file/src/apprentice.c

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/*
 * 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.
 */
/*
 * apprentice - make one pass through /etc/magic, learning its secrets.
 */

#include "file.h"
#include "magic.h"
#include <stdlib.h>
#ifdef HAVE_UNISTD_H
#include <unistd.h>
#endif
#include <string.h>
#include <ctype.h>
#include <fcntl.h>
#include <sys/stat.h>
#include <sys/param.h>
#ifdef QUICK
#include <sys/mman.h>
#endif

#ifndef lint
FILE_RCSID("@(#)$Id: apprentice.c,v 1.84 2005/03/25 18:03:18 christos Exp $")
#endif  /* lint */

#define EATAB {while (isascii((unsigned char) *l) && \
                      isspace((unsigned char) *l))  ++l;}
#define LOWCASE(l) (isupper((unsigned char) (l)) ? \
                        tolower((unsigned char) (l)) : (l))
/*
 * Work around a bug in headers on Digital Unix.
 * At least confirmed for: OSF1 V4.0 878
 */
#if defined(__osf__) && defined(__DECC)
#ifdef MAP_FAILED
#undef MAP_FAILED
#endif
#endif

#ifndef MAP_FAILED
#define MAP_FAILED (void *) -1
#endif

#ifndef MAP_FILE
#define MAP_FILE 0
#endif

#ifndef MAXPATHLEN
#define MAXPATHLEN      1024
#endif

#define IS_PLAINSTRING(t) ((t) == FILE_STRING || (t) == FILE_PSTRING || \
    (t) == FILE_BESTRING16 || (t) == FILE_LESTRING16)
    
#define IS_STRING(t) (IS_PLAINSTRING(t) || (t) == FILE_REGEX || \
    (t) == FILE_SEARCH)

/*@unchecked@*/
private size_t maxmagic = 0;
/*@unchecked@*/
private size_t magicsize = sizeof(struct magic);

private int getvalue(struct magic_set *ms, struct magic *m, char **p)
        /*@globals fileSystem @*/
        /*@modifies ms, m, *p, fileSystem @*/;
private int hextoint(int)
        /*@*/;
/*@null@*/
private char *getstr(struct magic_set *ms, /*@returned@*/ char *s, char *p, int plen, int *slen)
        /*@modifies ms, *p, *slen @*/;
private int parse(struct magic_set *ms, struct magic **magicp, uint32_t *nmagicp, char *l, int action)
        /*@globals maxmagic, fileSystem @*/
        /*@modifies ms, *magicp, *nmagicp, maxmagic, fileSystem @*/;
private void eatsize(char **p)
        /*@modifies *p @*/;
private int apprentice_1(struct magic_set *ms, const char *fn, int action, struct mlist *mlist)
        /*@globals fileSystem, internalState @*/
        /*@modifies ms, mlist, fileSystem, internalState @*/;
private int apprentice_file(struct magic_set *ms, struct magic **magicp, uint32_t *nmagicp,
    const char *fn, int action)
        /*@globals maxmagic, fileSystem @*/
        /*@modifies ms, *magicp, *nmagicp, maxmagic, fileSystem @*/;
private void byteswap(struct magic *magic, uint32_t nmagic)
        /*@modifies magic @*/;
private void bs1(struct magic *m)
        /*@modifies m @*/;
private uint16_t swap2(uint16_t sv)
        /*@*/;
private uint32_t swap4(uint32_t sv)
        /*@*/;
private char *mkdbname(const char *fn, /*@returned@*/ char *buf, size_t, int)
        /*@modifies buf @*/;
private int apprentice_map(struct magic_set *ms, struct magic **magicp, uint32_t *nmagicp,
    const char *fn)
        /*@globals fileSystem, internalState @*/
        /*@modifies ms, *magicp, *nmagicp, fileSystem, internalState @*/;
private int apprentice_compile(struct magic_set *ms, struct magic **magicp, uint32_t * nmagicp,
    const char *fn)
        /*@globals fileSystem, internalState @*/
        /*@modifies ms, fileSystem, internalState @*/;
private int check_format(struct magic_set *ms, struct magic *m)
        /*@globals fileSystem @*/
        /*@modifies fileSystem @*/;

