agent: clear clippy len_zero warnings

Use `.is_empty()` instead of `.len() == 0`, `.len() >0`
and `.len() != 0`

Signed-off-by: bin liu <bin@hyper.sh>

src/agent/rustjail/src/cgroups/fs/mod.rs

@@ -126,7 +126,7 @@ impl CgroupManager for Manager {
         }
 
         // set hugepages resources
-        if r.hugepage_limits.len() > 0 {
+        if !r.hugepage_limits.is_empty() {
             set_hugepages_resources(&cg, &r.hugepage_limits, res)?;
         }
 
@@ -789,7 +789,7 @@ https://github.com/opencontainers/runc/blob/a5847db387ae28c0ca4ebe4beee1a76900c8
 
 fn get_blkio_stat_blkiodata(blkiodata: &[BlkIoData]) -> RepeatedField<BlkioStatsEntry> {
     let mut m = RepeatedField::new();
-    if blkiodata.len() == 0 {
+    if blkiodata.is_empty() {
         return m;
     }
 
@@ -812,7 +812,7 @@ fn get_blkio_stat_blkiodata(blkiodata: &[BlkIoData]) -> RepeatedField<BlkioStats
 fn get_blkio_stat_ioservice(services: &[IoService]) -> RepeatedField<BlkioStatsEntry> {
     let mut m = RepeatedField::new();
 
-    if services.len() == 0 {
+    if services.is_empty() {
         return m;
     }
 
@@ -874,7 +874,7 @@ fn get_blkio_stats(cg: &cgroups::Cgroup) -> SingularPtrField<BlkioStats> {
     let mut m = BlkioStats::new();
     let io_serviced_recursive = blkio.io_serviced_recursive;
 
-    if io_serviced_recursive.len() == 0 {
+    if io_serviced_recursive.is_empty() {
         // fall back to generic stats
         // blkio.throttle.io_service_bytes,
         // maybe io_service_bytes_recursive?

src/agent/rustjail/src/container.rs

@@ -547,7 +547,7 @@ fn do_init_child(cwfd: RawFd) -> Result<()> {
 
     setid(uid, gid)?;
 
-    if guser.additional_gids.len() > 0 {
+    if !guser.additional_gids.is_empty() {
         setgroups(guser.additional_gids.as_slice()).map_err(|e| {
             let _ = write_sync(
                 cwfd,

src/agent/rustjail/src/validator.rs

@@ -88,7 +88,7 @@ fn hostname(oci: &Spec) -> Result<()> {
 
 fn security(oci: &Spec) -> Result<()> {
     let linux = oci.linux.as_ref().unwrap();
-    if linux.masked_paths.len() == 0 && linux.readonly_paths.len() == 0 {
+    if linux.masked_paths.is_empty() && linux.readonly_paths.is_empty() {
         return Ok(());
     }
 
@@ -124,7 +124,7 @@ fn usernamespace(oci: &Spec) -> Result<()> {
         idmapping(&linux.gid_mappings)?;
     } else {
         // no user namespace but idmap
-        if linux.uid_mappings.len() != 0 || linux.gid_mappings.len() != 0 {
+        if !linux.uid_mappings.is_empty() || !linux.gid_mappings.is_empty() {
             return Err(anyhow!(nix::Error::from_errno(Errno::EINVAL)));
         }
     }
@@ -222,7 +222,7 @@ fn rootless_euid_mapping(oci: &Spec) -> Result<()> {
         return Err(anyhow!(nix::Error::from_errno(Errno::EINVAL)));
     }
 
-    if linux.uid_mappings.len() == 0 || linux.gid_mappings.len() == 0 {
+    if linux.uid_mappings.is_empty() || linux.gid_mappings.is_empty() {
         // rootless containers requires at least one UID/GID mapping
         return Err(anyhow!(nix::Error::from_errno(Errno::EINVAL)));
     }

src/agent/src/mount.rs

@@ -190,11 +190,11 @@ impl<'a> BareMount<'a> {
         let cstr_dest: CString;
         let cstr_fs_type: CString;
 
