Feb 14

闲来无事写的摩斯码、英语的互译命令行工具：trans

project 5 Comments

trans程序的源代码在Msys下用gcc编译调试通过。

使用说明：trans  [-r/-s] srcfile objfile

    其中，-R 将摩斯码翻译成英文；
          -S 将英语翻译成摩斯码。
          srcfile为需要翻译的文本文件。运行成功后结果会保存在objfile文件中。

    注意：若是翻译英文，须保证所有字母均为大写字母。且标点符号仅可为“.”和“,”

代码已上传至github https://github.com/longqzh/MorseCode_Translator

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/* *******************************
 *
 * Translator for Morse Code
 *
 * Author: Long Qianzhi
 * Date:2010/1/28
 *
 * *******************************/
 
#include <stdio.h>
#include <string.h>
#include <stdlib.h>
 
#define MAX 39
 
struct table{
    char letter;
    char mor[8];
}table[]={
    {'A',".-"},{'B',"-..."},{'C',"-.-."},
    {'D',"-.."},{'E',"."},{'F',"..-."},
    {'G',"--."},{'H',"...."},{'I',".."},
    {'J',".---"},{'K',"-.-"},{'L',".-.."},
    {'M',"--"},{'N',"-."},{'O',"---"},
    {'P',".--."},{'Q',"--.-"},{'R',".-."},
    {'S',"..."},{'T',"-"},{'U',"..-"},
    {'V',"...-"},{'W',".--"},{'X',"-..-"},
    {'Y',"-.--"},{'Z',"--.."},{'0',"-----"},
    {'1',".----"},{'2',"..---"},{'3',"...--"},
    {'4',"....-"},{'5',"....."},{'6',"-...."},
    {'7',"--..."},{'8',"---.."},{'9',"----."},
    {'.',".-.-.-"},{',',"--..--"},{' ',".--.-."},
    {'\n',""}
};
 
FILE *infp=NULL, *outfp=NULL;
 
void check_file(char *in, char *out)
{
    if((infp=fopen(in,"r"))==NULL){
        printf("\nCan't open source file : %s\n", in);
        exit(1);
    }
    else if ((outfp=fopen(out,"w"))==NULL){
        printf("\nCan't open output file : %s\n", out);
        exit(1);
    }
    return;
}
 
int file_size(FILE *fp)
{
    int fsize=0;
    char c;
    while((c=fgetc(fp))!=EOF)
        fsize++;
    rewind(fp);
    return fsize;
}
 
char* make_buf(int n)
{
    char *pstr;
    pstr=(char *)malloc(n*sizeof(char));
    if(pstr==NULL){
        printf("\nMalloc failed!\n");
        exit(1);
    }
    return pstr;
}
 
void m2t()
{
    char *buffer;
    int fnum,n=0,i=0;
    char tmp[8]="";
 
    /* Read all of the data from srcfile to buffer.*/
    fnum=file_size(infp);
    buffer=make_buf(fnum+1);
    if((fread(buffer,sizeof(char),fnum,infp))!=fnum){
        printf("\nSomething wrong about reading file!\n");
        exit(1);
    }
    *(buffer+fnum)='\0';
    fclose(infp);
 
    printf("%s\n",buffer);fflush(stdout);
 
    while(*buffer!='\0'){
 
        /* Read a word from buffer to tmp.*/
        while(*buffer!=' ' && *buffer!='\0'){
            tmp[n++]=*buffer++;
            if(n>7){
                tmp[7]='\0';
                printf(" %s : Bad MorseCode!\n", tmp);
                exit(1);
            }
        }
        tmp[n]='\0';
        n=0;
        printf("%s\t",tmp);fflush(stdout);
         
 
        while(strcmp(tmp,table[i++].mor)){
            if(i>=MAX && *(buffer+1)!='\0'){
                printf(" %s : CANNOT find it!\n", tmp);
                exit(1);
            }
        }
 
        fputc(table[--i].letter,outfp);
        printf("%c\t",table[i].letter);fflush(stdout);
        i=0;
        buffer++;
    }
    fclose(outfp);
    printf("The translated file is created.\n");
    fflush(stdout);
}
 
void t2m()
{
    char *buffer;
    int fnum,i=0;
 