#ifdef COMPILE_ONLY

int main(int, char *[]);

int
main(int argc, char *argv[])
{
        int ret;
        struct magic_set *ms;
        char *progname;

        if ((progname = strrchr(argv[0], '/')) != NULL)
                progname++;
        else
                progname = argv[0];

        if (argc != 2) {
                (void)fprintf(stderr, "Usage: %s file\n", progname);
                return 1;
        }

        if ((ms = magic_open(MAGIC_CHECK)) == NULL) {
                (void)fprintf(stderr, "%s: %s\n", progname, strerror(errno));
                return 1;
        }
        ret = magic_compile(ms, argv[1]) == -1 ? 1 : 0;
        if (ret == 1)
                (void)fprintf(stderr, "%s: %s\n", progname, magic_error(ms));
        magic_close(ms);
        return ret;
}
#endif /* COMPILE_ONLY */


/*
 * Handle one file.
 */
private int
apprentice_1(struct magic_set *ms, const char *fn, int action,
    struct mlist *mlist)
{
        struct magic *magic = NULL;
        uint32_t nmagic = 0;
        struct mlist *ml;
        int rv = -1;
        int mapped;

        if (magicsize != FILE_MAGICSIZE) {
                file_error(ms, 0, "magic element size %lu != %lu",
                    (unsigned long)sizeof(*magic),
                    (unsigned long)FILE_MAGICSIZE);
                return -1;
        }

        if (action == FILE_COMPILE) {
                rv = apprentice_file(ms, &magic, &nmagic, fn, action);
                if (rv != 0)
                        return -1;
                rv = apprentice_compile(ms, &magic, &nmagic, fn);
                free(magic);
                return rv;
        }
#ifndef COMPILE_ONLY
        if ((rv = apprentice_map(ms, &magic, &nmagic, fn)) == -1) {
                if (ms->flags & MAGIC_CHECK)
                        file_magwarn(ms, "using regular magic file `%s'", fn);
                rv = apprentice_file(ms, &magic, &nmagic, fn, action);
                if (rv != 0)
                        return -1;
                mapped = 0;
        }

        if (rv == -1)
                return rv;
        mapped = rv;
             
        if (magic == NULL || nmagic == 0) {
                file_delmagic(magic, mapped, nmagic);
                return -1;
        }

        if ((ml = malloc(sizeof(*ml))) == NULL) {
                file_delmagic(magic, mapped, nmagic);
                file_oomem(ms);
                return -1;
        }

        ml->magic = magic;
        ml->nmagic = nmagic;
        ml->mapped = mapped;

        mlist->prev->next = ml;
        ml->prev = mlist->prev;
        ml->next = mlist;
        mlist->prev = ml;

        return 0;
#endif /* COMPILE_ONLY */
}

protected void
file_delmagic(struct magic *p, int type, size_t entries)
{
        if (p == NULL)
                return;
        switch (type) {
        case 2:
                p--;
                (void)munmap((void *)p, sizeof(*p) * (entries + 1));
                break;
        case 1:
                p--;
                /*@fallthrough@*/
        case 0:
                free(p);
                break;
        default:
                abort();
        }
}


/* const char *fn: list of magic files */
protected struct mlist *
file_apprentice(struct magic_set *ms, const char *fn, int action)
{
        char *p, *mfn, *afn = NULL;
        int file_err, errs = -1;
        struct mlist *mlist;

        if (fn == NULL)
                fn = getenv("MAGIC");
        if (fn == NULL)
                fn = MAGIC;

        if ((fn = mfn = strdup(fn)) == NULL) {
                file_oomem(ms);
                return NULL;
        }

        if ((mlist = malloc(sizeof(*mlist))) == NULL) {
                free(mfn);
                file_oomem(ms);
                return NULL;
        }
        mlist->next = mlist->prev = mlist;

        while (fn) {
                p = strchr(fn, PATHSEP);
                if (p)
                        *p++ = '\0';
                if (*fn == '\0')
                        break;
                if (ms->flags & MAGIC_MIME) {
                        if ((afn = malloc(strlen(fn) + 5 + 1)) == NULL) {
                                free(mfn);
                                free(mlist);
                                file_oomem(ms);
                                return NULL;
                        }
                        (void)strcpy(afn, fn);
                        (void)strcat(afn, ".mime");
                        fn = afn;
                }
                file_err = apprentice_1(ms, fn, action, mlist);
                if (file_err > errs)
                        errs = file_err;
                if (afn) {
                        free(afn);
                        afn = NULL;
                }
                fn = p;
        }
        if (errs == -1) {
                free(mfn);
                free(mlist);
                mlist = NULL;
                file_error(ms, 0, "could not find any magic files!");
                return NULL;
        }
        free(mfn);
        return mlist;
}

