optimize and refactor: read_to_string and read_i[u]64_from

There's so many Duplicated read_string_from method in different
subsystem's implementation, so as read_u64_from/read_i64_from methods.
(1) Move the read_string_from method into `lib.rs`,
called by each subsystem implementation as needed.
(2) Refactor read_u[i]64_from method with the help Rust Generic f
unction `read_from` and wrapped by read_u64_from or read_i64_from.

fix: #20

Signed-off-by: LiYa'nan <oliverliyn@gmail.com>

src/blkio.rs

@@ -8,13 +8,13 @@
 //!
 //! See the Kernel's documentation for more information about this subsystem, found at:
 //!  [Documentation/cgroup-v1/blkio-controller.txt](https://www.kernel.org/doc/Documentation/cgroup-v1/blkio-controller.txt)
-use std::fs::File;
+use std::io::Write;
-use std::io::{Read, Write};
 use std::path::PathBuf;
 
 use crate::error::ErrorKind::*;
 use crate::error::*;
 
+use crate::{read_string_from, read_u64_from};
 use crate::{
     BlkIoResources, ControllIdentifier, ControllerInternal, Controllers, Resources, Subsystem,
 };
@@ -401,25 +401,6 @@ impl<'a> From<&'a Subsystem> for &'a BlkIoController {
     }
 }
 
-fn read_string_from(mut file: File) -> Result<String> {
-    let mut string = String::new();
-    match file.read_to_string(&mut string) {
-        Ok(_) => Ok(string.trim().to_string()),
-        Err(e) => Err(Error::with_cause(ReadFailed, e)),
-    }
-}
-
-fn read_u64_from(mut file: File) -> Result<u64> {
-    let mut string = String::new();
-    match file.read_to_string(&mut string) {
-        Ok(_) => string
-            .trim()
-            .parse()
-            .map_err(|e| Error::with_cause(ParseError, e)),
-        Err(e) => Err(Error::with_cause(ReadFailed, e)),
-    }
-}
-
 impl BlkIoController {
     /// Constructs a new `BlkIoController` with `root` serving as the root of the control group.
     pub fn new(root: PathBuf, v2: bool) -> Self {

src/cpu.rs

@@ -15,7 +15,7 @@ use std::path::PathBuf;
 
 use crate::error::ErrorKind::*;
 use crate::error::*;
-use crate::{parse_max_value, read_i64_from};
+use crate::{parse_max_value, read_i64_from, read_u64_from};
 
 use crate::{
     ControllIdentifier, ControllerInternal, Controllers, CpuResources, CustomizedAttribute,
@@ -110,17 +110,6 @@ impl<'a> From<&'a Subsystem> for &'a CpuController {
     }
 }
 
-fn read_u64_from(mut file: File) -> Result<u64> {
-    let mut string = String::new();
-    match file.read_to_string(&mut string) {
-        Ok(_) => string
-            .trim()
-            .parse()
-            .map_err(|e| Error::with_cause(ParseError, e)),
-        Err(e) => Err(Error::with_cause(ReadFailed, e)),
-    }
-}
-
 impl CpuController {
     /// Contructs a new `CpuController` with `root` serving as the root of the control group.
     pub fn new(root: PathBuf, v2: bool) -> Self {

src/cpuacct.rs

@@ -7,13 +7,13 @@
 //!
 //! See the Kernel's documentation for more information about this subsystem, found at:
 //!  [Documentation/cgroup-v1/cpuacct.txt](https://www.kernel.org/doc/Documentation/cgroup-v1/cpuacct.txt)
-use std::fs::File;
+use std::io::Write;
-use std::io::{Read, Write};
 use std::path::PathBuf;
 
 use crate::error::ErrorKind::*;
 use crate::error::*;
 
+use crate::{read_string_from, read_u64_from};
 use crate::{ControllIdentifier, ControllerInternal, Controllers, Resources, Subsystem};
 
 /// A controller that allows controlling the `cpuacct` subsystem of a Cgroup.
@@ -97,26 +97,6 @@ impl<'a> From<&'a Subsystem> for &'a CpuAcctController {
     }
 }
 
