/*      $NetBSD: input.c,v 1.76 2024/10/14 08:15:43 kre Exp $   */

/*-
 * Copyright (c) 1991, 1993
 *      The Regents of the University of California.  All rights reserved.
 *
 * This code is derived from software contributed to Berkeley by
 * Kenneth Almquist.
 *
 * 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/cdefs.h>
#ifndef lint
#if 0
static char sccsid[] = "@(#)input.c     8.3 (Berkeley) 6/9/95";
#else
__RCSID("$NetBSD: input.c,v 1.76 2024/10/14 08:15:43 kre Exp $");
#endif
#endif /* not lint */

#include <stdio.h>      /* defines BUFSIZ */
#include <fcntl.h>
#include <errno.h>
#include <unistd.h>
#include <limits.h>
#include <stdlib.h>
#include <string.h>
#include <sys/stat.h>

/*
 * This file implements the input routines used by the parser.
 */

#include "shell.h"
#include "redir.h"
#include "syntax.h"
#include "input.h"
#include "output.h"
#include "options.h"
#include "memalloc.h"
#include "error.h"
#include "alias.h"
#include "parser.h"
#include "myhistedit.h"
#include "show.h"

#define EOF_NLEFT -99           /* value of parsenleft when EOF pushed back */

MKINIT
struct strpush {
        struct strpush *prev;   /* preceding string on stack */
        const char *prevstring;
        int prevnleft;
        int prevlleft;
        struct alias *ap;       /* if push was associated with an alias */
};

/*
 * The parsefile structure pointed to by the global variable parsefile
 * contains information about the current file being read.
 */

MKINIT
struct parsefile {
        struct parsefile *prev; /* preceding file on stack */
        int linno;              /* current line */
        int fd;                 /* file descriptor (or -1 if string) */
        int nleft;              /* number of chars left in this line */
        int lleft;              /* number of chars left in this buffer */
        int nskip;              /* number of \0's dropped in previous line */
        const char *nextc;      /* next char in buffer */
        char *buf;              /* input buffer */
        struct strpush *strpush; /* for pushing strings at this level */
        struct strpush basestrpush; /* so pushing one is fast */
};


int plinno = 1;                 /* input line number */
int parsenleft;                 /* copy of parsefile->nleft */
MKINIT int parselleft;          /* copy of parsefile->lleft */
const char *parsenextc;         /* copy of parsefile->nextc */
MKINIT struct parsefile basepf; /* top level input file */
MKINIT char basebuf[BUFSIZ];    /* buffer for top level input file */
struct parsefile *parsefile = &basepf;  /* current input file */
int init_editline = 0;          /* editline library initialized? */
int whichprompt;                /* 1 == PS1, 2 == PS2 */

STATIC void pushfile(void);
static int preadfd(void);

#ifdef mkinit
INCLUDE <stdio.h>
INCLUDE "input.h"
INCLUDE "error.h"

INIT {
        basepf.nextc = basepf.buf = basebuf;
}

RESET {
        if (exception != EXSHELLPROC)
                parselleft = parsenleft = 0;    /* clear input buffer */
        popallfiles();
}

SHELLPROC {
        popallfiles();
}
#endif


#if 0           /* this is unused */
/*
 * Read a line from the script.
 */

char *
pfgets(char *line, int len)
{
        char *p = line;
        int nleft = len;
        int c;

        while (--nleft > 0) {
                c = pgetc_macro();
                if (c == PFAKE)         /* consecutive PFAKEs is impossible */
                        c = pgetc_macro();
                if (c == PEOF) {
                        if (p == line)
                                return NULL;
                        break;
                }
                *p++ = c;
                if (c == '\n') {
                        plinno++;
                        break;
                }
        }
        *p = '\0';
        return line;
}
#endif


/*
 * Read a character from the script, returning PEOF on end of file.
 * Nul characters in the input are silently discarded.
 */

int
pgetc(void)
{
        int c;

        c = pgetc_macro();
        if (c == PFAKE)
                c = pgetc_macro();
        return c;
}


static int
preadfd(void)
{
        int nr;
        char *buf =  parsefile->buf;
        parsenextc = buf;

 retry:
#ifndef SMALL
        if (parsefile->fd == 0 && el) {
                static const char *rl_cp;
                static int el_len;

                if (rl_cp == NULL)
                        rl_cp = el_gets(el, &el_len);
                if (rl_cp == NULL)
                        nr = el_len == 0 ? 0 : -1;
                else {
                        nr = el_len;
                        if (nr > BUFSIZ - 8)
                                nr = BUFSIZ - 8;
                        memcpy(buf, rl_cp, nr);
                        if (nr != el_len) {
                                el_len -= nr;
                                rl_cp += nr;
                        } else
                                rl_cp = 0;
                }

