ascmagic.c

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/*  $OpenBSD: ascmagic.c,v 1.11 2009/10/27 23:59:37 deraadt Exp $ */
/*
 * Copyright (c) Ian F. Darwin 1986-1995.
 * Software written by Ian F. Darwin and others;
 * maintained 1995-present by Christos Zoulas and others.
 *
 * 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 immediately at the beginning of the file, without modification,
 *    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.
 */
/*
 * ASCII magic -- file types that we know based on keywords
 * that can appear anywhere in the file.
 *
 * Extensively modified by Eric Fischer <enf@pobox.com> in July, 2000,
 * to handle character codes other than ASCII on a unified basis.
 *
 * Joerg Wunsch <joerg@freebsd.org> wrote the original support for 8-bit
 * international characters, now subsumed into this file.
 */
#include <rz_userconf.h>
 
#if !USE_LIB_MAGIC
 
#include "file.h"
#include <stdio.h>
#include <string.h>
#include <memory.h>
#include <ctype.h>
#include <stdlib.h>
#include "names.h"
 
#define MAXLINELEN 300 /* longest sane line length */
#define ISSPC(x)   ((x) == ' ' || (x) == '\t' || (x) == '\r' || (x) == '\n' || (x) == 0x85 || (x) == '\f')
 
static int looks_ascii(const ut8 *, size_t, unichar *, size_t *);
static int looks_utf8_with_BOM(const ut8 *, size_t, unichar *,
    size_t *);
int file_looks_utf8(const ut8 *, size_t, unichar *, size_t *);
static int looks_ucs16(const ut8 *, size_t, unichar *, size_t *);
static int looks_latin1(const ut8 *, size_t, unichar *, size_t *);
static int looks_extended(const ut8 *, size_t, unichar *, size_t *);
static void from_ebcdic(const ut8 *, size_t, ut8 *);
static int ascmatch(const ut8 *, const unichar *, size_t);
static ut8 *encode_utf8(ut8 *, size_t, unichar *, size_t);
 
int file_ascmagic(RzMagic *ms, const ut8 *buf, size_t nbytes) {
    return 0;
    size_t i;
    ut8 *nbuf = NULL, *utf8_buf = NULL, *utf8_end;
    unichar *ubuf = NULL;
    size_t ulen, mlen;
    const struct names *p;
    int rv = -1;
    int mime = ms->flags & RZ_MAGIC_MIME;
 
    const char *code = NULL;
    const char *code_mime = NULL;
    const char *type = NULL;
    const char *subtype = NULL;
    const char *subtype_mime = NULL;
 
    int has_escapes = 0;
    int has_backspace = 0;
    int seen_cr = 0;
 
    int n_crlf = 0;
    int n_lf = 0;
    int n_cr = 0;
    int n_nel = 0;
 
    size_t last_line_end = (size_t)-1;
    int has_long_lines = 0;
 
    /*
     * Undo the NUL-termination kindly provided by process()
     * but leave at least one byte to look at
     */
    while (nbytes > 1 && buf[nbytes - 1] == '\0') {
        nbytes--;
    }
 
    if (!(nbuf = calloc(1, (nbytes + 1) * sizeof(nbuf[0])))) {
        goto done;
    }
    if (!(ubuf = calloc(1, (nbytes + 1) * sizeof(ubuf[0])))) {
        goto done;
    }
 
    /*
     * Then try to determine whether it's any character code we can
     * identify.  Each of these tests, if it succeeds, will leave
     * the text converted into one-unichar-per-character Unicode in
     * ubuf, and the number of characters converted in ulen.
     */
    if (looks_ascii(buf, nbytes, ubuf, &ulen)) {
        code = "ASCII";
        code_mime = "us-ascii";
        type = "text";
    } else if (looks_utf8_with_BOM(buf, nbytes, ubuf, &ulen) > 0) {
        code = "UTF-8 Unicode (with BOM)";
        code_mime = "utf-8";
        type = "text";
    } else if (file_looks_utf8(buf, nbytes, ubuf, &ulen) > 1) {
        code = "UTF-8 Unicode";
        code_mime = "utf-8";
        type = "text";
    } else if ((i = looks_ucs16(buf, nbytes, ubuf, &ulen)) != 0) {
        if (i == 1) {
            code = "Little-endian UTF-16 Unicode";
        } else {
            code = "Big-endian UTF-16 Unicode";
        }
 