    /* Read all of the data from srcfile to buffer.*/
    fnum=file_size(infp);
 
    buffer=make_buf(fnum+1);
    if((fread(buffer,sizeof(char),fnum,infp))!=fnum){
        printf("\nSomething wrong about reading file!\n");
        exit(1);
    }
    *(buffer+fnum)='\0';
    fclose(infp);
 
    printf("%s %d\n", buffer,(int)(*buffer));fflush(stdout);
 
    while(*buffer!='\0'){
        /* find the MorseCode according to character.*/
        while(*buffer!=table[i].letter){
             
            i++;
            fflush(stdout);
            if(i>MAX && *buffer!=EOF){
                printf(" %c %d: Bad character\n", *buffer,(int)(*buffer));
                exit(1);
            }
        }
        buffer++;
        printf("%c-->%s\t\n",table[i].letter,table[i].mor);fflush(stdout);
 
        fputs(table[i].mor,outfp);
        fputc(' ',outfp);
        i=0;
    }
    fclose(outfp);
    printf("The translated file is created.\n");
    fflush(stdout);
}
 
int main(int argc,char *argv[])
{
    if (argc!=4){
        printf("Usage: trans [-R/-S] srcfile outfile\n");
        printf("\n\t -r translate Morse to English.");
        printf("\n\t -s translate English to Morse.");
        printf("\n\t -h show this help information.\n");
        fflush(stdout);
        return 1;
    }
 
    if (!strcmp(argv[1],"-r") || !strcmp(argv[1],"-R")){
        check_file(argv[2],argv[3]);
        m2t();
    }
    else if (!strcmp(argv[1],"-s") || !strcmp(argv[1],"-S")){
        check_file(argv[2],argv[3]);
        t2m();
    }else{
        printf("You input wrong arguments!\n");
        printf("Please type \"trans -h\".\n");
        fflush(stdout);
    }
    return 0;
}
Dec 16

Unix programming的学弟们，你们有福了～

project 8 Comments

公布期末设计Smallshell的完整源代码：

 

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smalls.c
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/* *************************************************
 *
 *          Small shell on Unix/Linux
 *
 *   This shell finished all the functions which
 *   are required. And I added new inner functions
 *   "help" and "exit" by myself.
 * 
 *   Enjoy it!
 *
 *   author: Longqianzhi 용성지
 *   Stu_ID: 12094817
 *   data:   Dec/27/2010
 *
 * *************************************************/
 
#include <errno.h>
#include <stdio.h>
#include <stdlib.h>
#include <string.h>
#include <unistd.h>
#include <sys/wait.h>
#include <fcntl.h>
#include <signal.h>
 
#define MAX_CMD_ARG 10
#define MAX_CMD_LIST 10
 
const char *prompt = "# ";
 
char* cmdlist[MAX_CMD_LIST];
char* cmdargs[MAX_CMD_ARG];
char  cmdline[BUFSIZ];
 
void fatal(char *str);
void execute_cmd(char *cmd);
void execute_cmdline(char* cmdline);
int makeargv(char *s, const char *delimiters,
                 char** argvp, int MAX_LIST);
void help();
void cd(char *path);
void catchint(int);
void join();                    /* Use one pipe to communication.*/
int join2();                    /* Use two pipe to communication.*/
int dpipe_test();               /* It's useless.Just for test.*/
void parse_filter(char *cmd);   /* A filter for argument*/
 
 
int main(int argc, char**argv){
    int i=0;
    static struct sigaction act;
 
    /*Cope with the signal*/
 
    act.sa_handler=catchint;
    sigfillset(&(act.sa_mask));
    sigaction(SIGINT,&act,NULL);
    sigaction(SIGQUIT,&act,NULL);
 
    while (1) {    
        fputs(prompt, stdout);
        fgets(cmdline, BUFSIZ, stdin);
        cmdline[ strlen(cmdline) -1] ='\0';
 
        execute_cmdline(cmdline);
        printf("\n");
    }
    return 0;
}
 
void fatal(char *str){
    perror(str);
    exit(1);
}
 
void execute_cmdline(char* cmdline){
    int count = 0;
    int i=0;
    count = makeargv(cmdline, "!", cmdlist, MAX_CMD_LIST);
 
