source: MondoRescue/branches/3.2/mindi-busybox/editors/sed.c@ 3232

/* vi: set sw=4 ts=4: */
/*
 * sed.c - very minimalist version of sed
 *
 * Copyright (C) 1999,2000,2001 by Lineo, inc. and Mark Whitley
 * Copyright (C) 1999,2000,2001 by Mark Whitley <markw@codepoet.org>
 * Copyright (C) 2002  Matt Kraai
 * Copyright (C) 2003 by Glenn McGrath
 * Copyright (C) 2003,2004 by Rob Landley <rob@landley.net>
 *
 * MAINTAINER: Rob Landley <rob@landley.net>
 *
 * Licensed under GPLv2, see file LICENSE in this source tree.
 */

/* Code overview.
 *
 * Files are laid out to avoid unnecessary function declarations.  So for
 * example, every function add_cmd calls occurs before add_cmd in this file.
 *
 * add_cmd() is called on each line of sed command text (from a file or from
 * the command line).  It calls get_address() and parse_cmd_args().  The
 * resulting sed_cmd_t structures are appended to a linked list
 * (G.sed_cmd_head/G.sed_cmd_tail).
 *
 * add_input_file() adds a FILE* to the list of input files.  We need to
 * know all input sources ahead of time to find the last line for the $ match.
 *
 * process_files() does actual sedding, reading data lines from each input FILE*
 * (which could be stdin) and applying the sed command list (sed_cmd_head) to
 * each of the resulting lines.
 *
 * sed_main() is where external code calls into this, with a command line.
 */

/* Supported features and commands in this version of sed:
 *
 * - comments ('#')
 * - address matching: num|/matchstr/[,num|/matchstr/|$]command
 * - commands: (p)rint, (d)elete, (s)ubstitue (with g & I flags)
 * - edit commands: (a)ppend, (i)nsert, (c)hange
 * - file commands: (r)ead
 * - backreferences in substitution expressions (\0, \1, \2...\9)
 * - grouped commands: {cmd1;cmd2}
 * - transliteration (y/source-chars/dest-chars/)
 * - pattern space hold space storing / swapping (g, h, x)
 * - labels / branching (: label, b, t, T)
 *
 * (Note: Specifying an address (range) to match is *optional*; commands
 * default to the whole pattern space if no specific address match was
 * requested.)
 *
 * Todo:
 * - Create a wrapper around regex to make libc's regex conform with sed
 *
 * Reference
 * http://www.opengroup.org/onlinepubs/007904975/utilities/sed.html
 * http://pubs.opengroup.org/onlinepubs/9699919799/utilities/sed.html
 */

//usage:#define sed_trivial_usage
//usage:       "[-inr] [-f FILE]... [-e CMD]... [FILE]...\n"
//usage:       "or: sed [-inr] CMD [FILE]..."
//usage:#define sed_full_usage "\n\n"
//usage:       "    -e CMD  Add CMD to sed commands to be executed"
//usage:     "\n    -f FILE Add FILE contents to sed commands to be executed"
//usage:     "\n    -i[SFX] Edit files in-place (otherwise sends to stdout)"
//usage:     "\n        Optionally back files up, appending SFX"
//usage:     "\n    -n  Suppress automatic printing of pattern space"
//usage:     "\n    -r  Use extended regex syntax"
//usage:     "\n"
//usage:     "\nIf no -e or -f, the first non-option argument is the sed command string."
//usage:     "\nRemaining arguments are input files (stdin if none)."
//usage:
//usage:#define sed_example_usage
//usage:       "$ echo \"foo\" | sed -e 's/f[a-zA-Z]o/bar/g'\n"
//usage:       "bar\n"

#include "libbb.h"
#include "xregex.h"

#if 0
# define dbg(...) bb_error_msg(__VA_ARGS__)
#else
# define dbg(...) ((void)0)
#endif


enum {
    OPT_in_place = 1 << 0,
};

/* Each sed command turns into one of these structures. */
typedef struct sed_cmd_s {
    /* Ordered by alignment requirements: currently 36 bytes on x86 */
    struct sed_cmd_s *next; /* Next command (linked list, NULL terminated) */

    /* address storage */
    regex_t *beg_match;     /* sed -e '/match/cmd' */
    regex_t *end_match;     /* sed -e '/match/,/end_match/cmd' */
    regex_t *sub_match;     /* For 's/sub_match/string/' */
    int beg_line;           /* 'sed 1p'   0 == apply commands to all lines */
    int beg_line_orig;      /* copy of the above, needed for -i */
    int end_line;           /* 'sed 1,3p' 0 == one line only. -1 = last line ($) */

    FILE *sw_file;          /* File (sw) command writes to, -1 for none. */
    char *string;           /* Data string for (saicytb) commands. */

    unsigned which_match;   /* (s) Which match to replace (0 for all) */

    /* Bitfields (gcc won't group them if we don't) */
    unsigned invert:1;      /* the '!' after the address */
    unsigned in_match:1;    /* Next line also included in match? */
    unsigned sub_p:1;       /* (s) print option */

    char sw_last_char;      /* Last line written by (sw) had no '\n' */

    /* GENERAL FIELDS */
    char cmd;               /* The command char: abcdDgGhHilnNpPqrstwxy:={} */
} sed_cmd_t;

static const char semicolon_whitespace[] ALIGN1 = "; \n\r\t\v";

struct globals {
    /* options */
    int be_quiet, regex_type;
    FILE *nonstdout;
    char *outname, *hold_space;

    /* List of input files */
    int input_file_count, current_input_file;
    FILE **input_file_list;

    regmatch_t regmatch[10];
    regex_t *previous_regex_ptr;

    /* linked list of sed commands */
    sed_cmd_t *sed_cmd_head, **sed_cmd_tail;

    /* Linked list of append lines */
    llist_t *append_head;

    char *add_cmd_line;

    struct pipeline {
        char *buf;  /* Space to hold string */
        int idx;    /* Space used */
        int len;    /* Space allocated */
    } pipeline;
} FIX_ALIASING;
#define G (*(struct globals*)&bb_common_bufsiz1)
struct BUG_G_too_big {
    char BUG_G_too_big[sizeof(G) <= COMMON_BUFSIZE ? 1 : -1];
};
#define INIT_G() do { \
    G.sed_cmd_tail = &G.sed_cmd_head; \
} while (0)


#if ENABLE_FEATURE_CLEAN_UP
static void sed_free_and_close_stuff(void)
{
    sed_cmd_t *sed_cmd = G.sed_cmd_head;

    llist_free(G.append_head, free);

    while (sed_cmd) {
        sed_cmd_t *sed_cmd_next = sed_cmd->next;

        if (sed_cmd->sw_file)
            xprint_and_close_file(sed_cmd->sw_file);

        if (sed_cmd->beg_match) {
            regfree(sed_cmd->beg_match);
            free(sed_cmd->beg_match);
        }
        if (sed_cmd->end_match) {
            regfree(sed_cmd->end_match);
            free(sed_cmd->end_match);
        }
        if (sed_cmd->sub_match) {
            regfree(sed_cmd->sub_match);
            free(sed_cmd->sub_match);
        }
        free(sed_cmd->string);
        free(sed_cmd);
        sed_cmd = sed_cmd_next;
    }

    free(G.hold_space);

    while (G.current_input_file < G.input_file_count)
        fclose(G.input_file_list[G.current_input_file++]);
}
#else
void sed_free_and_close_stuff(void);
#endif

/* If something bad happens during -i operation, delete temp file */

static void cleanup_outname(void)
{
    if (G.outname) unlink(G.outname);
}

/* strcpy, replacing "\from" with 'to'. If to is NUL, replacing "\any" with 'any' */

static void parse_escapes(char *dest, const char *string, int len, char from, char to)
{
    int i = 0;

    while (i < len) {
        if (string[i] == '\\') {
            if (!to || string[i+1] == from) {
                *dest++ = to ? to : string[i+1];
                i += 2;
                continue;
            }
            *dest++ = string[i++];
        }
        /* TODO: is it safe wrt a string with trailing '\\' ? */
        *dest++ = string[i++];
    }
    *dest = '\0';
}

static char *copy_parsing_escapes(const char *string, int len)
{
    const char *s;
    char *dest = xmalloc(len + 1);

    /* sed recognizes \n */
    /* GNU sed also recognizes \t and \r */
    for (s = "\nn\tt\rr"; *s; s += 2) {
        parse_escapes(dest, string, len, s[1], s[0]);
        string = dest;
        len = strlen(dest);
    }
    return dest;
}


/*
 * index_of_next_unescaped_regexp_delim - walks left to right through a string
 * beginning at a specified index and returns the index of the next regular
 * expression delimiter (typically a forward slash ('/')) not preceded by
 * a backslash ('\').  A negative delimiter disables square bracket checking.
 */
static int index_of_next_unescaped_regexp_delim(int delimiter, const char *str)
{
    int bracket = -1;
    int escaped = 0;
    int idx = 0;
    char ch;

    if (delimiter < 0) {
        bracket--;
        delimiter = -delimiter;
    }

    for (; (ch = str[idx]) != '\0'; idx++) {
        if (bracket >= 0) {
            if (ch == ']'
             && !(bracket == idx - 1 || (bracket == idx - 2 && str[idx - 1] == '^'))
            ) {
                bracket = -1;
            }
        } else if (escaped)
            escaped = 0;
        else if (ch == '\\')
            escaped = 1;
        else if (bracket == -1 && ch == '[')
            bracket = idx;
        else if (ch == delimiter)
            return idx;
    }

    /* if we make it to here, we've hit the end of the string */
    bb_error_msg_and_die("unmatched '%c'", delimiter);
}

/*
 *  Returns the index of the third delimiter
 */
static int parse_regex_delim(const char *cmdstr, char **match, char **replace)
{
    const char *cmdstr_ptr = cmdstr;
    unsigned char delimiter;
    int idx = 0;

    /* verify that the 's' or 'y' is followed by something.  That something
     * (typically a 'slash') is now our regexp delimiter... */
    if (*cmdstr == '\0')
        bb_error_msg_and_die("bad format in substitution expression");
    delimiter = *cmdstr_ptr++;

    /* save the match string */
    idx = index_of_next_unescaped_regexp_delim(delimiter, cmdstr_ptr);
    *match = copy_parsing_escapes(cmdstr_ptr, idx);

    /* save the replacement string */
    cmdstr_ptr += idx + 1;
    idx = index_of_next_unescaped_regexp_delim(- (int)delimiter, cmdstr_ptr);
    *replace = copy_parsing_escapes(cmdstr_ptr, idx);

    return ((cmdstr_ptr - cmdstr) + idx);
}

/*
 * returns the index in the string just past where the address ends.
 */
static int get_address(const char *my_str, int *linenum, regex_t ** regex)
{
    const char *pos = my_str;

    if (isdigit(*my_str)) {
        *linenum = strtol(my_str, (char**)&pos, 10);
        /* endstr shouldnt ever equal NULL */
    } else if (*my_str == '$') {
        *linenum = -1;
        pos++;
    } else if (*my_str == '/' || *my_str == '\\') {
        int next;
        char delimiter;
        char *temp;

        delimiter = '/';
        if (*my_str == '\\')
            delimiter = *++pos;
        next = index_of_next_unescaped_regexp_delim(delimiter, ++pos);
        temp = copy_parsing_escapes(pos, next);
        *regex = xzalloc(sizeof(regex_t));
        xregcomp(*regex, temp, G.regex_type|REG_NEWLINE);
        free(temp);
        /* Move position to next character after last delimiter */
        pos += (next+1);
    }
    return pos - my_str;
}

/* Grab a filename.  Whitespace at start is skipped, then goes to EOL. */
static int parse_file_cmd(/*sed_cmd_t *sed_cmd,*/ const char *filecmdstr, char **retval)
{
    int start = 0, idx, hack = 0;

    /* Skip whitespace, then grab filename to end of line */
    while (isspace(filecmdstr[start]))
        start++;
    idx = start;
    while (filecmdstr[idx] && filecmdstr[idx] != '\n')
        idx++;

    /* If lines glued together, put backslash back. */
    if (filecmdstr[idx] == '\n')
        hack = 1;
    if (idx == start)
        bb_error_msg_and_die("empty filename");
    *retval = xstrndup(filecmdstr+start, idx-start+hack+1);
    if (hack)
        (*retval)[idx] = '\\';

    return idx;
}

static int parse_subst_cmd(sed_cmd_t *sed_cmd, const char *substr)
{
    int cflags = G.regex_type;
    char *match;
    int idx;

