/* main.c: This file contains the main control and user-interface routines
   for the ed line editor. */
/*-
 * SPDX-License-Identifier: BSD-2-Clause
 *
 * Copyright (c) 1993 Andrew Moore, Talke Studio.
 * 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.
 */

/*
 * CREDITS
 *
 *      This program is based on the editor algorithm described in
 *      Brian W. Kernighan and P. J. Plauger's book "Software Tools
 *      in Pascal," Addison-Wesley, 1981.
 *
 *      The buffering algorithm is attributed to Rodney Ruddock of
 *      the University of Guelph, Guelph, Ontario.
 *
 */

#include <sys/types.h>

#include <sys/ioctl.h>
#include <sys/wait.h>
#include <ctype.h>
#include <locale.h>
#include <pwd.h>
#include <setjmp.h>

#include "ed.h"


#ifdef _POSIX_SOURCE
static sigjmp_buf env;
#else
static jmp_buf env;
#endif

/* static buffers */
char stdinbuf[1];               /* stdin buffer */
static char *shcmd;             /* shell command buffer */
static int shcmdsz;             /* shell command buffer size */
static int shcmdi;              /* shell command buffer index */
char *ibuf;                     /* ed command-line buffer */
int ibufsz;                     /* ed command-line buffer size */
char *ibufp;                    /* pointer to ed command-line buffer */

/* global flags */
static int garrulous = 0;       /* if set, print all error messages */
int isbinary;                   /* if set, buffer contains ASCII NULs */
int isglobal;                   /* if set, doing a global command */
int modified;                   /* if set, buffer modified since last write */
int mutex = 0;                  /* if set, signals set "sigflags" */
static int red = 0;             /* if set, restrict shell/directory access */
int scripted = 0;               /* if set, suppress diagnostics */
int sigflags = 0;               /* if set, signals received while mutex set */
static int sigactive = 0;       /* if set, signal handlers are enabled */

static char old_filename[PATH_MAX] = ""; /* default filename */
long current_addr;              /* current address in editor buffer */
long addr_last;                 /* last address in editor buffer */
int lineno;                     /* script line number */
static const char *prompt;      /* command-line prompt */
static const char *dps = "*";   /* default command-line prompt */

static const char *usage = "usage: %s [-] [-sx] [-p string] [file]\n";

/* ed: line editor */
int
main(volatile int argc, char ** volatile argv)
{
        int c, n;
        long status = 0;

        (void)setlocale(LC_ALL, "");

        red = (n = strlen(argv[0])) > 2 && argv[0][n - 3] == 'r';
top:
        while ((c = getopt(argc, argv, "p:sx")) != -1)
                switch(c) {
                case 'p':                               /* set prompt */
                        prompt = optarg;
                        break;
                case 's':                               /* run script */
                        scripted = 1;
                        break;
                case 'x':                               /* use crypt */
                        fprintf(stderr, "crypt unavailable\n?\n");
                        break;

                default:
                        fprintf(stderr, usage, red ? "red" : "ed");
                        exit(1);
                }
        argv += optind;
        argc -= optind;
        if (argc && **argv == '-') {
                scripted = 1;
                if (argc > 1) {
                        optind = 1;
                        goto top;
                }
                argv++;
                argc--;
        }
        /* assert: reliable signals! */
#ifdef SIGWINCH
        handle_winch(SIGWINCH);
        if (isatty(0)) signal(SIGWINCH, handle_winch);
#endif
        signal(SIGHUP, signal_hup);
        signal(SIGQUIT, SIG_IGN);
        signal(SIGINT, signal_int);
#ifdef _POSIX_SOURCE
        if ((status = sigsetjmp(env, 1)))
#else
        if ((status = setjmp(env)))
#endif
        {
                fputs("\n?\n", stderr);
                errmsg = "interrupt";
        } else {
                init_buffers();
                sigactive = 1;                  /* enable signal handlers */
                if (argc && **argv && is_legal_filename(*argv)) {
                        if (read_file(*argv, 0) < 0 && !isatty(0))
                                quit(2);
                        else if (**argv != '!')
                                if (strlcpy(old_filename, *argv, sizeof(old_filename))
                                    >= sizeof(old_filename))
                                        quit(2);
                } else if (argc) {
                        fputs("?\n", stderr);
                        if (**argv == '\0')
                                errmsg = "invalid filename";
                        if (!isatty(0))
                                quit(2);
                }
        }
        for (;;) {
                if (status < 0 && garrulous)
                        fprintf(stderr, "%s\n", errmsg);
                if (prompt) {
                        printf("%s", prompt);
                        fflush(stdout);
                }
                if ((n = get_tty_line()) < 0) {
                        status = ERR;
                        continue;
                } else if (n == 0) {
                        if (modified && !scripted) {
                                fputs("?\n", stderr);
                                errmsg = "warning: file modified";
                                if (!isatty(0)) {
                                        if (garrulous)
                                                fprintf(stderr,
                                                    "script, line %d: %s\n",
                                                    lineno, errmsg);
                                        quit(2);
                                }
                                clearerr(stdin);
                                modified = 0;
                                status = EMOD;
                                continue;
                        } else
                                quit(0);
                } else if (ibuf[n - 1] != '\n') {
                        /* discard line */
                        errmsg = "unexpected end-of-file";
                        clearerr(stdin);
                        status = ERR;
                        continue;
                }
                isglobal = 0;
                if ((status = extract_addr_range()) >= 0 &&
                    (status = exec_command()) >= 0)
                        if (!status ||
                            (status = display_lines(current_addr, current_addr,
                                status)) >= 0)
                                continue;
                switch (status) {
                case EOF:
                        quit(0);
                case EMOD:
                        modified = 0;
                        fputs("?\n", stderr);           /* give warning */
                        errmsg = "warning: file modified";
                        if (!isatty(0)) {
                                if (garrulous)
                                        fprintf(stderr, "script, line %d: %s\n",
                                            lineno, errmsg);
                                quit(2);
                        }
                        break;
                case FATAL:
                        if (!isatty(0)) {
                                if (garrulous)
                                        fprintf(stderr, "script, line %d: %s\n",
                                            lineno, errmsg);
                        } else if (garrulous)
                                fprintf(stderr, "%s\n", errmsg);
                        quit(3);
                default:
                        fputs("?\n", stderr);
                        if (!isatty(0)) {
                                if (garrulous)
                                        fprintf(stderr, "script, line %d: %s\n",
                                            lineno, errmsg);
                                quit(2);
                        }
                        break;
                }
        }
        /*NOTREACHED*/
}

