www.pudn.com > nasm-src.rar > disasm.c


/* disasm.c   where all the _work_ gets done in the Netwide Disassembler 
 * 
 * The Netwide Assembler is copyright (C) 1996 Simon Tatham and 
 * Julian Hall. All rights reserved. The software is 
 * redistributable under the licence given in the file "Licence" 
 * distributed in the NASM archive. 
 * 
 * initial version 27/iii/95 by Simon Tatham 
 */ 
 
#include  
#include  
 
#include "nasm.h" 
#include "disasm.h" 
#include "sync.h" 
#include "insns.h" 
 
#include "names.c" 
 
extern struct itemplate **itable[]; 
 
/* 
 * Flags that go into the `segment' field of `insn' structures 
 * during disassembly. 
 */ 
#define SEG_RELATIVE 1 
#define SEG_32BIT 2 
#define SEG_RMREG 4 
#define SEG_DISP8 8 
#define SEG_DISP16 16 
#define SEG_DISP32 32 
#define SEG_NODISP 64 
#define SEG_SIGNED 128 
 
static int whichreg(long regflags, int regval) 
{ 
#include "regdis.c" 
 
    if (!(REG_AL & ~regflags)) 
        return R_AL; 
    if (!(REG_AX & ~regflags)) 
        return R_AX; 
    if (!(REG_EAX & ~regflags)) 
        return R_EAX; 
    if (!(REG_DL & ~regflags)) 
        return R_DL; 
    if (!(REG_DX & ~regflags)) 
        return R_DX; 
    if (!(REG_EDX & ~regflags)) 
        return R_EDX; 
    if (!(REG_CL & ~regflags)) 
        return R_CL; 
    if (!(REG_CX & ~regflags)) 
        return R_CX; 
    if (!(REG_ECX & ~regflags)) 
        return R_ECX; 
    if (!(FPU0 & ~regflags)) 
        return R_ST0; 
    if (!(REG_CS & ~regflags)) 
        return (regval == 1) ? R_CS : 0; 
    if (!(REG_DESS & ~regflags)) 
        return (regval == 0 || regval == 2 
                || regval == 3 ? sreg[regval] : 0); 
    if (!(REG_FSGS & ~regflags)) 
        return (regval == 4 || regval == 5 ? sreg[regval] : 0); 
    if (!(REG_SEG67 & ~regflags)) 
        return (regval == 6 || regval == 7 ? sreg[regval] : 0); 
 
    /* All the entries below look up regval in an 8-entry array */ 
    if (regval < 0 || regval > 7) 
        return 0; 
 
    if (!((REGMEM | BITS8) & ~regflags)) 
        return reg8[regval]; 
    if (!((REGMEM | BITS16) & ~regflags)) 
        return reg16[regval]; 
    if (!((REGMEM | BITS32) & ~regflags)) 
        return reg32[regval]; 
    if (!(REG_SREG & ~regflags)) 
        return sreg[regval]; 
    if (!(REG_CREG & ~regflags)) 
        return creg[regval]; 
    if (!(REG_DREG & ~regflags)) 
        return dreg[regval]; 
    if (!(REG_TREG & ~regflags)) 
        return treg[regval]; 
    if (!(FPUREG & ~regflags)) 
        return fpureg[regval]; 
    if (!(MMXREG & ~regflags)) 
        return mmxreg[regval]; 
    if (!(XMMREG & ~regflags)) 
        return xmmreg[regval]; 
 
    return 0; 
} 
 
static const char *whichcond(int condval) 
{ 
    static int conds[] = { 
        C_O, C_NO, C_C, C_NC, C_Z, C_NZ, C_NA, C_A, 
        C_S, C_NS, C_PE, C_PO, C_L, C_NL, C_NG, C_G 
    }; 
    return conditions[conds[condval]]; 
} 
 