        type = "character data";
        code_mime = "utf-16"; /* is this defined? */
    } else if (looks_latin1(buf, nbytes, ubuf, &ulen)) {
        if (!memcmp(buf, "\xff\xff\xff\xff", 4)) {
            // uninitialized memory is not iso-8859!!
            goto done;
        }
        code = "ISO-8859";
        type = "text";
        code_mime = "iso-8859-1";
    } else if (looks_extended(buf, nbytes, ubuf, &ulen)) {
        code = "Non-ISO extended-ASCII";
        type = "text";
        code_mime = "unknown";
    } else {
        from_ebcdic(buf, nbytes, nbuf);
 
        if (looks_ascii(nbuf, nbytes, ubuf, &ulen)) {
            code = "EBCDIC";
            type = "character data";
            code_mime = "ebcdic";
        } else if (looks_latin1(nbuf, nbytes, ubuf, &ulen)) {
            code = "International EBCDIC";
            type = "character data";
            code_mime = "ebcdic";
        } else {
            rv = 0;
            goto done; /* doesn't look like text at all */
        }
    }
 
    if (nbytes <= 1) {
        rv = 0;
        goto done;
    }
 
    /* Convert ubuf to UTF-8 and try text soft magic */
    /* If original was ASCII or UTF-8, could use nbuf instead of
       re-converting. */
    /* malloc size is a conservative overestimate; could be
       re-converting improved, or at least realloced after
       re-converting conversion. */
    mlen = ulen * 6;
    if (!(utf8_buf = malloc(mlen))) {
        file_oomem(ms, mlen);
        goto done;
    }
    if (!(utf8_end = encode_utf8(utf8_buf, mlen, ubuf, ulen))) {
        goto done;
    }
    if (file_softmagic(ms, utf8_buf, utf8_end - utf8_buf, TEXTTEST) != 0) {
        rv = 1;
        goto done;
    }
 
    /* look for tokens from names.h - this is expensive! */
    if ((ms->flags & RZ_MAGIC_NO_CHECK_TOKENS) != 0) {
        goto subtype_identified;
    }
 
    i = 0;
    while (i < ulen) {
        size_t end;
 
        /* skip past any leading space */
        while (i < ulen && ISSPC(ubuf[i])) {
            i++;
        }
        if (i >= ulen) {
            break;
        }
 
        /* find the next whitespace */
        for (end = i + 1; end < nbytes; end++) {
            if (ISSPC(ubuf[end])) {
                break;
            }
        }
 
        /* compare the word thus isolated against the token list */
        for (p = names; p < names + NNAMES; p++) {
            if (ascmatch((const ut8 *)p->name, ubuf + i,
                    end - i)) {
                subtype = types[p->type].human;
                subtype_mime = types[p->type].mime;
                goto subtype_identified;
            }
        }
 
        i = end;
    }
 
subtype_identified:
 
    /* Now try to discover other details about the file. */
    for (i = 0; i < ulen; i++) {
        if (ubuf[i] == '\n') {
            if (seen_cr) {
                n_crlf++;
            } else {
                n_lf++;
            }
            last_line_end = i;
        } else if (seen_cr) {
            n_cr++;
        }
 
        seen_cr = (ubuf[i] == '\r');
        if (seen_cr) {
            last_line_end = i;
        }
 
        if (ubuf[i] == 0x85) { /* X3.64/ECMA-43 "next line" character */
            n_nel++;
            last_line_end = i;
        }
        /* If this line is _longer_ than MAXLINELEN, remember it. */
        if (i > last_line_end + MAXLINELEN) {
            has_long_lines = 1;
        }
 
        if (ubuf[i] == '\033') {
            has_escapes = 1;
        }
        if (ubuf[i] == '\b') {
            has_backspace = 1;
        }
    }
 
