clippy: Disallow len_without_is_empty and len_zero

BUG=b:283512997
TEST=none

Change-Id: I0477583b3f8c8eefeb1d79f11302b1b28a8bd770
Reviewed-on: https://chromium-review.googlesource.com/c/crosvm/crosvm/+/4549999
Reviewed-by: Dennis Kempin <denniskempin@google.com>
Commit-Queue: Vikram Auradkar <auradkar@google.com>

.cargo/config.toml

@@ -14,8 +14,6 @@ rustflags = [
     "-Aclippy::collapsible_if",
     "-Aclippy::enum_variant_names",
     "-Aclippy::identity_op",
-    "-Aclippy::len_without_is_empty",
-    "-Aclippy::len_zero",
     "-Aclippy::match_bool",
     "-Aclippy::match_wild_err_arm",
     "-Aclippy::needless_bool",

common/data_model/src/sys/windows.rs

@@ -86,6 +86,11 @@ impl<'a> IoBufMut<'a> {
         self.buf.len as usize
     }
 
+    #[inline]
+    pub fn is_empty(&self) -> bool {
+        self.buf.len == 0
+    }
+
     /// Gets a const pointer to this slice's memory.
     #[inline]
     pub fn as_ptr(&self) -> *const u8 {

cros_async/src/mem.rs

@@ -94,6 +94,10 @@ impl VecIoWrapper {
         self.inner.len()
     }
 
+    pub fn is_empty(&self) -> bool {
+        self.len() == 0
+    }
+
     // Check that the offsets are all valid in the backing vec.
     fn check_addrs(&self, mem_range: &MemRegion) -> Result<()> {
         let end = mem_range

devices/src/bus_stats.rs

@@ -191,7 +191,7 @@ impl BusStatistics {
 
     /// Merge several BusStatistics into one.
     pub fn merged(stats: &[Arc<Mutex<BusStatistics>>]) -> BusStatistics {
-        if stats.len() == 0 {
+        if stats.is_empty() {
             return BusStatistics::new();
         }
 

devices/src/usb/xhci/scatter_gather_buffer.rs

@@ -70,6 +70,10 @@ impl ScatterGatherBuffer {
         Ok(total_len)
     }
 
+    pub fn is_empty(&self) -> Result<bool> {
+        Ok(self.len()? == 0)
+    }
+
     /// Get the guest address and length of the TRB's data buffer.
     /// This is usually a separate buffer pointed to by the TRB,
     /// but it can also be within the TRB itself in the case of immediate data.

devices/src/virtio/iommu/memory_mapper.rs

@@ -257,6 +257,11 @@ impl BasicMemoryMapper {
     pub fn len(&self) -> usize {
         self.maps.len()
     }
+
+    #[cfg(test)]
+    pub fn is_empty(&self) -> bool {
+        self.maps.is_empty()
+    }
 }
 
 impl MemoryMapper for BasicMemoryMapper {

devices/src/virtio/snd/vios_backend/streams.rs

@@ -304,7 +304,7 @@ impl Stream {
             }
             StreamState::Prepared => {} // Do nothing, any buffers will be processed after start
             _ => {
-                if self.buffer_queue.len() > 0 {
+                if !self.buffer_queue.is_empty() {
                     warn!("virtio-snd: Buffers received while in unexpected state");
                 }
             }

devices/src/virtio/vhost/user/device/vvu/device.rs

@@ -104,7 +104,7 @@ impl VfioReceiver {
                 .context("failed to receive data")
                 .map_err(RecvIntoBufsError::Fatal)?;
 
-            if data.len() == 0 {
+            if data.is_empty() {
                 // TODO(b/216407443): We should change `self.state` and exit gracefully.
                 info!("VVU connection is closed");
                 return Err(RecvIntoBufsError::Disconnect);

devices/src/virtio/video/decoder/backend/ffmpeg.rs

@@ -82,6 +82,10 @@ impl AvBufferSource for InputBuffer {
     fn len(&self) -> usize {
         self.mapping.size()
     }
+
+    fn is_empty(&self) -> bool {
+        self.len() == 0
+    }
 }
 
 /// Types of input job we can receive from the crosvm decoder code.

devices/src/virtio/video/encoder/backend/ffmpeg.rs

@@ -84,6 +84,10 @@ impl AvBufferSource for InputBuffer {
     fn len(&self) -> usize {
         self.mapping.size()
     }
+
+    fn is_empty(&self) -> bool {
+        self.len() == 0
+    }
 }
 
 enum CodecJob {

devices/src/virtio/video/encoder/backend/vda.rs

@@ -62,7 +62,7 @@ impl LibvdaEncoder {
             output_formats,
         } = instance.get_capabilities();
 
-        if input_formats.len() == 0 || output_formats.len() == 0 {
+        if input_formats.is_empty() || output_formats.is_empty() {
             error!("No input or output formats.");
             return Err(VideoError::InvalidFormat);
         }

devices/src/virtio/video/encoder/mod.rs

@@ -328,7 +328,7 @@ impl<T: EncoderSession> Stream<T> {
             ));
         }
 
-        if responses.len() > 0 {
+        if !responses.is_empty() {
             Some(responses)
         } else {
             None
@@ -783,7 +783,7 @@ impl<T: Encoder> EncoderDevice<T> {
                 // We currently only support single-buffer formats, but some clients may mistake
                 // color planes with memory planes and submit several planes to us. This doesn't
                 // matter as we will only consider the first one.
-                if data_sizes.len() < 1 {
+                if data_sizes.is_empty() {
                     return Err(VideoError::InvalidParameter);
                 }
 
@@ -1035,8 +1035,8 @@ impl<T: Encoder> EncoderDevice<T> {
         let mut create_session = stream.encoder_session.is_none();
         // TODO(ishitatsuyuki): We should additionally check that no resources are *attached* while
         //                      a params is being set.
-        let src_resources_queued = stream.src_resources.len() > 0;
-        let dst_resources_queued = stream.dst_resources.len() > 0;
+        let src_resources_queued = !stream.src_resources.is_empty();
+        let dst_resources_queued = !stream.dst_resources.is_empty();
 
         // Dynamic framerate changes are allowed. The framerate can be set on either the input or
         // output queue. Changing the framerate can influence the selected H.264 level, as the
@@ -1273,7 +1273,7 @@ impl<T: Encoder> EncoderDevice<T> {
             .get_mut(&stream_id)
             .ok_or(VideoError::InvalidStreamId(stream_id))?;
         let mut recreate_session = false;
-        let resources_queued = stream.src_resources.len() > 0 || stream.dst_resources.len() > 0;
+        let resources_queued = !stream.src_resources.is_empty() || !stream.dst_resources.is_empty();
 
         match ctrl_val {
             CtrlVal::BitrateMode(bitrate_mode) => {

devices/src/virtio/video/ffmpeg.rs

@@ -45,6 +45,10 @@ impl AvBufferSource for MemoryMappingAvBufferSource {
     fn len(&self) -> usize {
         self.0.size()
     }
+
+    fn is_empty(&self) -> bool {
+        self.len() == 0
+    }
 }
 
 pub trait TryAsAvFrameExt {
@@ -156,7 +160,7 @@ impl TryFrom<Format> for AvPixelFormat {
         })
         .map_err(|_|
             // The error case should never happen as long as we use valid constant values, but
-            // don't panic in case something goes wrong. 
+            // don't panic in case something goes wrong.
             TryFromFormatError(()))
     }
 }

devices/src/virtio/video/utils.rs

@@ -63,7 +63,7 @@ impl<T> EventQueue<T> {
 
     /// Remove all the posted events for which `predicate` returns `false`.
     pub fn retain<P: FnMut(&T) -> bool>(&mut self, predicate: P) {
-        if self.pending_events.len() > 0 {
+        if !self.pending_events.is_empty() {
             let _ = self
                 .event
                 .wait_timeout(Duration::from_millis(0))

hypervisor/src/x86_64.rs

@@ -958,4 +958,9 @@ impl Xsave {
     pub fn len(&self) -> usize {
         self.len
     }
+
+    /// Returns true is length of XSAVE data is zero
+    pub fn is_empty(&self) -> bool {
+        self.len() == 0
+    }
 }

hypervisor/tests/kvm/x86_64.rs

@@ -39,14 +39,14 @@ use vm_memory::GuestMemory;
 fn get_supported_cpuid() {
     let hypervisor = Kvm::new().unwrap();
     let cpuid = hypervisor.get_supported_cpuid().unwrap();
-    assert!(cpuid.cpu_id_entries.len() > 0);
+    assert!(!cpuid.cpu_id_entries.is_empty());
 }
 
 #[test]
 fn get_emulated_cpuid() {
     let hypervisor = Kvm::new().unwrap();
     let cpuid = hypervisor.get_emulated_cpuid().unwrap();
-    assert!(cpuid.cpu_id_entries.len() > 0);
+    assert!(!cpuid.cpu_id_entries.is_empty());
 }
 