        } else
#endif
                nr = read(parsefile->fd, buf, BUFSIZ - 8);


        if (nr <= 0) {
                if (nr < 0) {
                        if (errno == EINTR)
                                goto retry;
                        if (parsefile->fd == 0 && errno == EWOULDBLOCK) {
                                int flags = fcntl(0, F_GETFL, 0);

                                if (flags >= 0 && flags & O_NONBLOCK) {
                                        flags &=~ O_NONBLOCK;
                                        if (fcntl(0, F_SETFL, flags) >= 0) {
                                                out2str("sh: turning off NDELAY mode\n");
                                                goto retry;
                                        }
                                }
                        }
                }
                nr = -1;
        }
        return nr;
}

/*
 * Refill the input buffer and return the next input character:
 *
 * 1) If a string was pushed back on the input, pop it;
 * 2) If an EOF was pushed back (parsenleft == EOF_NLEFT) or we are reading
 *    from a string so we can't refill the buffer, return EOF.
 * 3) If there is more stuff in this buffer, use it else call read to fill it.
 * 4) Process input up to the next newline, deleting nul characters.
 */

int
preadbuffer(void)
{
        char *p, *q;
        int more;
#ifndef SMALL
        int something;
#endif
        char savec;

        while (parsefile->strpush) {
                if (parsenleft == -1 && parsefile->strpush->ap != NULL)
                        return PFAKE;
                popstring();
                if (--parsenleft >= 0)
                        return (*parsenextc++);
        }
        if (parsenleft == EOF_NLEFT || parsefile->buf == NULL)
                return PEOF;
        flushout(&output);
        flushout(&errout);

 again:
        if (parselleft <= 0) {
                if ((parselleft = preadfd()) == -1) {
                        parselleft = parsenleft = EOF_NLEFT;
                        return PEOF;
                }
                parsefile->nskip = 0;
        }

                /* jump over slots for any \0 chars that were dropped */
        parsenextc += parsefile->nskip;
        parsefile->nskip = 0;

                /* p = (not const char *)parsenextc; */
        p = parsefile->buf + (parsenextc - parsefile->buf);
        q = p;

        /* delete nul characters */
#ifndef SMALL
        something = 0;
#endif
        for (more = 1; more;) {
                switch (*p) {
                case '\0':
#ifdef REJECT_NULS
                        parsenleft = parselleft = 0;
                        error("nul ('\\0') in shell input");
                        /* NOTREACHED */
#else
                        p++;    /* Skip nul */
                        parsefile->nskip++;
                        goto check;
#endif

                case '\t':
                case ' ':
                        break;

                case '\n':
                        parsenleft = q - parsenextc;
                        more = 0; /* Stop processing here */
                        break;

                default:
#ifndef SMALL
                        something = 1;
#endif
                        break;
                }

                if (parsefile->nskip)
                        *q++ = *p++;
                else
                        q = ++p;

#ifndef REJECT_NULS
 check:;
#endif
                if (--parselleft <= 0) {
                        parsenleft = q - parsenextc - 1;
                        if (parsenleft < 0)
                                goto again;
                        *q = '\0';
                        more = 0;
                }
        }

        savec = *q;
        *q = '\0';

#ifndef SMALL
        if (parsefile->fd == 0 && hist && (something || whichprompt == 2)) {
                HistEvent he;

                INTOFF;
                history(hist, &he, whichprompt != 2 ? H_ENTER : H_APPEND,
                    parsenextc);
                if (whichprompt != 2 && HistFP != NULL) {
                        history(hist, &he, H_NSAVE_FP, (size_t)0, HistFP);
                        fflush(HistFP);
                }
                INTON;
        }
#endif

        if (vflag) {
                out2str(parsenextc);
                flushout(out2);
        }

        *q = savec;

        return *parsenextc++;
}

/*
 * Test whether we have reached EOF on input stream.
 * Return true only if certain (without attempting a read).
 *
 * Note the similarity to the opening section of preadbuffer()
 */
int
at_eof(void)
{
        struct strpush *sp = parsefile->strpush;

        if (parsenleft > 0)     /* more chars are in the buffer */
                return 0;

        while (sp != NULL) {
                /*
                 * If any pushed string has any remaining data,
                 * then we are not at EOF  (simulating popstring())
                 */
                if (sp->prevnleft > 0)
                        return 0;
                sp = sp->prev;
        }

        /*
         * If we reached real EOF and pushed it back,
         * or if we are just processing a string (not reading a file)
         * then there is no more.   Note that if a file pushes a
         * string, the file's ->buf remains present.
         */
        if (parsenleft == EOF_NLEFT || parsefile->buf == NULL)
                return 1;

        /*
         * In other cases, there might be more
         */
        return 0;
}

/*
 * Undo the last call to pgetc.  Only one character may be pushed back.
 * PEOF may be pushed back.
 */

void
pungetc(void)
{
        parsenleft++;
        parsenextc--;
}

/*
 * Push a string back onto the input at this current parsefile level.
 * We handle aliases this way.
 */
void
pushstring(const char *s, int len, struct alias *ap)
{
        struct strpush *sp;

        VTRACE(DBG_INPUT,
            ("pushstring(\"%.*s\", %d)%s%s%s had: nl=%d ll=%d \"%.*s\"\n",
            len, s, len, ap ? " for alias:'" : "",
            ap ? ap->name : "", ap ? "'" : "",
            parsenleft, parselleft, parsenleft, parsenextc));

        INTOFF;
        if (parsefile->strpush) {
                sp = ckmalloc(sizeof (struct strpush));
                sp->prev = parsefile->strpush;
                parsefile->strpush = sp;
        } else
                sp = parsefile->strpush = &(parsefile->basestrpush);

        sp->prevstring = parsenextc;
        sp->prevnleft = parsenleft;
        sp->prevlleft = parselleft;
        sp->ap = ap;
        if (ap)
                ap->flag |= ALIASINUSE;
        parsenextc = s;
        parsenleft = len;
        INTON;
}

void
popstring(void)
{
        struct strpush *sp = parsefile->strpush;

        INTOFF;
        if (sp->ap) {
                int alen;

                if ((alen = strlen(sp->ap->val)) > 0 &&
                    (sp->ap->val[alen - 1] == ' ' ||
                     sp->ap->val[alen - 1] == '\t'))
                        checkkwd |= CHKALIAS;
                sp->ap->flag &= ~ALIASINUSE;
        }
        parsenextc = sp->prevstring;
        parsenleft = sp->prevnleft;
        parselleft = sp->prevlleft;

        VTRACE(DBG_INPUT, ("popstring()%s%s%s nl=%d ll=%d \"%.*s\"\n",
            sp->ap ? " from alias:'" : "", sp->ap ? sp->ap->name : "",
            sp->ap ? "'" : "", parsenleft, parselleft, parsenleft, parsenextc));

        parsefile->strpush = sp->prev;
        if (sp != &(parsefile->basestrpush))
                ckfree(sp);
        INTON;
}

/*
 * Set the input to take input from a file.  If push is set, push the
 * old input onto the stack first.
 */

void
setinputfile(const char *fname, int push)
{
        unsigned char magic[4];
        int fd;
        int fd2;
        struct stat sb;

        CTRACE(DBG_INPUT,("setinputfile(\"%s\", %spush)\n",fname,push?"":"no"));

        INTOFF;
        if ((fd = open(fname, O_RDONLY)) < 0)
                error("Can't open %s", fname);

        /* Since the message "Syntax error: "(" unexpected" is not very
         * helpful, we check if the file starts with the ELF magic to
         * avoid that message. The first lseek tries to make sure that
         * we can later rewind the file.
         */
        if (fstat(fd, &sb) == 0 && S_ISREG(sb.st_mode) &&
            lseek(fd, 0, SEEK_SET) == 0) {
                if (read(fd, magic, 4) == 4) {
                        if (memcmp(magic, "\177ELF", 4) == 0) {
                                (void)close(fd);
                                error("Cannot execute ELF binary %s", fname);
                        }
                }
                if (lseek(fd, 0, SEEK_SET) != 0) {
                        (void)close(fd);
                        error("Cannot rewind the file %s", fname);
                }
        }

        fd2 = to_upper_fd(fd);  /* closes fd, returns higher equiv */
        if (fd2 == fd) {
                (void) close(fd);
                error("Out of file descriptors");
        }

        setinputfd(fd2, push);
        INTON;
}

/*
 * When a shell fd needs to be altered (when the user wants to use
 * the same fd - rare, but happens - we need to locate the ref to
 * the fd, and update it.  This happens via a callback.
 * This is the callback func for fd's used for shell input
 */
static void
input_fd_swap(int from, int to)
{
        struct parsefile *pf;

        pf = parsefile;
        while (pf != NULL) {            /* don't need to stop at basepf */
                if (pf->fd == from)
                        pf->fd = to;
                pf = pf->prev;
        }
}

