protocol: allow explicitly polling for a single packet

When using *blocking* I/O wait_for_* functions need to be
able to not read past their awaited packet.

Signed-off-by: Wolfgang Bumiller <w.bumiller@proxmox.com>

proxmox-protocol/src/c_client.rs

@@ -273,7 +273,7 @@ pub extern "C" fn proxmox_backup_continue_upload(me: *mut CClient) -> c_int {
 #[no_mangle]
 pub extern "C" fn proxmox_backup_poll_read(me: *mut CClient) -> c_int {
     let me = unsafe { &mut *me };
-    match me.client.poll_read() {
+    match me.client.poll_read(false) {
         Ok(_) => 0,
         Err(e) => me.set_error(e),
     }

proxmox-protocol/src/client.rs

@@ -103,7 +103,7 @@ where
 
     pub fn wait_for_handshake(&mut self) -> Result<bool> {
         if !self.handshake_done {
-            self.poll_read()?;
+            self.poll_read(true)?;
         }
         Ok(self.handshake_done)
     }
@@ -126,8 +126,10 @@ where
     }
 
     pub fn wait_for_hashes(&mut self) -> Result<bool> {
-        if self.hash_download.is_some() {
-            self.poll_read()?;
+        while self.hash_download.is_some() {
+            if !self.poll_read(true)? {
+                break;
+            }
         }
         Ok(self.hash_download.is_none())
     }
@@ -254,8 +256,8 @@ where
         }
     }
 
-    // generic data polling method
-    pub fn poll_read(&mut self) -> Result<()> {
+    // generic data polling method, returns true if at least one packet was received
+    pub fn poll_read(&mut self, one: bool) -> Result<bool> {
         if self.common.eof {
             // polls after EOF are errors:
             bail!("server disconnected");
@@ -266,7 +268,7 @@ where
             if self.common.eof {
                 bail!("server disconnected");
             }
-            return Ok(());
+            return Ok(false);
         }
 
         loop {
@@ -280,11 +282,12 @@ where
                     self.common.current_packet_type as u32,
                 ),
             }
-            if !self.common.next()? {
+            self.common.next()?;
+            if one || !self.common.poll_read()? {
                 break;
             }
         }
-        Ok(())
+        Ok(true)
     }
 
     // None => nothing was queued
@@ -414,19 +417,23 @@ where
         if !self.waiting_ids.contains_key(&id.0) {
             bail!("wait_for_id() called on unexpected id {}", id.0);
         }
-        self.poll_read()?;
 
-        use hash_map::Entry::*;
+        loop {
+            if !self.poll_read(true)? {
+                return Ok(false);
+            }
 
-        match self.waiting_ids.entry(id.0) {
-            Vacant(_) => Ok(true),
-            Occupied(entry) => match entry.get() {
-                AckState::Received => {
-                    entry.remove();
-                    Ok(true)
-                }
-                _ => Ok(false),
-            },
+            use hash_map::Entry::*;
+            match self.waiting_ids.entry(id.0) {
+                Vacant(_) => return Ok(true),
+                Occupied(entry) => match entry.get() {
+                    AckState::Received => {
+                        entry.remove();
+                        return Ok(true);
+                    }
+                    _ => continue,
+                },
+            }
         }
     }
 

proxmox-protocol/src/common.rs

@@ -138,7 +138,7 @@ where
         &self.buffer[beg..end]
     }
 
-    pub fn next(&mut self) -> Result<bool> {
+    pub fn next(&mut self) -> Result<()> {
         let pktlen = self.packet_length();
         unsafe {
             if self.buffer.len() != pktlen {
@@ -150,7 +150,7 @@ where
             }
             self.buffer.set_len(self.buffer.len() - pktlen);
         }
-        self.poll_data_do()
+        Ok(())
     }
 
     // NOTE: After calling this you must `self.buffer.set_len()` when done!

proxmox-protocol/src/server.rs

@@ -184,7 +184,8 @@ where
                     self.common.current_packet_type as u32,
                 ),
             };
-            if !self.common.next()? {
+            self.common.next()?;
+            if !self.common.poll_read()? {
                 break;
             }
         }