    /*
     * A substitution command should look something like this:
     *    s/match/replace/ #gIpw
     *    ||     |        |||
     *    mandatory       optional
     */
    idx = parse_regex_delim(substr, &match, &sed_cmd->string);

    /* determine the number of back references in the match string */
    /* Note: we compute this here rather than in the do_subst_command()
     * function to save processor time, at the expense of a little more memory
     * (4 bits) per sed_cmd */

    /* process the flags */

    sed_cmd->which_match = 1;
    while (substr[++idx]) {
        /* Parse match number */
        if (isdigit(substr[idx])) {
            if (match[0] != '^') {
                /* Match 0 treated as all, multiple matches we take the last one. */
                const char *pos = substr + idx;
/* FIXME: error check? */
                sed_cmd->which_match = (unsigned)strtol(substr+idx, (char**) &pos, 10);
                idx = pos - substr;
            }
            continue;
        }
        /* Skip spaces */
        if (isspace(substr[idx]))
            continue;

        switch (substr[idx]) {
        /* Replace all occurrences */
        case 'g':
            if (match[0] != '^')
                sed_cmd->which_match = 0;
            break;
        /* Print pattern space */
        case 'p':
            sed_cmd->sub_p = 1;
            break;
        /* Write to file */
        case 'w':
        {
            char *temp;
            idx += parse_file_cmd(/*sed_cmd,*/ substr+idx, &temp);
            break;
        }
        /* Ignore case (gnu exension) */
        case 'I':
            cflags |= REG_ICASE;
            break;
        /* Comment */
        case '#':
            // while (substr[++idx]) continue;
            idx += strlen(substr + idx); // same
            /* Fall through */
        /* End of command */
        case ';':
        case '}':
            goto out;
        default:
            bb_error_msg_and_die("bad option in substitution expression");
        }
    }
 out:
    /* compile the match string into a regex */
    if (*match != '\0') {
        /* If match is empty, we use last regex used at runtime */
        sed_cmd->sub_match = xzalloc(sizeof(regex_t));
        dbg("xregcomp('%s',%x)", match, cflags);
        xregcomp(sed_cmd->sub_match, match, cflags);
        dbg("regcomp ok");
    }
    free(match);

    return idx;
}

/*
 *  Process the commands arguments
 */
static const char *parse_cmd_args(sed_cmd_t *sed_cmd, const char *cmdstr)
{
    static const char cmd_letters[] = "saicrw:btTydDgGhHlnNpPqx={}";
    enum {
        IDX_s = 0,
        IDX_a,
        IDX_i,
        IDX_c,
        IDX_r,
        IDX_w,
        IDX_colon,
        IDX_b,
        IDX_t,
        IDX_T,
        IDX_y,
        IDX_d,
        IDX_D,
        IDX_g,
        IDX_G,
        IDX_h,
        IDX_H,
        IDX_l,
        IDX_n,
        IDX_N,
        IDX_p,
        IDX_P,
        IDX_q,
        IDX_x,
        IDX_equal,
        IDX_lbrace,
        IDX_rbrace,
        IDX_nul
    };
    struct chk { char chk[sizeof(cmd_letters)-1 == IDX_nul ? 1 : -1]; };

    unsigned idx = strchrnul(cmd_letters, sed_cmd->cmd) - cmd_letters;

    /* handle (s)ubstitution command */
    if (idx == IDX_s) {
        cmdstr += parse_subst_cmd(sed_cmd, cmdstr);
    }
    /* handle edit cmds: (a)ppend, (i)nsert, and (c)hange */
    else if (idx <= IDX_c) { /* a,i,c */
        if (idx < IDX_c) { /* a,i */
            if (sed_cmd->end_line || sed_cmd->end_match)
                bb_error_msg_and_die("command '%c' uses only one address", sed_cmd->cmd);
        }
        for (;;) {
            if (*cmdstr == '\n' || *cmdstr == '\\') {
                cmdstr++;
                break;
            }
            if (!isspace(*cmdstr))
                break;
            cmdstr++;
        }
        sed_cmd->string = xstrdup(cmdstr);
        /* "\anychar" -> "anychar" */
        parse_escapes(sed_cmd->string, sed_cmd->string, strlen(cmdstr), '\0', '\0');
        cmdstr += strlen(cmdstr);
    }
    /* handle file cmds: (r)ead */
    else if (idx <= IDX_w) { /* r,w */
        if (idx < IDX_w) { /* r */
            if (sed_cmd->end_line || sed_cmd->end_match)
                bb_error_msg_and_die("command '%c' uses only one address", sed_cmd->cmd);
        }
        cmdstr += parse_file_cmd(/*sed_cmd,*/ cmdstr, &sed_cmd->string);
        if (sed_cmd->cmd == 'w') {
            sed_cmd->sw_file = xfopen_for_write(sed_cmd->string);
            sed_cmd->sw_last_char = '\n';
        }
    }
    /* handle branch commands */
    else if (idx <= IDX_T) { /* :,b,t,T */
        int length;

        cmdstr = skip_whitespace(cmdstr);
        length = strcspn(cmdstr, semicolon_whitespace);
        if (length) {
            sed_cmd->string = xstrndup(cmdstr, length);
            cmdstr += length;
        }
    }
    /* translation command */
    else if (idx == IDX_y) {
        char *match, *replace;
        int i = cmdstr[0];

        cmdstr += parse_regex_delim(cmdstr, &match, &replace)+1;
        /* \n already parsed, but \delimiter needs unescaping. */
        parse_escapes(match, match, strlen(match), i, i);
        parse_escapes(replace, replace, strlen(replace), i, i);

        sed_cmd->string = xzalloc((strlen(match) + 1) * 2);
        for (i = 0; match[i] && replace[i]; i++) {
            sed_cmd->string[i*2] = match[i];
            sed_cmd->string[i*2+1] = replace[i];
        }
        free(match);
        free(replace);
    }
    /* if it wasnt a single-letter command that takes no arguments
     * then it must be an invalid command.
     */
    else if (idx >= IDX_nul) { /* not d,D,g,G,h,H,l,n,N,p,P,q,x,=,{,} */
        bb_error_msg_and_die("unsupported command %c", sed_cmd->cmd);
    }