-        if self.source.len() == 0 {
+        if self.source.is_empty() {
             return Err(anyhow!("need mount source"));
         }
 
-        if self.destination.len() == 0 {
+        if self.destination.is_empty() {
             return Err(anyhow!("need mount destination"));
         }
 
@@ -204,14 +204,14 @@ impl<'a> BareMount<'a> {
         cstr_dest = CString::new(self.destination)?;
         dest = cstr_dest.as_ptr();
 
-        if self.fs_type.len() == 0 {
+        if self.fs_type.is_empty() {
             return Err(anyhow!("need mount FS type"));
         }
 
         cstr_fs_type = CString::new(self.fs_type)?;
         fs_type = cstr_fs_type.as_ptr();
 
-        if self.options.len() > 0 {
+        if !self.options.is_empty() {
             cstr_options = CString::new(self.options)?;
             options = cstr_options.as_ptr() as *const c_void;
         }
@@ -407,14 +407,14 @@ fn parse_mount_flags_and_options(options_vec: Vec<&str>) -> (MsFlags, String) {
     let mut options: String = "".to_string();
 
     for opt in options_vec {
-        if opt.len() != 0 {
+        if !opt.is_empty() {
             match FLAGS.get(opt) {
                 Some(x) => {
                     let (_, f) = *x;
                     flags |= f;
                 }
                 None => {
-                    if options.len() > 0 {
+                    if !options.is_empty() {
                         options.push_str(format!(",{}", opt).as_str());
                     } else {
                         options.push_str(opt.to_string().as_str());
@@ -455,7 +455,7 @@ pub fn add_storages(
         // Todo need to rollback the mounted storage if err met.
         let mount_point = handler(&logger, &storage, sandbox.clone())?;
 
-        if mount_point.len() > 0 {
+        if !mount_point.is_empty() {
             mount_list.push(mount_point);
         }
     }

src/agent/src/network.rs

@@ -48,7 +48,7 @@ pub fn setup_guest_dns(logger: Logger, dns_list: Vec<String>) -> Result<()> {
 fn do_setup_guest_dns(logger: Logger, dns_list: Vec<String>, src: &str, dst: &str) -> Result<()> {
     let logger = logger.new(o!( "subsystem" => "network"));
 
-    if dns_list.len() == 0 {
+    if dns_list.is_empty() {
         info!(
             logger,
             "Did not set sandbox DNS as DNS not received as part of request."

src/agent/src/rpc.rs

@@ -609,7 +609,7 @@ impl protocols::agent_ttrpc::AgentService for agentService {
         }
 
         // format "table"
-        if args.len() == 0 {
+        if args.is_empty() {
             // default argument
             args = vec!["-ef".to_string()];
         }
@@ -1007,7 +1007,7 @@ impl protocols::agent_ttrpc::AgentService for agentService {
                 });
             }
 
-            if req.sandbox_id.len() > 0 {
+            if !req.sandbox_id.is_empty() {
                 s.id = req.sandbox_id.clone();
             }
 
@@ -1248,7 +1248,7 @@ fn get_memory_info(block_size: bool, hotplug: bool) -> Result<(u64, bool)> {
     if block_size {
         match fs::read_to_string(SYSFS_MEMORY_BLOCK_SIZE_PATH) {
             Ok(v) => {
-                if v.len() == 0 {
+                if v.is_empty() {
                     info!(sl!(), "string in empty???");
                     return Err(anyhow!("Invalid block size"));
                 }

src/agent/src/sandbox.rs

@@ -184,7 +184,7 @@ impl Sandbox {
         // This means a separate pause process has not been created. We treat the
         // first container created as the infra container in that case
         // and use its pid namespace in case pid namespace needs to be shared.
-        if self.sandbox_pidns.is_none() && self.containers.len() == 0 {
+        if self.sandbox_pidns.is_none() && self.containers.is_empty() {
             let init_pid = c.init_process_pid;
             if init_pid == -1 {
                 return Err(anyhow!(