/* 
 * Process an effective address (ModRM) specification. 
 */ 
static unsigned char *do_ea(unsigned char *data, int modrm, int asize, 
                            int segsize, operand * op) 
{ 
    int mod, rm, scale, index, base; 
 
    mod = (modrm >> 6) & 03; 
    rm = modrm & 07; 
 
    if (mod == 3) {             /* pure register version */ 
        op->basereg = rm; 
        op->segment |= SEG_RMREG; 
        return data; 
    } 
 
    op->addr_size = 0; 
 
    if (asize == 16) { 
        /* 
         *  specifies the displacement size (none, byte or 
         * word), and  specifies the register combination. 
         * Exception: mod=0,rm=6 does not specify [BP] as one might 
         * expect, but instead specifies [disp16]. 
         */ 
        op->indexreg = op->basereg = -1; 
        op->scale = 1;          /* always, in 16 bits */ 
        switch (rm) { 
        case 0: 
            op->basereg = R_BX; 
            op->indexreg = R_SI; 
            break; 
        case 1: 
            op->basereg = R_BX; 
            op->indexreg = R_DI; 
            break; 
        case 2: 
            op->basereg = R_BP; 
            op->indexreg = R_SI; 
            break; 
        case 3: 
            op->basereg = R_BP; 
            op->indexreg = R_DI; 
            break; 
        case 4: 
            op->basereg = R_SI; 
            break; 
        case 5: 
            op->basereg = R_DI; 
            break; 
        case 6: 
            op->basereg = R_BP; 
            break; 
        case 7: 
            op->basereg = R_BX; 
            break; 
        } 
        if (rm == 6 && mod == 0) {      /* special case */ 
            op->basereg = -1; 
            if (segsize != 16) 
                op->addr_size = 16; 
            mod = 2;            /* fake disp16 */ 
        } 
        switch (mod) { 
        case 0: 
            op->segment |= SEG_NODISP; 
            break; 
        case 1: 
            op->segment |= SEG_DISP8; 
            op->offset = (signed char)*data++; 
            break; 
        case 2: 
            op->segment |= SEG_DISP16; 
            op->offset = *data++; 
            op->offset |= ((unsigned)*data++) << 8; 
            break; 
        } 
        return data; 
    } else { 
        /* 
         * Once again,  specifies displacement size (this time 
         * none, byte or *dword*), while  specifies the base 
         * register. Again, [EBP] is missing, replaced by a pure 
         * disp32 (this time that's mod=0,rm=*5*). However, rm=4 
         * indicates not a single base register, but instead the 
         * presence of a SIB byte... 
         */ 
        op->indexreg = -1; 
        switch (rm) { 
        case 0: 
            op->basereg = R_EAX; 
            break; 
        case 1: 
            op->basereg = R_ECX; 
            break; 
        case 2: 
            op->basereg = R_EDX; 
            break; 
        case 3: 
            op->basereg = R_EBX; 
            break; 
        case 5: 
            op->basereg = R_EBP; 
            break; 
        case 6: 
            op->basereg = R_ESI; 
            break; 
        case 7: 
            op->basereg = R_EDI; 
            break; 
        } 
        if (rm == 5 && mod == 0) { 
            op->basereg = -1; 
            if (segsize != 32) 
                op->addr_size = 32; 
            mod = 2;            /* fake disp32 */ 
        } 
        if (rm == 4) {          /* process SIB */ 
            scale = (*data >> 6) & 03; 
            index = (*data >> 3) & 07; 
            base = *data & 07; 
            data++; 
 
            op->scale = 1 << scale; 
            switch (index) { 
            case 0: 
                op->indexreg = R_EAX; 
                break; 
            case 1: 
                op->indexreg = R_ECX; 
                break; 
            case 2: 
                op->indexreg = R_EDX; 
                break; 
            case 3: 
                op->indexreg = R_EBX; 
                break; 
            case 4: 
                op->indexreg = -1; 
                break; 
            case 5: 
                op->indexreg = R_EBP; 
                break; 
            case 6: 
                op->indexreg = R_ESI; 
                break; 
            case 7: 
                op->indexreg = R_EDI; 
                break; 
            } 
 
