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git/send: fix delta caching

The delta table refers to the buffer within the object,
so it should hold a reference to the object. While in
here, clean up the code a bit.

--- a/delta.c

+++ b/delta.c

@@ -124,7 +124,7 @@

 }

 void

-dtinit(Dtab *dt, void *base, int nbase)

+dtinit(Dtab *dt, Object *obj)

 {

 	uchar *s, *e;

 	u64int h;

@@ -131,13 +131,14 @@

 	vlong n, o;

 	o = 0;

-	s = base;

-	e = s + nbase;

+	s = (uchar*)obj->data;

+	e = s + obj->size;

+	dt->o = ref(obj);

 	dt->nb = 0;

 	dt->sz = 128;

 	dt->b = eamalloc(dt->sz, sizeof(Dblock));

-	dt->base = base;

-	dt->nbase = nbase;

+	dt->base = (uchar*)obj->data;

+	dt->nbase = obj->size;

 	while(s != e){

 		n = nextblk(s, e);

 		h = hash(s, n);

@@ -150,6 +151,7 @@

 void

 dtclear(Dtab *dt)

 {

+	unref(dt->o);

 	free(dt->b);

 }

@@ -190,7 +192,7 @@

 }

 Delta*

-deltify(void *targ, int ntarg, Dtab *dt, int *pnd)

+deltify(Object *obj, Dtab *dt, int *pnd)

 {

 	Delta *d;

 	Dblock *b;

@@ -199,8 +201,8 @@

 	o = 0;

 	d = nil;

-	s = targ;

-	e = s + ntarg;

+	s = (uchar*)obj->data;

+	e = s + obj->size;

 	*pnd = 0;

 	while(s != e){

 		n = nextblk(s, e);

--- a/git.h

+++ b/git.h

@@ -152,6 +152,7 @@

 };

 struct Dtab {

+	Object	*o;

 	uchar	*base;

 	int	nbase;

 	Dblock	*b;

@@ -287,9 +288,9 @@

 int	showprogress(int, int);

 /* packing */

-void	dtinit(Dtab *, void *, int);

+void	dtinit(Dtab *, Object*);

 void	dtclear(Dtab*);

-Delta*	deltify(void*, int, Dtab*, int*);

+Delta*	deltify(Object*, Dtab*, int*);

 /* proto handling */

 int	readpkt(Conn*, char*, int);

--- a/pack.c

+++ b/pack.c

@@ -25,8 +25,7 @@

 	/* The best delta we picked */

 	Meta	*head;

-	Meta *prev;

-	Object	*base;

+	Meta	*prev;

 	Delta	*delta;

 	int	ndelta;

 	int	nchain;

@@ -516,7 +515,6 @@

 		werrstr("object too big");

 		return -1;

 	}

-

 	switch(t){

 	default:

 		werrstr("invalid object at %lld", Boffset(f));

@@ -1361,7 +1359,6 @@

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

 		m = meta[i];

 		pct = showprogress((i*100) / nmeta, pct);

-		m->base = nil;

 		m->delta = nil;

 		m->ndelta = 0;

 		if(m->obj->type == GCommit || m->obj->type == GTag)

@@ -1368,16 +1365,16 @@

 			continue;

 		if((o = readobject(m->obj->hash)) == nil)

 			sysfatal("readobject %H: %r", m->obj->hash);

-		best = o->size;

-		dtinit(&m->dtab, o->data, o->size);

+		dtinit(&m->dtab, o);

 		if(i >= 11)

 			dtclear(&meta[i-11]->dtab);

+		best = o->size;

 		for(j = max(0, i - 10); j < i; j++){

 			p = meta[j];

 			/* long chains make unpacking slow */

 			if(p->nchain >= 128 || p->obj->type != o->type)

 				continue;

-			d = deltify(o->data, o->size, &p->dtab, &nd);

+			d = deltify(o, &p->dtab, &nd);

 			sz = deltasz(d, nd);

 			if(sz + 32 < best){

 				/*

@@ -1393,9 +1390,6 @@

 				m->head = p->head;

 				if(m->head == nil)

 					m->head = p;

-				if((m->base = readobject(p->obj->hash)) == nil)

-					sysfatal("readobject %H: %r", p->obj->hash);

-				unref(m->base);

 			}else

 				free(d);

 		}

@@ -1564,7 +1558,7 @@

 	DigestState *st;

 	Biobuf *bfd;

 	Meta *m;

-	Object *o;

+	Object *o, *b;

 	char *p, buf[32];

 	st = nil;

@@ -1587,8 +1581,9 @@

 	if(interactive)

 		fprint(2, "writing %d objects:   0%%", nmeta);

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

-		m = meta[i];

 		pct = showprogress((i*100)/nmeta, pct);

+		m = meta[i];

+		m->off = Boffset(bfd);

 		if((o = readobject(m->obj->hash)) == nil)

 			return -1;

 		if(m->delta == nil){

@@ -1597,8 +1592,9 @@

 			if(hcompress(bfd, o->data, o->size, &st) == -1)

 				goto error;

 		}else{

-			m->off = Boffset(bfd);

-			nd = encodedelta(m, o, m->base, &p);

+			b = readobject(m->prev->obj->hash);

+			nd = encodedelta(m, o, b, &p);

+			unref(b);

 			if(odelta && m->prev->off != 0){

 				nh = 0;

 				nh += packhdr(buf, GOdelta, nd);

@@ -1607,7 +1603,7 @@

 			}else{

 				nh = packhdr(buf, GRdelta, nd);

 				hwrite(bfd, buf, nh, &st);

-				hwrite(bfd, m->base->hash.h, sizeof(m->base->hash.h), &st);

+				hwrite(bfd, m->prev->obj->hash.h, sizeof(m->prev->obj->hash.h), &st);

 			}

 			res = hcompress(bfd, p, nd, &st);

 			free(p);