/*************************************************************************** *                                                                         * *     File:          Download Unix File Utility                           * *     Function:  This program demostrating download file managment        * *                                                                         * *     Author:              Long Yun Liang                                 * *     Copyright (c) 1,23,1996        All rights reserved                  * *                                                                         * ***************************************************************************/#include <stdio.h>#include <string.h>#include <stdlib.h>#include <fcntl.h>#include <termio.h>#include "fget.h"/************************************************************************** *       Revised XMODEM/YMODEM CRC protocol                               * *                                                                        * *  A data packet is defined as:                                          * *       typedef struct {                                                 * *               BYTE    soh;            - Start of heading               * *               BYTE    seq#;           - sequence number                * *               BYTE    not_seq#;       - ~seq#                          * *               BYTE    data[128];      - data buffer                    * *               BYTE    bc;             - block checksum                 * *       } dataPacketRec;                                                 * **************************************************************************/unsigned short Checksum(BYTE *, int);int main(int argc,char *argv[]){    FILE        *fp;    char        filename[128];    int         ack_reply;    int         fd;    int         retry;    PacketRec   packet;    BYTE        *ptr;    int         n;    long        i;    int         buflen;    unsigned short     bc;    struct  termio     savetty;    struct  termio     tdes;    if (argc<2)  {	 printf ("Download File Utility  Version 1.00\n");	 printf ("Copyright (c) Software Engineering 1996-1997.  All rights reserved.\n\n");	 printf ("Writen by: Long Yunliang . Xi'An China .\n\n");	 printf ("Usage:  fget TransferFile\n");	 return 1;    }    ioctl (1,TCGETA,&savetty);     /* save original tty */    ioctl (1,TCGETA,&tdes);    tdes.c_oflag &= ~OPOST;    tdes.c_lflag &= ~ECHO;    tdes.c_lflag &= ~ICANON;    tdes.c_lflag &= ~XCASE;     tdes.c_cc[VMIN]  = 1;    tdes.c_cc[VTIME] = 1;    ioctl (1,TCSETA,&tdes);        /* set new tty mode */    strcpy (filename,argv[1]);    if ((fd = open(filename, O_RDONLY )) < 0)  {	printf ("File not found .\n");	ioctl (1,TCSETA,&savetty);	return (OPENFAIL);      /* Open file failed */    }     printf ("\x1b[1Y");         /* Support a certain smart phone */        packet.soh = SOH;           /* XMODEM transfer file header */    packet.seq = 0;             /* initialize seqence# */    for(;;)  {       ack_reply = getchar();       if (ack_reply == CRC)   break;    }    if ((ack_reply) != CRC)	return(DISCONN);    while ( buflen = read(fd, packet.buffer, DATALEN) ) {	if (buflen < DATALEN)           /* end of file */	   for (i = buflen;i < DATALEN;i++)	       packet.buffer[i] = SUB; 	if (packet.seq == 255)          /* next sequence # */	    packet.seq = 0;	else	    packet.seq++;	packet.nseq  = ~packet.seq;	packet.bc[0] = 0x00;	packet.bc[1] = 0x00;	bc = Checksum((BYTE *)&packet.buffer, DATALEN);	packet.bc[0] = (bc >> 8) & 0x00FF;	packet.bc[1] = bc & 0x00FF;	retry = MAXRETRY; 		do  {	} while ((ack_reply = getch()) != -1);	do  {	    ptr = (BYTE *)&packet;	   		     /* Sending packet */	    for (n = 0; n < PACKETSIZE; n++, ptr++) {		 putchar (*ptr); 	    }	    for (i = 0;i < 10000;i++)  {		ack_reply = getchar()&0xff;		if (ack_reply == CRC) continue;		if (ack_reply != 0xff) break;	    }    		    /* wait for ACK from receiver */	    switch (ack_reply) {		case NAK:       /* packet was received incorrectly */		case 0xff:      /* packet/ACK might get lost */		    if (--retry == 0)  {         /* DIS-CONNECT */			ioctl (1,TCSETA,&savetty);			return(DISCONN);		    }		    break;		case ACK:		    retry = 0;		    break;	    }	} while (retry > 0);    }    close(fd);    /* Sending EOT */    retry = MAXRETRY;    do {	if (putchar(EOT) == 0) {	    close(fd);	    ioctl (1,TCSETA,&savetty);	    return(DISCONN);	}		/* wait for ACK from receiver */	switch (ack_reply = getchar()&0xff) {	    case NAK:           /* packet was received incorrectly */	    case 0xff:          /* packet/ACK might get lost */		if (--retry == 0)  {         /* DIS-CONNECT */		    ioctl (1,TCSETA,&savetty);		    return(DISCONN);		}		break;	    case ACK:		retry = 0;		break;	}    } while (retry > 0);      ioctl (1,TCSETA,&savetty);    return(SUCCEED);            /* Send successfully */}/*************************************************************************** *                                                                         *     * Function:    Checksum() - compute crc's                                 * *                                                                         * * crc-16 is based on the polynomial x^16+x^15+x^2+1                       * *  The data is assumed to be fed in from least to most significant bit    * * crc-ccitt is based on the polynomial x^16+x^12+x^5+1                    * *  The data is fed in from most to least significant bit                  * * The prescription for determining the mask to use for a given polynomial * *    is as follows:                                                       * *        1.  Represent the polynomial by a 17-bit number                  * *        2.  Assume that the most and least significant bits are 1        * *        3.  Place the right 16 bits into an integer                      * *        4.  Bit reverse if serial LSB's are sent first                   * *                                                                         * ***************************************************************************//* function declarations */unsigned short updcrc(unsigned int,int,unsigned int);unsigned short Checksum(BYTE *buf, int buflen){    /* variables */    unsigned int crctt;    int ch;    int num;    crctt=0;    for (num=0;num<buflen;num++)    {	ch=*(buf+num);	crctt=updcrc(crctt,ch,CRC_CCITT);    }    return (crctt);}/* update crc */unsigned short updcrc(unsigned int crc,int c,unsigned int mask){    int i;    c<<=8;    for(i=0;i<8;i++)    {	if((crc ^ c) & 0x8000) crc=(crc<<1)^mask;	else crc<<=1;	c<<=1;    }    return crc;}