    /* Execute the commands with different way.*/  
 
    /*Just a single command.*/
    if(count==1){
     
        /* First of all,try to make sure whether
         * the command is "cd".
         */
        if(cmdlist[0][0]=='c'&&cmdlist[0][1]=='d'){
            parse_filter(cmdlist[0]); 
            count = makeargv(cmdlist[0], " \t", cmdargs, MAX_CMD_ARG);
            if(!strcmp("cd",cmdargs[0])){
                if(chdir(cmdargs[1]))  fatal("cd");
                return;
            }
        }
     
        /* Fork a child process to run every
         * commands except "cd"
        */
          
        switch(fork())
        {
        case -1: fatal("fork error");
        case  0: execute_cmd(cmdlist[0]);
        default:
            wait(NULL);
            fflush(stdout);
        }
    }
     
    /*Execute two programs with a pipe.*/
    if(count==2){
        join();
    }
 
    /*Execute three programs with two pipes.*/
    if(count==3){
        join2();
    }
 
    /*There are too many commands*/
    if(count>=4){
        printf("Too many pipes!\n");
        return;
    }
}
 
/* *****************************************
 * Execute a single commands with arguments.
 *
 * *****************************************/
void execute_cmd(char *cmd){
    int i=0;
    int count = 0;
     
    parse_filter(cmd); 
    count = makeargv(cmd, " \t", cmdargs, MAX_CMD_ARG);
 
    /*
     * Recognize some inner functions
     * like cd,help,exit and so on.
     * Also you can add some new inner
     * functions by yourself here.
     *
     */
    if(!strcmp("help",cmdargs[0])){
        help();
        return ;
    }
 
    if(!strcmp("exit",cmdargs[0])){
        kill(getppid(),SIGKILL); /*kill parent process*/
        raise(SIGKILL); /*kill myself*/
        exit(0);
    }
 
    execvp(cmdargs[0], cmdargs);
    fatal("exec error");
}
 
/* *****************************************
 *  Count the arguments'number in a command.
 *
 * ***************************************/
int makeargv(char *s, const char *delimiters,
                    char** argvp, int MAX_LIST) {
 
    int i = 0;
    int numtokens = 0;
    char *snew = NULL;
 
    if( (s==NULL) || (delimiters==NULL) ) return -1;
 
    snew = s + strspn(s, delimiters);  
    if( (argvp[numtokens]=strtok(snew, delimiters)) == NULL )
    return numtokens;
     
    numtokens = 1;
    while(1){
        if( (argvp[numtokens]=strtok(NULL, delimiters)) == NULL)
            break;
        if(numtokens == (MAX_LIST-1)) return -1;
            numtokens++;
    }
    return numtokens;
}
 
/* *********************************
 * Inner fnuction: help().
 * Show some infomations to the stdin
 *
 ***********************************/
void help(){
    printf("\n  * *************************************** *");
    printf("\n  *                                         *");
    printf("\n  *         WELCOME TO SMALL SHELL !        *");
    printf("\n  *                                         *");
    printf("\n  * *************************************** *");
    printf("\n  *                                         *");
    printf("\n  *  There are 3 inner functions in shell.  *");
    printf("\n  *                                         *");
    printf("\n  *  1) cd :Change the current directory.   *");
    printf("\n  *  2) exit :Quit from the small shell.    *");
    printf("\n  *  3) help :Show this message for help.   *");
    printf("\n  *                                         *");
    printf("\n  *        IF YOU FIND ANY BUGS OR          *");
    printf("\n  *          HAVE ANY QUESTIONS             *");
    printf("\n  *                                         *");
    printf("\n  *    mail to me:longqianzhi@gmail.com     *");
    printf("\n  *                                         *");
    printf("\n  * *************************************** *\n");
    exit(0);
}
 
 
/* ***************************
 * Inner function:cd().
 * Change the current directory.
 *
 * ***************************/
  
void cd(char *path){
    if(chdir(path))
        fatal("cd");
}
 
 
/* ************************************
 * The function about act.sa_handler
 * If press the Ctrl+c, resume the shell.
 *
 * ************************************/
  
void catchint(int signo){
    printf("\nReceive a signo=%d\n",signo);
    printf("Returning to the shell\n");
 