    /* Beware, if the data has been truncated, the final CR could have
       been followed by a LF.  If we have HOWMANY bytes, it indicates
       that the data might have been truncated, probably even before
       this function was called. */
    if (seen_cr && nbytes < HOWMANY) {
        n_cr++;
    }
 
    if (mime) {
        if (mime & RZ_MAGIC_MIME_TYPE) {
            if (subtype_mime) {
                if (file_printf(ms, subtype_mime) == -1) {
                    goto done;
                }
            } else {
                if (file_printf(ms, "text/plain") == -1) {
                    goto done;
                }
            }
        }
 
        if ((mime == 0 || mime == RZ_MAGIC_MIME) && code_mime) {
            if ((mime & RZ_MAGIC_MIME_TYPE) &&
                file_printf(ms, " charset=") == -1) {
                goto done;
            }
            if (file_printf(ms, code_mime) == -1) {
                goto done;
            }
        }
 
        if (mime == RZ_MAGIC_MIME_ENCODING) {
            if (file_printf(ms, "binary") == -1) {
                rv = 1;
                goto done;
            }
        }
    } else {
        if (file_printf(ms, code) == -1) {
            goto done;
        }
 
        if (subtype) {
            if (file_printf(ms, " ") == -1) {
                goto done;
            }
            if (file_printf(ms, subtype) == -1) {
                goto done;
            }
        }
 
        if (file_printf(ms, " ") == -1) {
            goto done;
        }
        if (file_printf(ms, type) == -1) {
            goto done;
        }
 
        if (has_long_lines) {
            if (file_printf(ms, ", with very long lines") == -1) {
                goto done;
            }
        }
 
        /*
         * Only report line terminators if we find one other than LF,
         * or if we find none at all.
         */
        if ((n_crlf == 0 && n_cr == 0 && n_nel == 0 && n_lf == 0) ||
            (n_crlf != 0 || n_cr != 0 || n_nel != 0)) {
            if (file_printf(ms, ", with") == -1) {
                goto done;
            }
 
            if (n_crlf == 0 && n_cr == 0 && n_nel == 0 && n_lf == 0) {
                if (file_printf(ms, " no") == -1) {
                    goto done;
                }
            } else {
                if (n_crlf) {
                    if (file_printf(ms, " CRLF") == -1) {
                        goto done;
                    }
                    if (n_cr || n_lf || n_nel) {
                        if (file_printf(ms, ",") == -1) {
                            goto done;
                        }
                    }
                }
                if (n_cr) {
                    if (file_printf(ms, " CR") == -1) {
                        goto done;
                    }
                    if (n_lf || n_nel) {
                        if (file_printf(ms, ",") == -1) {
                            goto done;
                        }
                    }
                }
                if (n_lf) {
                    if (file_printf(ms, " LF") == -1) {
                        goto done;
                    }
                    if (n_nel) {
                        if (file_printf(ms, ",") == -1) {
                            goto done;
                        }
                    }
                }
                if (n_nel) {
                    if (file_printf(ms, " NEL") == -1) {
                        goto done;
                    }
                }
            }
 
            if (file_printf(ms, " line terminators") == -1) {
                goto done;
            }
        }
 
        if (has_escapes) {
            if (file_printf(ms, ", with escape sequences") == -1) {
                goto done;
            }
        }
        if (has_backspace) {
            if (file_printf(ms, ", with overstriking") == -1) {
                goto done;
            }
        }
    }
    rv = 1;
done:
    free(nbuf);
    free(ubuf);
    free(utf8_buf);
    return rv;
}
 
static int ascmatch(const ut8 *s, const unichar *us, size_t ulen) {
    size_t i;
    for (i = 0; i < ulen; i++) {
        if (s[i] != us[i]) {
            return 0;
        }
    }
    return s[i] ? 0 : 1;
}
 
/*
 * This table reflects a particular philosophy about what constitutes
 * "text," and there is room for disagreement about it.
 *
 * Version 3.31 of the file command considered a file to be ASCII if
 * each of its characters was approved by either the isascii() or
 * isalpha() function.  On most systems, this would mean that any
 * file consisting only of characters in the range 0x00 ... 0x7F
 * would be called ASCII text, but many systems might reasonably
 * consider some characters outside this range to be alphabetic,
 * so the file command would call such characters ASCII.  It might
 * have been more accurate to call this "considered textual on the
 * local system" than "ASCII."
 *
 * It considered a file to be "International language text" if each
 * of its characters was either an ASCII printing character (according
 * to the real ASCII standard, not the above test), a character in
 * the range 0x80 ... 0xFF, or one of the following control characters:
 * backspace, tab, line feed, vertical tab, form feed, carriage return,
 * escape.  No attempt was made to determine the language in which files
 * of this type were written.
 *
 *
 * The table below considers a file to be ASCII if all of its characters
 * are either ASCII printing characters (again, according to the X3.4
 * standard, not isascii()) or any of the following controls: bell,
 * backspace, tab, line feed, form feed, carriage return, esc, nextline.
 *
 * I include bell because some programs (particularly shell scripts)
 * use it literally, even though it is rare in normal text.  I exclude
 * vertical tab because it never seems to be used in real text.  I also
 * include, with hesitation, the X3.64/ECMA-43 control nextline (0x85),
 * because that's what the dd EBCDIC->ASCII table maps the EBCDIC newline
 * character to.  It might be more appropriate to include it in the 8859
 * set instead of the ASCII set, but it's got to be included in *something*
 * we recognize or EBCDIC files aren't going to be considered textual.
 * Some old Unix source files use SO/SI (^N/^O) to shift between Greek
 * and Latin characters, so these should possibly be allowed.  But they
 * make a real mess on VT100-style displays if they're not paired properly,
 * so we are probably better off not calling them text.
 *
 * A file is considered to be ISO-8859 text if its characters are all
 * either ASCII, according to the above definition, or printing characters
 * from the ISO-8859 8-bit extension, characters 0xA0 ... 0xFF.
 *
 * Finally, a file is considered to be international text from some other
 * character code if its characters are all either ISO-8859 (according to
 * the above definition) or characters in the range 0x80 ... 0x9F, which
 * ISO-8859 considers to be control characters but the IBM PC and Macintosh
 * consider to be printing characters.
 */
 
#define F 0 /* character never appears in text */
#define T 1 /* character appears in plain ASCII text */
#define I 2 /* character appears in ISO-8859 text */
#define X 3 /* character appears in non-ISO extended ASCII (Mac, IBM PC) */
 
static char text_chars[256] = {
    /*                  BEL BS HT LF    FF CR    */
    F, F, F, F, F, F, F, T, T, T, T, F, T, T, F, F, /* 0x0X */
    /*                              ESC          */
    F, F, F, F, F, F, F, F, F, F, F, T, F, F, F, F, /* 0x1X */
    T, T, T, T, T, T, T, T, T, T, T, T, T, T, T, T, /* 0x2X */
    T, T, T, T, T, T, T, T, T, T, T, T, T, T, T, T, /* 0x3X */
    T, T, T, T, T, T, T, T, T, T, T, T, T, T, T, T, /* 0x4X */
    T, T, T, T, T, T, T, T, T, T, T, T, T, T, T, T, /* 0x5X */
    T, T, T, T, T, T, T, T, T, T, T, T, T, T, T, T, /* 0x6X */
    T, T, T, T, T, T, T, T, T, T, T, T, T, T, T, F, /* 0x7X */
    /*            NEL                            */
    X, X, X, X, X, T, X, X, X, X, X, X, X, X, X, X, /* 0x8X */
    X, X, X, X, X, X, X, X, X, X, X, X, X, X, X, X, /* 0x9X */
    I, I, I, I, I, I, I, I, I, I, I, I, I, I, I, I, /* 0xaX */
    I, I, I, I, I, I, I, I, I, I, I, I, I, I, I, I, /* 0xbX */
    I, I, I, I, I, I, I, I, I, I, I, I, I, I, I, I, /* 0xcX */
    I, I, I, I, I, I, I, I, I, I, I, I, I, I, I, I, /* 0xdX */
    I, I, I, I, I, I, I, I, I, I, I, I, I, I, I, I, /* 0xeX */
    I, I, I, I, I, I, I, I, I, I, I, I, I, I, I, I /* 0xfX */
};
 