long first_addr, second_addr;
static long addr_cnt;

/* extract_addr_range: get line addresses from the command buffer until an
   illegal address is seen; return status */
int
extract_addr_range(void)
{
        long addr;

        addr_cnt = 0;
        first_addr = second_addr = current_addr;
        while ((addr = next_addr()) >= 0) {
                addr_cnt++;
                first_addr = second_addr;
                second_addr = addr;
                if (*ibufp != ',' && *ibufp != ';')
                        break;
                else if (*ibufp++ == ';')
                        current_addr = addr;
        }
        if ((addr_cnt = min(addr_cnt, 2)) == 1 || second_addr != addr)
                first_addr = second_addr;
        return (addr == ERR) ? ERR : 0;
}


#define SKIP_BLANKS() while (isspace((unsigned char)*ibufp) && *ibufp != '\n') ibufp++

#define MUST_BE_FIRST() do {                                    \
        if (!first) {                                           \
                errmsg = "invalid address";                     \
                return ERR;                                     \
        }                                                       \
} while (0)

/*  next_addr: return the next line address in the command buffer */
long
next_addr(void)
{
        const char *hd;
        long addr = current_addr;
        long n;
        int first = 1;
        int c;

        SKIP_BLANKS();
        for (hd = ibufp;; first = 0)
                switch (c = *ibufp) {
                case '+':
                case '\t':
                case ' ':
                case '-':
                case '^':
                        ibufp++;
                        SKIP_BLANKS();
                        if (isdigit((unsigned char)*ibufp)) {
                                STRTOL(n, ibufp);
                                addr += (c == '-' || c == '^') ? -n : n;
                        } else if (!isspace((unsigned char)c))
                                addr += (c == '-' || c == '^') ? -1 : 1;
                        break;
                case '0': case '1': case '2':
                case '3': case '4': case '5':
                case '6': case '7': case '8': case '9':
                        MUST_BE_FIRST();
                        STRTOL(addr, ibufp);
                        break;
                case '.':
                case '$':
                        MUST_BE_FIRST();
                        ibufp++;
                        addr = (c == '.') ? current_addr : addr_last;
                        break;
                case '/':
                case '?':
                        MUST_BE_FIRST();
                        if ((addr = get_matching_node_addr(
                            get_compiled_pattern(), c == '/')) < 0)
                                return ERR;
                        else if (c == *ibufp)
                                ibufp++;
                        break;
                case '\'':
                        MUST_BE_FIRST();
                        ibufp++;
                        if ((addr = get_marked_node_addr(*ibufp++)) < 0)
                                return ERR;
                        break;
                case '%':
                case ',':
                case ';':
                        if (first) {
                                ibufp++;
                                addr_cnt++;
                                second_addr = (c == ';') ? current_addr : 1;
                                if ((addr = next_addr()) < 0)
                                        addr = addr_last;
                                break;
                        }
                        /* FALLTHROUGH */
                default:
                        if (ibufp == hd)
                                return EOF;
                        else if (addr < 0 || addr_last < addr) {
                                errmsg = "invalid address";
                                return ERR;
                        } else
                                return addr;
                }
        /* NOTREACHED */
}