    /* Init the cmdline Array.
     * If not,the shell will try to run
     * commands in the memory.
     */
    cmdline[0]='\0';
}
 
 
/* ************************************
 * An easy way to use double pipe.
 *
 * But this function is just for test and  
 * debug in the project,because I wrote 
 * a new one by myself. The new one is
 * called "join2".
 *
 * ***********************************/
 
int dpipe_test(){
 
    /*build command string with normal format.*/
 
    char newstr[128];
    strcpy(newstr,cmdlist[0]);
    strcat(newstr,"|");
    strcat(newstr,cmdlist[1]);
    strcat(newstr,"|");
    strcat(newstr,cmdlist[2]);
     
    /*call system shell to run the commmands*/
    system(newstr);
    return 0;
}
 
 
/* **************************************
 * Delete special character from argument.
 * If there is any special charater,
 * this function will change them to '\32'
 *
 * ***************************************/
  
void parse_filter(char *cmd){
    int i=0;
    int CMAX=strlen(cmd);
     
    while(cmd[i]!=' '&&i<CMAX) i++;
     
    if((++i)<CMAX){
        if (cmd[i++]=='-')  {  
            while(cmd[i]!=' '&&i<CMAX){
             
                if(cmd[i]<'0'||(cmd[i]>'9'&&cmd[i]<'A')||
                    (cmd[i]>'Z'&&cmd[i]<'a')||cmd[i]>'z'){
 
                    char tmp=cmd[i-1];         
                    cmd[i]=tmp;
                }
                i++;
            }
        }
    }
     
}
 
/* ***********************************
 * Link the child process's stdout to
 * grandchild process's stdin with pipe.
 *
 * ***********************************/
  
void join(){
    int p[2],status;
 
    switch (fork()){
        case -1:fatal("1st fork call in join()");
        case 0:break;
        default:wait(&status);
                return;
    }
     
    /* Try to make a new pipe.*/
    if(pipe(p)==-1) fatal("pipe call in join()");
 
    switch(fork()){
        case -1:fatal("2nd fork call in join()");
        case 0:
                dup2(p[1],1);
                close(p[0]);
                close(p[1]);
                execute_cmd(cmdlist[0]);
                fatal("1st execvp call in join()");
        default:
                dup2(p[0],0);
                close(p[0]);
                close(p[1]);
                execute_cmd(cmdlist[1]);
                fatal("2nd execvp call in join()");
    }
}
 
 
 
/* *************************************
 * Link three child/grandchild processes
 * one by one with two pipes.
 *
 * ************************************/
 
int join2(){
    int status,p1[2],p2[2];
     
    /*Test the double pipe.*/  
    if(dpipe_test()==0) return 0; 
 
    /* Grandparent process */
    switch(fork()){
        case -1:fatal("1st fork call");
        case 0:break;
        default:
               wait(&status);
               return status;
    }
 
 
    /* Parent process.Run the last command.*/
 
    if(pipe(p1)<0) fatal ("pipe call"); /*make a pipe.*/
 
    switch(fork()){
        case -1:fatal("2nd fork call");
        case 0:break;
        default:
               dup2(p1[0],0);
               close(p1[0]);
               close(p1[1]);
 
               execute_cmd(cmdlist[2]);
               fatal("1st exec call");
    }
     
    /* Try to make a new pipe.*/
 
    if(pipe(p2)<0) fatal("pipe call");
 
    /* Child process.Run the second command.*/
     
    switch(fork()){
        case -1:fatal("3th fork call");
        case 0:break;
        default:
               dup2(p1[1],1);
               dup2(p2[0],0);
               close(p1[0]);
               close(p1[1]);
               close(p2[0]);
               close(p2[1]);
 
               execute_cmd(cmdlist[1]);
               fatal("2nd exec call");
    }
 
    /* Grandchild process.Run the first command.*/
     
    dup2(p2[1],1);
    close(p2[0]);
    close(p2[1]);
 
    execute_cmd(cmdlist[0]);
    fatal("3th exec call");
 
}

 

Jul 16

全屏编辑器Screen-Editor的完整源码

project 1 Comments

    DOS下虽然有edit编辑器和更加原始的EDLIN行编辑器，但近几天我把《THE CRAFT OF C》中关于Screen-Editor的代码全部输机，想自己再弄出个新的文本编辑器。

