vi っぽいテキストエディタを 120 行で作る

#include <ctype.h>
#include <curses.h>
#define T isspace(*(t=Z(p)))&&
#define V return
#define _ while
int d,i,j,m,n,p,q,x,y;char*c,b[BUF],*f,*g=b,*h,k[]="hjklHJKL[]tbixWRQ",*t;
char*Z(a){if(a<0)V b;V b+a+(b+a<g?0:h-g);}P(a)char*a;{V
a-b-(a<h?0:h-g);}S(){p=0;}bf(){n=p=P(c);}Q(){q=1;}C(){clear();Y();}
G(){t=Z(p);_(t<g)*--h= *--g;_(h<t)*g++= *h++;p=P(h);}B(){_(!T b<t)--p;_(T
b<t)--p;}M(a){_(b<(t=Z(--a))&&*t-'\n');V
b<t?++a:0;}N(a){_((t=Z(a++))<c&&*t-'\n');V
t<c?a:P(c);}A(a,j){i=0;_((t=Z(a))<c&&*t-'\n'&&i<j){i+= *t-'\t'?1:8-(i&7);++a;}V
a;}L(){0<p&&--p;}R(){p<P(c)&&++p;}U(){p=A(M(M(p)-1),x);}
D(){p=A(N(p),x);}H(){p=M(p);}E(){p=N(p);L();}
J(){m=p=M(n-1);_(0<y--)D();n=P(c);}K(){j=d;_(0<--j)m=M(m-1),U();}
I(){G();_((j=getch())-'\f'){if(j-'\b')g-h&&(*g++=j-'\r'?j:'\n');else
b<g&&--g;p=P(h);Y();}}X(){G();p=h<c?P(++h):p;}
F(){j=p;p=0;G();write(i=creat(f,MODE),h,(int)(c-h));close(i);p=j;}W(){_(!T
t<c)++p;_(T
t<c)++p;}int(*z[])()={L,D,U,R,B,J,K,W,H,E,S,bf,I,X,F,C,Q,G};
Y(){m=p<m?M(p):m;if(n<=p){m=N(p);i=m-P(c)?d:d-2;_(0<i--)m=M(m-1);}
move(0,0);i=j=0;n=m;_(1){p-n||(y=i,x=j);t=Z(n);if(d<=i||c<=t)break;
if(*t-'\r')addch(*t),j+= *t-'\t'?1:8-(j&7);if(*t=='\n'||COLS<=j)
++i,j=0;++n;}clrtobot();++i<d&&mvaddstr(i,0,"<< EOF >>");move(y,x);
refresh();}main(u,v)char**v;{h=c=b+BUF;if(u<2)V
2;initscr();d=LINES;raw();noecho();idlok(stdscr,1);if(0<(i=open(f= *++v,0))){
g+=read(i,b,BUF);g=g<b?b:g;close(i);}S();_(!q){Y();i=0;j=getch();
_(k[i]&&j-k[i])++i;(*z[i])();}endwin();V 0;}

// ae2019.cpp	Anthony's Editor 2019.
// compile: g++ -std=c++1z ae2019.cpp -lcurses
#include <curses.h>
#include <fstream>
#include <vector>
#include <unordered_map>

using namespace std;
enum { kESC=27,kBS=8,kDEL=127,kCtrlD=4,kCtrlU=21,kCtrlR=18,kCtrlS=19,kCtrlQ=17, };
const char *gFileName;
vector<char> gBuf;
bool gDone=false;
int gIndex=0 /* offset of cursor pos */,gPageStart=0,gPageEnd=0;
int gCol,gRow;

int lineTop(const int inOffset) {
	int offset=inOffset-1;
	while(offset>=0 && gBuf[offset]!='\n') { offset--; }
	return offset<=0 ? 0 : ++offset;
}
int nextLineTop(const int inOffset) {
	int offset=inOffset;
	while(offset<gBuf.size() && gBuf[offset++]!='\n') { /* empty */ }
	return offset<gBuf.size() ? offset : gBuf.size()-1;
}

int adjust(const int inOffset,const int inCol) {
	int offset=inOffset;
	for(int i=0; offset<gBuf.size() && gBuf[offset]!='\n' && i<inCol; offset++) {
		i += gBuf[offset]=='\t' ? 8-(i&7) : 1;
	}
	return offset;
}