#ifdef BACKWARDS
/* GET_THIRD_ADDR: get a legal address from the command buffer */
#define GET_THIRD_ADDR(addr) \
{ \
        long ol1, ol2; \
\
        ol1 = first_addr, ol2 = second_addr; \
        if (extract_addr_range() < 0) \
                return ERR; \
        else if (addr_cnt == 0) { \
                errmsg = "destination expected"; \
                return ERR; \
        } else if (second_addr < 0 || addr_last < second_addr) { \
                errmsg = "invalid address"; \
                return ERR; \
        } \
        addr = second_addr; \
        first_addr = ol1, second_addr = ol2; \
}
#else   /* BACKWARDS */
/* GET_THIRD_ADDR: get a legal address from the command buffer */
#define GET_THIRD_ADDR(addr) \
{ \
        long ol1, ol2; \
\
        ol1 = first_addr, ol2 = second_addr; \
        if (extract_addr_range() < 0) \
                return ERR; \
        if (second_addr < 0 || addr_last < second_addr) { \
                errmsg = "invalid address"; \
                return ERR; \
        } \
        addr = second_addr; \
        first_addr = ol1, second_addr = ol2; \
}
#endif


/* GET_COMMAND_SUFFIX: verify the command suffix in the command buffer */
#define GET_COMMAND_SUFFIX() { \
        int done = 0; \
        do { \
                switch(*ibufp) { \
                case 'p': \
                        gflag |= GPR, ibufp++; \
                        break; \
                case 'l': \
                        gflag |= GLS, ibufp++; \
                        break; \
                case 'n': \
                        gflag |= GNP, ibufp++; \
                        break; \
                default: \
                        done++; \
                } \
        } while (!done); \
        if (*ibufp++ != '\n') { \
                errmsg = "invalid command suffix"; \
                return ERR; \
        } \
}


/* sflags */
#define SGG 001         /* complement previous global substitute suffix */
#define SGP 002         /* complement previous print suffix */
#define SGR 004         /* use last regex instead of last pat */
#define SGF 010         /* repeat last substitution */

int patlock = 0;        /* if set, pattern not freed by get_compiled_pattern() */

long rows = 22;         /* scroll length: ws_row - 2 */

/* exec_command: execute the next command in command buffer; return print
   request, if any */
int
exec_command(void)
{
        static pattern_t *pat = NULL;
        static int sgflag = 0;
        static long sgnum = 0;

        pattern_t *tpat;
        char *fnp;
        int gflag = 0;
        int sflags = 0;
        long addr = 0;
        int n = 0;
        int c;