/*
 * parse from a file
 * const char *fn: name of magic file
 */
private int
apprentice_file(struct magic_set *ms, struct magic **magicp, uint32_t *nmagicp,
    const char *fn, int action)
{
        private const char hdr[] =
                "cont\toffset\ttype\topcode\tmask\tvalue\tdesc";
        FILE *f;
        char line[BUFSIZ+1];
        int errs = 0;

        f = fopen(ms->file = fn, "r");
        if (f == NULL) {
                if (errno != ENOENT)
                        file_error(ms, errno, "cannot read magic file `%s'",
                            fn);
                return -1;
        }

        maxmagic = MAXMAGIS;
        *magicp = (struct magic *) calloc(maxmagic, sizeof(struct magic));
        if (*magicp == NULL) {
                (void)fclose(f);
                file_oomem(ms);
                return -1;
        }

        /* print silly verbose header for USG compat. */
        if (action == FILE_CHECK)
                (void)fprintf(stderr, "%s\n", hdr);

        /* parse it */
        for (ms->line = 1; fgets(line, BUFSIZ, f) != NULL; ms->line++) {
                size_t len;
                if (line[0]=='#')       /* comment, do not parse */
                        continue;
                len = strlen(line);
                if (len < 2) /* null line, garbage, etc */
                        continue;
                line[len - 1] = '\0'; /* delete newline */
                if (parse(ms, magicp, nmagicp, line, action) != 0)
                        errs = 1;
        }

        (void)fclose(f);
        if (errs) {
                free(*magicp);
                *magicp = NULL;
                *nmagicp = 0;
        }
        return errs;
}

/*
 * extend the sign bit if the comparison is to be signed
 */
protected uint32_t
file_signextend(struct magic_set *ms, struct magic *m, uint32_t v)
{
        if (!(m->flag & UNSIGNED))
                switch(m->type) {
                /*
                 * Do not remove the casts below.  They are
                 * vital.  When later compared with the data,
                 * the sign extension must have happened.
                 */
                case FILE_BYTE:
                        v = (char) v;
                        break;
                case FILE_SHORT:
                case FILE_BESHORT:
                case FILE_LESHORT:
                        v = (short) v;
                        break;
                case FILE_DATE:
                case FILE_BEDATE:
                case FILE_LEDATE:
                case FILE_LDATE:
                case FILE_BELDATE:
                case FILE_LELDATE:
                case FILE_LONG:
                case FILE_BELONG:
                case FILE_LELONG:
                        v = (int32_t) v;
                        break;
                case FILE_STRING:
                case FILE_PSTRING:
                case FILE_BESTRING16:
                case FILE_LESTRING16:
                case FILE_REGEX:
                case FILE_SEARCH:
                        break;
                default:
                        if (ms->flags & MAGIC_CHECK)
                            file_magwarn(ms, "cannot happen: m->type=%d\n",
                                    m->type);
                        return ~0U;
                }
        return v;
}

/*
 * parse one line from magic file, put into magic[index++] if valid
 */
private int
parse(struct magic_set *ms, struct magic **magicp, uint32_t *nmagicp, char *l,
    int action)
{
        int i = 0;
        struct magic *m;
        char *t;
/*@observer@*/
        private const char *fops = FILE_OPS;
        uint32_t val;

#define ALLOC_INCR      200
        if (*nmagicp + 1 >= maxmagic){
                maxmagic += ALLOC_INCR;
/*@-unqualifiedtrans@*/
                if ((m = (struct magic *) realloc(*magicp,
                    sizeof(struct magic) * maxmagic)) == NULL) {
                        file_oomem(ms);
                        if (*magicp)
                                free(*magicp);
                        return -1;
                }
/*@=unqualifiedtrans@*/
                *magicp = m;
                memset(&(*magicp)[*nmagicp], 0, sizeof(struct magic)
                    * ALLOC_INCR);
        }
        m = &(*magicp)[*nmagicp];
        m->flag = 0;
        m->cont_level = 0;

        while (*l == '>') {
                ++l;            /* step over */
                m->cont_level++; 
        }

        if (m->cont_level != 0 && *l == '&') {
                ++l;            /* step over */
                m->flag |= OFFADD;
        }
        if (m->cont_level != 0 && *l == '(') {
                ++l;            /* step over */
                m->flag |= INDIR;
                if (m->flag & OFFADD)
                        m->flag = (m->flag & ~OFFADD) | INDIROFFADD;
        }
        if (m->cont_level != 0 && *l == '&') {
                ++l;            /* step over */
                m->flag |= OFFADD;
        }