static int looks_ascii(const ut8 *buf, size_t nbytes, unichar *ubuf, size_t *ulen) {
    size_t i;
    *ulen = 0;
    for (i = 0; i < nbytes; i++) {
        int t = text_chars[buf[i]];
        if (t != T) {
            return 0;
        }
        ubuf[(*ulen)++] = buf[i];
    }
    return 1;
}
 
static int looks_latin1(const ut8 *buf, size_t nbytes, unichar *ubuf, size_t *ulen) {
    size_t i;
    *ulen = 0;
 
    for (i = 0; i < nbytes; i++) {
        int t = text_chars[buf[i]];
        if (t != T && t != I) {
            return 0;
        }
        ubuf[(*ulen)++] = buf[i];
    }
    return 1;
}
 
static int looks_extended(const ut8 *buf, size_t nbytes, unichar *ubuf, size_t *ulen) {
    size_t i;
    *ulen = 0;
    for (i = 0; i < nbytes; i++) {
        int t = text_chars[buf[i]];
        if (t != T && t != I && t != X) {
            return 0;
        }
        ubuf[(*ulen)++] = buf[i];
    }
    return 1;
}
 
/*
 * Encode Unicode string as UTF-8, returning pointer to character
 * after end of string, or NULL if an invalid character is found.
 */
static ut8 *
encode_utf8(ut8 *buf, size_t len, unichar *ubuf, size_t ulen) {
    size_t i;
    ut8 *end = buf + len;
 
    for (i = 0; i < ulen; i++) {
        if (ubuf[i] <= 0x7f) {
            if (end - buf < 1) {
                return NULL;
            }
            *buf++ = (ut8)ubuf[i];
        } else if (ubuf[i] <= 0x7ff) {
            if (end - buf < 2) {
                return NULL;
            }
            *buf++ = (ut8)((ubuf[i] >> 6) + 0xc0);
            *buf++ = (ut8)((ubuf[i] & 0x3f) + 0x80);
        } else if (ubuf[i] <= 0xffff) {
            if (end - buf < 3) {
                return NULL;
            }
            *buf++ = (ut8)((ubuf[i] >> 12) + 0xe0);
            *buf++ = (ut8)(((ubuf[i] >> 6) & 0x3f) + 0x80);
            *buf++ = (ut8)((ubuf[i] & 0x3f) + 0x80);
        } else if (ubuf[i] <= 0x1fffff) {
            if (end - buf < 4) {
                return NULL;
            }
            *buf++ = (ut8)((ubuf[i] >> 18) + 0xf0);
            *buf++ = (ut8)(((ubuf[i] >> 12) & 0x3f) + 0x80);
            *buf++ = (ut8)(((ubuf[i] >> 6) & 0x3f) + 0x80);
            *buf++ = (ut8)((ubuf[i] & 0x3f) + 0x80);
        } else if (ubuf[i] <= 0x3ffffff) {
            if (end - buf < 5) {
                return NULL;
            }
            *buf++ = (ut8)((ubuf[i] >> 24) + 0xf8);
            *buf++ = (ut8)(((ubuf[i] >> 18) & 0x3f) + 0x80);
            *buf++ = (ut8)(((ubuf[i] >> 12) & 0x3f) + 0x80);
            *buf++ = (ut8)(((ubuf[i] >> 6) & 0x3f) + 0x80);
            *buf++ = (ut8)((ubuf[i] & 0x3f) + 0x80);
        } else if (ubuf[i] <= 0x7fffffff) {
            if (end - buf < 6) {
                return NULL;
            }
            *buf++ = (ut8)((ubuf[i] >> 30) + 0xfc);
            *buf++ = (ut8)(((ubuf[i] >> 24) & 0x3f) + 0x80);
            *buf++ = (ut8)(((ubuf[i] >> 18) & 0x3f) + 0x80);
            *buf++ = (ut8)(((ubuf[i] >> 12) & 0x3f) + 0x80);
            *buf++ = (ut8)(((ubuf[i] >> 6) & 0x3f) + 0x80);
            *buf++ = (ut8)((ubuf[i] & 0x3f) + 0x80);
        } else { /* Invalid character */
            return NULL;
        }
    }
 