/*
 * Like setinputfile, but takes an open file descriptor.  Call this with
 * interrupts off.
 */

void
setinputfd(int fd, int push)
{
        VTRACE(DBG_INPUT, ("setinputfd(%d, %spush)\n", fd, push?"":"no"));

        INTOFF;
        register_sh_fd(fd, input_fd_swap);
        (void) fcntl(fd, F_SETFD, FD_CLOEXEC);
        if (push)
                pushfile();
        if (parsefile->fd > 0)
                sh_close(parsefile->fd);
        parsefile->fd = fd;
        if (parsefile->buf == NULL)
                parsefile->buf = ckmalloc(BUFSIZ);
        parselleft = parsenleft = 0;
        plinno = 1;
        INTON;

        CTRACE(DBG_INPUT, ("setinputfd(%d, %spush) done; plinno=1\n", fd,
            push ? "" : "no"));
}


/*
 * Like setinputfile, but takes input from a string.
 */

void
setinputstring(const char *string, int push, int line1)
{

        INTOFF;
        if (push)               /* XXX: always, as it happens */
                pushfile();
        parsenextc = string;
        parselleft = parsenleft = strlen(string);
        plinno = line1;
        INTON;

        CTRACE(DBG_INPUT,
            ("setinputstring(\"%.20s%s\" (%d), %spush, @ %d)\n", string,
            (parsenleft > 20 ? "..." : ""), parsenleft, push?"":"no", line1));
}



/*
 * To handle the "." command, a stack of input files is used.  Pushfile
 * adds a new entry to the stack and popfile restores the previous level.
 */

STATIC void
pushfile(void)
{
        struct parsefile *pf;

        VTRACE(DBG_INPUT,
            ("pushfile(): fd=%d buf=%p nl=%d ll=%d \"%.*s\" plinno=%d\n",
            parsefile->fd, parsefile->buf, parsenleft, parselleft,
            parsenleft, parsenextc, plinno));

        parsefile->nleft = parsenleft;
        parsefile->lleft = parselleft;
        parsefile->nextc = parsenextc;
        parsefile->linno = plinno;
        pf = (struct parsefile *)ckmalloc(sizeof (struct parsefile));
        pf->prev = parsefile;
        pf->fd = -1;
        pf->strpush = NULL;
        pf->basestrpush.prev = NULL;
        pf->buf = NULL;
        parsefile = pf;
}


void
popfile(void)
{
        struct parsefile *pf = parsefile;

        INTOFF;
        if (pf->fd >= 0)
                sh_close(pf->fd);
        if (pf->buf)
                ckfree(pf->buf);
        while (pf->strpush)
                popstring();
        parsefile = pf->prev;
        ckfree(pf);
        parsenleft = parsefile->nleft;
        parselleft = parsefile->lleft;
        parsenextc = parsefile->nextc;

        VTRACE(DBG_INPUT,
            ("popfile(): fd=%d buf=%p nl=%d ll=%d \"%.*s\" plinno:%d->%d\n",
            parsefile->fd, parsefile->buf, parsenleft, parselleft,
            parsenleft, parsenextc, plinno, parsefile->linno));

        plinno = parsefile->linno;
        INTON;
}

/*
 * Return current file (to go back to it later using popfilesupto()).
 */

struct parsefile *
getcurrentfile(void)
{
        return parsefile;
}


/*
 * Pop files until the given file is on top again. Useful for regular
 * builtins that read shell commands from files or strings.
 * If the given file is not an active file, an error is raised.
 */

void
popfilesupto(struct parsefile *file)
{
        while (parsefile != file && parsefile != &basepf)
                popfile();
        if (parsefile != file)
                error("popfilesupto() misused");
}


/*
 * Return to top level.
 */

void
popallfiles(void)
{
        while (parsefile != &basepf)
                popfile();
}



/*
 * Close the file(s) that the shell is reading commands from.  Called
 * after a fork is done.
 *
 * Takes one arg, vfork, which tells it to not modify its global vars
 * as it is still running in the parent.
 *
 * This code is (probably) unnecessary as the 'close on exec' flag is
 * set and should be enough.  In the vfork case it is definitely wrong
 * to close the fds as another fork() may be done later to feed data
 * from a 'here' document into a pipe and we don't want to close the
 * pipe!
 */

void
closescript(int vforked)
{
        if (vforked)
                return;
        popallfiles();
        if (parsefile->fd > 0) {
                sh_close(parsefile->fd);
                parsefile->fd = 0;
        }
}