page: add caching from Plan 9

http://codereview.appspot.com/105070

cmd/page/cache.c

@@ -0,0 +1,196 @@
+#include <u.h>
+#include <libc.h>
+#include <draw.h>
+#include <cursor.h>
+#include <event.h>
+#include <bio.h>
+#include <plumb.h>
+#include <ctype.h>
+#include <keyboard.h>
+#include <thread.h>
+#include "page.h"
+
+typedef struct Cached Cached;
+struct Cached
+{
+	Document *doc;
+	int page;
+	int angle;
+	Image *im;
+};
+
+static Cached cache[5];
+static int rabusy;
+
+static Image*
+questionmark(void)
+{
+	static Image *im;
+
+	if(im)
+		return im;	
+	im = xallocimage(display, Rect(0,0,50,50), GREY1, 1, DBlack);
+	if(im == nil)
+		return nil;
+	string(im, ZP, display->white, ZP, display->defaultfont, "?");
+	return im;
+}
+
+void
+cacheflush(void)
+{
+	int i;
+	Cached *c;
+
+	for(i=0; i<nelem(cache); i++){
+		c = &cache[i];
+		if(c->im)
+			freeimage(c->im);
+		c->im = nil;
+		c->doc = nil;
+	}
+}
+
+static Image*
+_cachedpage(Document *doc, int angle, int page, char *ra)
+{
+	int i;
+	Cached *c, old;
+	Image *im, *tmp;
+
+	if((page < 0 || page >= doc->npage) && !doc->fwdonly)
+		return nil;
+
+Again:
+	for(i=0; i<nelem(cache); i++){
+		c = &cache[i];
+		if(c->doc == doc && c->angle == angle && c->page == page){
+			if(chatty) fprint(2, "cache%s hit %d\n", ra, page);
+			goto Found;
+		}
+		if(c->doc == nil)
+			break;
+	}
+
+	if(i >= nelem(cache))
+		i = nelem(cache)-1;
+	c = &cache[i];
+	if(c->im)
+		freeimage(c->im);
+	c->im = nil;
+	c->doc = nil;
+	c->page = -1;
+
+	if(chatty) fprint(2, "cache%s load %d\n", ra, page);
+	im = doc->drawpage(doc, page);
+	if(im == nil){
+		if(doc->fwdonly)	/* end of file */
+			wexits(0);
+		im = questionmark();
+		if(im == nil){
+		Flush:
+			if(i > 0){
+				cacheflush();
+				goto Again;
+			}
+			fprint(2, "out of memory: %r\n");
+			wexits("memory");
+		}
+		return im;
+	}
+
+	if(im->r.min.x != 0 || im->r.min.y != 0){
+		/* translate to 0,0 */
+		tmp = xallocimage(display, Rect(0, 0, Dx(im->r), Dy(im->r)), im->chan, 0, DNofill);
+		if(tmp == nil){
+			freeimage(im);
+			goto Flush;
+		}
+		drawop(tmp, tmp->r, im, nil, im->r.min, S);
+		freeimage(im);
+		im = tmp;
+	}
+
+	switch(angle){
+	case 90:
+		im = rot90(im);
+		break;
+	case 180:
+		rot180(im);
+		break;
+	case 270:
+		im = rot270(im);
+		break;
+	}
+	if(im == nil)
+		goto Flush;
+
+	c->doc = doc;
+	c->page = page;
+	c->angle = angle;
+	c->im = im;
+
+Found:
+	if(chatty) fprint(2, "cache%s mtf %d @%d:", ra, c->page, i);
+	old = *c;
+	memmove(cache+1, cache, (c-cache)*sizeof cache[0]);
+	cache[0] = old;
+	if(chatty){
+		for(i=0; i<nelem(cache); i++)
+			fprint(2, " %d", cache[i].page);
+		fprint(2, "\n");
+	}
+	if(chatty) fprint(2, "cache%s return %d %p\n", ra, old.page, old.im);
+	return old.im;
+}
+
+static void
+raproc(void *a)
+{
+	Cached *c;
+	
+	c = a;
+	lockdisplay(display);
+	_cachedpage(c->doc, c->angle, c->page, "-ra");
+	rabusy = 0;
+	unlockdisplay(display);
+	free(c);
+	threadexits(0);
+}
+
+Image*
+cachedpage(Document *doc, int angle, int page)
+{
+	static int lastpage = -1;
+	Cached *c;
+	Image *im;
+	int ra;
+	
+	if(doc->npage < 1)
+		return display->white;
+
+	im = _cachedpage(doc, angle, page, "");
+	if(im == nil)
+		return nil;
+
+	/* readahead */
+	ra = -1;
+	if(!rabusy){
+		if(page == lastpage+1)
+			ra = page+1;
+		else if(page == lastpage-1)
+			ra = page-1;
+	}
+	lastpage = page;
+	if(ra >= 0){
+		c = emalloc(sizeof(*c));
+		c->doc = doc;
+		c->angle = angle;
+		c->page = ra;
+		c->im = nil;
+		rabusy = 1;
+		if(proccreate(raproc, c, mainstacksize) == -1)
+			rabusy = 0;
+	}
+	return im;
+}