            switch (base) { 
            case 0: 
                op->basereg = R_EAX; 
                break; 
            case 1: 
                op->basereg = R_ECX; 
                break; 
            case 2: 
                op->basereg = R_EDX; 
                break; 
            case 3: 
                op->basereg = R_EBX; 
                break; 
            case 4: 
                op->basereg = R_ESP; 
                break; 
            case 6: 
                op->basereg = R_ESI; 
                break; 
            case 7: 
                op->basereg = R_EDI; 
                break; 
            case 5: 
                if (mod == 0) { 
                    mod = 2; 
                    op->basereg = -1; 
                } else 
                    op->basereg = R_EBP; 
                break; 
            } 
        } 
        switch (mod) { 
        case 0: 
            op->segment |= SEG_NODISP; 
            break; 
        case 1: 
            op->segment |= SEG_DISP8; 
            op->offset = (signed char)*data++; 
            break; 
        case 2: 
            op->segment |= SEG_DISP32; 
            op->offset = *data++; 
            op->offset |= ((unsigned)*data++) << 8; 
            op->offset |= ((long)*data++) << 16; 
            op->offset |= ((long)*data++) << 24; 
            break; 
        } 
        return data; 
    } 
} 
 
/* 
 * Determine whether the instruction template in t corresponds to the data 
 * stream in data. Return the number of bytes matched if so. 
 */ 
static int matches(struct itemplate *t, unsigned char *data, int asize, 
                   int osize, int segsize, int rep, insn * ins) 
{ 
    unsigned char *r = (unsigned char *)(t->code); 
    unsigned char *origdata = data; 
    int a_used = FALSE, o_used = FALSE; 
    int drep = 0; 
 
    if (rep == 0xF2) 
        drep = P_REPNE; 
    else if (rep == 0xF3) 
        drep = P_REP; 
 