        /* get offset, then skip over it */
        m->offset = (uint32_t)strtoul(l, &t, 0);
        if (l == t)
                if (ms->flags & MAGIC_CHECK)
                        file_magwarn(ms, "offset `%s' invalid", l);
        l = t;

        if (m->flag & INDIR) {
                m->in_type = FILE_LONG;
                m->in_offset = 0;
                /*
                 * read [.lbs][+-]nnnnn)
                 */
                if (*l == '.') {
                        l++;
                        switch (*l) {
                        case 'l':
                                m->in_type = FILE_LELONG;
                                break;
                        case 'L':
                                m->in_type = FILE_BELONG;
                                break;
                        case 'h':
                        case 's':
                                m->in_type = FILE_LESHORT;
                                break;
                        case 'H':
                        case 'S':
                                m->in_type = FILE_BESHORT;
                                break;
                        case 'c':
                        case 'b':
                        case 'C':
                        case 'B':
                                m->in_type = FILE_BYTE;
                                break;
                        default:
                                if (ms->flags & MAGIC_CHECK)
                                        file_magwarn(ms,
                                            "indirect offset type `%c' invalid",
                                            *l);
                                break;
                        }
                        l++;
                }
                if (*l == '~') {
                        m->in_op |= FILE_OPINVERSE;
                        l++;
                }
                switch (*l) {
                case '&':
                        m->in_op |= FILE_OPAND;
                        l++;
                        break;
                case '|':
                        m->in_op |= FILE_OPOR;
                        l++;
                        break;
                case '^':
                        m->in_op |= FILE_OPXOR;
                        l++;
                        break;
                case '+':
                        m->in_op |= FILE_OPADD;
                        l++;
                        break;
                case '-':
                        m->in_op |= FILE_OPMINUS;
                        l++;
                        break;
                case '*':
                        m->in_op |= FILE_OPMULTIPLY;
                        l++;
                        break;
                case '/':
                        m->in_op |= FILE_OPDIVIDE;
                        l++;
                        break;
                case '%':
                        m->in_op |= FILE_OPMODULO;
                        l++;
                        break;
                }
                if (*l == '(') {
                        m->in_op |= FILE_OPINDIRECT;
                        l++;
                }
                if (isdigit((unsigned char)*l) || *l == '-') 
                        m->in_offset = (int32_t)strtol(l, &t, 0);
                else
                        t = l;
                if (*t++ != ')' ||
                    ((m->in_op & FILE_OPINDIRECT) && *t++ != ')')) 
                        if (ms->flags & MAGIC_CHECK)
                                file_magwarn(ms,
                                    "missing ')' in indirect offset");
                l = t;
        }


        while (isascii((unsigned char)*l) && isdigit((unsigned char)*l))
                ++l;
        EATAB;

#define NBYTE           4
#define NSHORT          5
#define NLONG           4
#define NSTRING         6
#define NDATE           4
#define NBESHORT        7
#define NBELONG         6
#define NBEDATE         6
#define NLESHORT        7
#define NLELONG         6
#define NLEDATE         6
#define NPSTRING        7
#define NLDATE          5
#define NBELDATE        7
#define NLELDATE        7
#define NREGEX          5
#define NBESTRING16     10
#define NLESTRING16     10
#define NSEARCH         6

        if (*l == 'u') {
                ++l;
                m->flag |= UNSIGNED;
        }