    return buf;
}
 
/*
 * Decide whether some text looks like UTF-8. Returns:
 *
 *     -1: invalid UTF-8
 *      0: uses odd control characters, so doesn't look like text
 *      1: 7-bit text
 *      2: definitely UTF-8 text (valid high-bit set bytes)
 *
 * If ubuf is non-NULL on entry, text is decoded into ubuf, *ulen;
 * ubuf must be big enough!
 */
int file_looks_utf8(const ut8 *buf, size_t nbytes, unichar *ubuf, size_t *ulen) {
    size_t i;
    int n;
    unichar c;
    int gotone = 0, ctrl = 0;
 
    if (ubuf) {
        *ulen = 0;
    }
 
    for (i = 0; i < nbytes; i++) {
        if ((buf[i] & 0x80) == 0) { /* 0xxxxxxx is plain ASCII */
            /*
             * Even if the whole file is valid UTF-8 sequences,
             * still reject it if it uses weird control characters.
             */
 
            if (text_chars[buf[i]] != T) {
                ctrl = 1;
            }
 
            if (ubuf) {
                ubuf[(*ulen)++] = buf[i];
            }
        } else if ((buf[i] & 0x40) == 0) { /* 10xxxxxx never 1st byte */
            return -1;
        } else { /* 11xxxxxx begins UTF-8 */
            int following;
 
            if ((buf[i] & 0x20) == 0) { /* 110xxxxx */
                c = buf[i] & 0x1f;
                following = 1;
            } else if ((buf[i] & 0x10) == 0) { /* 1110xxxx */
                c = buf[i] & 0x0f;
                following = 2;
            } else if ((buf[i] & 0x08) == 0) { /* 11110xxx */
                c = buf[i] & 0x07;
                following = 3;
            } else if ((buf[i] & 0x04) == 0) { /* 111110xx */
                c = buf[i] & 0x03;
                following = 4;
            } else if ((buf[i] & 0x02) == 0) { /* 1111110x */
                c = buf[i] & 0x01;
                following = 5;
            } else {
                return -1;
            }
 
            for (n = 0; n < following; n++) {
                i++;
                if (i >= nbytes) {
                    goto done;
                }
 
                if ((buf[i] & 0x80) == 0 || (buf[i] & 0x40)) {
                    return -1;
                }
 
                c = (c << 6) + (buf[i] & 0x3f);
            }
 
            if (ubuf) {
                ubuf[(*ulen)++] = c;
            }
            gotone = 1;
        }
    }
done:
    return ctrl ? 0 : (gotone ? 2 : 1);
}
 
/*
 * Decide whether some text looks like UTF-8 with BOM. If there is no
 * BOM, return -1; otherwise return the result of looks_utf8 on the
 * rest of the text.
 */
static int looks_utf8_with_BOM(const ut8 *buf, size_t nbytes, unichar *ubuf, size_t *ulen) {
    if (nbytes > 3 && buf[0] == 0xef && buf[1] == 0xbb && buf[2] == 0xbf) {
        return file_looks_utf8(buf + 3, nbytes - 3, ubuf, ulen);
    }
    return -1;
}
 
static int looks_ucs16(const ut8 *buf, size_t nbytes, unichar *ubuf, size_t *ulen) {
    int bigend;
    size_t i;
 
    if (nbytes < 2) {
        return 0;
    }
 
    if (buf[0] == 0xff && buf[1] == 0xfe) {
        bigend = 0;
    } else if (buf[0] == 0xfe && buf[1] == 0xff) {
        bigend = 1;
    } else {
        return 0;
    }
 
    *ulen = 0;
 
    for (i = 2; i + 1 < nbytes; i += 2) {
        /* XXX fix to properly handle chars > 65536 */
 
        if (bigend) {
            ubuf[(*ulen)++] = buf[i + 1] + 256 * buf[i];
        } else {
            ubuf[(*ulen)++] = buf[i] + 256 * buf[i + 1];
        }
 
        if (ubuf[*ulen - 1] == 0xfffe) {
            return 0;
        }
        if (ubuf[*ulen - 1] < 128 && text_chars[(size_t)ubuf[*ulen - 1]] != T) {
            return 0;
        }
    }
    return 1 + bigend;
}
 