    while (*r) { 
        int c = *r++; 
        if (c >= 01 && c <= 03) { 
            while (c--) 
                if (*r++ != *data++) 
                    return FALSE; 
        } 
        if (c == 04) { 
            switch (*data++) { 
            case 0x07: 
                ins->oprs[0].basereg = 0; 
                break; 
            case 0x17: 
                ins->oprs[0].basereg = 2; 
                break; 
            case 0x1F: 
                ins->oprs[0].basereg = 3; 
                break; 
            default: 
                return FALSE; 
            } 
        } 
        if (c == 05) { 
            switch (*data++) { 
            case 0xA1: 
                ins->oprs[0].basereg = 4; 
                break; 
            case 0xA9: 
                ins->oprs[0].basereg = 5; 
                break; 
            default: 
                return FALSE; 
            } 
        } 
        if (c == 06) { 
            switch (*data++) { 
            case 0x06: 
                ins->oprs[0].basereg = 0; 
                break; 
            case 0x0E: 
                ins->oprs[0].basereg = 1; 
                break; 
            case 0x16: 
                ins->oprs[0].basereg = 2; 
                break; 
            case 0x1E: 
                ins->oprs[0].basereg = 3; 
                break; 
            default: 
                return FALSE; 
            } 
        } 
        if (c == 07) { 
            switch (*data++) { 
            case 0xA0: 
                ins->oprs[0].basereg = 4; 
                break; 
            case 0xA8: 
                ins->oprs[0].basereg = 5; 
                break; 
            default: 
                return FALSE; 
            } 
        } 
        if (c >= 010 && c <= 012) { 
            int t = *r++, d = *data++; 
            if (d < t || d > t + 7) 
                return FALSE; 
            else { 
                ins->oprs[c - 010].basereg = d - t; 
                ins->oprs[c - 010].segment |= SEG_RMREG; 
            } 
        } 
        if (c == 017) 
            if (*data++) 
                return FALSE; 
        if (c >= 014 && c <= 016) { 
            ins->oprs[c - 014].offset = (signed char)*data++; 
            ins->oprs[c - 014].segment |= SEG_SIGNED; 
        } 
        if (c >= 020 && c <= 022) 
            ins->oprs[c - 020].offset = *data++; 
        if (c >= 024 && c <= 026) 
            ins->oprs[c - 024].offset = *data++; 
        if (c >= 030 && c <= 032) { 
            ins->oprs[c - 030].offset = *data++; 
            ins->oprs[c - 030].offset |= (((unsigned)*data++) << 8); 
        } 
        if (c >= 034 && c <= 036) { 
            ins->oprs[c - 034].offset = *data++; 
            ins->oprs[c - 034].offset |= (((unsigned)*data++) << 8); 
            if (osize == 32) { 
                ins->oprs[c - 034].offset |= (((long)*data++) << 16); 
                ins->oprs[c - 034].offset |= (((long)*data++) << 24); 
            } 
            if (segsize != asize) 
                ins->oprs[c - 034].addr_size = asize; 
        } 
        if (c >= 040 && c <= 042) { 
            ins->oprs[c - 040].offset = *data++; 
            ins->oprs[c - 040].offset |= (((unsigned)*data++) << 8); 
            ins->oprs[c - 040].offset |= (((long)*data++) << 16); 
            ins->oprs[c - 040].offset |= (((long)*data++) << 24); 
        } 
        if (c >= 044 && c <= 046) { 
            ins->oprs[c - 044].offset = *data++; 
            ins->oprs[c - 044].offset |= (((unsigned)*data++) << 8); 
            if (asize == 32) { 
                ins->oprs[c - 044].offset |= (((long)*data++) << 16); 
                ins->oprs[c - 044].offset |= (((long)*data++) << 24); 
            } 
            if (segsize != asize) 
                ins->oprs[c - 044].addr_size = asize; 
        } 
        if (c >= 050 && c <= 052) { 
            ins->oprs[c - 050].offset = (signed char)*data++; 
            ins->oprs[c - 050].segment |= SEG_RELATIVE; 
        } 
        if (c >= 060 && c <= 062) { 
            ins->oprs[c - 060].offset = *data++; 
