int
do_unpack(TARG,gimme,arglast)
STR *TARG;
int gimme;
int *arglast;
{
    STR **st = stack->ary_array;
    register int sp = arglast[0] + 1;
    register char *pat = str_get(st[sp++]);
    register char *s = str_get(st[sp]);
    char *strend = s + st[sp--]->str_cur;
    char *strbeg = s;
    register char *patend = pat + st[sp]->str_cur;
    int datumtype;
    register int len;
    register int bits;

    /* These must not be in registers: */
    short ashort;
    int aint;
    long along;
#ifdef QUAD
    quad aquad;
#endif
    unsigned short aushort;
    unsigned int auint;
    unsigned long aulong;
#ifdef QUAD
    unsigned quad auquad;
#endif
    char *aptr;
    float afloat;
    double adouble;
    int checksum = 0;
    unsigned long culong;
    double cdouble;

    if (gimme != G_ARRAY) {		/* arrange to do first one only */
	/*SUPPRESS 530*/
	for (patend = pat; !isALPHA(*patend) || *patend == 'x'; patend++) ;
	if (index("aAbBhH", *patend) || *pat == '%') {
	    patend++;
	    while (isDIGIT(*patend) || *patend == '*')
		patend++;
	}
	else
	    patend++;
    }
    sp--;
    while (pat < patend) {
      reparse:
	datumtype = *pat++;
	if (pat >= patend)
	    len = 1;
	else if (*pat == '*') {
	    len = strend - strbeg;	/* long enough */
	    pat++;
	}
	else if (isDIGIT(*pat)) {
	    len = *pat++ - '0';
	    while (isDIGIT(*pat))
		len = (len * 10) + (*pat++ - '0');
	}
	else
	    len = (datumtype != '@');
	switch(datumtype) {
	default:
	    break;
	case '%':
	    if (len == 1 && pat[-1] != '1')
		len = 16;
	    checksum = len;
	    culong = 0;
	    cdouble = 0;
	    if (pat < patend)
		goto reparse;
	    break;
	case '@':
	    if (len > strend - strbeg)
		fatal("@ outside of string");
	    s = strbeg + len;
	    break;
	case 'X':
	    if (len > s - strbeg)
		fatal("X outside of string");
	    s -= len;
	    break;
	case 'x':
	    if (len > strend - s)
		fatal("x outside of string");
	    s += len;
	    break;
	case 'A':
	case 'a':
	    if (len > strend - s)
		len = strend - s;
	    if (checksum)
		goto uchar_checksum;
	    TARG = Str_new(35,len);
	    str_nset(TARG,s,len);
	    s += len;
	    if (datumtype == 'A') {
		aptr = s;	/* borrow register */
		s = TARG->str_ptr + len - 1;
		while (s >= TARG->str_ptr && (!*s || isSPACE(*s)))
		    s--;
		*++s = '\0';
		TARG->str_cur = s - TARG->str_ptr;
		s = aptr;	/* unborrow register */
	    }
	    (void)astore(stack, ++sp, str_2mortal(TARG));
	    break;
	case 'B':
	case 'b':
	    if (pat[-1] == '*' || len > (strend - s) * 8)
		len = (strend - s) * 8;
	    TARG = Str_new(35, len + 1);
	    TARG->str_cur = len;
	    TARG->str_pok = 1;
	    aptr = pat;			/* borrow register */
	    pat = TARG->str_ptr;
	    if (datumtype == 'b') {
		aint = len;
		for (len = 0; len < aint; len++) {
		    if (len & 7)		/*SUPPRESS 595*/
			bits >>= 1;
		    else
			bits = *s++;
		    *pat++ = '0' + (bits & 1);
		}
	    }
	    else {
		aint = len;
		for (len = 0; len < aint; len++) {
		    if (len & 7)
			bits <<= 1;
		    else
			bits = *s++;
		    *pat++ = '0' + ((bits & 128) != 0);
		}