#undef F
#undef T
#undef I
#undef X
 
/*
 * This table maps each EBCDIC character to an (8-bit extended) ASCII
 * character, as specified in the rationale for the dd(1) command in
 * draft 11.2 (September, 1991) of the POSIX P1003.2 standard.
 *
 * Unfortunately it does not seem to correspond exactly to any of the
 * five variants of EBCDIC documented in IBM's _Enterprise Systems
 * Architecture/390: Principles of Operation_, SA22-7201-06, Seventh
 * Edition, July, 1999, pp. I-1 - I-4.
 *
 * Fortunately, though, all versions of EBCDIC, including this one, agree
 * on most of the printing characters that also appear in (7-bit) ASCII.
 * Of these, only '|', '!', '~', '^', '[', and ']' are in question at all.
 *
 * Fortunately too, there is general agreement that codes 0x00 through
 * 0x3F represent control characters, 0x41 a nonbreaking space, and the
 * remainder printing characters.
 *
 * This is sufficient to allow us to identify EBCDIC text and to distinguish
 * between old-style and internationalized examples of text.
 */
 
static ut8 ebcdic_to_ascii[] = {
    0, 1, 2, 3, 156, 9, 134, 127, 151, 141, 142, 11, 12, 13, 14, 15,
    16, 17, 18, 19, 157, 133, 8, 135, 24, 25, 146, 143, 28, 29, 30, 31,
    128, 129, 130, 131, 132, 10, 23, 27, 136, 137, 138, 139, 140, 5, 6, 7,
    144, 145, 22, 147, 148, 149, 150, 4, 152, 153, 154, 155, 20, 21, 158, 26,
    ' ', 160, 161, 162, 163, 164, 165, 166, 167, 168, 213, '.', '<', '(', '+', '|',
    '&', 169, 170, 171, 172, 173, 174, 175, 176, 177, '!', '$', '*', ')', ';', '~',
    '-', '/', 178, 179, 180, 181, 182, 183, 184, 185, 203, ',', '%', '_', '>', '?',
    186, 187, 188, 189, 190, 191, 192, 193, 194, '`', ':', '#', '@', '\'', '=', '"',
    195, 'a', 'b', 'c', 'd', 'e', 'f', 'g', 'h', 'i', 196, 197, 198, 199, 200, 201,
    202, 'j', 'k', 'l', 'm', 'n', 'o', 'p', 'q', 'r', '^', 204, 205, 206, 207, 208,
    209, 229, 's', 't', 'u', 'v', 'w', 'x', 'y', 'z', 210, 211, 212, '[', 214, 215,
    216, 217, 218, 219, 220, 221, 222, 223, 224, 225, 226, 227, 228, ']', 230, 231,
    '{', 'A', 'B', 'C', 'D', 'E', 'F', 'G', 'H', 'I', 232, 233, 234, 235, 236, 237,
    '}', 'J', 'K', 'L', 'M', 'N', 'O', 'P', 'Q', 'R', 238, 239, 240, 241, 242, 243,
    '\\', 159, 'S', 'T', 'U', 'V', 'W', 'X', 'Y', 'Z', 244, 245, 246, 247, 248, 249,
    '0', '1', '2', '3', '4', '5', '6', '7', '8', '9', 250, 251, 252, 253, 254, 255
};
 