void display() {
	if(gIndex<gPageStart) { gPageStart=lineTop(gIndex); }
	if(gPageEnd<=gIndex) {
		gPageStart=nextLineTop(gIndex);
		int n = gPageStart==gBuf.size()-1 ? LINES-2 : LINES;
		for(int i=0; i<n; i++) { gPageStart=lineTop(gPageStart-1); }
	}
	move(0,0);
	int i=0, j=0;
	gPageEnd=gPageStart;
	for(auto p=gBuf.begin()+gPageEnd; /*empty */; gPageEnd++,p++) {
		if(gIndex==gPageEnd) { gRow=i; gCol=j; }	// update cursor pos.
		if(LINES<=i || gBuf.size()<=gPageEnd) { break; }
		if(*p!='\r') { addch(*p); j += *p=='\t' ? 8-(j&7) : 1; }
		if(*p=='\n' || COLS<=j) { ++i; j=0; }
	}
	clrtobot();
	if(++i<LINES) { mvaddstr(i,0,"<< EOF >>"); }
	move(gRow,gCol);
	refresh();
}

void left() { if(0<gIndex) { --gIndex; } }
void right(){ if(gIndex<gBuf.size()) { ++gIndex; }}
void up()   { gIndex=adjust(lineTop(lineTop(gIndex)-1),gCol); }
void down() { gIndex=adjust(nextLineTop(gIndex),gCol); }
void lineBegin() { gIndex=lineTop(gIndex); }
void lineEnd()	 { gIndex=nextLineTop(gIndex); left(); }
void top()  	 { gIndex=0; }
void bottom()	 { gIndex=gBuf.size()-1; }
void del()    { if(gIndex<gBuf.size()-1) { gBuf.erase(gBuf.begin()+gIndex); } }
void quit()   { gDone=true; }
void redraw() { clear(); display(); }

static void insert() {
	for(int ch; (ch=getch())!=kESC; display()) { 
		if(gIndex>0 && (ch==kBS || ch==kDEL)) {
			--gIndex; gBuf.erase(gBuf.begin()+gIndex);
		} else {
			gBuf.insert(gBuf.begin()+gIndex,ch=='\r' ? '\n' : ch);
			gIndex++;
		}
	}
}

void wordLeft() {
	while(!isspace(gBuf[gIndex]) && 0<gIndex) { --gIndex; }
	while( isspace(gBuf[gIndex]) && 0<gIndex) { --gIndex; } 
}
void wordRight() {
	while(!isspace(gBuf[gIndex]) && gIndex<gBuf.size()) { ++gIndex; }
	while( isspace(gBuf[gIndex]) && gIndex<gBuf.size()) { ++gIndex; }
}
void pageDown() {
	gPageStart=gIndex=lineTop(gPageEnd-1);
	while(0<gRow--) { down(); }
	gPageEnd=gBuf.size()-1;
}
void pageUp() { for(int i=LINES; 0<--i; up()) { gPageStart=lineTop(gPageStart-1); } }

void save() {
	ofstream ofs(gFileName,ios::binary);
	ostream_iterator<char> output_iterator(ofs);
    copy(gBuf.begin(),gBuf.end(),output_iterator);
}

unordered_map<char,void(*)()> gAction={
	{'h',left},{'l',right},{'k',up},{'j',down},
	{'b',wordLeft},{'w',wordRight},{kCtrlD,pageDown},{kCtrlU,pageUp},
	{'0',lineBegin},{'$',lineEnd},{'t',top},{'G',bottom},
	{'i',insert},{'x',del},{kCtrlQ,quit},{kCtrlR,redraw},{kCtrlS,save},
};

int main(int argc,char **argv) {
	if(argc<2) { return 2; }
	initscr(); raw(); noecho(); idlok(stdscr,true);	// init screen.
	gFileName=argv[1]; ifstream ifs(gFileName,ios::binary);
	gBuf.assign(istreambuf_iterator<char>(ifs),istreambuf_iterator<char>());
	while(!gDone) {
		display();
		char ch=getch(); if(gAction.count(ch)>0) { gAction[ch](); }
	}
	endwin();
	return 0;
}

i = 0;
ch = getch();
while (key[i] != '\0' && ch != key[i])
    ++i;
(*func[i])();

char ch=getch();
if(gAction.count(ch)>0) { gAction[ch](); }

void lineBegin() { gIndex=lineTop(gIndex); }

void down() { gIndex=adjust(nextLineTop(gIndex),gCol); }

void up()   { gIndex=adjust(lineTop(lineTop(gIndex)-1),gCol); }

void pageDown() {
    gPageStart=gIndex=lineTop(gPageEnd-1);
    while(0<gRow--) { down(); }
    gPageEnd=gBuf.size()-1;
}
void pageUp() { for(int i=LINES; 0<--i; up()) { gPageStart=lineTop(gPageStart-1); } }