/*
	e screen editor

	(C) G. Nigel Gilbert, MICROLOGY, 1981

	August-December 1981

	FILE: e8

	FUNCTIONS: loc,gettext,getline,inject,deltp,puttext,readtext,getc,
			opentext,balloc,error

	PURPOSE: get and put text lines into and out of storage

*/

#include "e.h"

loc(line,move)	/*returns line+move, adjusted to be within text*/
int line, move;
{
	int y;

	if ( (y=line+move) < 1) y=1;
	if (lastl == UNKNOWN && y > lastread) readtext(y);
	if (y > lastl) return lastl;
	return y;
}

gettext(line)	/*makes 'line' the current line*/
int line;
{
	strcpy(text,getline(line));
	cline=line;
}

char *getline(line)	/*returns address of text of line 'line' and updates
		  	  page usage*/
int line;
{
	int slot;

	line=loc(line,0);
	if ( (slot=pageloc[tp[line].page]) <= 0)
		slot=swappin(tp[line].page);
	if (usage[slot] > FREE) usage[slot]=++clock;
	return slotaddr[slot] + tp[line].moffset;
}

inject(line,txt)	/* inserts 'txt' after 'line' */
int line;
char *txt;
{
	int l, p, balloc();
	struct addr anaddr;

	if ( &tp[lastread+2] >= slotaddr[tppages]) {
		/*need another slot to store tp's in */
		if (tppages+2 == slotsinmem) {
			error("Too many lines of text");
			return FAIL;
			}
		if (usage[tppages] == NOTAVAIL) /*ie page is being alloc'ed into*/
			allocp=PAGESIZE+1; /*force alloc into new page*/
		swapout(tppages);
		usage[tppages++]=NOTAVAIL;
		}
	if (++line < ++lastread)
		movmem(&tp[line],&tp[line+1],(lastread-line)*sizeof(anaddr));
	tp[line].moffset=p=balloc(1+strlen(txt));
	tp[line].page=newpage;
	strcpy(p+npaddr,txt);
	if (lastl != UNKNOWN)lastl++;
	return line;
}

deltp(from,num)	/*deletes 'num' lines from 'from' onwards by shifting pointers*/
int from, num;
{
	struct addr anaddr;

	movmem(&tp[from+num],&tp[from],(lastread+1-(from+num))*sizeof(anaddr));
	if (lastl != UNKNOWN) lastl-=num;
	lastread-=num;
	if (lastl < 1)lastl=1;
	if (lastread < 1)lastread=1;
}

puttext()	/*replaces cline's text if it has been altered*/
{
	int p, cp, balloc();

	if (altered) {
		if (!trail) {
			for (cp=strlen(text)-1; cp >= 0 && isspace(text[cp]);
				 cp--) text[cp]='\0';
			}
		tp[cline].moffset=p=balloc(1+strlen(text));
		tp[cline].page=newpage;
		strcpy(p+npaddr,text);
		altered=NO;
		}
}

readtext(line)	/*reads file being edited into virtual memory until 'line'
		  is read, or eof.  If eof, sets lastl to number of last line
		  read.  File is assumed to be already open*/
int line;
{
	char txt[LLIM], *t;
	int i, c, l;

	while (lastread < line) {
		for (i=0, t=&txt[0]; i < LLIM && ((c=getc(textbuf)) >= ' ' ||
			c != '\n' && c != FAIL && c != ENDFILE); i++)
			    if (c) *(t++)=c;
			else i--;
		if (txt[i-1] == '\r') t--; 
		*t='\0';
		if ( (l=inject(lastread,txt)) == FAIL) goto toomuch;
		else if ((lastread=l)%100 == 0) putlineno(lastread);
		if ( (goteof= c == ENDFILE || c == FAIL) )  goto eof;
		}
	return;

eof: 
	fclose(textbuf);
toomuch: 
	lastl=lastread;
}

opentext(name)	/*open the file being edited for reading*/
char *name;
{
	if (fopen(name,textbuf) == FAIL) {
		error("Can't open file");
		name[0]='\0';
		lastl=1;
		return FAIL;
		}
	return YES;
}

balloc(n)	/*allocate and return the offset in newpage of a vector size n*/
unsigned n;
{
	sint slot;

	if (allocp  + n >= PAGESIZE) {
		/*no room in current newpage; get another*/
		if (pageloc[newpage] > 0)usage[pageloc[newpage]]=INUSE;
		pageloc[++newpage]=slot=freememslot();
		usage[slot]=NOTAVAIL;
		allocp=0; 
		npaddr=slotaddr[slot];
		}
	allocp+=n;
	return allocp-n;
}

error(message)
char *message;
{
	if (errmess != NULL) return;
	gotoxy(32,0);
	puts(errmess=message);
	resetcursor();
	inbufp=0;
}

ifting pointers*/
int from, num;
{
	struct addr anaddr;

	mov