	    }
	    *pat = '\0';
	    pat = aptr;			/* unborrow register */
	    (void)astore(stack, ++sp, str_2mortal(TARG));
	    break;
	case 'H':
	case 'h':
	    if (pat[-1] == '*' || len > (strend - s) * 2)
		len = (strend - s) * 2;
	    TARG = Str_new(35, len + 1);
	    TARG->str_cur = len;
	    TARG->str_pok = 1;
	    aptr = pat;			/* borrow register */
	    pat = TARG->str_ptr;
	    if (datumtype == 'h') {
		aint = len;
		for (len = 0; len < aint; len++) {
		    if (len & 1)
			bits >>= 4;
		    else
			bits = *s++;
		    *pat++ = hexdigit[bits & 15];
		}
	    }
	    else {
		aint = len;
		for (len = 0; len < aint; len++) {
		    if (len & 1)
			bits <<= 4;
		    else
			bits = *s++;
		    *pat++ = hexdigit[(bits >> 4) & 15];
		}
	    }
	    *pat = '\0';
	    pat = aptr;			/* unborrow register */
	    (void)astore(stack, ++sp, str_2mortal(TARG));
	    break;
	case 'c':
	    if (len > strend - s)
		len = strend - s;
	    if (checksum) {
		while (len-- > 0) {
		    aint = *s++;
		    if (aint >= 128)	/* fake up signed chars */
			aint -= 256;
		    culong += aint;
		}
	    }
	    else {
		while (len-- > 0) {
		    aint = *s++;
		    if (aint >= 128)	/* fake up signed chars */
			aint -= 256;
		    TARG = Str_new(36,0);
		    str_numset(TARG,(double)aint);
		    (void)astore(stack, ++sp, str_2mortal(TARG));
		}
	    }
	    break;
	case 'C':
	    if (len > strend - s)
		len = strend - s;
	    if (checksum) {
	      uchar_checksum:
		while (len-- > 0) {
		    auint = *s++ & 255;
		    culong += auint;
		}
	    }
	    else {
		while (len-- > 0) {
		    auint = *s++ & 255;
		    TARG = Str_new(37,0);
		    str_numset(TARG,(double)auint);
		    (void)astore(stack, ++sp, str_2mortal(TARG));
		}
	    }
	    break;
	case 's':
	    along = (strend - s) / sizeof(short);
	    if (len > along)
		len = along;
	    if (checksum) {
		while (len-- > 0) {
		    Copy(s,&ashort,1,short);
		    s += sizeof(short);
		    culong += ashort;
		}
	    }
	    else {
		while (len-- > 0) {
		    Copy(s,&ashort,1,short);
		    s += sizeof(short);
		    TARG = Str_new(38,0);
		    str_numset(TARG,(double)ashort);
		    (void)astore(stack, ++sp, str_2mortal(TARG));
		}
	    }
	    break;
	case 'v':
	case 'n':
	case 'S':
	    along = (strend - s) / sizeof(unsigned short);
	    if (len > along)
		len = along;
	    if (checksum) {
		while (len-- > 0) {
		    Copy(s,&aushort,1,unsigned short);
		    s += sizeof(unsigned short);
#ifdef HAS_NTOHS
		    if (datumtype == 'n')
			aushort = ntohs(aushort);
#endif
#ifdef HAS_VTOHS
		    if (datumtype == 'v')
			aushort = vtohs(aushort);
#endif
		    culong += aushort;
		}
	    }
	    else {
		while (len-- > 0) {
		    Copy(s,&aushort,1,unsigned short);
		    s += sizeof(unsigned short);
		    TARG = Str_new(39,0);
#ifdef HAS_NTOHS
		    if (datumtype == 'n')
			aushort = ntohs(aushort);
#endif
#ifdef HAS_VTOHS
		    if (datumtype == 'v')
			aushort = vtohs(aushort);
#endif
		    str_numset(TARG,(double)aushort);
		    (void)astore(stack, ++sp, str_2mortal(TARG));
		}
	    }
	    break;
	case 'i':
