/*      $OpenBSD: csplit.c,v 1.12 2023/03/08 04:43:10 guenther Exp $    */
/*      $FreeBSD: src/usr.bin/csplit/csplit.c,v 1.9 2004/03/22 11:15:03 tjr Exp $       */

/*-
 * Copyright (c) 2002 Tim J. Robbins.
 * All rights reserved.
 *
 * 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.
 *
 * THIS SOFTWARE IS PROVIDED BY THE AUTHOR 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 AUTHOR 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.
 */

/*
 * csplit -- split files based on context
 *
 * This utility splits its input into numbered output files by line number
 * or by a regular expression. Regular expression matches have an optional
 * offset with them, allowing the split to occur a specified number of
 * lines before or after the match.
 *
 * To handle negative offsets, we stop reading when the match occurs and
 * store the offset that the file should have been split at, then use
 * this output file as input until all the "overflowed" lines have been read.
 * The file is then closed and truncated to the correct length.
 *
 * We assume that the output files can be seeked upon (ie. they cannot be
 * symlinks to named pipes or character devices), but make no such
 * assumption about the input.
 */

#include <sys/types.h>

#include <ctype.h>
#include <err.h>
#include <errno.h>
#include <limits.h>
#include <regex.h>
#include <signal.h>
#include <stdint.h>
#include <stdio.h>
#include <stdlib.h>
#include <string.h>
#include <unistd.h>

void     cleanup(void);
void     do_lineno(const char *);
void     do_rexp(const char *);
char    *get_line(void);
void     handlesig(int);
FILE    *newfile(void);
void     toomuch(FILE *, long);
static void __dead usage(void);

/*
 * Command line options
 */
const char *prefix;             /* File name prefix */
long     sufflen;               /* Number of decimal digits for suffix */
int      sflag;                 /* Suppress output of file names */
int      kflag;                 /* Keep output if error occurs */

/*
 * Other miscellaneous globals (XXX too many)
 */
long     lineno;                /* Current line number in input file */
long     reps;                  /* Number of repetitions for this pattern */
long     nfiles;                /* Number of files output so far */
long     maxfiles;              /* Maximum number of files we can create */
char     currfile[PATH_MAX];    /* Current output file */
const char *infn;               /* Name of the input file */
FILE    *infile;                /* Input file handle */
FILE    *overfile;              /* Overflow file for toomuch() */
off_t    truncofs;              /* Offset this file should be truncated at */
int      doclean;               /* Should cleanup() remove output? */

int
main(int argc, char *argv[])
{
        struct sigaction sa;
        long i;
        int ch;
        const char *expr;
        char *ep, *p;
        FILE *ofp;

        if (pledge("stdio rpath wpath cpath", NULL) == -1)
                err(1, "pledge");

        kflag = sflag = 0;
        prefix = "xx";
        sufflen = 2;
        while ((ch = getopt(argc, argv, "f:kn:s")) != -1) {
                switch (ch) {
                case 'f':
                        prefix = optarg;
                        break;
                case 'k':
                        kflag = 1;
                        break;
                case 'n':
                        errno = 0;
                        sufflen = strtol(optarg, &ep, 10);
                        if (sufflen <= 0 || *ep != '\0' || errno != 0)
                                errx(1, "%s: bad suffix length", optarg);
                        break;
                case 's':
                        sflag = 1;
                        break;
                default:
                        usage();
                }
        }

        if (sufflen + strlen(prefix) >= PATH_MAX)
                errx(1, "name too long");

        argc -= optind;
        argv += optind;

        if ((infn = *argv++) == NULL)
                usage();
        if (strcmp(infn, "-") == 0) {
                infile = stdin;
                infn = "stdin";
        } else if ((infile = fopen(infn, "r")) == NULL)
                err(1, "%s", infn);

        if (!kflag) {
                doclean = 1;
                atexit(cleanup);
                sa.sa_flags = 0;
                sa.sa_handler = handlesig;
                sigemptyset(&sa.sa_mask);
                sigaddset(&sa.sa_mask, SIGHUP);
                sigaddset(&sa.sa_mask, SIGINT);
                sigaddset(&sa.sa_mask, SIGTERM);
                sigaction(SIGHUP, &sa, NULL);
                sigaction(SIGINT, &sa, NULL);
                sigaction(SIGTERM, &sa, NULL);
        }

        lineno = 0;
        nfiles = 0;
        truncofs = 0;
        overfile = NULL;