        SKIP_BLANKS();
        switch(c = *ibufp++) {
        case 'a':
                GET_COMMAND_SUFFIX();
                if (!isglobal) clear_undo_stack();
                if (append_lines(second_addr) < 0)
                        return ERR;
                break;
        case 'c':
                if (check_addr_range(current_addr, current_addr) < 0)
                        return ERR;
                GET_COMMAND_SUFFIX();
                if (!isglobal) clear_undo_stack();
                if (delete_lines(first_addr, second_addr) < 0 ||
                    append_lines(current_addr) < 0)
                        return ERR;
                break;
        case 'd':
                if (check_addr_range(current_addr, current_addr) < 0)
                        return ERR;
                GET_COMMAND_SUFFIX();
                if (!isglobal) clear_undo_stack();
                if (delete_lines(first_addr, second_addr) < 0)
                        return ERR;
                else if ((addr = INC_MOD(current_addr, addr_last)) != 0)
                        current_addr = addr;
                break;
        case 'e':
                if (modified && !scripted)
                        return EMOD;
                /* FALLTHROUGH */
        case 'E':
                if (addr_cnt > 0) {
                        errmsg = "unexpected address";
                        return ERR;
                } else if (!isspace((unsigned char)*ibufp)) {
                        errmsg = "unexpected command suffix";
                        return ERR;
                } else if ((fnp = get_filename()) == NULL)
                        return ERR;
                GET_COMMAND_SUFFIX();
                if (delete_lines(1, addr_last) < 0)
                        return ERR;
                clear_undo_stack();
                if (close_sbuf() < 0)
                        return ERR;
                else if (open_sbuf() < 0)
                        return FATAL;
                if (*fnp && *fnp != '!')
                         strlcpy(old_filename, fnp, PATH_MAX);
#ifdef BACKWARDS
                if (*fnp == '\0' && *old_filename == '\0') {
                        errmsg = "no current filename";
                        return ERR;
                }
#endif
                if (read_file(*fnp ? fnp : old_filename, 0) < 0)
                        return ERR;
                clear_undo_stack();
                modified = 0;
                u_current_addr = u_addr_last = -1;
                break;
        case 'f':
                if (addr_cnt > 0) {
                        errmsg = "unexpected address";
                        return ERR;
                } else if (!isspace((unsigned char)*ibufp)) {
                        errmsg = "unexpected command suffix";
                        return ERR;
                } else if ((fnp = get_filename()) == NULL)
                        return ERR;
                else if (*fnp == '!') {
                        errmsg = "invalid redirection";
                        return ERR;
                }
                GET_COMMAND_SUFFIX();
                if (*fnp)
                        strlcpy(old_filename, fnp, PATH_MAX);
                printf("%s\n", strip_escapes(old_filename));
                break;
        case 'g':
        case 'v':
        case 'G':
        case 'V':
                if (isglobal) {
                        errmsg = "cannot nest global commands";
                        return ERR;
                } else if (check_addr_range(1, addr_last) < 0)
                        return ERR;
                else if (build_active_list(c == 'g' || c == 'G') < 0)
                        return ERR;
                else if ((n = (c == 'G' || c == 'V')))
                        GET_COMMAND_SUFFIX();
                isglobal++;
                if (exec_global(n, gflag) < 0)
                        return ERR;
                break;
        case 'h':
                if (addr_cnt > 0) {
                        errmsg = "unexpected address";
                        return ERR;
                }
                GET_COMMAND_SUFFIX();
                if (*errmsg) fprintf(stderr, "%s\n", errmsg);
                break;
        case 'H':
                if (addr_cnt > 0) {
                        errmsg = "unexpected address";
                        return ERR;
                }
                GET_COMMAND_SUFFIX();
                if ((garrulous = 1 - garrulous) && *errmsg)
                        fprintf(stderr, "%s\n", errmsg);
                break;
        case 'i':
                if (second_addr == 0) {
                        errmsg = "invalid address";
                        return ERR;
                }
                GET_COMMAND_SUFFIX();
                if (!isglobal) clear_undo_stack();
                if (append_lines(second_addr - 1) < 0)
                        return ERR;
                break;
        case 'j':
                if (check_addr_range(current_addr, current_addr + 1) < 0)
                        return ERR;
                GET_COMMAND_SUFFIX();
                if (!isglobal) clear_undo_stack();
                if (first_addr != second_addr &&
                    join_lines(first_addr, second_addr) < 0)
                        return ERR;
                break;
        case 'k':
                c = *ibufp++;
                if (second_addr == 0) {
                        errmsg = "invalid address";
                        return ERR;
                }
                GET_COMMAND_SUFFIX();
                if (mark_line_node(get_addressed_line_node(second_addr), c) < 0)
                        return ERR;
                break;
        case 'l':
                if (check_addr_range(current_addr, current_addr) < 0)
                        return ERR;
                GET_COMMAND_SUFFIX();
                if (display_lines(first_addr, second_addr, gflag | GLS) < 0)
                        return ERR;
                gflag = 0;
                break;
        case 'm':
                if (check_addr_range(current_addr, current_addr) < 0)
                        return ERR;
                GET_THIRD_ADDR(addr);
                if (first_addr <= addr && addr < second_addr) {
                        errmsg = "invalid destination";
                        return ERR;
                }
                GET_COMMAND_SUFFIX();
                if (!isglobal) clear_undo_stack();
                if (move_lines(addr) < 0)
                        return ERR;
                break;
        case 'n':
                if (check_addr_range(current_addr, current_addr) < 0)
                        return ERR;
                GET_COMMAND_SUFFIX();
                if (display_lines(first_addr, second_addr, gflag | GNP) < 0)
                        return ERR;
                gflag = 0;
                break;
        case 'p':
                if (check_addr_range(current_addr, current_addr) < 0)
                        return ERR;
                GET_COMMAND_SUFFIX();
                if (display_lines(first_addr, second_addr, gflag | GPR) < 0)
                        return ERR;
                gflag = 0;
                break;
        case 'P':
                if (addr_cnt > 0) {
                        errmsg = "unexpected address";
                        return ERR;
                }
                GET_COMMAND_SUFFIX();
                prompt = prompt ? NULL : optarg ? optarg : dps;
                break;
        case 'q':
        case 'Q':
                if (addr_cnt > 0) {
                        errmsg = "unexpected address";
                        return ERR;
                }
                GET_COMMAND_SUFFIX();
                gflag =  (modified && !scripted && c == 'q') ? EMOD : EOF;
                break;
        case 'r':
                if (!isspace((unsigned char)*ibufp)) {
                        errmsg = "unexpected command suffix";
                        return ERR;
                } else if (addr_cnt == 0)
                        second_addr = addr_last;
                if ((fnp = get_filename()) == NULL)
                        return ERR;
                GET_COMMAND_SUFFIX();
                if (!isglobal) clear_undo_stack();