代码如下：（在turboc下成功编译通过，但无法正常运行）

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/* A Screen Editor Subsystem*/
 
#define TURBOC
 
#include <stdio.h>
#include <dos.h>
#include <string.h>
#include <bios.h>
#include <conio.h>
 
#define BUF_SIZE 32000
#define LINE_LEN 79
#define MAX_LINES 24
#define KILL_BUF_SIZE 4*LINE_LEN
char buf[BUF_SIZE];
char *curloc,*endloc;
int scrnx,scrny;
char killbuf[KILL_BUF_SIZE];
 
char *helpline=
    "F1:save  F2:load  F3:find  F4:replace\
    ^K:Kill line  ^Y:Yank  ^Z:Quit ";
 
void edit(char *fname),help();
void gotoxy(int x,int y),clrline(int y);
void edit_clr_eol(int x,int y),clrscr();
void printline(char *p),delete_char(void);
void search(),kill_line();
void upline();
void downline(),left(),right();
void scrolldn (int x,int y);
void scrollup(int topx,int topy,int endx,int endy);
void display_scrn(int x,int y,char *p);
void pagedown(),pageup(),replace();
void home(),gotoend(),yank();
int load(char *fname),save(char *fname);
void edit_gets(char *str);
 
main(int argc,char *argv[])
{
    if (argc==2) edit(argv[1]);
    clrscr();
    return 0;
}
 
/*  This is the editor's entry function and contains
    its main loop.
 
    Call it with the name of the file you want to edit.
*/
 
void edit(char *fname)
{
    union k{
        char ch[2];
        unsigned i;
    }key;
    char name[80];
 
    /*try to load the file*/
    if(!load(fname)) curloc=endloc=buf;
    strcpy(name,fname);
 
    clrscr();
 
    scrnx=scrny=0;
 
    display_scrn(0,0,curloc);
    help();
    gotoxy(0,0);
 
    /*Editor main loop*/
    do{
        key.i=bioskey(0);
        if(!key.ch[0]){
            switch(key.ch[1]){
                case 59: /*F1 save*/
                    save (name);
                    break;
                case 60: /*F2 load*/
                    clrline(MAX_LINES);
                    gotoxy(0,MAX_LINES);
                    printf ("Enter filename:");
                    edit_gets(name);
                    if (*name) load (name);
                    help();
                    display_scrn(0,0,curloc);
                    scrnx=scrny=0;
                    break;
                case 61: /*F3 search*/
                    search();
                    break;
                case 62: /*F4 relace*/
                    replace();
                    break;
                case 71: /*home*/
                    home();
                    break;
                case 79: /*end*/
                    gotoend();
                    break;
                case 75: /* left*/
                    left();
                    break;
                case 77: /*right*/
                    right();
                    break;
                case 72: /*up*/
                    upline();
                    break;
                case 80: /*down*/
                    downline();
                    break;
                case 73: /*page up*/
                    pageup();
                    break;
                case 81: /*page down*/
                    pagedown();
                    break;
                case 83: /*del*/
                    if(curloc<endloc) delete_char();
                    break;
            }
        if(curloc<buf){
        scrnx=scrny=0;
                curloc=buf;
            }
            gotoxy(scrnx,scrny);
        }
        else{   /* enter keystroke into file*/
            switch(key.ch[0]){
                case '\r': /* Carriage return*/
                    /*see if buffer is full*/
                    if(endloc==buf+BUF_SIZE-2) break;
 
                    /* move contents of file below current
                       location down one byte to make room
                       for the RETURN
                    */
                    memmove(curloc+1,curloc,endloc-curloc+1);
 
                    *curloc=key.ch[0];
                    curloc++;
 
                    /*clear rest of line*/
                    edit_clr_eol(scrnx,scrny);
                    scrnx=0;
                    scrny++;
 
                    /*move text on the screen down*/
                    if (scrny==MAX_LINES){
                        scrny=MAX_LINES-1;
                        scrollup(0,0,LINE_LEN,scrny);
                    }
                    else scrolldn(scrnx,scrny);
 
                    gotoxy(scrnx,scrny);
                    printline(curloc);
                    endloc++;
                    break;
 
                case '\b': /*backspace*/
                    if(curloc==buf) break;
                    left ();
                    delete_char();
                    break;
 
                case 11: /*C-K:kiil line*/
                    kill_line();
                    break;
        case 25: /*C-Y:yank kill buffer*/
                    yank();
                    break;
                default:
                    if(endloc==buf+BUF_SIZE-2) break;
 