        /* Ensure 10^sufflen < LONG_MAX. */
        for (maxfiles = 1, i = 0; i < sufflen; i++) {
                if (maxfiles > LONG_MAX / 10)
                        errx(1, "%ld: suffix too long (limit %ld)",
                            sufflen, i);
                maxfiles *= 10;
        }

        /* Create files based on supplied patterns. */
        while (nfiles < maxfiles - 1 && (expr = *argv++) != NULL) {
                /* Look ahead & see if this pattern has any repetitions. */
                if (*argv != NULL && **argv == '{') {
                        errno = 0;
                        reps = strtol(*argv + 1, &ep, 10);
                        if (reps < 0 || *ep != '}' || errno != 0)
                                errx(1, "%s: bad repetition count", *argv + 1);
                        argv++;
                } else
                        reps = 0;

                if (*expr == '/' || *expr == '%') {
                        do {
                                do_rexp(expr);
                        } while (reps-- != 0 && nfiles < maxfiles - 1);
                } else if (isdigit((unsigned char)*expr))
                        do_lineno(expr);
                else
                        errx(1, "%s: unrecognised pattern", expr);
        }

        /* Copy the rest into a new file. */
        if (!feof(infile)) {
                ofp = newfile();
                while ((p = get_line()) != NULL && fputs(p, ofp) == 0)
                        ;
                if (!sflag)
                        printf("%jd\n", (intmax_t)ftello(ofp));
                if (fclose(ofp) != 0)
                        err(1, "%s", currfile);
        }

        toomuch(NULL, 0);
        doclean = 0;

        return (0);
}

static void __dead
usage(void)
{
        extern char *__progname;

        fprintf(stderr,
            "usage: %s [-ks] [-f prefix] [-n number] file arg ...\n",
            __progname);
        exit(1);
}

void
handlesig(int sig)
{
        const char msg[] = "csplit: caught signal, cleaning up\n";

        write(STDERR_FILENO, msg, sizeof(msg) - 1);
        cleanup();
        _exit(2);
}

/* Create a new output file. */
FILE *
newfile(void)
{
        FILE *fp;

        if ((size_t)snprintf(currfile, sizeof(currfile), "%s%0*ld", prefix,
            (int)sufflen, nfiles) >= sizeof(currfile))
                errc(1, ENAMETOOLONG, "%s", currfile);
        if ((fp = fopen(currfile, "w+")) == NULL)
                err(1, "%s", currfile);
        nfiles++;

        return (fp);
}

/* Remove partial output, called before exiting. */
void
cleanup(void)
{
        char fnbuf[PATH_MAX];
        long i;

        if (!doclean)
                return;

        /*
         * NOTE: One cannot portably assume to be able to call snprintf() from
         * inside a signal handler.  It is, however, safe to do on OpenBSD.
         */
        for (i = 0; i < nfiles; i++) {
                snprintf(fnbuf, sizeof(fnbuf), "%s%0*ld", prefix,
                    (int)sufflen, i);
                unlink(fnbuf);
        }
}

/* Read a line from the input into a static buffer. */
char *
get_line(void)
{
        static char lbuf[LINE_MAX];
        FILE *src;

        src = overfile != NULL ? overfile : infile;

again: if (fgets(lbuf, sizeof(lbuf), src) == NULL) {
                if (src == overfile) {
                        src = infile;
                        goto again;
                }
                return (NULL);
        }
        if (ferror(src))
                err(1, "%s", infn);
        lineno++;

        return (lbuf);
}

/* Conceptually rewind the input (as obtained by get_line()) back `n' lines. */
void
toomuch(FILE *ofp, long n)
{
        char buf[BUFSIZ];
        size_t i, nread;

        if (overfile != NULL) {
                /*
                 * Truncate the previous file we overflowed into back to
                 * the correct length, close it.
                 */
                if (fflush(overfile) != 0)
                        err(1, "overflow");
                if (ftruncate(fileno(overfile), truncofs) != 0)
                        err(1, "overflow");
                if (fclose(overfile) != 0)
                        err(1, "overflow");
                overfile = NULL;
        }

        if (n == 0)
                /* Just tidying up */
                return;

        lineno -= n;