                if (*old_filename == '\0' && *fnp != '!')
                        strlcpy(old_filename, fnp, PATH_MAX);
#ifdef BACKWARDS
                if (*fnp == '\0' && *old_filename == '\0') {
                        errmsg = "no current filename";
                        return ERR;
                }
#endif
                if ((addr = read_file(*fnp ? fnp : old_filename, second_addr)) < 0)
                        return ERR;
                else if (addr && addr != addr_last)
                        modified = 1;
                break;
        case 's':
                do {
                        switch(*ibufp) {
                        case '\n':
                                sflags |=SGF;
                                break;
                        case 'g':
                                sflags |= SGG;
                                ibufp++;
                                break;
                        case 'p':
                                sflags |= SGP;
                                ibufp++;
                                break;
                        case 'r':
                                sflags |= SGR;
                                ibufp++;
                                break;
                        case '0': case '1': case '2': case '3': case '4':
                        case '5': case '6': case '7': case '8': case '9':
                                STRTOL(sgnum, ibufp);
                                sflags |= SGF;
                                sgflag &= ~GSG;         /* override GSG */
                                break;
                        default:
                                if (sflags) {
                                        errmsg = "invalid command suffix";
                                        return ERR;
                                }
                        }
                } while (sflags && *ibufp != '\n');
                if (sflags && !pat) {
                        errmsg = "no previous substitution";
                        return ERR;
                } else if (sflags & SGG)
                        sgnum = 0;              /* override numeric arg */
                if (*ibufp != '\n' && *(ibufp + 1) == '\n') {
                        errmsg = "invalid pattern delimiter";
                        return ERR;
                }
                tpat = pat;
                SPL1();
                if ((!sflags || (sflags & SGR)) &&
                    (tpat = get_compiled_pattern()) == NULL) {
                        SPL0();
                        return ERR;
                } else if (tpat != pat) {
                        if (pat) {
                                regfree(pat);
                                free(pat);
                        }
                        pat = tpat;
                        patlock = 1;            /* reserve pattern */
                }
                SPL0();
                if (!sflags && extract_subst_tail(&sgflag, &sgnum) < 0)
                        return ERR;
                else if (isglobal)
                        sgflag |= GLB;
                else
                        sgflag &= ~GLB;
                if (sflags & SGG)
                        sgflag ^= GSG;
                if (sflags & SGP)
                        sgflag ^= GPR, sgflag &= ~(GLS | GNP);
                do {
                        switch(*ibufp) {
                        case 'p':
                                sgflag |= GPR, ibufp++;
                                break;
                        case 'l':
                                sgflag |= GLS, ibufp++;
                                break;
                        case 'n':
                                sgflag |= GNP, ibufp++;
                                break;
                        default:
                                n++;
                        }
                } while (!n);
                if (check_addr_range(current_addr, current_addr) < 0)
                        return ERR;
                GET_COMMAND_SUFFIX();
                if (!isglobal) clear_undo_stack();
                if (search_and_replace(pat, sgflag, sgnum) < 0)
                        return ERR;
                break;
        case 't':
                if (check_addr_range(current_addr, current_addr) < 0)
                        return ERR;
                GET_THIRD_ADDR(addr);
                GET_COMMAND_SUFFIX();
                if (!isglobal) clear_undo_stack();
                if (copy_lines(addr) < 0)
                        return ERR;
                break;
        case 'u':
                if (addr_cnt > 0) {
                        errmsg = "unexpected address";
                        return ERR;
                }
                GET_COMMAND_SUFFIX();
                if (pop_undo_stack() < 0)
                        return ERR;
                break;
        case 'w':
        case 'W':
                if ((n = *ibufp) == 'q' || n == 'Q') {
                        gflag = EOF;
                        ibufp++;
                }
                if (!isspace((unsigned char)*ibufp)) {
                        errmsg = "unexpected command suffix";
                        return ERR;
                } else if ((fnp = get_filename()) == NULL)
                        return ERR;
                if (addr_cnt == 0 && !addr_last)
                        first_addr = second_addr = 0;
                else if (check_addr_range(1, addr_last) < 0)
                        return ERR;
                GET_COMMAND_SUFFIX();
                if (*old_filename == '\0' && *fnp != '!')
                        strlcpy(old_filename, fnp, PATH_MAX);
#ifdef BACKWARDS
                if (*fnp == '\0' && *old_filename == '\0') {
                        errmsg = "no current filename";
                        return ERR;
                }
#endif
                if ((addr = write_file(*fnp ? fnp : old_filename,
                    (c == 'W') ? "a" : "w", first_addr, second_addr)) < 0)
                        return ERR;
                else if (addr == addr_last && *fnp != '!')
                        modified = 0;
                else if (modified && !scripted && n == 'q')
                        gflag = EMOD;
                break;
        case 'x':
                if (addr_cnt > 0) {
                        errmsg = "unexpected address";
                        return ERR;
                }
                GET_COMMAND_SUFFIX();
                errmsg = "crypt unavailable";
                return ERR;
        case 'z':
#ifdef BACKWARDS
                if (check_addr_range(first_addr = 1, current_addr + 1) < 0)
#else
                if (check_addr_range(first_addr = 1, current_addr + !isglobal) < 0)
#endif
                        return ERR;
                else if ('0' < *ibufp && *ibufp <= '9')
                        STRTOL(rows, ibufp);
                GET_COMMAND_SUFFIX();
                if (display_lines(second_addr, min(addr_last,
                    second_addr + rows), gflag) < 0)
                        return ERR;
                gflag = 0;
                break;
        case '=':
                GET_COMMAND_SUFFIX();
                printf("%ld\n", addr_cnt ? second_addr : addr_last);
                break;
        case '!':
                if (addr_cnt > 0) {
                        errmsg = "unexpected address";
                        return ERR;
                } else if ((sflags = get_shell_command()) < 0)
                        return ERR;
                GET_COMMAND_SUFFIX();
                if (sflags) printf("%s\n", shcmd + 1);
                system(shcmd + 1);
                if (!scripted) printf("!\n");
                break;
        case '\n':
#ifdef BACKWARDS
                if (check_addr_range(first_addr = 1, current_addr + 1) < 0
#else
                if (check_addr_range(first_addr = 1, current_addr + !isglobal) < 0
#endif
                 || display_lines(second_addr, second_addr, 0) < 0)
                        return ERR;
                break;
        default:
                errmsg = "unknown command";
                return ERR;
        }
        return gflag;
}


