while(r >= '0' && r <= '9'){
				i = i * 10 + r - '0';
				if(isrunes){
					r = *(Rune*)fmt;
					fmt = (Rune*)fmt + 1;
				}else{
					r = *(char*)fmt;
					fmt = (char*)fmt + 1;
				}
			}
			if(isrunes)
				fmt = (Rune*)fmt - 1;
			else
				fmt = (char*)fmt - 1;
		numflag:
			if(f->flags & FmtWidth){
				f->flags |= FmtPrec;
				f->prec = i;
			}else{
				f->flags |= FmtWidth;
				f->width = i;
			}
			continue;
		case '*':
			i = va_arg(f->args, int);
			if(i < 0){
				/*
				 * negative precision =>
				 * ignore the precision.
				 */
				if(f->flags & FmtPrec){
					f->flags &= ~FmtPrec;
					f->prec = 0;
					continue;
				}
				i = -i;
				f->flags |= FmtLeft;
			}
			goto numflag;
		}
		n = (*fmtfmt(r))(f);
		if(n < 0)
			return nil;
		if(n == 0)
			return fmt;
	}
}