	    along = (strend - s) / sizeof(int);
	    if (len > along)
		len = along;
	    if (checksum) {
		while (len-- > 0) {
		    Copy(s,&aint,1,int);
		    s += sizeof(int);
		    if (checksum > 32)
			cdouble += (double)aint;
		    else
			culong += aint;
		}
	    }
	    else {
		while (len-- > 0) {
		    Copy(s,&aint,1,int);
		    s += sizeof(int);
		    TARG = Str_new(40,0);
		    str_numset(TARG,(double)aint);
		    (void)astore(stack, ++sp, str_2mortal(TARG));
		}
	    }
	    break;
	case 'I':
	    along = (strend - s) / sizeof(unsigned int);
	    if (len > along)
		len = along;
	    if (checksum) {
		while (len-- > 0) {
		    Copy(s,&auint,1,unsigned int);
		    s += sizeof(unsigned int);
		    if (checksum > 32)
			cdouble += (double)auint;
		    else
			culong += auint;
		}
	    }
	    else {
		while (len-- > 0) {
		    Copy(s,&auint,1,unsigned int);
		    s += sizeof(unsigned int);
		    TARG = Str_new(41,0);
		    str_numset(TARG,(double)auint);
		    (void)astore(stack, ++sp, str_2mortal(TARG));
		}
	    }
	    break;
	case 'l':
	    along = (strend - s) / sizeof(long);
	    if (len > along)
		len = along;
	    if (checksum) {
		while (len-- > 0) {
		    Copy(s,&along,1,long);
		    s += sizeof(long);
		    if (checksum > 32)
			cdouble += (double)along;
		    else
			culong += along;
		}
	    }
	    else {
		while (len-- > 0) {
		    Copy(s,&along,1,long);
		    s += sizeof(long);
		    TARG = Str_new(42,0);
		    str_numset(TARG,(double)along);
		    (void)astore(stack, ++sp, str_2mortal(TARG));
		}
	    }
	    break;
	case 'V':
	case 'N':
	case 'L':
	    along = (strend - s) / sizeof(unsigned long);
	    if (len > along)
		len = along;
	    if (checksum) {
		while (len-- > 0) {
		    Copy(s,&aulong,1,unsigned long);
		    s += sizeof(unsigned long);
#ifdef HAS_NTOHL
		    if (datumtype == 'N')
			aulong = ntohl(aulong);
#endif
#ifdef HAS_VTOHL
		    if (datumtype == 'V')
			aulong = vtohl(aulong);
#endif
		    if (checksum > 32)
			cdouble += (double)aulong;
		    else
			culong += aulong;
		}
	    }
	    else {
		while (len-- > 0) {
		    Copy(s,&aulong,1,unsigned long);
		    s += sizeof(unsigned long);
		    TARG = Str_new(43,0);
#ifdef HAS_NTOHL
		    if (datumtype == 'N')
			aulong = ntohl(aulong);
#endif
#ifdef HAS_VTOHL
		    if (datumtype == 'V')
			aulong = vtohl(aulong);
#endif
		    str_numset(TARG,(double)aulong);
		    (void)astore(stack, ++sp, str_2mortal(TARG));
		}
	    }
	    break;
	case 'p':
	    along = (strend - s) / sizeof(char*);
	    if (len > along)
		len = along;
	    while (len-- > 0) {
		if (sizeof(char*) > strend - s)
		    break;
		else {
		    Copy(s,&aptr,1,char*);
		    s += sizeof(char*);
		}
		TARG = Str_new(44,0);
		if (aptr)
		    str_set(TARG,aptr);
		(void)astore(stack, ++sp, str_2mortal(TARG));
	    }
	    break;
#ifdef QUAD
	case 'q':
	    while (len-- > 0) {
		if (s + sizeof(quad) > strend)
		    aquad = 0;
		else {
		    Copy(s,&aquad,1,quad);
		    s += sizeof(quad);
		}
		TARG = Str_new(42,0);
		str_numset(TARG,(double)aquad);
		(void)astore(stack, ++sp, str_2mortal(TARG));