                    /*can't type past end of line*/
                    if(scrnx==LINE_LEN) break;
                    memmove(curloc+1,curloc,endloc-curloc+1);
                    *curloc=key.ch[0];
                    putch(*curloc);
                    scrnx++;
                    gotoxy(scrnx,scrny);
                    printline(curloc+1);
                    curloc++;
                    endloc++;
            }
            gotoxy(scrnx,scrny);
        }
    }while(key.ch[0]!=26);
}
 
 
/* Display a line pointed to by P.*/
void printline(register char *p)
{
    register int i;
    i=scrnx;
    while(*p!='\r'&& *p && i<LINE_LEN){
        putch(*p);
        p++;
        i++;
    }
}
 
/*Insert previously killed line*/
void yank()
{
    char *p;
 
    p=killbuf;
    while(*p){
        memmove(curloc+1,curloc,endloc-curloc+1);
        *curloc=*p;
        if(scrnx<LINE_LEN){
            putch(*curloc);
            scrnx++;
        }
        curloc++;
        endloc++;
        p++;
    }
    printline (curloc);
}
 
/*Delete the line at the current location*/
void kill_line()
{
    register int i;
    char *p,*killbufptr;
    if(*curloc=='\r'){
        delete_char();
        return;
    }
 
    edit_clr_eol(scrnx,scrny);
 
    /*find out how many characters are in the line*/
    p=curloc;
    i=0;
    killbufptr=killbuf;
    while(*p!='\r' && p<endloc){
        i++;
        *killbufptr=*p;
        p++;
        if(killbufptr<killbuf+KILL_BUF_SIZE-2) killbufptr++;
    }
    *killbufptr='\0';
 
    /*remove the line*/
    memmove(curloc,curloc+1,endloc-curloc);
    endloc-=i;
}
 
 
/*Global search and replace*/
void replace()
{
    register int len1;
    char str1[80],str2[80];
    char *p,*p2;
 
    clrline(MAX_LINES);
    gotoxy(0,MAX_LINES);
    printf("enter string to replace: ");
    edit_gets(str1);
 
    clrline(MAX_LINES);
    gotoxy(0,MAX_LINES);
    printf ("enter replacement: ");
    edit_gets(str2);
 
    p=curloc;
    len1=strlen(str1);
 
    while(*str1){
        /*search for a string*/
    while(*p && strncmp(str1,p,len1)) p++;
        if (!p) break;
 
        /*remove old string*/
        memmove(p,p+len1,endloc-p);
        endloc-=len1;
 
        /*insert new string*/
        p2=str2;
        while(*p2){
            memmove(p+1,p,endloc-p+1);
            *p=*p2;
            p++;
            endloc++;
            p2++;
        }
    }
    clrscr();
 
    /*find location of top of screen*/
    p=curloc;
    for(len1=scrny;len1>=0&&p>buf;){
        p--;
        if(*p=='\r') len1--;
    }
    if(*p=='\r') p++;
 
    /*redisplay current screen*/
    display_scrn(0,0,p);
    help();
}
 
 
/*Delete character at the current location.*/
void delete_char()
{
    gotoxy(scrnx,scrny);
    if(*curloc=='\r'){
        scrollup(0,scrny+1,LINE_LEN,MAX_LINES-1);
        memmove(curloc,curloc+1,endloc-curloc);
        endloc--;
        display_scrn(scrnx,scrny,curloc);
        help();
    }
    else{
        memmove(curloc,curloc+1,endloc-curloc);
        endloc--;
    printline(curloc); printf(" ");
    }
}
 
 
/*Display help line*/
void help()
{
    gotoxy(0,MAX_LINES);
    printf(helpline);
}
 
/*Move current location left*/
void left()
{
    if(curloc==buf) return;
    scrnx--;
    if(scrnx<0){
        scrnx=0;
        upline();
        /*find end of line*/
        while(*curloc!='\r'){
            curloc++;
            scrnx++;
        }
    }
    else curloc--;
}
 
