Re: [musl] [PATCH 2/2] signal: add str2sig(3) from POSIX.1-2024

[Joakim Sindholt <opensource@zhasha.com>]

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On Sun, 4 Aug 2024 14:39:21 +0100 Pedro Falcato <pedro.falcato@gmail.com> wrote:
> To me it looks like the best way to implement these two functions is
> to create a table of some sorts (indexed by signal, so array[SIGINT] =
> "INT") and then use it.
> str2sig would just iterate the whole array with strcmps, which is a
> _little_ slow but this is probably not performance critical anyway.
> 
> Special casing would be required for RT signals, but that's no biggie.
> What do you think?

I was thinking the same thing for the sake of size.
There are a few more special cases though as some signal names refer to the
same signal numbers.

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#include <signal.h>
#include <errno.h>
#include <string.h>
#include <ctype.h>

#define SIG(s) [SIG##s] = #s

static const char signames[][8] = {
    SIG(HUP),
    SIG(INT),
    SIG(QUIT),
    SIG(ILL),
    SIG(TRAP),
    SIG(ABRT),
    SIG(BUS),
    SIG(FPE),
    SIG(KILL),
    SIG(USR1),
    SIG(SEGV),
    SIG(USR2),
    SIG(PIPE),
    SIG(ALRM),
    SIG(TERM),
    SIG(STKFLT),
    SIG(CHLD),
    SIG(CONT),
    SIG(STOP),
    SIG(TSTP),
    SIG(TTIN),
    SIG(TTOU),
    SIG(URG),
    SIG(XCPU),
    SIG(XFSZ),
    SIG(VTALRM),
    SIG(PROF),
    SIG(WINCH),
    SIG(POLL),
    SIG(PWR),
    SIG(SYS),

    [32] = "TIMER",
    [33] = "CANCEL",
    [34] = "SYNCCALL",
    [35] = "RTMIN",
#define RTMIN 35
#define RTMAX SIGRTMAX
};

int sig2str(int sig, char *str)
{
    const char *name;
    int i, num;

    if (sig < sizeof signames/sizeof *signames) {
        for (i = 0; i < sizeof *signames; i++)
            str[i] = signames[sig][i];
        str[sizeof *signames] = 0;
        return 0;
    }
    if (sig == RTMAX) {
        for (i = 0; i < 6; i++)
            str[i] = "RTMAX"[i];
        return 0;
    }
    if (sig > RTMIN && sig <= RTMAX) {
        if (sig <= (RTMIN+RTMAX)/2) {
            name = "RTMIN+";
            num = sig-RTMIN;
        } else {
            name = sig==RTMAX?"RTMAX":"RTMAX-";
            num = RTMAX-sig;
        }
        for (i = 0; i < 6; i++)
            str[i] = name[i];
        if (num > 10)
            str[i++] = '0'+num/10;
        if (num > 0)
            str[i++] = '0'+num%10;
        str[i] = 0;
        return 0;
    }
    errno = EINVAL;
    return -1;
}

int str2sig(const char *restrict str, int *restrict sig)
{
    int i, num;

    if (strnlen(str, sizeof *signames) <= sizeof *signames)
        for (i = 0; i < sizeof signames/sizeof *signames; i++)
            if (strncmp(str, signames[i], sizeof *signames) == 0)
                return (*sig = i, 0);
    if (strcmp(str, "IO") == 0)
        return (*sig = SIGIO, 0);
    if (strcmp(str, "IOT") == 0)
        return (*sig = SIGIOT, 0);
    if (strcmp(str, "UNUSED") == 0)
        return (*sig = SIGUNUSED, 0);
    if (strcmp(str, "RTMAX") == 0)
        return (*sig = RTMAX, 0);

    if (strncmp(str, "RTMIN+", 6) == 0 || strncmp(str, "RTMAX-", 6) == 0)
        i = 6;
    else if (isdigit(*str))
        i = 0;
    else
        return -1;
    if (str[i] < '1' || str[i] > '9')
        return -1;
    num = str[i++]-'0';
    if (isdigit(str[i]))
        num = num*10+str[i++]-'0';
    if (str[i])
        return -1;
    if (*str != 'R')
        return num<=RTMAX?(*sig = num, 0):-1;
    else if (num < RTMAX-RTMIN)
        return (*sig = str[5]=='+'?RTMIN+num:RTMAX-num, 0);
    else
        return -1;
}