	    }
	    break;
	case 'Q':
	    while (len-- > 0) {
		if (s + sizeof(unsigned quad) > strend)
		    auquad = 0;
		else {
		    Copy(s,&auquad,1,unsigned quad);
		    s += sizeof(unsigned quad);
		}
		TARG = Str_new(43,0);
		str_numset(TARG,(double)auquad);
		(void)astore(stack, ++sp, str_2mortal(TARG));
	    }
	    break;
#endif
	/* float and double added gnb@melba.bby.oz.au 22/11/89 */
	case 'f':
	case 'F':
	    along = (strend - s) / sizeof(float);
	    if (len > along)
		len = along;
	    if (checksum) {
		while (len-- > 0) {
		    Copy(s, &afloat,1, float);
		    s += sizeof(float);
		    cdouble += afloat;
		}
	    }
	    else {
		while (len-- > 0) {
		    Copy(s, &afloat,1, float);
		    s += sizeof(float);
		    TARG = Str_new(47, 0);
		    str_numset(TARG, (double)afloat);
		    (void)astore(stack, ++sp, str_2mortal(TARG));
		}
	    }
	    break;
	case 'd':
	case 'D':
	    along = (strend - s) / sizeof(double);
	    if (len > along)
		len = along;
	    if (checksum) {
		while (len-- > 0) {
		    Copy(s, &adouble,1, double);
		    s += sizeof(double);
		    cdouble += adouble;
		}
	    }
	    else {
		while (len-- > 0) {
		    Copy(s, &adouble,1, double);
		    s += sizeof(double);
		    TARG = Str_new(48, 0);
		    str_numset(TARG, (double)adouble);
		    (void)astore(stack, ++sp, str_2mortal(TARG));
		}
	    }
	    break;
	case 'u':
	    along = (strend - s) * 3 / 4;
	    TARG = Str_new(42,along);
	    while (s < strend && *s > ' ' && *s < 'a') {
		int a,b,c,d;
		char hunk[4];

		hunk[3] = '\0';
		len = (*s++ - ' ') & 077;
		while (len > 0) {
		    if (s < strend && *s >= ' ')
			a = (*s++ - ' ') & 077;
		    else
			a = 0;
		    if (s < strend && *s >= ' ')
			b = (*s++ - ' ') & 077;
		    else
			b = 0;
		    if (s < strend && *s >= ' ')
			c = (*s++ - ' ') & 077;
		    else
			c = 0;
		    if (s < strend && *s >= ' ')
			d = (*s++ - ' ') & 077;
		    else
			d = 0;
		    hunk[0] = a << 2 | b >> 4;
		    hunk[1] = b << 4 | c >> 2;
		    hunk[2] = c << 6 | d;
		    str_ncat(TARG,hunk, len > 3 ? 3 : len);
		    len -= 3;
		}
		if (*s == '\n')
		    s++;
		else if (s[1] == '\n')		/* possible checksum byte */
		    s += 2;
	    }
	    (void)astore(stack, ++sp, str_2mortal(TARG));
	    break;
	}
	if (checksum) {
	    TARG = Str_new(42,0);
	    if (index("fFdD", datumtype) ||
	      (checksum > 32 && index("iIlLN", datumtype)) ) {
		double modf();
		double trouble;

		adouble = 1.0;
		while (checksum >= 16) {
		    checksum -= 16;
		    adouble *= 65536.0;
		}
		while (checksum >= 4) {
		    checksum -= 4;
		    adouble *= 16.0;
		}
		while (checksum--)
		    adouble *= 2.0;
		along = (1 << checksum) - 1;
		while (cdouble < 0.0)
		    cdouble += adouble;
		cdouble = modf(cdouble / adouble, &trouble) * adouble;
		str_numset(TARG,cdouble);
	    }
	    else {
		if (checksum < 32) {
		    along = (1 << checksum) - 1;
		    culong &= (unsigned long)along;
		}
		str_numset(TARG,(double)culong);
	    }
	    (void)astore(stack, ++sp, str_2mortal(TARG));
	    checksum = 0;
	}
    }
    return sp;
}