 
/*Move currrent position right*/
void right()
{
    /*can't move rihgt*/
    if(curloc+1>endloc) return;
 
    scrnx++;
 
    /*if at end of line,go to next one*/
    if(scrnx>LINE_LEN||*curloc=='\r'){
        scrnx=0;
        scrny++;
        if(scrny==MAX_LINES){
            scrny=MAX_LINES-1;
            downline();
 
            /*move cursor and current loc to start
             of new line*/
            curloc--;
            while(*curloc!='\r') curloc--;
            curloc++;
            scrnx=0;
        }
        else curloc++;
    }
    else curloc++;
}
 
/*Find a string*/
void search()
{
    char str[80];
    register char *p;
    int len,i;
 
    clrline(MAX_LINES);
    gotoxy(0,MAX_LINES);
    printf("search string: ");
    edit_gets(str);
    if(!*str) return;
 
    p=curloc;
    len=strlen(str);
 
    /*search for the string*/
    while(*p && strncmp(str,p,len)) p++;
    if(!*p) return;
 
    /*back up to start of line*/
    i=0;
    while(p>buf&&*p!='\r'){
        p--;
        i++;
    }
    p++;
    i--;
 
    /*reposition current location to start of match*/
    curloc=p+i;
    scrnx=i;
    scrny=0;
 
    /*diplay screenof text at location of match*/
    clrscr();
    display_scrn(0,0,p);
    help();
}
 
/*Move up one line.*/
void upline()
{
    register int i;
    char *p;
    if(curloc==buf) return;
 
    p=curloc;
 
    if(*p=='\r') p--;
 
    /*back up loacator to start of current line.*/
    for(;*p!='\r'&&p>buf;p--);
    if(*p!='\r') return;
    curloc=p;
    curloc--;
    i=scrnx;
 
    /*find start of next line*/
    while(*curloc!='\r' && curloc>=buf) curloc--;
    scrny--;scrnx=0;
    curloc++;
 
    /*at top of screen,must scroll up*/
    if(scrny<0){
        scrolldn(0,0);
        scrny=0;
        gotoxy(0,0);
        printline(curloc);
    }
 
    /* position the cursor and current location at
     same scrnx position as previous line if possible*/
    while(i&& *curloc!='\r'){
        curloc++;
        scrnx++;
        i--;
    }
}
 
 
/* Move down one line. */
void downline()
{
    register int i;
    char *p;
    i=scrnx;
    p=curloc;
 
    /* advance current location to start to next line*/
    while(*p!='\r' && p<endloc) p++;
    if(p==endloc) return;
    p++;
    curloc=p;
    scrny++;scrnx=0;
 
    /*if moving down past the bottom of the screen*/
    if(scrny==MAX_LINES){
        scrny=MAX_LINES-1;
        scrollup(0,0,LINE_LEN,MAX_LINES-1);
        gotoxy(scrnx,scrny);
        printline(curloc);
    }
 
    /* advance to corresponding character in next line*/
    while(i && *curloc!='\r' && curloc<endloc){
        curloc++;
        scrnx++;
        i--;
    }
}
 
 
/* Display a screen full of text(up to 24lines)
   starting at the specified location.
*/
void display_scrn(int x,int y,char *p)
{
    register int i;
    gotoxy(x,y);
 
    i=0;
    while(y<MAX_LINES && *p){
        switch(*p){
            case '\r':printf("\n");
                y++;
                i=0;
                break;
            default:if(i<LINE_LEN) putch(*p);
                i++;
        }
        p++;
    }
}
 
 
/* Page down MAX_LINES lines.*/
void pagedown()
{
    register int i;
 
    clrscr();
 
    /*count down MAX_LINES lines.*/
    for(i=0;i<MAX_LINES && curloc<endloc;){
        if (*curloc=='\r') i++;
        curloc++;
    }
    help();
    scrnx=0;scrny=0;
    display_scrn(0,0,curloc);
}
 
/* Page up MAX_LINES lines*/
void pageup()
{
    register int i;
 
    clrscr();
    if (*curloc=='\r' && curloc>buf) curloc--;
 