/* check_addr_range: return status of address range check */
int
check_addr_range(long n, long m)
{
        if (addr_cnt == 0) {
                first_addr = n;
                second_addr = m;
        }
        if (first_addr > second_addr || 1 > first_addr ||
            second_addr > addr_last) {
                errmsg = "invalid address";
                return ERR;
        }
        return 0;
}


/* get_matching_node_addr: return the address of the next line matching a
   pattern in a given direction.  wrap around begin/end of editor buffer if
   necessary */
long
get_matching_node_addr(pattern_t *pat, int dir)
{
        char *s;
        long n = current_addr;
        line_t *lp;

        if (!pat) return ERR;
        do {
               if ((n = dir ? INC_MOD(n, addr_last) : DEC_MOD(n, addr_last))) {
                        lp = get_addressed_line_node(n);
                        if ((s = get_sbuf_line(lp)) == NULL)
                                return ERR;
                        if (isbinary)
                                NUL_TO_NEWLINE(s, lp->len);
                        if (!regexec(pat, s, 0, NULL, 0))
                                return n;
               }
        } while (n != current_addr);
        errmsg = "no match";
        return  ERR;
}


/* get_filename: return pointer to copy of filename in the command buffer */
char *
get_filename(void)
{
        static char *file = NULL;
        static int filesz = 0;

        int n;

        if (*ibufp != '\n') {
                SKIP_BLANKS();
                if (*ibufp == '\n') {
                        errmsg = "invalid filename";
                        return NULL;
                } else if ((ibufp = get_extended_line(&n, 1)) == NULL)
                        return NULL;
                else if (*ibufp == '!') {
                        ibufp++;
                        if ((n = get_shell_command()) < 0)
                                return NULL;
                        if (n)
                                printf("%s\n", shcmd + 1);
                        return shcmd;
                } else if (n > PATH_MAX - 1) {
                        errmsg = "filename too long";
                        return  NULL;
                }
        }
#ifndef BACKWARDS
        else if (*old_filename == '\0') {
                errmsg = "no current filename";
                return  NULL;
        }
#endif
        REALLOC(file, filesz, PATH_MAX, NULL);
        for (n = 0; *ibufp != '\n';)
                file[n++] = *ibufp++;
        file[n] = '\0';
        return is_legal_filename(file) ? file : NULL;
}


/* get_shell_command: read a shell command from stdin; return substitution
   status */
int
get_shell_command(void)
{
        static char *buf = NULL;
        static int n = 0;

        char *s;                        /* substitution char pointer */
        int i = 0;
        int j = 0;

        if (red) {
                errmsg = "shell access restricted";
                return ERR;
        } else if ((s = ibufp = get_extended_line(&j, 1)) == NULL)
                return ERR;
        REALLOC(buf, n, j + 1, ERR);
        buf[i++] = '!';                 /* prefix command w/ bang */
        while (*ibufp != '\n')
                switch (*ibufp) {
                default:
                        REALLOC(buf, n, i + 2, ERR);
                        buf[i++] = *ibufp;
                        if (*ibufp++ == '\\')
                                buf[i++] = *ibufp++;
                        break;
                case '!':
                        if (s != ibufp) {
                                REALLOC(buf, n, i + 1, ERR);
                                buf[i++] = *ibufp++;
                        }
#ifdef BACKWARDS
                        else if (shcmd == NULL || *(shcmd + 1) == '\0')
#else
                        else if (shcmd == NULL)
#endif
                        {
                                errmsg = "no previous command";
                                return ERR;
                        } else {
                                REALLOC(buf, n, i + shcmdi, ERR);
                                for (s = shcmd + 1; s < shcmd + shcmdi;)
                                        buf[i++] = *s++;
                                s = ibufp++;
                        }
                        break;
                case '%':
                        if (*old_filename  == '\0') {
                                errmsg = "no current filename";
                                return ERR;
                        }
                        j = strlen(s = strip_escapes(old_filename));
                        REALLOC(buf, n, i + j, ERR);
                        while (j--)
                                buf[i++] = *s++;
                        s = ibufp++;
                        break;
                }
        REALLOC(shcmd, shcmdsz, i + 1, ERR);
        memcpy(shcmd, buf, i);
        shcmd[shcmdi = i] = '\0';
        return *s == '!' || *s == '%';
}