            ins->oprs[c - 060].offset |= (((unsigned)*data++) << 8); 
            ins->oprs[c - 060].segment |= SEG_RELATIVE; 
            ins->oprs[c - 060].segment &= ~SEG_32BIT; 
        } 
        if (c >= 064 && c <= 066) { 
            ins->oprs[c - 064].offset = *data++; 
            ins->oprs[c - 064].offset |= (((unsigned)*data++) << 8); 
            if (osize == 32) { 
                ins->oprs[c - 064].offset |= (((long)*data++) << 16); 
                ins->oprs[c - 064].offset |= (((long)*data++) << 24); 
                ins->oprs[c - 064].segment |= SEG_32BIT; 
            } else 
                ins->oprs[c - 064].segment &= ~SEG_32BIT; 
            ins->oprs[c - 064].segment |= SEG_RELATIVE; 
            if (segsize != osize) { 
                ins->oprs[c - 064].type = 
                    (ins->oprs[c - 064].type & NON_SIZE) 
                    | ((osize == 16) ? BITS16 : BITS32); 
            } 
        } 
        if (c >= 070 && c <= 072) { 
            ins->oprs[c - 070].offset = *data++; 
            ins->oprs[c - 070].offset |= (((unsigned)*data++) << 8); 
            ins->oprs[c - 070].offset |= (((long)*data++) << 16); 
            ins->oprs[c - 070].offset |= (((long)*data++) << 24); 
            ins->oprs[c - 070].segment |= SEG_32BIT | SEG_RELATIVE; 
        } 
        if (c >= 0100 && c < 0130) { 
            int modrm = *data++; 
            ins->oprs[c & 07].basereg = (modrm >> 3) & 07; 
            ins->oprs[c & 07].segment |= SEG_RMREG; 
            data = do_ea(data, modrm, asize, segsize, 
                         &ins->oprs[(c >> 3) & 07]); 
        } 
        if (c >= 0130 && c <= 0132) { 
            ins->oprs[c - 0130].offset = *data++; 
            ins->oprs[c - 0130].offset |= (((unsigned)*data++) << 8); 
        } 
        if (c >= 0140 && c <= 0142) { 
            ins->oprs[c - 0140].offset = *data++; 
            ins->oprs[c - 0140].offset |= (((unsigned)*data++) << 8); 
            ins->oprs[c - 0140].offset |= (((long)*data++) << 16); 
            ins->oprs[c - 0140].offset |= (((long)*data++) << 24); 
        } 
        if (c >= 0200 && c <= 0277) { 
            int modrm = *data++; 
            if (((modrm >> 3) & 07) != (c & 07)) 
                return FALSE;   /* spare field doesn't match up */ 
            data = do_ea(data, modrm, asize, segsize, 
                         &ins->oprs[(c >> 3) & 07]); 
        } 
        if (c >= 0300 && c <= 0302) { 
            if (asize) 
                ins->oprs[c - 0300].segment |= SEG_32BIT; 
            else 
                ins->oprs[c - 0300].segment &= ~SEG_32BIT; 
            a_used = TRUE; 
        } 
        if (c == 0310) { 
            if (asize == 32) 
                return FALSE; 
            else 
                a_used = TRUE; 
        } 
        if (c == 0311) { 
            if (asize == 16) 
                return FALSE; 
            else 
                a_used = TRUE; 
        } 
        if (c == 0312) { 
            if (asize != segsize) 
                return FALSE; 
            else 
                a_used = TRUE; 
        } 
        if (c == 0320) { 
            if (osize == 32) 
                return FALSE; 
            else 
                o_used = TRUE; 
        } 
        if (c == 0321) { 
            if (osize == 16) 
                return FALSE; 
            else 
                o_used = TRUE; 
        } 
        if (c == 0322) { 
            if (osize != segsize) 
                return FALSE; 
            else 
                o_used = TRUE; 
        } 
        if (c == 0330) { 
            int t = *r++, d = *data++; 
            if (d < t || d > t + 15) 
                return FALSE; 
            else 
                ins->condition = d - t; 
        } 
        if (c == 0331) { 
            if (rep) 
                return FALSE; 
        } 
        if (c == 0332) { 
            if (drep == P_REP) 
                drep = P_REPE; 
        } 
        if (c == 0333) { 
            if (rep != 0xF3) 
                return FALSE; 
            drep = 0; 
        } 
    } 
 