        /* get type, skip it */
        if (strncmp(l, "char", NBYTE)==0) {     /* HP/UX compat */
                m->type = FILE_BYTE;
                l += NBYTE;
        } else if (strncmp(l, "byte", NBYTE)==0) {
                m->type = FILE_BYTE;
                l += NBYTE;
        } else if (strncmp(l, "short", NSHORT)==0) {
                m->type = FILE_SHORT;
                l += NSHORT;
        } else if (strncmp(l, "long", NLONG)==0) {
                m->type = FILE_LONG;
                l += NLONG;
        } else if (strncmp(l, "string", NSTRING)==0) {
                m->type = FILE_STRING;
                l += NSTRING;
        } else if (strncmp(l, "date", NDATE)==0) {
                m->type = FILE_DATE;
                l += NDATE;
        } else if (strncmp(l, "beshort", NBESHORT)==0) {
                m->type = FILE_BESHORT;
                l += NBESHORT;
        } else if (strncmp(l, "belong", NBELONG)==0) {
                m->type = FILE_BELONG;
                l += NBELONG;
        } else if (strncmp(l, "bedate", NBEDATE)==0) {
                m->type = FILE_BEDATE;
                l += NBEDATE;
        } else if (strncmp(l, "leshort", NLESHORT)==0) {
                m->type = FILE_LESHORT;
                l += NLESHORT;
        } else if (strncmp(l, "lelong", NLELONG)==0) {
                m->type = FILE_LELONG;
                l += NLELONG;
        } else if (strncmp(l, "ledate", NLEDATE)==0) {
                m->type = FILE_LEDATE;
                l += NLEDATE;
        } else if (strncmp(l, "pstring", NPSTRING)==0) {
                m->type = FILE_PSTRING;
                l += NPSTRING;
        } else if (strncmp(l, "ldate", NLDATE)==0) {
                m->type = FILE_LDATE;
                l += NLDATE;
        } else if (strncmp(l, "beldate", NBELDATE)==0) {
                m->type = FILE_BELDATE;
                l += NBELDATE;
        } else if (strncmp(l, "leldate", NLELDATE)==0) {
                m->type = FILE_LELDATE;
                l += NLELDATE;
        } else if (strncmp(l, "regex", NREGEX)==0) {
                m->type = FILE_REGEX;
                l += NREGEX;
        } else if (strncmp(l, "bestring16", NBESTRING16)==0) {
                m->type = FILE_BESTRING16;
                l += NBESTRING16;
        } else if (strncmp(l, "lestring16", NLESTRING16)==0) {
                m->type = FILE_LESTRING16;
                l += NLESTRING16;
        } else if (strncmp(l, "search", NSEARCH)==0) {
                m->type = FILE_SEARCH;
                l += NSEARCH;
        } else {
                if (ms->flags & MAGIC_CHECK)
                        file_magwarn(ms, "type `%s' invalid", l);
                return -1;
        }
        /* New-style anding: "0 byte&0x80 =0x80 dynamically linked" */
        /* New and improved: ~ & | ^ + - * / % -- exciting, isn't it? */
        if (*l == '~') {
                if (!IS_STRING(m->type))
                        m->mask_op |= FILE_OPINVERSE;
                ++l;
        }
        if ((t = strchr(fops,  *l)) != NULL) {
                uint32_t op = (uint32_t)(t - fops);
                if (op != FILE_OPDIVIDE || !IS_PLAINSTRING(m->type)) {
                        ++l;
                        m->mask_op |= op;
                        val = (uint32_t)strtoul(l, &l, 0);
                        m->mask = file_signextend(ms, m, val);
                        eatsize(&l);
                } else {
                        m->mask = 0L;
                        while (!isspace((unsigned char)*++l)) {
                                switch (*l) {
                                case CHAR_IGNORE_LOWERCASE:
                                        m->mask |= STRING_IGNORE_LOWERCASE;
                                        /*@switchbreak@*/ break;
                                case CHAR_COMPACT_BLANK:
                                        m->mask |= STRING_COMPACT_BLANK;
                                        /*@switchbreak@*/ break;
                                case CHAR_COMPACT_OPTIONAL_BLANK:
                                        m->mask |=
                                            STRING_COMPACT_OPTIONAL_BLANK;
                                        /*@switchbreak@*/ break;
                                default:
                                        if (ms->flags & MAGIC_CHECK)
                                                file_magwarn(ms,
                                                "string extension `%c' invalid",
                                                *l);
                                        return -1;
                                }
                        }
                        ++l;
                }
        }
        /*
         * We used to set mask to all 1's here, instead let's just not do
         * anything if mask = 0 (unless you have a better idea)
         */
        EATAB;
  
        switch (*l) {
        case '>':
        case '<':
        /* Old-style anding: "0 byte &0x80 dynamically linked" */
        case '&':
        case '^':
        case '=':
                m->reln = *l;
                ++l;
                if (*l == '=') {
                   /* HP compat: ignore &= etc. */
                   ++l;
                }
                break;
        case '!':
                m->reln = *l;
                ++l;
                break;
        default:
                if (*l == 'x' && ((isascii((unsigned char)l[1]) && 
                    isspace((unsigned char)l[1])) || !l[1])) {
                        m->reln = *l;
                        ++l;
                        goto GetDesc;   /* Bill The Cat */
                }
                m->reln = '=';
                break;
        }
        EATAB;
  
        if (getvalue(ms, m, &l))
                return -1;
        /*
         * TODO finish this macro and start using it!
         * #define offsetcheck {if (offset > HOWMANY-1) 
         *      magwarn("offset too big"); }
         */

        /*
         * now get last part - the description
         */
GetDesc:
        EATAB;
        if (l[0] == '\b') {
                ++l;
                m->nospflag = 1;
        } else if ((l[0] == '\\') && (l[1] == 'b')) {
                ++l;
                ++l;
                m->nospflag = 1;
        } else
                m->nospflag = 0;
        while ((m->desc[i++] = *l++) != '\0' && i < MAXDESC)
                /* NULLBODY */;

        if (ms->flags & MAGIC_CHECK) {
                if (!check_format(ms, m))
                        return -1;
        }
#ifndef COMPILE_ONLY
        if (action == FILE_CHECK) {
                file_mdump(m);
        }
#endif
        ++(*nmagicp);           /* make room for next */
        return 0;
}