-fn read_u64_from(mut file: File) -> Result<u64> {
-    let mut string = String::new();
-    let res = file.read_to_string(&mut string);
-    match res {
-        Ok(_) => match string.trim().parse() {
-            Ok(e) => Ok(e),
-            Err(e) => Err(Error::with_cause(ParseError, e)),
-        },
-        Err(e) => Err(Error::with_cause(ReadFailed, e)),
-    }
-}
-
-fn read_string_from(mut file: File) -> Result<String> {
-    let mut string = String::new();
-    match file.read_to_string(&mut string) {
-        Ok(_) => Ok(string.trim().to_string()),
-        Err(e) => Err(Error::with_cause(ReadFailed, e)),
-    }
-}
-
 impl CpuAcctController {
     /// Contructs a new `CpuAcctController` with `root` serving as the root of the control group.
     pub fn new(root: PathBuf) -> Self {

src/cpuset.rs

@@ -10,13 +10,13 @@
 //!  [Documentation/cgroup-v1/cpusets.txt](https://www.kernel.org/doc/Documentation/cgroup-v1/cpusets.txt)
 
 use log::*;
-use std::fs::File;
+use std::io::Write;
-use std::io::{Read, Write};
 use std::path::PathBuf;
 
 use crate::error::ErrorKind::*;
 use crate::error::*;
 
+use crate::{read_string_from, read_u64_from};
 use crate::{
     ControllIdentifier, ControllerInternal, Controllers, CpuResources, Resources, Subsystem,
 };
@@ -204,25 +204,6 @@ impl<'a> From<&'a Subsystem> for &'a CpuSetController {
     }
 }
 
-fn read_string_from(mut file: File) -> Result<String> {
-    let mut string = String::new();
-    match file.read_to_string(&mut string) {
-        Ok(_) => Ok(string.trim().to_string()),
-        Err(e) => Err(Error::with_cause(ReadFailed, e)),
-    }
-}
-
-fn read_u64_from(mut file: File) -> Result<u64> {
-    let mut string = String::new();
-    match file.read_to_string(&mut string) {
-        Ok(_) => string
-            .trim()
-            .parse()
-            .map_err(|e| Error::with_cause(ParseError, e)),
-        Err(e) => Err(Error::with_cause(ReadFailed, e)),
-    }
-}
-
 /// Parse a string like "1,2,4-5,8" into a list of (start, end) tuples.
 fn parse_range(s: String) -> Result<Vec<(u64, u64)>> {
     let mut fin = Vec::new();

src/hugetlb.rs

@@ -8,13 +8,12 @@
 //!
 //! See the Kernel's documentation for more information about this subsystem, found at:
 //!  [Documentation/cgroup-v1/hugetlb.txt](https://www.kernel.org/doc/Documentation/cgroup-v1/hugetlb.txt)
-use std::fs::File;
+use std::io::Write;
-use std::io::{Read, Write};
 use std::path::PathBuf;
 
 use crate::error::ErrorKind::*;
 use crate::error::*;
-use crate::flat_keyed_to_vec;
+use crate::{flat_keyed_to_vec, read_u64_from};
 
 use crate::{
     ControllIdentifier, ControllerInternal, Controllers, HugePageResources, Resources, Subsystem,
@@ -86,17 +85,6 @@ impl<'a> From<&'a Subsystem> for &'a HugeTlbController {
     }
 }
 
-fn read_u64_from(mut file: File) -> Result<u64> {
-    let mut string = String::new();
-    match file.read_to_string(&mut string) {
-        Ok(_) => string
-            .trim()
-            .parse()
-            .map_err(|e| Error::with_cause(ParseError, e)),
-        Err(e) => Err(Error::with_cause(ReadFailed, e)),
-    }
-}
-
 impl HugeTlbController {
     /// Constructs a new `HugeTlbController` with `root` serving as the root of the control group.
     pub fn new(root: PathBuf, v2: bool) -> Self {

src/lib.rs

@@ -10,6 +10,7 @@ use std::collections::HashMap;
 use std::fs::{self, File};
 use std::io::{BufRead, BufReader, Read, Write};
 use std::path::{Path, PathBuf};
+use std::str::FromStr;
 
 macro_rules! update_and_test {
     ($self: ident, $set_func:ident, $value:expr, $get_func:ident) => {
@@ -832,14 +833,35 @@ pub fn nested_keyed_to_hashmap(mut file: File) -> Result<HashMap<String, HashMap
     Ok(h)
 }
 