    /* go back MAX_LINES in buffer*/
    for(i=0;i<MAX_LINES+1 && curloc>buf;){
        if(*curloc=='\r') i++;
        curloc--;
    }
    if(i==MAX_LINES+1) curloc+=2;
 
    help();
    scrnx=0;scrny=0;
    display_scrn(0,0,curloc);
}
 
 
/* Go to the top of the file.*/
void home()
{
    clrscr();
    curloc=buf;
    scrnx=scrny=0;
    display_scrn(0,0,curloc);
    help();
}
 
/*  Go to the end of the file. */
void gotoend()
{
    clrscr();
    curloc=endloc;
    pageup();
}
 
/* Load a file.*/
load(char *fname)
{
    FILE *fp;
    char ch,*p;
 
    if((fp=fopen(fname,"rb"))==NULL)
        return 0;
 
    p=buf;
    while(!feof(fp) && p!=buf+BUF_SIZE-2){
        ch=getc(fp);
        if(ch!='\n' && ch!=EOF){
        *p=ch;
            p++;
        }
    }
    *p='\0';
    fclose (fp);
    curloc=buf;
    endloc=p;
    return 1;
}
 
/* Save a file.*/
save(char *fname)
{
    FILE *fp;
    char *p,name[80];
 
    if(!*fname){
        printf("filename: ");
        gets(name);
    }
    else strcpy(name,fname);
 
    if((fp=fopen(name,"wb"))==NULL)
        return 0;
 
    p=buf;
    while(p!=endloc){
        if(*p!='\r')
            putc(*p,fp);
        else{
            putc('\r',fp);
            putc('\n',fp);
        }
        p++;
    }
    fclose(fp);
    return 1;
}
 
 
/* Read a string from the keyboard,but do not
   scroll the display when a RETURN is entered.
*/
void edit_gets(char *str)
{
    char *p;
 
    p=str;
 
    for(;;){
        *str=getch();
        if(*str=='\r'){
            *str='\0';
            return;
        }
        if(*str=='\b'){
            if(str>p){
        str--;
        putch('\b');
        putch(' ');
        putch('\b');
            }
        }
        else{
            putch(*str);
            str++;
        }
    }
}
 
 
/* Read and save cursor coordinates.*/
void cursor_pos()
{
    union REGS i,o;
    i.h.bh=0;
    i.h.ah=3;
    int86(16,&i,&o);
}
 
/* Send cursor to specified X,Y (0,0 is
   Upper left corner.
*/
void gotoxy(int x,int y)
{
    union REGS i;
 
    i.h.dh=y;
    i.h.dl=x;
    i.h.ah=2;
    i.h.bh=0;
    int86(16,&i,&i);
}
 
/* Clear entire line given its Y coordinate.*/
void clrline(int y)
{
    register int i;
 
    gotoxy(0,y);
    for(i=0;i<LINE_LEN;i++) putch(' ');
}
 
/* Clear to end of specified line.*/
void edit_clr_eol(int x,int y)
{
    char *p;
 
    p=curloc;
    gotoxy(x,y);
    for(;x<LINE_LEN && *p!='\r' && *p;x++,p++){
        printf(" ");
    }
}
 
/* Clear the screen.*/
void clrscr()
{
    union REGS r;
    r.h.ah=6;
    r.h.al=0;
    r.h.ch=0;
    r.h.cl=0;
    r.h.dh=MAX_LINES;
    r.h.dl=LINE_LEN;
    r.h.bh=7;
    int86(0x10,&r,&r);
}
 
/*Scroll down the screen.*/
void scrolldn(int x,int y)
{
    union REGS r;
 
    r.h.ah=7;
    r.h.al=1;
    r.h.ch=y;
    r.h.cl=x;
    r.h.dh=MAX_LINES-1;
    r.h.dl=LINE_LEN;
    r.h.bh=7;
    int86(0x10,&r,&r);
}
 
/* Scroll up the screen using the specified coordinate.*/
void scrollup(int topx,int topy,int endx,int endy)
{
    union REGS r;
 
    r.h.ah=6;
    r.h.al=1;
    r.h.ch=topy;
    r.h.cl=topx;
    r.h.dh=endy;
    r.h.dl=endx;
    r.h.bh=7;
    int86(0x10,&r,&r);
}