/*
 * Check that the optional printf format in description matches
 * the type of the magic.
 */
private int
check_format(struct magic_set *ms, struct magic *m)
{
/*@-nullassign@*/
/*@observer@*/
        static const char *formats[] = { FILE_FORMAT_STRING };
/*@=nullassign@*/
/*@observer@*/
        static const char *names[] = { FILE_FORMAT_NAME };
        char *ptr;

        for (ptr = m->desc; *ptr; ptr++)
                if (*ptr == '%')
                        break;
        if (*ptr == '\0') {
                /* No format string; ok */
                return 1;
        }
        if (m->type >= sizeof(formats)/sizeof(formats[0])) {
                file_magwarn(ms, "Internal error inconsistency between m->type"
                    " and format strings");
                return 0;
        }
        if (formats[m->type] == NULL) {
                file_magwarn(ms, "No format string for `%s' with description "
                    "`%s'", m->desc, names[m->type]);
                return 0;
        }
        for (; *ptr; ptr++) {
                if (*ptr == 'l' || *ptr == 'h') {
                        /* XXX: we should really fix this one day */
                        continue;
                }
                if (islower((unsigned char)*ptr) || *ptr == 'X')
                        break;
        }
        if (*ptr == '\0') {
                /* Missing format string; bad */
                file_magwarn(ms, "Invalid format `%s' for type `%s'",
                        m->desc, names[m->type]);
                return 0;
        }
        if (strchr(formats[m->type], *ptr) == NULL) {
                file_magwarn(ms, "Printf format `%c' is not valid for type `%s'"
                    " in description `%s'",
                        *ptr, names[m->type], m->desc);
                return 0;
        }
        return 1;
}

/* 
 * Read a numeric value from a pointer, into the value union of a magic 
 * pointer, according to the magic type.  Update the string pointer to point 
 * just after the number read.  Return 0 for success, non-zero for failure.
 */
private int
getvalue(struct magic_set *ms, struct magic *m, char **p)
{
        int slen;

        switch (m->type) {
        case FILE_BESTRING16:
        case FILE_LESTRING16:
        case FILE_STRING:
        case FILE_PSTRING:
        case FILE_REGEX:
        case FILE_SEARCH:
                *p = getstr(ms, *p, m->value.s, sizeof(m->value.s), &slen);
                if (*p == NULL) {
                        if (ms->flags & MAGIC_CHECK)
                                file_magwarn(ms, "cannot get string from `%s'",
                                    m->value.s);
                        return -1;
                }
                m->vallen = slen;
                return 0;
        default:
                if (m->reln != 'x') {
                        m->value.l = file_signextend(ms, m,
                            (uint32_t)strtoul(*p, p, 0));
                        eatsize(p);
                }
                return 0;
        }
}

/*
 * Convert a string containing C character escapes.  Stop at an unescaped
 * space or tab.
 * Copy the converted version to "p", returning its length in *slen.
 * Return updated scan pointer as function result.
 */
private char *
getstr(struct magic_set *ms, char *s, char *p, int plen, int *slen)
{
        char    *origs = s, *origp = p;
        char    *pmax = p + plen - 1;
        int     c;
        int     val;

        while ((c = *s++) != '\0') {
                if (isspace((unsigned char) c))
                        break;
                if (p >= pmax) {
                        file_error(ms, 0, "string too long: `%s'", origs);
                        return NULL;
                }
                if(c == '\\') {
                        switch(c = *s++) {

                        case '\0':
                                goto out;

                        default:
                                *p++ = (char) c;
                                /*@switchbreak@*/ break;

                        case 'n':
                                *p++ = '\n';
                                /*@switchbreak@*/ break;

                        case 'r':
                                *p++ = '\r';
                                /*@switchbreak@*/ break;

                        case 'b':
                                *p++ = '\b';
                                /*@switchbreak@*/ break;

                        case 't':
                                *p++ = '\t';
                                /*@switchbreak@*/ break;

                        case 'f':
                                *p++ = '\f';
                                /*@switchbreak@*/ break;

                        case 'v':
                                *p++ = '\v';
                                /*@switchbreak@*/ break;