/* append_lines: insert text from stdin to after line n; stop when either a
   single period is read or EOF; return status */
int
append_lines(long n)
{
        int l;
        const char *lp = ibuf;
        const char *eot;
        undo_t *up = NULL;

        for (current_addr = n;;) {
                if (!isglobal) {
                        if ((l = get_tty_line()) < 0)
                                return ERR;
                        else if (l == 0 || ibuf[l - 1] != '\n') {
                                clearerr(stdin);
                                return  l ? EOF : 0;
                        }
                        lp = ibuf;
                } else if (*(lp = ibufp) == '\0')
                        return 0;
                else {
                        while (*ibufp++ != '\n')
                                ;
                        l = ibufp - lp;
                }
                if (l == 2 && lp[0] == '.' && lp[1] == '\n') {
                        return 0;
                }
                eot = lp + l;
                SPL1();
                do {
                        if ((lp = put_sbuf_line(lp)) == NULL) {
                                SPL0();
                                return ERR;
                        } else if (up)
                                up->t = get_addressed_line_node(current_addr);
                        else if ((up = push_undo_stack(UADD, current_addr,
                            current_addr)) == NULL) {
                                SPL0();
                                return ERR;
                        }
                } while (lp != eot);
                modified = 1;
                SPL0();
        }
        /* NOTREACHED */
}


/* join_lines: replace a range of lines with the joined text of those lines */
int
join_lines(long from, long to)
{
        static char *buf = NULL;
        static int n;

        char *s;
        int size = 0;
        line_t *bp, *ep;

        ep = get_addressed_line_node(INC_MOD(to, addr_last));
        bp = get_addressed_line_node(from);
        for (; bp != ep; bp = bp->q_forw) {
                if ((s = get_sbuf_line(bp)) == NULL)
                        return ERR;
                REALLOC(buf, n, size + bp->len, ERR);
                memcpy(buf + size, s, bp->len);
                size += bp->len;
        }
        REALLOC(buf, n, size + 2, ERR);
        memcpy(buf + size, "\n", 2);
        if (delete_lines(from, to) < 0)
                return ERR;
        current_addr = from - 1;
        SPL1();
        if (put_sbuf_line(buf) == NULL ||
            push_undo_stack(UADD, current_addr, current_addr) == NULL) {
                SPL0();
                return ERR;
        }
        modified = 1;
        SPL0();
        return 0;
}


/* move_lines: move a range of lines */
int
move_lines(long addr)
{
        line_t *b1, *a1, *b2, *a2;
        long n = INC_MOD(second_addr, addr_last);
        long p = first_addr - 1;
        int done = (addr == first_addr - 1 || addr == second_addr);

        SPL1();
        if (done) {
                a2 = get_addressed_line_node(n);
                b2 = get_addressed_line_node(p);
                current_addr = second_addr;
        } else if (push_undo_stack(UMOV, p, n) == NULL ||
            push_undo_stack(UMOV, addr, INC_MOD(addr, addr_last)) == NULL) {
                SPL0();
                return ERR;
        } else {
                a1 = get_addressed_line_node(n);
                if (addr < first_addr) {
                        b1 = get_addressed_line_node(p);
                        b2 = get_addressed_line_node(addr);
                                        /* this get_addressed_line_node last! */
                } else {
                        b2 = get_addressed_line_node(addr);
                        b1 = get_addressed_line_node(p);
                                        /* this get_addressed_line_node last! */
                }
                a2 = b2->q_forw;
                REQUE(b2, b1->q_forw);
                REQUE(a1->q_back, a2);
                REQUE(b1, a1);
                current_addr = addr + ((addr < first_addr) ?
                    second_addr - first_addr + 1 : 0);
        }
        if (isglobal)
                unset_active_nodes(b2->q_forw, a2);
        modified = 1;
        SPL0();
        return 0;
}


/* copy_lines: copy a range of lines; return status */
int
copy_lines(long addr)
{
        line_t *lp, *np = get_addressed_line_node(first_addr);
        undo_t *up = NULL;
        long n = second_addr - first_addr + 1;
        long m = 0;

        current_addr = addr;
        if (first_addr <= addr && addr < second_addr) {
                n =  addr - first_addr + 1;
                m = second_addr - addr;
        }
        for (; n > 0; n=m, m=0, np = get_addressed_line_node(current_addr + 1))
                for (; n-- > 0; np = np->q_forw) {
                        SPL1();
                        if ((lp = dup_line_node(np)) == NULL) {
                                SPL0();
                                return ERR;
                        }
                        add_line_node(lp);
                        if (up)
                                up->t = lp;
                        else if ((up = push_undo_stack(UADD, current_addr,
                            current_addr)) == NULL) {
                                SPL0();
                                return ERR;
                        }
                        modified = 1;
                        SPL0();
                }
        return 0;
}


/* delete_lines: delete a range of lines */
int
delete_lines(long from, long to)
{
        line_t *n, *p;

        SPL1();
        if (push_undo_stack(UDEL, from, to) == NULL) {
                SPL0();
                return ERR;
        }
        n = get_addressed_line_node(INC_MOD(to, addr_last));
        p = get_addressed_line_node(from - 1);
                                        /* this get_addressed_line_node last! */
        if (isglobal)
                unset_active_nodes(p->q_forw, n);
        REQUE(p, n);
        addr_last -= to - from + 1;
        current_addr = from - 1;
        modified = 1;
        SPL0();
        return 0;
}