src/cmd/page/mkfile

@@ -4,6 +4,7 @@ TARG=page
 
 HFILES=page.h
 OFILES=\
+	cache.$O\
 	filter.$O\
 	gfx.$O\
 	gs.$O\

src/cmd/page/page.c

@@ -228,6 +228,8 @@ threadmain(int argc, char **argv)
 		fprint(2, "page: initdraw failed: %r\n");
 		wexits("initdraw");
 	}
+	display->locking = 1;
+	
 	truecolor = screen->depth > 8;
 	viewer(doc);
 	wexits(0);

src/cmd/page/page.h

@@ -96,6 +96,8 @@ void	wexits(char*);
 Image*	xallocimage(Display*, Rectangle, ulong, int, ulong);
 int	bell(void*, char*);
 Image*	convert(Graphic *g);
+Image*	cachedpage(Document*, int, int);
+void	cacheflush(void);
 
 extern int stdinfd;
 extern int truecolor;

src/cmd/page/view.c

@@ -115,55 +115,17 @@ menugen(int n)
 void
 showpage(int page, Menu *m)
 {
-	Image *tmp;
-
 	if(doc->fwdonly)
 		m->lasthit = 0;	/* this page */
 	else
 		m->lasthit = reverse ? doc->npage-1-page : page;
 	
 	setcursor(mc, &reading);
-	freeimage(im);
-	if((page < 0 || page >= doc->npage) && !doc->fwdonly){
-		im = nil;
-		return;
-	}
-	im = doc->drawpage(doc, page);
-	if(im == nil) {
-		if(doc->fwdonly)	/* this is how we know we're out of pages */
-			wexits(0);
-
-		im = xallocimage(display, Rect(0,0,50,50), GREY1, 1, DBlack);
-		if(im == nil) {
-			fprint(2, "out of memory: %r\n");
-			wexits("memory");
-		}
-		string(im, ZP, display->white, ZP, display->defaultfont, "?");
-	}else if(resizing){
+	im = cachedpage(doc, angle, page);
+	if(im == nil)
+		wexits(0);
+	if(resizing)
 		resize(Dx(im->r), Dy(im->r));
-	}
-	if(im->r.min.x > 0 || im->r.min.y > 0) {
-		tmp = xallocimage(display, Rect(0, 0, Dx(im->r), Dy(im->r)), im->chan, 0, DNofill);
-		if(tmp == nil) {
-			fprint(2, "out of memory during showpage: %r\n");
-			wexits("memory");
-		}
-		drawop(tmp, tmp->r, im, nil, im->r.min, S);
-		freeimage(im);
-		im = tmp;
-	}
-
-	switch(angle){
-	case 90:
-		im = rot90(im);
-		break;
-	case 180:
-		rot180(im);
-		break;
-	case 270:
-		im = rot270(im);
-		break;
-	}
 
 	setcursor(mc, nil);
 	if(showbottom){
@@ -268,7 +230,7 @@ void
 viewer(Document *dd)
 {
 	int i, fd, n, oldpage;
-	int nxt;
+	int nxt, a;
 	Channel *cp;
 	Menu menu, midmenu;
 	Mouse m;
@@ -372,7 +334,10 @@ viewer(Document *dd)
 		 * a fair amount.  we don't care about doc->npage anymore, and
 		 * all that can be done is select the next page.
 		 */
-		switch(alt(alts)) {
+		unlockdisplay(display);
+		a = alt(alts);
+		lockdisplay(display);
+		switch(a) {
 		case CKeyboard:
 			if(run <= 0xFF && isdigit(run)) {
 				nxt = nxt*10+run-'0';
@@ -622,22 +587,12 @@ viewer(Document *dd)
 						break;
 					}
 				case Rot:	/* rotate 90 */
-					setcursor(mc, &reading);
-					im = rot90(im);
-					setcursor(mc, nil);
 					angle = (angle+90) % 360;
-					redraw(screen);
-					flushimage(display, 1);
+					showpage(page, &menu);
 					break;
 				case Upside: 	/* upside-down */
-					if(im==nil)
-						break;
-					setcursor(mc, &reading);
-					rot180(im);
-					setcursor(mc, nil);
 					angle = (angle+180) % 360;
-					redraw(screen);
-					flushimage(display, 1);
+					showpage(page, &menu);
 					break;
 				case Restore:	/* restore */
 					showpage(page, &menu);