1 files changed, 159 insertions, 0 deletions
diff --git a/sys/src/cmd/hgfs/patch.c b/sys/src/cmd/hgfs/patch.c
new file mode 100644
index 000000000..a3d6ef37a
--- /dev/null
+++ b/sys/src/cmd/hgfs/patch.c
@@ -0,0 +1,159 @@
+#include <u.h>
+#include <libc.h>
+#include <thread.h>
+#include "dat.h"
+#include "fns.h"
+
+int
+fcopy(int dfd, int sfd, vlong len)
+{
+	uchar buf[BUFSZ];
+	int n;
+
+	while(len > 0){
+		if((n = BUFSZ) > len)
+			n = len;
+		if((n = read(sfd, buf, n)) < 0)
+			return -1;
+		if(write(dfd, buf, n) != n)
+			return -1;
+		len -= n;
+	}
+	return 0;
+}
+
+static uchar patchmark[12] = {
+	0xff, 0xff, 0xff, 0xff,
+	0xff, 0xff, 0xff, 0xff,
+	0xff, 0xff, 0xff, 0xff,
+};
+
+int
+fpatchmark(int pfd, char *)
+{
+	if(write(pfd, patchmark, 12) != 12)
+		return -1;
+	return 0;
+}
+
+typedef struct Frag Frag;
+struct Frag
+{
+	Frag	*next;
+	int	fd;
+	vlong	len;
+	vlong	off;
+};
+
+int
+fpatch(int ofd, int bfd, int pfd)
+{
+	vlong off, fstart, fend, start, end, len;
+	int err, front, back;
+	Frag *h, *f, *p;
+	uchar buf[12];
+
+	h = nil;
+	err = -1;
+
+	if(bfd >= 0){
+		h = malloc(sizeof(Frag));
+		h->next = nil;
+		h->off = 0;
+		h->fd = bfd;
+		h->len = seek(h->fd, 0, 2);
+		if(h->len < 0)
+			goto errout;
+	}
+
+	off = 0;
+	while(pfd >= 0){
+		if(readn(pfd, buf, 12) != 12)
+			break;
+
+		if(memcmp(buf, patchmark, 12) == 0){
+			off = 0;
+			continue;
+		}
+
+		start = buf[0]<<24 | buf[1]<<16 | buf[2]<<8 | buf[3];
+		end = buf[4]<<24 | buf[5]<<16 | buf[6]<<8 | buf[7];
+		len = buf[8]<<24 | buf[9]<<16 | buf[10]<<8 | buf[11];
+
+		if(start > end){
+			werrstr("bad patch: start > end");
+			goto errout;
+		}
+
+		start += off;
+		end += off;
+		off += start + len - end;
+
+		fstart = 0;
+		for(f = h; f; f = f->next, fstart = fend){
+			fend = fstart + f->len;
+			if(fend <= start)
+				continue;
+			if(fstart >= end)
+				break;
+
+			front = start > fstart;
+			back = end < fend;
+			if(front && back){
+				p = malloc(sizeof(Frag));
+				*p = *f;
+				f->next = p;
+				f->len = start - fstart;
+				p->off += end - fstart;
+				p->len -= end - fstart;
+				break;
+			} else if(back){
+				f->off += end - fstart;
+				f->len -= end - fstart;
+				break;
+			} else if(front){
+				f->len = start - fstart;
+			} else {
+				f->len = 0;
+			}
+		}
+
+		fstart = 0;
+		for(p = nil, f = h; f && fstart < start; p = f, f = f->next)
+			fstart += f->len;
+
+		f = malloc(sizeof(Frag));
+		f->fd = pfd;
+		f->len = len;
+		f->off = seek(f->fd, 0, 1);
+
+		if(p){
+			f->next = p->next;
+			p->next = f;
+		} else {
+			f->next = h;
+			h = f;
+		}
+
+		if(f->off < 0)
+			goto errout;
+		if(seek(pfd, f->len, 1) < 0)
+			goto errout;
+	}
+
+	for(f = h; f; f = f->next){
+		if(seek(f->fd, f->off, 0) < 0)
+			goto errout;
+		if(fcopy(ofd, f->fd, f->len) < 0)
+			goto errout;
+	}
+	err = 0;
+
+errout:
+	while(f = h){
+		h = f->next;
+		free(f);
+	}
+
+	return err;
+}