        /*
         * Wind the overflow file backwards to `n' lines before the
         * current one.
         */
        do {
                if (ftello(ofp) < (off_t)sizeof(buf))
                        rewind(ofp);
                else
                        fseeko(ofp, -(off_t)sizeof(buf), SEEK_CUR);
                if (ferror(ofp))
                        errx(1, "%s: can't seek", currfile);
                if ((nread = fread(buf, 1, sizeof(buf), ofp)) == 0)
                        errx(1, "can't read overflowed output");
                if (fseeko(ofp, -(off_t)nread, SEEK_CUR) != 0)
                        err(1, "%s", currfile);
                for (i = 1; i <= nread; i++)
                        if (buf[nread - i] == '\n' && n-- == 0)
                                break;
                if (ftello(ofp) == 0)
                        break;
        } while (n > 0);
        if (fseeko(ofp, (off_t)(nread - i + 1), SEEK_CUR) != 0)
                err(1, "%s", currfile);

        /*
         * get_line() will read from here. Next call will truncate to
         * truncofs in this file.
         */
        overfile = ofp;
        truncofs = ftello(overfile);
}

/* Handle splits for /regexp/ and %regexp% patterns. */
void
do_rexp(const char *expr)
{
        regex_t cre;
        intmax_t nwritten;
        long ofs;
        int first;
        char *ecopy, *ep, *p, *pofs, *re;
        FILE *ofp;

        if ((ecopy = strdup(expr)) == NULL)
                err(1, "strdup");

        re = ecopy + 1;
        if ((pofs = strrchr(ecopy, *expr)) == NULL || pofs[-1] == '\\')
                errx(1, "%s: missing trailing %c", expr, *expr);
        *pofs++ = '\0';

        if (*pofs != '\0') {
                errno = 0;
                ofs = strtol(pofs, &ep, 10);
                if (*ep != '\0' || errno != 0)
                        errx(1, "%s: bad offset", pofs);
        } else
                ofs = 0;

        if (regcomp(&cre, re, REG_BASIC|REG_NOSUB) != 0)
                errx(1, "%s: bad regular expression", re);

        if (*expr == '/')
                /* /regexp/: Save results to a file. */
                ofp = newfile();
        else {
                /* %regexp%: Make a temporary file for overflow. */
                if ((ofp = tmpfile()) == NULL)
                        err(1, "tmpfile");
        }

        /* Read and output lines until we get a match. */
        first = 1;
        while ((p = get_line()) != NULL) {
                if (fputs(p, ofp) != 0)
                        break;
                if (!first && regexec(&cre, p, 0, NULL, 0) == 0)
                        break;
                first = 0;
        }

        if (p == NULL) {
                toomuch(NULL, 0);
                errx(1, "%s: no match", re);
        }

        if (ofs <= 0) {
                /*
                 * Negative (or zero) offset: throw back any lines we should
                 * not have read yet.
                  */
                if (p != NULL) {
                        toomuch(ofp, -ofs + 1);
                        nwritten = (intmax_t)truncofs;
                } else
                        nwritten = (intmax_t)ftello(ofp);
        } else {
                /*
                 * Positive offset: copy the requested number of lines
                 * after the match.
                 */
                while (--ofs > 0 && (p = get_line()) != NULL)
                        fputs(p, ofp);
                toomuch(NULL, 0);
                nwritten = (intmax_t)ftello(ofp);
                if (fclose(ofp) != 0)
                        err(1, "%s", currfile);
        }

        if (!sflag && *expr == '/')
                printf("%jd\n", nwritten);

        regfree(&cre);
        free(ecopy);
}

/* Handle splits based on line number. */
void
do_lineno(const char *expr)
{
        long lastline, tgtline;
        char *ep, *p;
        FILE *ofp;

        errno = 0;
        tgtline = strtol(expr, &ep, 10);
        if (tgtline <= 0 || errno != 0 || *ep != '\0')
                errx(1, "%s: bad line number", expr);
        lastline = tgtline;
        if (lastline <= lineno)
                errx(1, "%s: can't go backwards", expr);

        while (nfiles < maxfiles - 1) {
                ofp = newfile();
                while (lineno + 1 != lastline) {
                        if ((p = get_line()) == NULL)
                                errx(1, "%ld: out of range", lastline);
                        if (fputs(p, ofp) != 0)
                                break;
                }
                if (!sflag)
                        printf("%jd\n", (intmax_t)ftello(ofp));
                if (fclose(ofp) != 0)
                        err(1, "%s", currfile);
                if (reps-- == 0)
                        break;
                lastline += tgtline;
        } 
}