    /* give back whatever's left over */
    return cmdstr;
}


/* Parse address+command sets, skipping comment lines. */

static void add_cmd(const char *cmdstr)
{
    sed_cmd_t *sed_cmd;
    unsigned len, n;

    /* Append this line to any unfinished line from last time. */
    if (G.add_cmd_line) {
        char *tp = xasprintf("%s\n%s", G.add_cmd_line, cmdstr);
        free(G.add_cmd_line);
        cmdstr = G.add_cmd_line = tp;
    }

    /* If this line ends with unescaped backslash, request next line. */
    n = len = strlen(cmdstr);
    while (n && cmdstr[n-1] == '\\')
        n--;
    if ((len - n) & 1) { /* if odd number of trailing backslashes */
        if (!G.add_cmd_line)
            G.add_cmd_line = xstrdup(cmdstr);
        G.add_cmd_line[len-1] = '\0';
        return;
    }

    /* Loop parsing all commands in this line. */
    while (*cmdstr) {
        /* Skip leading whitespace and semicolons */
        cmdstr += strspn(cmdstr, semicolon_whitespace);

        /* If no more commands, exit. */
        if (!*cmdstr) break;

        /* if this is a comment, jump past it and keep going */
        if (*cmdstr == '#') {
            /* "#n" is the same as using -n on the command line */
            if (cmdstr[1] == 'n')
                G.be_quiet++;
            cmdstr = strpbrk(cmdstr, "\n\r");
            if (!cmdstr) break;
            continue;
        }

        /* parse the command
         * format is: [addr][,addr][!]cmd
         *            |----||-----||-|
         *            part1 part2  part3
         */

        sed_cmd = xzalloc(sizeof(sed_cmd_t));

        /* first part (if present) is an address: either a '$', a number or a /regex/ */
        cmdstr += get_address(cmdstr, &sed_cmd->beg_line, &sed_cmd->beg_match);
        sed_cmd->beg_line_orig = sed_cmd->beg_line;

        /* second part (if present) will begin with a comma */
        if (*cmdstr == ',') {
            int idx;

            cmdstr++;
            idx = get_address(cmdstr, &sed_cmd->end_line, &sed_cmd->end_match);
            if (!idx)
                bb_error_msg_and_die("no address after comma");
            cmdstr += idx;
        }

        /* skip whitespace before the command */
        cmdstr = skip_whitespace(cmdstr);

        /* Check for inversion flag */
        if (*cmdstr == '!') {
            sed_cmd->invert = 1;
            cmdstr++;

            /* skip whitespace before the command */
            cmdstr = skip_whitespace(cmdstr);
        }

        /* last part (mandatory) will be a command */
        if (!*cmdstr)
            bb_error_msg_and_die("missing command");
        sed_cmd->cmd = *cmdstr++;
        cmdstr = parse_cmd_args(sed_cmd, cmdstr);

        /* Add the command to the command array */
        *G.sed_cmd_tail = sed_cmd;
        G.sed_cmd_tail = &sed_cmd->next;
    }

    /* If we glued multiple lines together, free the memory. */
    free(G.add_cmd_line);
    G.add_cmd_line = NULL;
}

/* Append to a string, reallocating memory as necessary. */

#define PIPE_GROW 64

static void pipe_putc(char c)
{
    if (G.pipeline.idx == G.pipeline.len) {
        G.pipeline.buf = xrealloc(G.pipeline.buf,
                G.pipeline.len + PIPE_GROW);
        G.pipeline.len += PIPE_GROW;
    }
    G.pipeline.buf[G.pipeline.idx++] = c;
}

static void do_subst_w_backrefs(char *line, char *replace)
{
    int i, j;

    /* go through the replacement string */
    for (i = 0; replace[i]; i++) {
        /* if we find a backreference (\1, \2, etc.) print the backref'ed text */
        if (replace[i] == '\\') {
            unsigned backref = replace[++i] - '0';
            if (backref <= 9) {
                /* print out the text held in G.regmatch[backref] */
                if (G.regmatch[backref].rm_so != -1) {
                    j = G.regmatch[backref].rm_so;
                    while (j < G.regmatch[backref].rm_eo)
                        pipe_putc(line[j++]);
                }
                continue;
            }
            /* I _think_ it is impossible to get '\' to be
             * the last char in replace string. Thus we dont check
             * for replace[i] == NUL. (counterexample anyone?) */
            /* if we find a backslash escaped character, print the character */
            pipe_putc(replace[i]);
            continue;
        }
        /* if we find an unescaped '&' print out the whole matched text. */
        if (replace[i] == '&') {
            j = G.regmatch[0].rm_so;
            while (j < G.regmatch[0].rm_eo)
                pipe_putc(line[j++]);
            continue;
        }
        /* Otherwise just output the character. */
        pipe_putc(replace[i]);
    }
}

static int do_subst_command(sed_cmd_t *sed_cmd, char **line_p)
{
    char *line = *line_p;
    unsigned match_count = 0;
    bool altered = 0;
    bool prev_match_empty = 1;
    bool tried_at_eol = 0;
    regex_t *current_regex;

    current_regex = sed_cmd->sub_match;
    /* Handle empty regex. */
    if (!current_regex) {
        current_regex = G.previous_regex_ptr;
        if (!current_regex)
            bb_error_msg_and_die("no previous regexp");
    }
    G.previous_regex_ptr = current_regex;

    /* Find the first match */
    dbg("matching '%s'", line);
    if (REG_NOMATCH == regexec(current_regex, line, 10, G.regmatch, 0)) {
        dbg("no match");
        return 0;
    }
    dbg("match");

    /* Initialize temporary output buffer. */
    G.pipeline.buf = xmalloc(PIPE_GROW);
    G.pipeline.len = PIPE_GROW;
    G.pipeline.idx = 0;

    /* Now loop through, substituting for matches */
    do {
        int start = G.regmatch[0].rm_so;
        int end = G.regmatch[0].rm_eo;
        int i;

        match_count++;

