Several utils-related little refactorings

src/error.rs

@@ -40,7 +40,6 @@ pub enum Error {
     InvalidLinuxVersion,
     MalformedStatm,
     MalformedPressureFile,
-    StringFromBytes,
     ParseInt,
     ParseFloat,
     SysConfFailed,

src/memory/pressure.rs

@@ -2,7 +2,7 @@ use std::fs::File;
 use std::io::Read;
 
 use crate::error::{Error, Result};
-use crate::utils::str_from_u8;
+use crate::utils::str_from_bytes;
 
 macro_rules! malformed {
     () => {
@@ -22,8 +22,9 @@ pub fn pressure_some_avg10(buf: &mut [u8]) -> Result<f32> {
 
     // `buf` won't be large enough to fit all of `/proc/pressure/memory`
     // but will be large enough to hold at least the first line, which has the data we want
-    let _ = file.read(buf)?;
-    let contents = str_from_u8(buf)?;
+    file.read(buf)?;
+    let contents = str_from_bytes(buf)?;
+
     let line = contents.lines().next().ok_or(malformed!())?;
     let mut words = line.split_ascii_whitespace();
     if let Some(indicator) = words.next() {

src/process.rs

@@ -6,7 +6,7 @@ use libc::getpgid;
 use crate::checked_ffi;
 use crate::{
     error::{Error, Result},
-    utils::{self, str_from_u8},
+    utils::{self, str_from_bytes},
 };
 
 #[derive(Debug, Default)]
@@ -53,7 +53,7 @@ impl Process {
             let _ = file.read(buf)?;
         }
 
-        str_from_u8(buf)
+        str_from_bytes(buf)
     }
 
     pub fn oom_score_from_pid(pid: u32, buf: &mut [u8]) -> Result<i16> {
@@ -63,7 +63,7 @@ impl Process {
             buf.fill(0);
             let _ = file.read(buf)?;
 
-            str_from_u8(buf)?.trim()
+            str_from_bytes(buf)?.trim()
         };
 
         Ok(contents.parse()?)
@@ -80,7 +80,7 @@ impl Process {
             buf.fill(0);
             let _ = file.read(buf)?;
 
-            str_from_u8(buf)?.split_ascii_whitespace()
+            str_from_bytes(buf)?.split_ascii_whitespace()
         };
         let vm_rss: i64 = columns.nth(1).ok_or(Error::MalformedStatm)?.parse()?;
 
@@ -115,7 +115,7 @@ impl Process {
             buf.fill(0);
             let _ = file.read(buf)?;
 
-            str_from_u8(buf)?.trim()
+            str_from_bytes(buf)?.trim()
         };
 
         Ok(contents.parse()?)

src/uname.rs

@@ -4,7 +4,6 @@ use std::mem;
 use crate::checked_ffi;
 use crate::error::{Error, Result};
 use crate::linux_version::LinuxVersion;
-use crate::utils::str_from_u8;
 use libc::{uname, utsname};
 
 pub struct Uname {
@@ -35,10 +34,10 @@ impl Uname {
         let release = unsafe { CStr::from_ptr(self.uts_struct.release.as_ptr()) };
         let arch = unsafe { CStr::from_ptr(self.uts_struct.machine.as_ptr()) };
 
-        let sysname = str_from_u8(sysname.to_bytes())?;
-        let hostname = str_from_u8(hostname.to_bytes())?;
-        let release = str_from_u8(release.to_bytes())?;
-        let arch = str_from_u8(arch.to_bytes())?;
+        let sysname = sysname.to_str()?;
+        let hostname = hostname.to_str()?;
+        let release = release.to_str()?;
+        let arch = arch.to_str()?;
 
         println!("OS:           {}", sysname);
         println!("Hostname:     {}", hostname);

src/utils.rs

@@ -1,4 +1,7 @@
+use std::ffi::OsStr;
 use std::fs::File;
+use std::os::unix::prelude::OsStrExt;
+use std::path::Path;
 use std::{ffi::CStr, mem, ptr, str};
 
 use libc::_SC_PAGESIZE;
@@ -83,18 +86,28 @@ pub fn get_username() -> Option<String> {
     None
 }
 
-/// Construct a string slice ranging from the first position to the position of the first nul byte
-pub fn str_from_u8(buf: &[u8]) -> Result<&str> {
-    let first_nul_idx = memchr(b'0', buf).unwrap_or(buf.len());
+fn bytes_until_first_nil(buf: &[u8]) -> &[u8] {
+    let first_nul_idx = memchr(0, buf).unwrap_or(buf.len());
+
+    &buf[0..first_nul_idx]
+}
 
-    let bytes = buf.get(0..first_nul_idx).ok_or(Error::StringFromBytes)?;
+/// Construct a string slice ranging from the first position to the position of the first nul byte
+pub fn str_from_bytes(buf: &[u8]) -> Result<&str> {
+    let bytes = bytes_until_first_nil(buf);
 
     Ok(str::from_utf8(bytes)?)
 }
 
+fn path_from_bytes(buf: &[u8]) -> &Path {
+    let bytes = bytes_until_first_nil(buf);
+
+    Path::new(OsStr::from_bytes(bytes))
+}
+
 /// Given a slice of bytes, try to interpret it as a file path and open the corresponding file.
 pub fn file_from_buffer(buf: &[u8]) -> Result<File> {
-    let path = str_from_u8(buf)?;
+    let path = path_from_bytes(buf);
     let file = File::open(path)?;
     Ok(file)
 }
@@ -106,11 +119,11 @@ pub fn bytes_to_megabytes(bytes: impl Into<u64>, mem_unit: impl Into<u64>) -> u6
 
 #[cfg(test)]
 mod tests {
-    use super::str_from_u8;
+    use super::str_from_bytes;
 
     #[test]
     fn should_construct_string_slice_from_bytes() {
-        assert_eq!(str_from_u8(b"ABC\0").unwrap(), "ABC");
-        assert_eq!(str_from_u8(b"ABC\0abc").unwrap(), "ABC");
+        assert_eq!(str_from_bytes(b"ABC\0").unwrap(), "ABC");
+        assert_eq!(str_from_bytes(b"ABC\0abc").unwrap(), "ABC");
     }
 }