/* display_lines: print a range of lines to stdout */
int
display_lines(long from, long to, int gflag)
{
        line_t *bp;
        line_t *ep;
        char *s;

        if (!from) {
                errmsg = "invalid address";
                return ERR;
        }
        ep = get_addressed_line_node(INC_MOD(to, addr_last));
        bp = get_addressed_line_node(from);
        for (; bp != ep; bp = bp->q_forw) {
                if ((s = get_sbuf_line(bp)) == NULL)
                        return ERR;
                if (put_tty_line(s, bp->len, current_addr = from++, gflag) < 0)
                        return ERR;
        }
        return 0;
}


#define MAXMARK 26                      /* max number of marks */

static line_t *mark[MAXMARK];           /* line markers */
static int markno;                      /* line marker count */

/* mark_line_node: set a line node mark */
int
mark_line_node(line_t *lp, int n)
{
        if (!islower((unsigned char)n)) {
                errmsg = "invalid mark character";
                return ERR;
        } else if (mark[n - 'a'] == NULL)
                markno++;
        mark[n - 'a'] = lp;
        return 0;
}


/* get_marked_node_addr: return address of a marked line */
long
get_marked_node_addr(int n)
{
        if (!islower((unsigned char)n)) {
                errmsg = "invalid mark character";
                return ERR;
        }
        return get_line_node_addr(mark[n - 'a']);
}


/* unmark_line_node: clear line node mark */
void
unmark_line_node(line_t *lp)
{
        int i;

        for (i = 0; markno && i < MAXMARK; i++)
                if (mark[i] == lp) {
                        mark[i] = NULL;
                        markno--;
                }
}


/* dup_line_node: return a pointer to a copy of a line node */
line_t *
dup_line_node(line_t *lp)
{
        line_t *np;

        if ((np = (line_t *) malloc(sizeof(line_t))) == NULL) {
                fprintf(stderr, "%s\n", strerror(errno));
                errmsg = "out of memory";
                return NULL;
        }
        np->seek = lp->seek;
        np->len = lp->len;
        return np;
}


/* has_trailing_escape:  return the parity of escapes preceding a character
   in a string */
int
has_trailing_escape(char *s, char *t)
{
    return (s == t || *(t - 1) != '\\') ? 0 : !has_trailing_escape(s, t - 1);
}


/* strip_escapes: return a copy of escaped string of at most length PATH_MAX */
char *
strip_escapes(char *s)
{
        static char *file = NULL;
        static int filesz = 0;

        int i = 0;

        REALLOC(file, filesz, PATH_MAX, NULL);
        while (i < filesz - 1   /* Worry about a possible trailing escape */
               && (file[i++] = (*s == '\\') ? *++s : *s))
                s++;
        return file;
}


void
signal_hup(int signo)
{
        if (mutex)
                sigflags |= (1 << (signo - 1));
        else
                handle_hup(signo);
}


void
signal_int(int signo)
{
        if (mutex)
                sigflags |= (1 << (signo - 1));
        else
                handle_int(signo);
}


void
handle_hup(int signo)
{
        char *hup = NULL;               /* hup filename */
        char *s;
        char ed_hup[] = "ed.hup";
        size_t n;

        if (!sigactive)
                quit(1);
        sigflags &= ~(1 << (signo - 1));
        if (addr_last && write_file(ed_hup, "w", 1, addr_last) < 0 &&
            (s = getenv("HOME")) != NULL &&
            (n = strlen(s)) + 8 <= PATH_MAX &&  /* "ed.hup" + '/' */
            (hup = (char *) malloc(n + 10)) != NULL) {
                strcpy(hup, s);
                if (hup[n - 1] != '/')
                        hup[n] = '/', hup[n+1] = '\0';
                strcat(hup, "ed.hup");
                write_file(hup, "w", 1, addr_last);
        }
        quit(2);
}


void
handle_int(int signo)
{
        if (!sigactive)
                quit(1);
        sigflags &= ~(1 << (signo - 1));
#ifdef _POSIX_SOURCE
        siglongjmp(env, -1);
#else
        longjmp(env, -1);
#endif
}


int cols = 72;                          /* wrap column */

void
handle_winch(int signo)
{
        int save_errno = errno;

        struct winsize ws;              /* window size structure */

        sigflags &= ~(1 << (signo - 1));
        if (ioctl(0, TIOCGWINSZ, (char *) &ws) >= 0) {
                if (ws.ws_row > 2) rows = ws.ws_row - 2;
                if (ws.ws_col > 8) cols = ws.ws_col - 8;
        }
        errno = save_errno;
}


/* is_legal_filename: return a legal filename */
int
is_legal_filename(char *s)
{
        if (red && (*s == '!' || !strcmp(s, "..") || strchr(s, '/'))) {
                errmsg = "shell access restricted";
                return 0;
        }
        return 1;
}