-/// read and parse an i64 data
+fn read_from<T>(mut file: File) -> Result<T>
-fn read_i64_from(mut file: File) -> Result<i64> {
+where
+    T: FromStr,
+    <T as FromStr>::Err: 'static + Send + Sync + std::error::Error,
+{
     let mut string = String::new();
     match file.read_to_string(&mut string) {
         Ok(_) => string
             .trim()
-            .parse()
+            .parse::<T>()
             .map_err(|e| Error::with_cause(ParseError, e)),
         Err(e) => Err(Error::with_cause(ReadFailed, e)),
     }
 }
+
+fn read_string_from(mut file: File) -> Result<String> {
+    let mut string = String::new();
+    match file.read_to_string(&mut string) {
+        Ok(_) => Ok(string.trim().to_string()),
+        Err(e) => Err(Error::with_cause(ReadFailed, e)),
+    }
+}
+
+/// read and parse an u64 data
+fn read_u64_from(file: File) -> Result<u64> {
+    read_from::<u64>(file)
+}
+
+/// read and parse an i64 data
+fn read_i64_from(file: File) -> Result<i64> {
+    read_from::<i64>(file)
+}

src/memory.rs

@@ -9,15 +9,14 @@
 //! See the Kernel's documentation for more information about this subsystem, found at:
 //!  [Documentation/cgroup-v1/memory.txt](https://www.kernel.org/doc/Documentation/cgroup-v1/memory.txt)
 use std::collections::HashMap;
-use std::fs::File;
+use std::io::Write;
-use std::io::{Read, Write};
 use std::path::PathBuf;
 use std::sync::mpsc::Receiver;
 
 use crate::error::ErrorKind::*;
 use crate::error::*;
 use crate::events;
-use crate::read_i64_from;
+use crate::{read_i64_from, read_string_from, read_u64_from};
 
 use crate::flat_keyed_to_hashmap;
 
@@ -870,25 +869,6 @@ impl<'a> From<&'a Subsystem> for &'a MemController {
     }
 }
 
-fn read_u64_from(mut file: File) -> Result<u64> {
-    let mut string = String::new();
-    match file.read_to_string(&mut string) {
-        Ok(_) => string
-            .trim()
-            .parse()
-            .map_err(|e| Error::with_cause(ParseError, e)),
-        Err(e) => Err(Error::with_cause(ReadFailed, e)),
-    }
-}
-
-fn read_string_from(mut file: File) -> Result<String> {
-    let mut string = String::new();
-    match file.read_to_string(&mut string) {
-        Ok(_) => Ok(string.trim().to_string()),
-        Err(e) => Err(Error::with_cause(ReadFailed, e)),
-    }
-}
-
 #[cfg(test)]
 mod tests {
     use crate::memory::{

src/net_cls.rs

@@ -7,13 +7,13 @@
 //!
 //! See the Kernel's documentation for more information about this subsystem, found at:
 //!  [Documentation/cgroup-v1/net_cls.txt](https://www.kernel.org/doc/Documentation/cgroup-v1/net_cls.txt)
-use std::fs::File;
+use std::io::Write;
-use std::io::{Read, Write};
 use std::path::PathBuf;
 
 use crate::error::ErrorKind::*;
 use crate::error::*;
 
+use crate::read_u64_from;
 use crate::{
     ControllIdentifier, ControllerInternal, Controllers, NetworkResources, Resources, Subsystem,
 };
@@ -74,17 +74,6 @@ impl<'a> From<&'a Subsystem> for &'a NetClsController {
     }
 }
 