    /* 
     * Check for unused rep or a/o prefixes. 
     */ 
    ins->nprefix = 0; 
    if (drep) 
        ins->prefixes[ins->nprefix++] = drep; 
    if (!a_used && asize != segsize) 
        ins->prefixes[ins->nprefix++] = (asize == 16 ? P_A16 : P_A32); 
    if (!o_used && osize != segsize) 
        ins->prefixes[ins->nprefix++] = (osize == 16 ? P_O16 : P_O32); 
 
    return data - origdata; 
} 
 
long disasm(unsigned char *data, char *output, int outbufsize, int segsize, 
            long offset, int autosync, unsigned long prefer) 
{ 
    struct itemplate **p, **best_p; 
    int length, best_length = 0; 
    char *segover; 
    int rep, lock, asize, osize, i, slen, colon; 
    unsigned char *origdata; 
    int works; 
    insn tmp_ins, ins; 
    unsigned long goodness, best; 
 
    /* 
     * Scan for prefixes. 
     */ 
    asize = osize = segsize; 
    segover = NULL; 
    rep = lock = 0; 
    origdata = data; 
    for (;;) { 
        if (*data == 0xF3 || *data == 0xF2) 
            rep = *data++; 
        else if (*data == 0xF0) 
            lock = *data++; 
        else if (*data == 0x2E || *data == 0x36 || *data == 0x3E || 
                 *data == 0x26 || *data == 0x64 || *data == 0x65) { 
            switch (*data++) { 
            case 0x2E: 
                segover = "cs"; 
                break; 
            case 0x36: 
                segover = "ss"; 
                break; 
            case 0x3E: 
                segover = "ds"; 
                break; 
            case 0x26: 
                segover = "es"; 
                break; 
            case 0x64: 
                segover = "fs"; 
                break; 
            case 0x65: 
                segover = "gs"; 
                break; 
            } 
        } else if (*data == 0x66) 
            osize = 48 - segsize, data++; 
        else if (*data == 0x67) 
            asize = 48 - segsize, data++; 
        else 
            break; 
    } 
 
    tmp_ins.oprs[0].segment = tmp_ins.oprs[1].segment = 
        tmp_ins.oprs[2].segment = 
        tmp_ins.oprs[0].addr_size = tmp_ins.oprs[1].addr_size = 
        tmp_ins.oprs[2].addr_size = (segsize == 16 ? 0 : SEG_32BIT); 
    tmp_ins.condition = -1; 
    best = ~0UL;                /* Worst possible */ 
    best_p = NULL; 
    for (p = itable[*data]; *p; p++) { 
        if ((length = matches(*p, data, asize, osize, 
                              segsize, rep, &tmp_ins))) { 
            works = TRUE; 
            /* 
             * Final check to make sure the types of r/m match up. 
             */ 
            for (i = 0; i < (*p)->operands; i++) { 
                if ( 
                       /* If it's a mem-only EA but we have a register, die. */ 
                       ((tmp_ins.oprs[i].segment & SEG_RMREG) && 
                        !(MEMORY & ~(*p)->opd[i])) || 
                       /* If it's a reg-only EA but we have a memory ref, die. */ 
                       (!(tmp_ins.oprs[i].segment & SEG_RMREG) && 
                        !(REGNORM & ~(*p)->opd[i]) && 
                        !((*p)->opd[i] & REG_SMASK)) || 
                       /* Register type mismatch (eg FS vs REG_DESS): die. */ 
                       ((((*p)->opd[i] & (REGISTER | FPUREG)) || 
                         (tmp_ins.oprs[i].segment & SEG_RMREG)) && 
                        !whichreg((*p)->opd[i], 
                                  tmp_ins.oprs[i].basereg))) { 
                    works = FALSE; 
                    break; 
                } 
            } 
 
            if (works) { 
                goodness = ((*p)->flags & IF_PFMASK) ^ prefer; 
                if (goodness < best) { 
                    /* This is the best one found so far */ 
                    best = goodness; 
                    best_p = p; 
                    best_length = length; 
                    ins = tmp_ins; 
                } 
            } 
        } 
    } 
 
    if (!best_p) 
        return 0;               /* no instruction was matched */ 
 
    /* Pick the best match */ 
    p = best_p; 
    length = best_length; 
 
    slen = 0; 
 
    /* TODO: snprintf returns the value that the string would have if 
     *      the buffer were long enough, and not the actual length of  
     *      the returned string, so each instance of using the return 
     *      value of snprintf should actually be checked to assure that 
     *      the return value is "sane."  Maybe a macro wrapper could 
     *      be used for that purpose. 
     */ 
    if (lock) 
        slen += snprintf(output + slen, outbufsize - slen, "lock "); 
    for (i = 0; i < ins.nprefix; i++) 
        switch (ins.prefixes[i]) { 
        case P_REP: 
            slen += snprintf(output + slen, outbufsize - slen, "rep "); 
            break; 
        case P_REPE: 
            slen += snprintf(output + slen, outbufsize - slen, "repe "); 
            break; 
        case P_REPNE: 
            slen += snprintf(output + slen, outbufsize - slen, "repne "); 
            break; 
        case P_A16: 
            slen += snprintf(output + slen, outbufsize - slen, "a16 "); 
            break; 
        case P_A32: 
            slen += snprintf(output + slen, outbufsize - slen, "a32 "); 
            break; 
        case P_O16: 
            slen += snprintf(output + slen, outbufsize - slen, "o16 "); 
            break; 
        case P_O32: 
            slen += snprintf(output + slen, outbufsize - slen, "o32 "); 
            break; 
        } 
 