        /* If we aren't interested in this match, output old line to
         * end of match and continue */
        if (sed_cmd->which_match
         && (sed_cmd->which_match != match_count)
        ) {
            for (i = 0; i < end; i++)
                pipe_putc(*line++);
            /* Null match? Print one more char */
            if (start == end && *line)
                pipe_putc(*line++);
            goto next;
        }

        /* Print everything before the match */
        for (i = 0; i < start; i++)
            pipe_putc(line[i]);

        /* Then print the substitution string,
         * unless we just matched empty string after non-empty one.
         * Example: string "cccd", pattern "c*", repl "R":
         * result is "RdR", not "RRdR": first match "ccc",
         * second is "" before "d", third is "" after "d".
         * Second match is NOT replaced!
         */
        if (prev_match_empty || start != 0 || start != end) {
            //dbg("%d %d %d", prev_match_empty, start, end);
            dbg("inserting replacement at %d in '%s'", start, line);
            do_subst_w_backrefs(line, sed_cmd->string);
            /* Flag that something has changed */
            altered = 1;
        } else {
            dbg("NOT inserting replacement at %d in '%s'", start, line);
        }

        /* If matched string is empty (f.e. "c*" pattern),
         * copy verbatim one char after it before attempting more matches
         */
        prev_match_empty = (start == end);
        if (prev_match_empty) {
            if (!line[end]) {
                tried_at_eol = 1;
            } else {
                pipe_putc(line[end]);
                end++;
            }
        }

        /* Advance past the match */
        dbg("line += %d", end);
        line += end;

        /* if we're not doing this globally, get out now */
        if (sed_cmd->which_match != 0)
            break;
 next:
        /* Exit if we are at EOL and already tried matching at it */
        if (*line == '\0') {
            if (tried_at_eol)
                break;
            tried_at_eol = 1;
        }

//maybe (end ? REG_NOTBOL : 0) instead of unconditional REG_NOTBOL?
    } while (regexec(current_regex, line, 10, G.regmatch, REG_NOTBOL) != REG_NOMATCH);

    /* Copy rest of string into output pipeline */
    while (1) {
        char c = *line++;
        pipe_putc(c);
        if (c == '\0')
            break;
    }

    free(*line_p);
    *line_p = G.pipeline.buf;
    return altered;
}

/* Set command pointer to point to this label.  (Does not handle null label.) */
static sed_cmd_t *branch_to(char *label)
{
    sed_cmd_t *sed_cmd;

    for (sed_cmd = G.sed_cmd_head; sed_cmd; sed_cmd = sed_cmd->next) {
        if (sed_cmd->cmd == ':' && sed_cmd->string && !strcmp(sed_cmd->string, label)) {
            return sed_cmd;
        }
    }
    bb_error_msg_and_die("can't find label for jump to '%s'", label);
}

static void append(char *s)
{
    llist_add_to_end(&G.append_head, xstrdup(s));
}

static void flush_append(void)
{
    char *data;

    /* Output appended lines. */
    while ((data = (char *)llist_pop(&G.append_head))) {
        fprintf(G.nonstdout, "%s\n", data);
        free(data);
    }
}

static void add_input_file(FILE *file)
{
    G.input_file_list = xrealloc_vector(G.input_file_list, 2, G.input_file_count);
    G.input_file_list[G.input_file_count++] = file;
}

/* Get next line of input from G.input_file_list, flushing append buffer and
 * noting if we ran out of files without a newline on the last line we read.
 */
enum {
    NO_EOL_CHAR = 1,
    LAST_IS_NUL = 2,
};
static char *get_next_line(char *gets_char)
{
    char *temp = NULL;
    int len;
    char gc;

    flush_append();

    /* will be returned if last line in the file
     * doesn't end with either '\n' or '\0' */
    gc = NO_EOL_CHAR;
    while (G.current_input_file < G.input_file_count) {
        FILE *fp = G.input_file_list[G.current_input_file];
        /* Read line up to a newline or NUL byte, inclusive,
         * return malloc'ed char[]. length of the chunk read
         * is stored in len. NULL if EOF/error */
        temp = bb_get_chunk_from_file(fp, &len);
        if (temp) {
            /* len > 0 here, it's ok to do temp[len-1] */
            char c = temp[len-1];
            if (c == '\n' || c == '\0') {
                temp[len-1] = '\0';
                gc = c;
                if (c == '\0') {
                    int ch = fgetc(fp);
                    if (ch != EOF)
                        ungetc(ch, fp);
                    else
                        gc = LAST_IS_NUL;
                }
            }
            /* else we put NO_EOL_CHAR into *gets_char */
            break;

        /* NB: I had the idea of peeking next file(s) and returning
         * NO_EOL_CHAR only if it is the *last* non-empty
         * input file. But there is a case where this won't work:
         * file1: "a woo\nb woo"
         * file2: "c no\nd no"
         * sed -ne 's/woo/bang/p' input1 input2 => "a bang\nb bang"
         * (note: *no* newline after "b bang"!) */
        }
        /* Close this file and advance to next one */
        fclose(fp);
        G.current_input_file++;
    }
    *gets_char = gc;
    return temp;
}

/* Output line of text. */
/* Note:
 * The tricks with NO_EOL_CHAR and last_puts_char are there to emulate gnu sed.
 * Without them, we had this:
 * echo -n thingy >z1
 * echo -n again >z2
 * >znull
 * sed "s/i/z/" z1 z2 znull | hexdump -vC
 * output:
 * gnu sed 4.1.5:
 * 00000000  74 68 7a 6e 67 79 0a 61  67 61 7a 6e              |thzngy.agazn|
 * bbox:
 * 00000000  74 68 7a 6e 67 79 61 67  61 7a 6e                 |thzngyagazn|
 */
static void puts_maybe_newline(char *s, FILE *file, char *last_puts_char, char last_gets_char)
{
    char lpc = *last_puts_char;

    /* Need to insert a '\n' between two files because first file's
     * last line wasn't terminated? */
    if (lpc != '\n' && lpc != '\0') {
        fputc('\n', file);
        lpc = '\n';
    }
    fputs(s, file);

    /* 'x' - just something which is not '\n', '\0' or NO_EOL_CHAR */
    if (s[0])
        lpc = 'x';