-fn read_u64_from(mut file: File) -> Result<u64> {
-    let mut string = String::new();
-    match file.read_to_string(&mut string) {
-        Ok(_) => string
-            .trim()
-            .parse()
-            .map_err(|e| Error::with_cause(ParseError, e)),
-        Err(e) => Err(Error::with_cause(ReadFailed, e)),
-    }
-}
-
 impl NetClsController {
     /// Constructs a new `NetClsController` with `root` serving as the root of the control group.
     pub fn new(root: PathBuf) -> Self {

src/net_prio.rs

@@ -8,13 +8,13 @@
 //! See the Kernel's documentation for more information about this subsystem, found at:
 //!  [Documentation/cgroup-v1/net_prio.txt](https://www.kernel.org/doc/Documentation/cgroup-v1/net_prio.txt)
 use std::collections::HashMap;
-use std::fs::File;
+use std::io::{BufRead, BufReader, Write};
-use std::io::{BufRead, BufReader, Read, Write};
 use std::path::PathBuf;
 
 use crate::error::ErrorKind::*;
 use crate::error::*;
 
+use crate::read_u64_from;
 use crate::{
     ControllIdentifier, ControllerInternal, Controllers, NetworkResources, Resources, Subsystem,
 };
@@ -77,17 +77,6 @@ impl<'a> From<&'a Subsystem> for &'a NetPrioController {
     }
 }
 
-fn read_u64_from(mut file: File) -> Result<u64> {
-    let mut string = String::new();
-    match file.read_to_string(&mut string) {
-        Ok(_) => string
-            .trim()
-            .parse()
-            .map_err(|e| Error::with_cause(ParseError, e)),
-        Err(e) => Err(Error::with_cause(ReadFailed, e)),
-    }
-}
-
 impl NetPrioController {
     /// Constructs a new `NetPrioController` with `root` serving as the root of the control group.
     pub fn new(root: PathBuf) -> Self {

src/pid.rs

@@ -8,13 +8,13 @@
 //!
 //! See the Kernel's documentation for more information about this subsystem, found at:
 //!  [Documentation/cgroups-v1/pids.txt](https://www.kernel.org/doc/Documentation/cgroup-v1/pids.txt)
-use std::fs::File;
 use std::io::{Read, Write};
 use std::path::PathBuf;
 
 use crate::error::ErrorKind::*;
 use crate::error::*;
 
+use crate::read_u64_from;
 use crate::{
     parse_max_value, ControllIdentifier, ControllerInternal, Controllers, MaxValue, PidResources,
     Resources, Subsystem,
@@ -89,17 +89,6 @@ impl<'a> From<&'a Subsystem> for &'a PidController {
     }
 }
 
-fn read_u64_from(mut file: File) -> Result<u64> {
-    let mut string = String::new();
-    match file.read_to_string(&mut string) {
-        Ok(_) => string
-            .trim()
-            .parse()
-            .map_err(|e| Error::with_cause(ParseError, e)),
-        Err(e) => Err(Error::with_cause(ReadFailed, e)),
-    }
-}
-
 impl PidController {
     /// Constructors a new `PidController` instance, with `root` serving as the controller's root
     /// directory.

src/rdma.rs

@@ -7,13 +7,13 @@
 //!
 //! See the Kernel's documentation for more information about this subsystem, found at:
 //!  [Documentation/cgroup-v1/rdma.txt](https://www.kernel.org/doc/Documentation/cgroup-v1/rdma.txt)
-use std::fs::File;
+use std::io::Write;
-use std::io::{Read, Write};
 use std::path::PathBuf;
 
 use crate::error::ErrorKind::*;
 use crate::error::*;
 
+use crate::read_string_from;
 use crate::{ControllIdentifier, ControllerInternal, Controllers, Resources, Subsystem};
 
 /// A controller that allows controlling the `rdma` subsystem of a Cgroup.
@@ -66,14 +66,6 @@ impl<'a> From<&'a Subsystem> for &'a RdmaController {
     }
 }
 
-fn read_string_from(mut file: File) -> Result<String> {
-    let mut string = String::new();
-    match file.read_to_string(&mut string) {
-        Ok(_) => Ok(string.trim().to_string()),
-        Err(e) => Err(Error::with_cause(ReadFailed, e)),
-    }
-}
-
 impl RdmaController {
     /// Constructs a new `RdmaController` with `root` serving as the root of the control group.
     pub fn new(root: PathBuf) -> Self {