edit.c

#define BUFFER_SIZE (32 * 1024)
#define COLOR 1 /* 0 for gray highlighting */

#if 0
   ----- crude text editor (doesn't read or write to disk yet) -----

   * inserts or deletes one character at a time into fixed-width buffer
   * internally a simple buffer, but user interface is line oriented...
   * displays text intermittantly, not a problem but limited screen space is
   * many improvements required to be usable... good luck!

#endif

#include <stdio.h>
#include <stdlib.h> /* exit() */
#include <ctype.h>  /* toupper(), tolower() */

char a[BUFFER_SIZE], b[BUFFER_SIZE];
char *buff, *scratch;
int pos, len;
int cmd_mode;

#define DIM  "\033[2m"
#define NORM "\033[0m"

#if COLOR
  #define HIGH "\033[1;31m" // bold red, that should do
  // #define HIGH "\033[35m" // try magenta...
  // #define HIGH "\033[30;41m" // black on red, stands out better
  // #define HIGH "\033[31m" // red
  #define CTRL "\033[34m" // blue
  #define LINE "\033[33m" // yellow
#else
  #define HIGH DIM
  #define CTRL DIM
  #define LINE DIM
#endif

#define RUB (-1)

/* needs up/down line, goto line, string search-find. some of those need input entry */
/* needs to read and save to file! input entry for filename might be needed          */

enum {
    cQuit=(int)'Q',
    cBack=(int)'B',
    cForward=(int)'F',
    cLit=(int)'V',
    cNewline=(int)'L',
    cRub=(int)'X',
    CMD=(int)'.'
};

void fBack();
void fFoward();
void fLit();
void fEsc();
void insert(int c); /* default action */

void fBack()   { if(pos > 0)   pos--; return; }
void fForward() { if(pos < len) pos++; return; }
void fLit(int *c) { *c = getc(stdin); if(*c != EOF) insert(*c); return; }

/* we swap buffers, with one char inserted (or one char skipped)                   */
/* it might be better to shift text in-place within one buffer, without swapping   */
/* it would be good to collect input text in a small buffer and insert all at once */
/* or port to a language with builtin string functions and use those to insert     */

void insert(int c) {
    char *tmp;
    int i, x, y;

    if(c == RUB && (len-pos) == 0) return;
    if(c != RUB && len == BUFFER_SIZE) return;

    x = 0;
    for(i = 0; i < pos; i++) scratch[x++] = buff[i];

    if(c != RUB) { scratch[x++] = c; y = pos; }
    else { y = pos + 1; }

    for(i = y; i < len; i++) scratch[x++] = buff[i];

    len = x;
    if(c != RUB) pos++;

    tmp = buff; buff = scratch; scratch = tmp;
    return;
}

void p_item(int c, char *txt) {
    int i;
    for(i = 0; txt[i] != '\0'; i++) {
        if(txt[i] == '~') printf("%s%c%s", CTRL, c, NORM);
        else printf("%c", txt[i]);
    }
    return;
}

/* dumps whole buffer, better to display lines new cursor when or else overrun screen */
/* when reasonable no. of lines fixed, maybe show extra info above + below text view  */

void display() {
    int i, c, prev, lineno;
    char *cchars = "@ABCDEFGHIJKLMNOPQRSTUVWXYZ[\\]^_";

    c = '\n';
    lineno = 0;

    for(i = 0; i < len; i++) {

        prev = c; c = buff[i];

        if(prev == '\n') {
            lineno++;
            printf("%s%4d%s ", LINE, lineno, NORM);
        }

        if(i == pos) printf("%s^%s", HIGH, NORM);

        if(c == '\n') printf("%s%c%s\n", CTRL, '$', NORM);
        else if(c < 32) printf("%s^%c%s", CTRL, cchars[c], NORM);
        else if(c >= 0x7f) printf("%s\\x%02x%s", CTRL, c, NORM);
        else printf("%c", c);
    }

    if(pos == len) {
        if(c == '\n') printf("%s%4d %s^%s", CTRL, lineno+1, HIGH, NORM);
        else printf("%s%c%s", HIGH, '^', NORM);
    }

    printf("\n");

    /* context sensitive help should be own function... */

    if(cmd_mode) {

        printf("[%d/%d] (cmd) ", pos, len);

        p_item(cQuit, "~uit ");
        p_item(cBack, "~ack "); p_item(cForward, "~orward ");
        p_item(cLit, "~=literal "); p_item(cNewline, "new~ine ");
        p_item(cRub, "~=delete ");

        p_item(CMD, "| '~' return to edit\n");

    }
    else {
        printf("[%d/%d] (edit) ", pos, len);
        p_item(CMD, "press '~' to enter cmd mode, ");
        printf("'%s%c%c%s' for a '%c', ", CTRL, CMD, CMD, NORM, CMD);
        printf("'%s%c%c%s' for newline\n", CTRL, CMD, cNewline, NORM);
    }
    return;
}

int main() {
    int c, n;

    buff = a; scratch = b;
    pos = 0; len = 0;
    cmd_mode = 0;

    display();
    c = getc(stdin);
    n = 0;

    while(c != EOF) {

        if(cmd_mode == 0) {
            if(c == CMD) { cmd_mode = 1; n = 0; }
            else if(c == '\n') display();
            else { insert(c); }
        }

        else {
            c = toupper(c);
            n++;
            switch(c) {
                case cQuit:    exit(0); break;
                case cBack:    fBack(); break;
                case cForward: fForward(); break;
                case cLit:     fLit(&c); if(c == '\n') display(); break;
                case cNewline: insert('\n'); if(n == 1) cmd_mode = 0; break;
                case cRub:     insert(RUB); break;
                case CMD:      if(n == 1) insert(CMD); cmd_mode = 0; break;

                case '\n': display(); break;
                default: /* ignore */ ;
            };
        }

        c = getc(stdin);
    }
    return 0;
}