    for (i = 0; i < elements(ico); i++) 
        if ((*p)->opcode == ico[i]) { 
            slen += 
                snprintf(output + slen, outbufsize - slen, "%s%s", icn[i], 
                         whichcond(ins.condition)); 
            break; 
        } 
    if (i >= elements(ico)) 
        slen += 
            snprintf(output + slen, outbufsize - slen, "%s", 
                     insn_names[(*p)->opcode]); 
    colon = FALSE; 
    length += data - origdata;  /* fix up for prefixes */ 
    for (i = 0; i < (*p)->operands; i++) { 
        output[slen++] = (colon ? ':' : i == 0 ? ' ' : ','); 
 
        if (ins.oprs[i].segment & SEG_RELATIVE) { 
            ins.oprs[i].offset += offset + length; 
            /* 
             * sort out wraparound 
             */ 
            if (!(ins.oprs[i].segment & SEG_32BIT)) 
                ins.oprs[i].offset &= 0xFFFF; 
            /* 
             * add sync marker, if autosync is on 
             */ 
            if (autosync) 
                add_sync(ins.oprs[i].offset, 0L); 
        } 
 
        if ((*p)->opd[i] & COLON) 
            colon = TRUE; 
        else 
            colon = FALSE; 
 
        if (((*p)->opd[i] & (REGISTER | FPUREG)) || 
            (ins.oprs[i].segment & SEG_RMREG)) { 
            ins.oprs[i].basereg = whichreg((*p)->opd[i], 
                                           ins.oprs[i].basereg); 
            if ((*p)->opd[i] & TO) 
                slen += snprintf(output + slen, outbufsize - slen, "to "); 
            slen += snprintf(output + slen, outbufsize - slen, "%s", 
                             reg_names[ins.oprs[i].basereg - 
                                       EXPR_REG_START]); 
        } else if (!(UNITY & ~(*p)->opd[i])) { 
            output[slen++] = '1'; 
        } else if ((*p)->opd[i] & IMMEDIATE) { 
            if ((*p)->opd[i] & BITS8) { 
                slen += 
                    snprintf(output + slen, outbufsize - slen, "byte "); 
                if (ins.oprs[i].segment & SEG_SIGNED) { 
                    if (ins.oprs[i].offset < 0) { 
                        ins.oprs[i].offset *= -1; 
                        output[slen++] = '-'; 
                    } else 
                        output[slen++] = '+'; 
                } 
            } else if ((*p)->opd[i] & BITS16) { 
                slen += 
                    snprintf(output + slen, outbufsize - slen, "word "); 
            } else if ((*p)->opd[i] & BITS32) { 
                slen += 
                    snprintf(output + slen, outbufsize - slen, "dword "); 
            } else if ((*p)->opd[i] & NEAR) { 
                slen += 
                    snprintf(output + slen, outbufsize - slen, "near "); 
            } else if ((*p)->opd[i] & SHORT) { 
                slen += 
                    snprintf(output + slen, outbufsize - slen, "short "); 
            } 
            slen += 
                snprintf(output + slen, outbufsize - slen, "0x%lx", 
                         ins.oprs[i].offset); 
        } else if (!(MEM_OFFS & ~(*p)->opd[i])) { 
            slen += 
                snprintf(output + slen, outbufsize - slen, "[%s%s%s0x%lx]", 
                         (segover ? segover : ""), (segover ? ":" : ""), 
                         (ins.oprs[i].addr_size == 
                          32 ? "dword " : ins.oprs[i].addr_size == 
                          16 ? "word " : ""), ins.oprs[i].offset); 
            segover = NULL; 
        } else if (!(REGMEM & ~(*p)->opd[i])) { 
            int started = FALSE; 
            if ((*p)->opd[i] & BITS8) 
                slen += 
                    snprintf(output + slen, outbufsize - slen, "byte "); 
            if ((*p)->opd[i] & BITS16) 
                slen += 
                    snprintf(output + slen, outbufsize - slen, "word "); 