 #[test]

kvm/tests/kvm_tests.rs

@@ -88,7 +88,7 @@ fn get_supported_cpuid() {
     let kvm = Kvm::new().unwrap();
     let mut cpuid = kvm.get_supported_cpuid().unwrap();
     let cpuid_entries = cpuid.mut_entries_slice();
-    assert!(cpuid_entries.len() > 0);
+    assert!(!cpuid_entries.is_empty());
 }
 
 #[test]

media/ffmpeg/src/avcodec.rs

@@ -584,6 +584,7 @@ pub trait AvBufferSource: Send {
         self.as_ptr() as *mut u8
     }
     fn len(&self) -> usize;
+    fn is_empty(&self) -> bool;
 }
 
 /// Wrapper around `AVBuffer` and `AVBufferRef`.
@@ -1023,6 +1024,10 @@ mod tests {
             fn len(&self) -> usize {
                 0
             }
+
+            fn is_empty(&self) -> bool {
+                true
+            }
         }
 
         let dropped = Arc::new(AtomicBool::new(false));

rutabaga_gfx/src/cross_domain/mod.rs

@@ -300,7 +300,7 @@ impl CrossDomainWorker {
             match event.token {
                 CrossDomainToken::ContextChannel => {
                     let (len, files) = self.state.receive_msg(receive_buf)?;
-                    if len != 0 || files.len() != 0 {
+                    if len != 0 || !files.is_empty() {
                         let mut cmd_receive: CrossDomainSendReceive = Default::default();
 
                         let num_files = files.len();

rutabaga_gfx/src/gfxstream.rs

@@ -625,7 +625,7 @@ impl RutabagaComponent for Gfxstream {
         fence_handler: RutabagaFenceHandler,
     ) -> RutabagaResult<Box<dyn RutabagaContext>> {
         let mut name: &str = "gpu_renderer";
-        if let Some(name_string) = context_name.filter(|s| s.len() > 0) {
+        if let Some(name_string) = context_name.filter(|s| !s.is_empty()) {
             name = name_string;
         }
 

rutabaga_gfx/src/virgl_renderer.rs

@@ -692,7 +692,7 @@ impl RutabagaComponent for VirglRenderer {
         _fence_handler: RutabagaFenceHandler,
     ) -> RutabagaResult<Box<dyn RutabagaContext>> {
         let mut name: &str = "gpu_renderer";
-        if let Some(name_string) = context_name.filter(|s| s.len() > 0) {
+        if let Some(name_string) = context_name.filter(|s| !s.is_empty()) {
             name = name_string;
         }
 

src/crosvm/plugin/mod.rs

@@ -494,7 +494,7 @@ pub fn run_config(cfg: Config) -> Result<()> {
         config.bind_mounts = true;
         let uid_map = format!("0 {} 1", geteuid());
         let gid_map = format!("0 {} 1", getegid());
-        let gid_map = if cfg.plugin_gid_maps.len() > 0 {
+        let gid_map = if !cfg.plugin_gid_maps.is_empty() {
             gid_map
                 + &cfg
                     .plugin_gid_maps

src/crosvm/sys/windows/broker.rs

@@ -883,7 +883,7 @@ impl Supervisor {
     }
 
     fn all_non_metrics_processes_exited(&self) -> bool {
-        self.children.len() == 0 || self.is_only_metrics_process_running()
+        self.children.is_empty() || self.is_only_metrics_process_running()
     }
 
     fn start_exit_timer(&mut self, timeout_token: Token) -> Result<()> {
@@ -1033,7 +1033,7 @@ impl Supervisor {
                             );
                         }
                         ensure_exit_code!(
-                            self.children.len() == 0,
+                            self.children.is_empty(),
                             Exit::BrokerMetricsExitedTimeout,
                             "metrics exited, but other broker children did not exit within the \
                             timeout",

vm_control/src/sys/unix.rs

@@ -171,7 +171,7 @@ static SHOULD_PREPARE_MEMORY_REGION: Lazy<bool> = Lazy::new(|| {
         // so avoid mapping the whole shared memory region if we're not
         // using the tdp mmu.
         match std::fs::read("/sys/module/kvm/parameters/tdp_mmu") {
-            Ok(bytes) if bytes.len() > 0 => bytes[0] == b'Y',
+            Ok(bytes) if !bytes.is_empty() => bytes[0] == b'Y',
             _ => false,
         }
     } else if cfg!(target_pointer_width = "64") {