    /* had trailing '\0' and it was last char of file? */
    if (last_gets_char == LAST_IS_NUL) {
        fputc('\0', file);
        lpc = 'x'; /* */
    } else
    /* had trailing '\n' or '\0'? */
    if (last_gets_char != NO_EOL_CHAR) {
        fputc(last_gets_char, file);
        lpc = last_gets_char;
    }

    if (ferror(file)) {
        xfunc_error_retval = 4;  /* It's what gnu sed exits with... */
        bb_error_msg_and_die(bb_msg_write_error);
    }
    *last_puts_char = lpc;
}

#define sed_puts(s, n) (puts_maybe_newline(s, G.nonstdout, &last_puts_char, n))

static int beg_match(sed_cmd_t *sed_cmd, const char *pattern_space)
{
    int retval = sed_cmd->beg_match && !regexec(sed_cmd->beg_match, pattern_space, 0, NULL, 0);
    if (retval)
        G.previous_regex_ptr = sed_cmd->beg_match;
    return retval;
}

/* Process all the lines in all the files */

static void process_files(void)
{
    char *pattern_space, *next_line;
    int linenum = 0;
    char last_puts_char = '\n';
    char last_gets_char, next_gets_char;
    sed_cmd_t *sed_cmd;
    int substituted;

    /* Prime the pump */
    next_line = get_next_line(&next_gets_char);

    /* Go through every line in each file */
 again:
    substituted = 0;

    /* Advance to next line.  Stop if out of lines. */
    pattern_space = next_line;
    if (!pattern_space)
        return;
    last_gets_char = next_gets_char;

    /* Read one line in advance so we can act on the last line,
     * the '$' address */
    next_line = get_next_line(&next_gets_char);
    linenum++;

    /* For every line, go through all the commands */
 restart:
    for (sed_cmd = G.sed_cmd_head; sed_cmd; sed_cmd = sed_cmd->next) {
        int old_matched, matched;

        old_matched = sed_cmd->in_match;

        /* Determine if this command matches this line: */

        dbg("match1:%d", sed_cmd->in_match);
        dbg("match2:%d", (!sed_cmd->beg_line && !sed_cmd->end_line
                && !sed_cmd->beg_match && !sed_cmd->end_match));
        dbg("match3:%d", (sed_cmd->beg_line > 0
            && (sed_cmd->end_line || sed_cmd->end_match
                ? (sed_cmd->beg_line <= linenum)
                : (sed_cmd->beg_line == linenum)
                )
            ));
        dbg("match4:%d", (beg_match(sed_cmd, pattern_space)));
        dbg("match5:%d", (sed_cmd->beg_line == -1 && next_line == NULL));

        /* Are we continuing a previous multi-line match? */
        sed_cmd->in_match = sed_cmd->in_match
            /* Or is no range necessary? */
            || (!sed_cmd->beg_line && !sed_cmd->end_line
                && !sed_cmd->beg_match && !sed_cmd->end_match)
            /* Or did we match the start of a numerical range? */
            || (sed_cmd->beg_line > 0
                && (sed_cmd->end_line || sed_cmd->end_match
                  /* note: even if end is numeric and is < linenum too,
                   * GNU sed matches! We match too, therefore we don't
                   * check here that linenum <= end.
                   * Example:
                   * printf '1\n2\n3\n4\n' | sed -n '1{N;N;d};1p;2,3p;3p;4p'
                   * first three input lines are deleted;
                   * 4th line is matched and printed
                   * by "2,3" (!) and by "4" ranges
                   */
                ? (sed_cmd->beg_line <= linenum)    /* N,end */
                : (sed_cmd->beg_line == linenum)    /* N */
                )
                )
            /* Or does this line match our begin address regex? */
            || (beg_match(sed_cmd, pattern_space))
            /* Or did we match last line of input? */
            || (sed_cmd->beg_line == -1 && next_line == NULL);

        /* Snapshot the value */
        matched = sed_cmd->in_match;

        dbg("cmd:'%c' matched:%d beg_line:%d end_line:%d linenum:%d",
            sed_cmd->cmd, matched, sed_cmd->beg_line, sed_cmd->end_line, linenum);

        /* Is this line the end of the current match? */

        if (matched) {
            /* once matched, "n,xxx" range is dead, disabling it */
            if (sed_cmd->beg_line > 0) {
                sed_cmd->beg_line = -2;
            }
            sed_cmd->in_match = !(
                /* has the ending line come, or is this a single address command? */
                (sed_cmd->end_line
                    ? sed_cmd->end_line == -1
                        ? !next_line
                        : (sed_cmd->end_line <= linenum)
                    : !sed_cmd->end_match
                )
                /* or does this line matches our last address regex */
                || (sed_cmd->end_match && old_matched
                     && (regexec(sed_cmd->end_match,
                        pattern_space, 0, NULL, 0) == 0)
                )
            );
        }

        /* Skip blocks of commands we didn't match */
        if (sed_cmd->cmd == '{') {
            if (sed_cmd->invert ? matched : !matched) {
                unsigned nest_cnt = 0;
                while (1) {
                    if (sed_cmd->cmd == '{')
                        nest_cnt++;
                    if (sed_cmd->cmd == '}') {
                        nest_cnt--;
                        if (nest_cnt == 0)
                            break;
                    }
                    sed_cmd = sed_cmd->next;
                    if (!sed_cmd)
                        bb_error_msg_and_die("unterminated {");
                }
            }
            continue;
        }

        /* Okay, so did this line match? */
        if (sed_cmd->invert ? matched : !matched)
            continue; /* no */

        /* Update last used regex in case a blank substitute BRE is found */
        if (sed_cmd->beg_match) {
            G.previous_regex_ptr = sed_cmd->beg_match;
        }

        /* actual sedding */
        dbg("pattern_space:'%s' next_line:'%s' cmd:%c",
                pattern_space, next_line, sed_cmd->cmd);
        switch (sed_cmd->cmd) {

        /* Print line number */
        case '=':
            fprintf(G.nonstdout, "%d\n", linenum);
            break;

        /* Write the current pattern space up to the first newline */
        case 'P':
        {
            char *tmp = strchr(pattern_space, '\n');
            if (tmp) {
                *tmp = '\0';
                /* TODO: explain why '\n' below */
                sed_puts(pattern_space, '\n');
                *tmp = '\n';
                break;
            }
            /* Fall Through */
        }

        /* Write the current pattern space to output */
        case 'p':
            /* NB: we print this _before_ the last line
             * (of current file) is printed. Even if
             * that line is nonterminated, we print
             * '\n' here (gnu sed does the same) */
            sed_puts(pattern_space, '\n');
            break;
        /* Delete up through first newline */
        case 'D':
        {
            char *tmp = strchr(pattern_space, '\n');
            if (tmp) {
                overlapping_strcpy(pattern_space, tmp + 1);
                goto restart;
            }
        }
        /* discard this line. */
        case 'd':
            goto discard_line;

        /* Substitute with regex */
        case 's':
            if (!do_subst_command(sed_cmd, &pattern_space))
                break;
            dbg("do_subst_command succeeded:'%s'", pattern_space);
            substituted |= 1;

            /* handle p option */
            if (sed_cmd->sub_p)
                sed_puts(pattern_space, last_gets_char);
            /* handle w option */
            if (sed_cmd->sw_file)
                puts_maybe_newline(
                    pattern_space, sed_cmd->sw_file,
                    &sed_cmd->sw_last_char, last_gets_char);
            break;

        /* Append line to linked list to be printed later */
        case 'a':
            append(sed_cmd->string);
            break;

        /* Insert text before this line */
        case 'i':
            sed_puts(sed_cmd->string, '\n');
            break;

        /* Cut and paste text (replace) */
        case 'c':
            /* Only triggers on last line of a matching range. */
            if (!sed_cmd->in_match)
                sed_puts(sed_cmd->string, '\n');
            goto discard_line;

        /* Read file, append contents to output */
        case 'r':
        {
            FILE *rfile;
            rfile = fopen_for_read(sed_cmd->string);
            if (rfile) {
                char *line;

                while ((line = xmalloc_fgetline(rfile))
                        != NULL)
                    append(line);
                xprint_and_close_file(rfile);
            }

            break;
        }

        /* Write pattern space to file. */
        case 'w':
            puts_maybe_newline(
                pattern_space, sed_cmd->sw_file,
                &sed_cmd->sw_last_char, last_gets_char);
            break;

        /* Read next line from input */
        case 'n':
            if (!G.be_quiet)
                sed_puts(pattern_space, last_gets_char);
            if (next_line) {
                free(pattern_space);
                pattern_space = next_line;
                last_gets_char = next_gets_char;
                next_line = get_next_line(&next_gets_char);
                substituted = 0;
                linenum++;
                break;
            }
            /* fall through */

        /* Quit.  End of script, end of input. */
        case 'q':
            /* Exit the outer while loop */
            free(next_line);
            next_line = NULL;
            goto discard_commands;

        /* Append the next line to the current line */
        case 'N':
        {
            int len;
            /* If no next line, jump to end of script and exit. */
            /* http://www.gnu.org/software/sed/manual/sed.html:
             * "Most versions of sed exit without printing anything
             * when the N command is issued on the last line of
             * a file. GNU sed prints pattern space before exiting
             * unless of course the -n command switch has been
             * specified. This choice is by design."
             */
            if (next_line == NULL) {
                //goto discard_line;
                goto discard_commands; /* GNU behavior */
            }
            /* Append next_line, read new next_line. */
            len = strlen(pattern_space);
            pattern_space = xrealloc(pattern_space, len + strlen(next_line) + 2);
            pattern_space[len] = '\n';
            strcpy(pattern_space + len+1, next_line);
            last_gets_char = next_gets_char;
            next_line = get_next_line(&next_gets_char);
            linenum++;
            break;
        }

        /* Test/branch if substitution occurred */
        case 't':
            if (!substituted) break;
            substituted = 0;
            /* Fall through */
        /* Test/branch if substitution didn't occur */
        case 'T':
            if (substituted) break;
            /* Fall through */
        /* Branch to label */
        case 'b':
            if (!sed_cmd->string) goto discard_commands;
            else sed_cmd = branch_to(sed_cmd->string);
            break;
        /* Transliterate characters */
        case 'y':
        {
            int i, j;
            for (i = 0; pattern_space[i]; i++) {
                for (j = 0; sed_cmd->string[j]; j += 2) {
                    if (pattern_space[i] == sed_cmd->string[j]) {
                        pattern_space[i] = sed_cmd->string[j + 1];
                        break;
                    }
                }
            }

            break;
        }
        case 'g':   /* Replace pattern space with hold space */
            free(pattern_space);
            pattern_space = xstrdup(G.hold_space ? G.hold_space : "");
            break;
        case 'G':   /* Append newline and hold space to pattern space */
        {
            int pattern_space_size = 2;
            int hold_space_size = 0;

            if (pattern_space)
                pattern_space_size += strlen(pattern_space);
            if (G.hold_space)
                hold_space_size = strlen(G.hold_space);
            pattern_space = xrealloc(pattern_space,
                    pattern_space_size + hold_space_size);
            if (pattern_space_size == 2)
                pattern_space[0] = 0;
            strcat(pattern_space, "\n");
            if (G.hold_space)
                strcat(pattern_space, G.hold_space);
            last_gets_char = '\n';

            break;
        }
        case 'h':   /* Replace hold space with pattern space */
            free(G.hold_space);
            G.hold_space = xstrdup(pattern_space);
            break;
        case 'H':   /* Append newline and pattern space to hold space */
        {
            int hold_space_size = 2;
            int pattern_space_size = 0;

            if (G.hold_space)
                hold_space_size += strlen(G.hold_space);
            if (pattern_space)
                pattern_space_size = strlen(pattern_space);
            G.hold_space = xrealloc(G.hold_space,
                    hold_space_size + pattern_space_size);

            if (hold_space_size == 2)
                *G.hold_space = 0;
            strcat(G.hold_space, "\n");
            if (pattern_space)
                strcat(G.hold_space, pattern_space);

            break;
        }
        case 'x': /* Exchange hold and pattern space */
        {
            char *tmp = pattern_space;
            pattern_space = G.hold_space ? G.hold_space : xzalloc(1);
            last_gets_char = '\n';
            G.hold_space = tmp;
            break;
        }
        } /* switch */
    } /* for each cmd */