                        /* \ and up to 3 octal digits */
                        case '0':
                        case '1':
                        case '2':
                        case '3':
                        case '4':
                        case '5':
                        case '6':
                        case '7':
                                val = c - '0';
                                c = *s++;  /* try for 2 */
                                if(c >= '0' && c <= '7') {
                                        val = (val<<3) | (c - '0');
                                        c = *s++;  /* try for 3 */
                                        if(c >= '0' && c <= '7')
                                                val = (val<<3) | (c-'0');
                                        else
                                                --s;
                                }
                                else
                                        --s;
                                *p++ = (char)val;
                                /*@switchbreak@*/ break;

                        /* \x and up to 2 hex digits */
                        case 'x':
                                val = 'x';      /* Default if no digits */
                                c = hextoint(*s++);     /* Get next char */
                                if (c >= 0) {
                                        val = c;
                                        c = hextoint(*s++);
                                        if (c >= 0)
                                                val = (val << 4) + c;
                                        else
                                                --s;
                                } else
                                        --s;
                                *p++ = (char)val;
                                /*@switchbreak@*/ break;
                        }
                } else
                        *p++ = (char)c;
        }
out:
        *p = '\0';
        *slen = p - origp;
        return s;
}


/* Single hex char to int; -1 if not a hex char. */
private int
hextoint(int c)
{
        if (!isascii((unsigned char) c))
                return -1;
        if (isdigit((unsigned char) c))
                return c - '0';
        if ((c >= 'a')&&(c <= 'f'))
                return c + 10 - 'a';
        if (( c>= 'A')&&(c <= 'F'))
                return c + 10 - 'A';
        return -1;
}


/*
 * Print a string containing C character escapes.
 */
protected void
file_showstr(FILE *fp, const char *s, size_t len)
{
        char    c;

        for (;;) {
                c = *s++;
                if (len == ~0U) {
                        if (c == '\0')
                                break;
                }
                else  {
                        if (len-- == 0)
                                break;
                }
                if(c >= 040 && c <= 0176)       /* TODO isprint && !iscntrl */
                        (void) fputc(c, fp);
                else {
                        (void) fputc('\\', fp);
                        switch (c) {
                        
                        case '\n':
                                (void) fputc('n', fp);
                                /*@switchbreak@*/ break;

                        case '\r':
                                (void) fputc('r', fp);
                                /*@switchbreak@*/ break;

                        case '\b':
                                (void) fputc('b', fp);
                                /*@switchbreak@*/ break;

                        case '\t':
                                (void) fputc('t', fp);
                                /*@switchbreak@*/ break;

                        case '\f':
                                (void) fputc('f', fp);
                                /*@switchbreak@*/ break;

                        case '\v':
                                (void) fputc('v', fp);
                                /*@switchbreak@*/ break;

                        default:
                                (void) fprintf(fp, "%.3o", c & 0377);
                                /*@switchbreak@*/ break;
                        }
                }
        }
}

/*
 * eatsize(): Eat the size spec from a number [eg. 10UL]
 */
private void
eatsize(char **p)
{
        char *l = *p;

        if (LOWCASE(*l) == 'u') 
                l++;

        switch (LOWCASE(*l)) {
        case 'l':    /* long */
        case 's':    /* short */
        case 'h':    /* short */
        case 'b':    /* char/byte */
        case 'c':    /* char/byte */
                l++;
                /*@fallthrough@*/
        default:
                break;
        }

        *p = l;
}

/*
 * handle a compiled file.
 */
private int
apprentice_map(struct magic_set *ms, struct magic **magicp, uint32_t *nmagicp,
    const char *fn)
{
        int fd;
        struct stat st;
        uint32_t *ptr;
        uint32_t version;
        int needsbyteswap;
        char buf[MAXPATHLEN];
        char *dbname = mkdbname(fn, buf, sizeof(buf), 0);
        void *mm = NULL;

        if (dbname == NULL)
                return -1;

        if ((fd = open(dbname, O_RDONLY)) == -1)
                return -1;

        if (fstat(fd, &st) == -1) {
                file_error(ms, errno, "cannot stat `%s'", dbname);
                goto error;
        }
        if (st.st_size < 16) {
                file_error(ms, 0, "file `%s' is too small", dbname);
                goto error;
        }