            if ((*p)->opd[i] & BITS32) 
                slen += 
                    snprintf(output + slen, outbufsize - slen, "dword "); 
            if ((*p)->opd[i] & BITS64) 
                slen += 
                    snprintf(output + slen, outbufsize - slen, "qword "); 
            if ((*p)->opd[i] & BITS80) 
                slen += 
                    snprintf(output + slen, outbufsize - slen, "tword "); 
            if ((*p)->opd[i] & FAR) 
                slen += snprintf(output + slen, outbufsize - slen, "far "); 
            if ((*p)->opd[i] & NEAR) 
                slen += 
                    snprintf(output + slen, outbufsize - slen, "near "); 
            output[slen++] = '['; 
            if (ins.oprs[i].addr_size) 
                slen += snprintf(output + slen, outbufsize - slen, "%s", 
                                 (ins.oprs[i].addr_size == 32 ? "dword " : 
                                  ins.oprs[i].addr_size == 
                                  16 ? "word " : "")); 
            if (segover) { 
                slen += 
                    snprintf(output + slen, outbufsize - slen, "%s:", 
                             segover); 
                segover = NULL; 
            } 
            if (ins.oprs[i].basereg != -1) { 
                slen += snprintf(output + slen, outbufsize - slen, "%s", 
                                 reg_names[(ins.oprs[i].basereg - 
                                            EXPR_REG_START)]); 
                started = TRUE; 
            } 
            if (ins.oprs[i].indexreg != -1) { 
                if (started) 
                    output[slen++] = '+'; 
                slen += snprintf(output + slen, outbufsize - slen, "%s", 
                                 reg_names[(ins.oprs[i].indexreg - 
                                            EXPR_REG_START)]); 
                if (ins.oprs[i].scale > 1) 
                    slen += 
                        snprintf(output + slen, outbufsize - slen, "*%d", 
                                 ins.oprs[i].scale); 
                started = TRUE; 
            } 
            if (ins.oprs[i].segment & SEG_DISP8) { 
                int sign = '+'; 
                if (ins.oprs[i].offset & 0x80) { 
                    ins.oprs[i].offset = -(signed char)ins.oprs[i].offset; 
                    sign = '-'; 
                } 
                slen += 
                    snprintf(output + slen, outbufsize - slen, "%c0x%lx", 
                             sign, ins.oprs[i].offset); 
            } else if (ins.oprs[i].segment & SEG_DISP16) { 
                if (started) 
                    output[slen++] = '+'; 
                slen += 
                    snprintf(output + slen, outbufsize - slen, "0x%lx", 
                             ins.oprs[i].offset); 
            } else if (ins.oprs[i].segment & SEG_DISP32) { 
                if (started) 
                    output[slen++] = '+'; 
                slen += 
                    snprintf(output + slen, outbufsize - slen, "0x%lx", 
                             ins.oprs[i].offset); 
            } 
            output[slen++] = ']'; 
        } else { 
            slen += 
                snprintf(output + slen, outbufsize - slen, "", 
                         i); 
        } 
    } 
    output[slen] = '\0'; 
    if (segover) {              /* unused segment override */ 
        char *p = output; 
        int count = slen + 1; 
        while (count--) 
            p[count + 3] = p[count]; 
        strncpy(output, segover, 2); 
        output[2] = ' '; 
    } 
    return length; 
} 
 
long eatbyte(unsigned char *data, char *output, int outbufsize) 
{ 
    snprintf(output, outbufsize, "db 0x%02X", *data); 
    return 1; 
}