    /*
     * Exit point from sedding...
     */
 discard_commands:
    /* we will print the line unless we were told to be quiet ('-n')
       or if the line was suppressed (ala 'd'elete) */
    if (!G.be_quiet)
        sed_puts(pattern_space, last_gets_char);

    /* Delete and such jump here. */
 discard_line:
    flush_append();
    free(pattern_space);

    goto again;
}

/* It is possible to have a command line argument with embedded
 * newlines.  This counts as multiple command lines.
 * However, newline can be escaped: 's/e/z\<newline>z/'
 * We check for this.
 */

static void add_cmd_block(char *cmdstr)
{
    char *sv, *eol;

    cmdstr = sv = xstrdup(cmdstr);
    do {
        eol = strchr(cmdstr, '\n');
 next:
        if (eol) {
            /* Count preceding slashes */
            int slashes = 0;
            char *sl = eol;

            while (sl != cmdstr && *--sl == '\\')
                slashes++;
            /* Odd number of preceding slashes - newline is escaped */
            if (slashes & 1) {
                overlapping_strcpy(eol - 1, eol);
                eol = strchr(eol, '\n');
                goto next;
            }
            *eol = '\0';
        }
        add_cmd(cmdstr);
        cmdstr = eol + 1;
    } while (eol);
    free(sv);
}

int sed_main(int argc, char **argv) MAIN_EXTERNALLY_VISIBLE;
int sed_main(int argc UNUSED_PARAM, char **argv)
{
    unsigned opt;
    llist_t *opt_e, *opt_f;
    char *opt_i;

#if ENABLE_LONG_OPTS
    static const char sed_longopts[] ALIGN1 =
        /* name             has_arg             short */
        "in-place\0"        Optional_argument   "i"
        "regexp-extended\0" No_argument         "r"
        "quiet\0"           No_argument         "n"
        "silent\0"          No_argument         "n"
        "expression\0"      Required_argument   "e"
        "file\0"            Required_argument   "f";
#endif

    int status = EXIT_SUCCESS;

    INIT_G();

    /* destroy command strings on exit */
    if (ENABLE_FEATURE_CLEAN_UP) atexit(sed_free_and_close_stuff);

    /* Lie to autoconf when it starts asking stupid questions. */
    if (argv[1] && strcmp(argv[1], "--version") == 0) {
        puts("This is not GNU sed version 4.0");
        return 0;
    }

    /* do normal option parsing */
    opt_e = opt_f = NULL;
    opt_i = NULL;
    opt_complementary = "e::f::" /* can occur multiple times */
                        "nn"; /* count -n */

    IF_LONG_OPTS(applet_long_options = sed_longopts);

    /* -i must be first, to match OPT_in_place definition */
    opt = getopt32(argv, "i::rne:f:", &opt_i, &opt_e, &opt_f,
                &G.be_quiet); /* counter for -n */
    //argc -= optind;
    argv += optind;
    if (opt & OPT_in_place) { // -i
        atexit(cleanup_outname);
    }
    if (opt & 0x2) G.regex_type |= REG_EXTENDED; // -r
    //if (opt & 0x4) G.be_quiet++; // -n
    while (opt_e) { // -e
        add_cmd_block(llist_pop(&opt_e));
    }
    while (opt_f) { // -f
        char *line;
        FILE *cmdfile;
        cmdfile = xfopen_for_read(llist_pop(&opt_f));
        while ((line = xmalloc_fgetline(cmdfile)) != NULL) {
            add_cmd(line);
            free(line);
        }
        fclose(cmdfile);
    }
    /* if we didn't get a pattern from -e or -f, use argv[0] */
    if (!(opt & 0x18)) {
        if (!*argv)
            bb_show_usage();
        add_cmd_block(*argv++);
    }
    /* Flush any unfinished commands. */
    add_cmd("");

    /* By default, we write to stdout */
    G.nonstdout = stdout;

    /* argv[0..(argc-1)] should be names of file to process. If no
     * files were specified or '-' was specified, take input from stdin.
     * Otherwise, we process all the files specified. */
    if (argv[0] == NULL) {
        if (opt & OPT_in_place)
            bb_error_msg_and_die(bb_msg_requires_arg, "-i");
        add_input_file(stdin);
    } else {
        int i;

        for (i = 0; argv[i]; i++) {
            struct stat statbuf;
            int nonstdoutfd;
            FILE *file;
            sed_cmd_t *sed_cmd;

            if (LONE_DASH(argv[i]) && !(opt & OPT_in_place)) {
                add_input_file(stdin);
                process_files();
                continue;
            }
            file = fopen_or_warn(argv[i], "r");
            if (!file) {
                status = EXIT_FAILURE;
                continue;
            }
            add_input_file(file);
            if (!(opt & OPT_in_place)) {
                continue;
            }

            /* -i: process each FILE separately: */

            G.outname = xasprintf("%sXXXXXX", argv[i]);
            nonstdoutfd = xmkstemp(G.outname);
            G.nonstdout = xfdopen_for_write(nonstdoutfd);

            /* Set permissions/owner of output file */
            fstat(fileno(file), &statbuf);
            /* chmod'ing AFTER chown would preserve suid/sgid bits,
             * but GNU sed 4.2.1 does not preserve them either */
            fchmod(nonstdoutfd, statbuf.st_mode);
            fchown(nonstdoutfd, statbuf.st_uid, statbuf.st_gid);

            process_files();
            fclose(G.nonstdout);
            G.nonstdout = stdout;

            if (opt_i) {
                char *backupname = xasprintf("%s%s", argv[i], opt_i);
                xrename(argv[i], backupname);
                free(backupname);
            }
            /* else unlink(argv[i]); - rename below does this */
            xrename(G.outname, argv[i]); //TODO: rollback backup on error?
            free(G.outname);
            G.outname = NULL;

            /* Re-enable disabled range matches */
            for (sed_cmd = G.sed_cmd_head; sed_cmd; sed_cmd = sed_cmd->next) {
                sed_cmd->beg_line = sed_cmd->beg_line_orig;
            }
        }
        /* Here, to handle "sed 'cmds' nonexistent_file" case we did:
         * if (G.current_input_file >= G.input_file_count)
         *  return status;
         * but it's not needed since process_files() works correctly
         * in this case too. */
    }
    process_files();

    return status;
}