it turns out you don't need -1/EGAIN to know edge triggering told you

there is no more data, it's enough to read/write less than you asked for

io/io_mmapwritefile.c

@@ -20,7 +20,7 @@ int64 io_mmapwritefile(int64 out,int64 in,uint64 off,uint64 bytes,io_write_callb
     const char* c;
     unsigned long left;
 #ifdef __MINGW32__
-    if (!e->mh) e->mh=CreateFileMapping(out,0,PAGE_READONLY,0,0,NULL);
+    if (!e->mh) e->mh=CreateFileMapping(in,0,PAGE_READONLY,0,0,NULL);
     if (!e->mh) goto readwrite;
 #endif
     do {
@@ -56,8 +56,7 @@ int64 io_mmapwritefile(int64 out,int64 in,uint64 off,uint64 bytes,io_write_callb
       while (left>0) {
 	m=writecb(out,c,left);
 	if (m<0) {
-	  e->canwrite=0;
+	  io_eagain(out);
-	  e->next_write=-1;
 	  if (errno!=EAGAIN) {
 #ifdef __MINGW32__
 	    UnmapViewOfFile(e->mmapped);
@@ -75,6 +74,11 @@ int64 io_mmapwritefile(int64 out,int64 in,uint64 off,uint64 bytes,io_write_callb
 	bytes-=m;
 	off+=m;
 	c+=m;
+	if (e && left>0) {
+	  e->canwrite=0;
+	  e->next_write=-1;
+	  return sent;
+	}
       }
     } while (bytes);
     if (e->mmapped) {
@@ -109,6 +113,11 @@ readwrite:
       n-=m;
       bytes-=m;
       tmp+=m;
+      if (e && m!=n) {
+	e->canwrite=0;
+	e->next_write=-1;
+	goto abort;
+      }
     }
   }
 abort:

io/io_sendfile.c

@@ -14,8 +14,14 @@
 int64 io_sendfile(int64 s,int64 fd,uint64 off,uint64 n) {
   off_t sbytes;
   int r=sendfile(fd,s,off,n,0,&sbytes,0);
-  if (r==-1)
+  if (r==-1) {
+    io_entry* e=iarray_get(&io_fds,s);
+    if (e) {
+      e->canwrite=0;
+      e->next_write=-1;
+    }
     return (errno==EAGAIN?(sbytes?sbytes:-1):-3);
+  }
   return n;
 }
 
@@ -31,6 +37,13 @@ int64 io_sendfile(int64 s,int64 fd,uint64 off,uint64 n) {
 int64 io_sendfile(int64 out,int64 in,uint64 off,uint64 bytes) {
   long long r=sendfile64(out,in,off,bytes,0,0);
   if (r==-1 && errno!=EAGAIN) r=-3;
+  if (r!=bytes) {
+    io_entry* e=iarray_get(&io_fds,s);
+    if (e) {
+      e->canwrite=0;
+      e->next_write=-1;
+    }
+  }
   return r;
 }
 
@@ -45,6 +58,13 @@ int64 io_sendfile(int64 out,int64 in,uint64 off,uint64 bytes) {
   off64_t o=off;
   long long r=sendfile64(out,in,&o,bytes);
   if (r==-1 && errno!=EAGAIN) r=-3;
+  if (r!=bytes) {
+    io_entry* e=iarray_get(&io_fds,s);
+    if (e) {
+      e->canwrite=0;
+      e->next_write=-1;
+    }
+  }
   return r;
 }
 
@@ -65,9 +85,16 @@ int64 io_sendfile(int64 out,int64 in,uint64 off,uint64 bytes) {
   p.file_bytes=bytes;
   p.trailer_data=0;
   p.trailer_length=0;
-  if (send_file(&destfd,&p,0)>=0)
+  if (send_file(&destfd,&p,0)>=0) {
+    if (p.bytes_sent != bytes) {
+      io_entry* e=iarray_get(&io_fds,s);
+      if (e) {
+	e->canwrite=0;
+	e->next_write=-1;
+      }
+    }
     return p.bytes_sent;
-  if (errno==EAGAIN)
+  } if (errno==EAGAIN)
     return -1;
   else
     return -3;
@@ -99,15 +126,17 @@ int64 io_sendfile(int64 s,int64 fd,uint64 off,uint64 n) {
       n-=todo;
       if (n==0) return done;
       continue;
-    } else if (i==-1) {
+    } else {
       if (e) {
 	e->canwrite=0;
 	e->next_write=-1;
       }
+      if (i==-1)
 	return (errno==EAGAIN?-1:-3);
-    } else
+      else
 	return done+i;
     }
+  }
   return 0;
 }
 #endif

io/io_tryread.c

@@ -86,7 +86,7 @@ int64 io_tryread(int64 d,char* buf,int64 len) {
   if (!e) { errno=EBADF; return -3; }
   if (!e->nonblock) {
     p.fd=d;
-    if (p.fd != d) { errno=EBADF; return -3; }	/* catch overflow */
+    if (p.fd!=d) { errno=EBADF; return -3; }	/* catch integer truncation */
     p.events=POLLIN;
     switch (poll(&p,1,0)) {
     case -1: return -3;
@@ -110,7 +110,7 @@ int64 io_tryread(int64 d,char* buf,int64 len) {
     if (errno!=EAGAIN)
       r=-3;
   }
-  if (r==-1 || r==0) {
+  if (r!=len) {
     e->canread=0;
 #if defined(HAVE_SIGIO) || defined(HAVE_EPOLL)
     if (d==alt_firstread) {

io/io_trywrite.c

@@ -104,7 +104,7 @@ int64 io_trywrite(int64 d,const char* buf,int64 len) {
     if (errno!=EAGAIN)
       r=-3;
   }
-  if (r==-1 || r==0) {
+  if (r!=len) {
     e->canwrite=0;
 #if defined(HAVE_SIGIO) || defined(HAVE_EPOLL)
     if (d==alt_firstwrite) {

io/io_waituntil2.c

@@ -125,8 +125,15 @@ int64 io_waituntil2(int64 milliseconds) {
     int n;
     struct epoll_event y[100];
     io_entry* e;
-    if (alt_firstread>=0 && (e=iarray_get(&io_fds,alt_firstread)) && e->canread) return 1;
+    if (alt_firstread>=0 && (e=iarray_get(&io_fds,alt_firstread)) && e->canread) {
-    if (alt_firstwrite>=0 && (e=iarray_get(&io_fds,alt_firstwrite)) && e->canwrite) return 1;
+//      write(1,"r",1);
+      return 1;
+    }
+    if (alt_firstwrite>=0 && (e=iarray_get(&io_fds,alt_firstwrite)) && e->canwrite) {
+//      write(1,"w",1);
+      return 1;
+    }
+//    write(1,".",1);
     if ((n=epoll_wait(io_master,y,100,milliseconds))==-1) return -1;
     for (i=0; i<n; ++i) {
       e=iarray_get(&io_fds,y[i].data.fd);

io/iob_send.c

@@ -237,6 +237,7 @@ eagain:
 	  goto abort;
 	}
       }
+      io_eagain(s);
     } else break;
   }
 abort: