From: mdw <mdw>
Date: Fri, 31 Oct 2003 13:56:14 +0000 (+0000)
Subject: Fix data corruption in channel\!
X-Git-Tag: 1.3.0~32
X-Git-Url: https://git.distorted.org.uk/~mdw/fwd/commitdiff_plain/08cb0dd89765683f47206905c9116b73949fee63

Fix data corruption in channel\!
---

diff --git a/chan.c b/chan.c
index ffec633..2e483cd 100644
--- a/chan.c
+++ b/chan.c
@@ -1,6 +1,6 @@
 /* -*-c-*-
  *
- * $Id: chan.c,v 1.5 2000/07/19 17:55:43 mdw Exp $
+ * $Id: chan.c,v 1.6 2003/10/31 13:56:14 mdw Exp $
  *
  * Channel management
  *
@@ -29,6 +29,9 @@
 /*----- Revision history --------------------------------------------------* 
  *
  * $Log: chan.c,v $
+ * Revision 1.6  2003/10/31 13:56:14  mdw
+ * Fix data corruption in channel\!
+ *
  * Revision 1.5  2000/07/19 17:55:43  mdw
  * (writechan): Pointless tweak: when the buffer is empty, reset the start
  * pointer to the beginning.  This saves doing slightly trickier
@@ -69,6 +72,12 @@
 #include "chan.h"
 #include "fw.h"
 
+#ifdef CHAN_DEBUG
+#  define D(x) x
+#else
+#  define D(x)
+#endif
+
 /*----- Main code ---------------------------------------------------------*/
 
 /* --- @writechan@ --- *
@@ -95,16 +104,22 @@ static void writechan(int fd, unsigned mode, void *vp)
 
     /* --- Do the write --- */
 
-    if (base + len <= CHAN_BUFSZ)
+    D( printf("writechan %d: base = %u, len = %u; ", fd, base, len); )
+    if (base + len <= CHAN_BUFSZ) {
+      D( printf("%u:%u", base, len); )
       w = write(fd, c->buf + base, len);
-    else {
+    } else {
       struct iovec iov[2];
       iov[0].iov_base = c->buf + base;
       iov[0].iov_len = CHAN_BUFSZ - base;
       iov[1].iov_base = c->buf;
       iov[1].iov_len = len - iov[0].iov_len;
+      D( printf("%u:%u, %u:%u",
+		base, CHAN_BUFSZ - base,
+		0, len + base - CHAN_BUFSZ); )
       w = writev(fd, iov, 2);
     }
+    D( printf("; returned %d\n", w); )
 
     /* --- Sift through the results --- */
 
@@ -118,6 +133,7 @@ static void writechan(int fd, unsigned mode, void *vp)
     else if (c->len == CHAN_BUFSZ && !(c->f & CHANF_CLOSE))
       sel_addfile(&c->r);
     c->len -= w;
+    c->base += w;
   }
   if (c->len == 0)
     sel_rmfile(&c->w);
@@ -153,21 +169,30 @@ static void readchan(int fd, unsigned mode, void *vp)
 {
   chan *c = vp;
   int r;
-  unsigned base = (c->base + c->len) & (CHAN_BUFSZ - 1);
-  unsigned len = CHAN_BUFSZ - c->len;
+  unsigned base = c->base;
+  unsigned len = c->len;
 
   /* --- Do the read --- */
 
-  if (base + len <= CHAN_BUFSZ)
-    r = read(fd, c->buf + base, len);
-  else {
+  D( printf("readchan %d: base = %u, len = %u; ", fd, base, len); )
+  if (base == 0) {
+    D( printf("%u:%u", len, CHAN_BUFSZ - len); )
+    r = read(fd, c->buf + len, CHAN_BUFSZ - len);
+  } else if (base + len >= CHAN_BUFSZ) {
+    D( printf("%u:%u", base + len - CHAN_BUFSZ, CHAN_BUFSZ - len); )
+    r = read(fd, c->buf + base + len - CHAN_BUFSZ, CHAN_BUFSZ - len);
+  } else {
     struct iovec iov[2];
-    iov[0].iov_base = c->buf + base;
-    iov[0].iov_len = CHAN_BUFSZ - base;
+    iov[0].iov_base = c->buf + base + len;
+    iov[0].iov_len = CHAN_BUFSZ - base - len;
     iov[1].iov_base = c->buf;
-    iov[1].iov_len = len - iov[0].iov_len;
+    iov[1].iov_len = base;
+    D( printf("%u:%u, %u:%u",
+	      base + len, CHAN_BUFSZ - base - len,
+	      0, base); )
     r = readv(fd, iov, 2);
   }
+  D( printf("; returned %d\n", r); )
 
   /* --- Sift through the results --- */