#ifdef notdef
/*
 * The following EBCDIC-to-ASCII table may relate more closely to reality,
 * or at least to modern reality.  It comes from
 *
 *   http://ftp.s390.ibm.com/products/oe/bpxqp9.html
 *
 * and maps the characters of EBCDIC code page 1047 (the code used for
 * Unix-derived software on IBM's 390 systems) to the corresponding
 * characters from ISO 8859-1.
 *
 * If this table is used instead of the above one, some of the special
 * cases for the NEL character can be taken out of the code.
 */
 
static ut8 ebcdic_1047_to_8859[] = {
    0x00, 0x01, 0x02, 0x03, 0x9C, 0x09, 0x86, 0x7F, 0x97, 0x8D, 0x8E, 0x0B, 0x0C, 0x0D, 0x0E, 0x0F,
    0x10, 0x11, 0x12, 0x13, 0x9D, 0x0A, 0x08, 0x87, 0x18, 0x19, 0x92, 0x8F, 0x1C, 0x1D, 0x1E, 0x1F,
    0x80, 0x81, 0x82, 0x83, 0x84, 0x85, 0x17, 0x1B, 0x88, 0x89, 0x8A, 0x8B, 0x8C, 0x05, 0x06, 0x07,
    0x90, 0x91, 0x16, 0x93, 0x94, 0x95, 0x96, 0x04, 0x98, 0x99, 0x9A, 0x9B, 0x14, 0x15, 0x9E, 0x1A,
    0x20, 0xA0, 0xE2, 0xE4, 0xE0, 0xE1, 0xE3, 0xE5, 0xE7, 0xF1, 0xA2, 0x2E, 0x3C, 0x28, 0x2B, 0x7C,
    0x26, 0xE9, 0xEA, 0xEB, 0xE8, 0xED, 0xEE, 0xEF, 0xEC, 0xDF, 0x21, 0x24, 0x2A, 0x29, 0x3B, 0x5E,
    0x2D, 0x2F, 0xC2, 0xC4, 0xC0, 0xC1, 0xC3, 0xC5, 0xC7, 0xD1, 0xA6, 0x2C, 0x25, 0x5F, 0x3E, 0x3F,
    0xF8, 0xC9, 0xCA, 0xCB, 0xC8, 0xCD, 0xCE, 0xCF, 0xCC, 0x60, 0x3A, 0x23, 0x40, 0x27, 0x3D, 0x22,
    0xD8, 0x61, 0x62, 0x63, 0x64, 0x65, 0x66, 0x67, 0x68, 0x69, 0xAB, 0xBB, 0xF0, 0xFD, 0xFE, 0xB1,
    0xB0, 0x6A, 0x6B, 0x6C, 0x6D, 0x6E, 0x6F, 0x70, 0x71, 0x72, 0xAA, 0xBA, 0xE6, 0xB8, 0xC6, 0xA4,
    0xB5, 0x7E, 0x73, 0x74, 0x75, 0x76, 0x77, 0x78, 0x79, 0x7A, 0xA1, 0xBF, 0xD0, 0x5B, 0xDE, 0xAE,
    0xAC, 0xA3, 0xA5, 0xB7, 0xA9, 0xA7, 0xB6, 0xBC, 0xBD, 0xBE, 0xDD, 0xA8, 0xAF, 0x5D, 0xB4, 0xD7,
    0x7B, 0x41, 0x42, 0x43, 0x44, 0x45, 0x46, 0x47, 0x48, 0x49, 0xAD, 0xF4, 0xF6, 0xF2, 0xF3, 0xF5,
    0x7D, 0x4A, 0x4B, 0x4C, 0x4D, 0x4E, 0x4F, 0x50, 0x51, 0x52, 0xB9, 0xFB, 0xFC, 0xF9, 0xFA, 0xFF,
    0x5C, 0xF7, 0x53, 0x54, 0x55, 0x56, 0x57, 0x58, 0x59, 0x5A, 0xB2, 0xD4, 0xD6, 0xD2, 0xD3, 0xD5,
    0x30, 0x31, 0x32, 0x33, 0x34, 0x35, 0x36, 0x37, 0x38, 0x39, 0xB3, 0xDB, 0xDC, 0xD9, 0xDA, 0x9F
};
#endif
 
/*
 * Copy buf[0 ... nbytes-1] into out[], translating EBCDIC to ASCII.
 */
static void from_ebcdic(const ut8 *buf, size_t nbytes, ut8 *out) {
    size_t i;
    for (i = 0; i < nbytes; i++) {
        out[i] = ebcdic_to_ascii[buf[i]];
    }
}
#endif