#ifdef QUICK
        if ((mm = mmap(0, (size_t)st.st_size, PROT_READ|PROT_WRITE,
            MAP_PRIVATE|MAP_FILE, fd, (off_t)0)) == MAP_FAILED) {
                file_error(ms, errno, "cannot map `%s'", dbname);
                goto error;
        }
#define RET     2
#else
        if ((mm = malloc((size_t)st.st_size)) == NULL) {
                file_oomem(ms);
                goto error;
        }
        if (read(fd, mm, (size_t)st.st_size) != (size_t)st.st_size) {
                file_badread(ms);
                goto error;
        }
#define RET     1
#endif
        *magicp = mm;
        (void)close(fd);
        fd = -1;
        ptr = (uint32_t *)(void *)*magicp;
        if (*ptr != MAGICNO) {
                if (swap4(*ptr) != MAGICNO) {
                        file_error(ms, 0, "bad magic in `%s'");
                        goto error;
                }
                needsbyteswap = 1;
        } else
                needsbyteswap = 0;
        if (needsbyteswap)
                version = swap4(ptr[1]);
        else
                version = ptr[1];
        if (version != VERSIONNO) {
                file_error(ms, 0, "version mismatch (%d != %d) in `%s'",
                    version, VERSIONNO, dbname);
                goto error;
        }
        *nmagicp = (uint32_t)(st.st_size / sizeof(struct magic)) - 1;
        (*magicp)++;
        if (needsbyteswap)
                byteswap(*magicp, *nmagicp);
        return RET;

error:
        if (fd != -1)
                (void)close(fd);
        if (mm) {
#ifdef QUICK
                (void)munmap((void *)mm, (size_t)st.st_size);
#else
                free(mm);
#endif
        } else {
                *magicp = NULL;
                *nmagicp = 0;
        }
        return -1;
}

/*@unchecked@*/ /*@observer@*/
private const uint32_t ar[] = {
    MAGICNO, VERSIONNO
};
/*
 * handle an mmaped file.
 */
private int
apprentice_compile(struct magic_set *ms, struct magic **magicp,
    uint32_t *nmagicp, const char *fn)
{
        int fd;
        char buf[MAXPATHLEN];
        char *dbname = mkdbname(fn, buf, sizeof(buf), 1);

        if (dbname == NULL) 
                return -1;

        if ((fd = open(dbname, O_WRONLY|O_CREAT|O_TRUNC, 0644)) == -1) {
                file_error(ms, errno, "cannot open `%s'", dbname);
                return -1;
        }

        if (write(fd, ar, sizeof(ar)) != (ssize_t)sizeof(ar)) {
                file_error(ms, errno, "error writing `%s'", dbname);
                return -1;
        }

        if (lseek(fd, (off_t)sizeof(struct magic), SEEK_SET)
            != sizeof(struct magic)) {
                file_error(ms, errno, "error seeking `%s'", dbname);
                return -1;
        }

        if (write(fd, *magicp, (sizeof(struct magic) * *nmagicp)) 
            != (ssize_t)(sizeof(struct magic) * *nmagicp)) {
                file_error(ms, errno, "error writing `%s'", dbname);
                return -1;
        }

        (void)close(fd);
        return 0;
}

/*@unchecked@*/ /*@observer@*/
private const char ext[] = ".mgc";
/*
 * make a dbname
 */
private char *
mkdbname(const char *fn, char *buf, size_t bufsiz, int strip)
{
        if (strip) {
                const char *p;
                if ((p = strrchr(fn, '/')) != NULL)
                        fn = ++p;
        }

        (void)snprintf(buf, bufsiz, "%s%s", fn, ext);
        return buf;
}

/*
 * Byteswap an mmap'ed file if needed
 */
private void
byteswap(struct magic *magic, uint32_t nmagic)
{
        uint32_t i;
        for (i = 0; i < nmagic; i++)
                bs1(&magic[i]);
}

/*
 * swap a short
 */
private uint16_t
swap2(uint16_t sv)
{
        uint16_t rv;
        uint8_t *s = (uint8_t *)(void *)&sv; 
        uint8_t *d = (uint8_t *)(void *)&rv; 
        d[0] = s[1];
        d[1] = s[0];
        return rv;
}

/*
 * swap an int
 */
private uint32_t
swap4(uint32_t sv)
{
        uint32_t rv;
        uint8_t *s = (uint8_t *)(void *)&sv; 
        uint8_t *d = (uint8_t *)(void *)&rv; 
        d[0] = s[3];
        d[1] = s[2];
        d[2] = s[1];
        d[3] = s[0];
        return rv;
}

/*
 * byteswap a single magic entry
 */
private void
bs1(struct magic *m)
{
        m->cont_level = swap2(m->cont_level);
        m->offset = swap4((uint32_t)m->offset);
        m->in_offset = swap4((uint32_t)m->in_offset);
        if (!IS_STRING(m->type))
                m->value.l = swap4(m->value.l);
        m->mask = swap4(m->mask);
}

---