Add support for /proc/partitions parsing

This parses the data looking like:

  $ cat /proc/partitions
  major minor  #blocks  name

   259        0 1000204632 nvme0n1
   259        1    1048576 nvme0n1p1
   259        2    1048576 nvme0n1p2
   259        3  104857600 nvme0n1p3
   259        4  893248512 nvme0n1p4
   253        0  104841216 dm-0
   252        0    8388608 zram0
   253        1  893232128 dm-1
     8        0    3953664 sda
     8        1    2097152 sda1
     8        2    1855488 sda2
   253        2    1853440 dm-2

with the first two lines discarded when parsing.

Signed-off-by: Daniel P. Berrangé <berrange@redhat.com>

procfs-core/src/lib.rs

@@ -365,6 +365,9 @@ pub use locks::*;
 mod mounts;
 pub use mounts::*;
 
+mod partitions;
+pub use partitions::*;
+
 mod meminfo;
 pub use meminfo::*;
 

procfs-core/src/partitions.rs

@@ -0,0 +1,87 @@
+use std::io::BufRead;
+
+use super::ProcResult;
+use std::str::FromStr;
+
+#[cfg(feature = "serde1")]
+use serde::{Deserialize, Serialize};
+
+/// A partition entry under `/proc/partitions`
+#[derive(Debug, Clone)]
+#[cfg_attr(feature = "serde1", derive(Serialize, Deserialize))]
+#[allow(non_snake_case)]
+pub struct PartitionEntry {
+    /// Device major number
+    pub major: u16,
+    /// Device minor number
+    pub minor: u16,
+    /// Number of 512 byte blocks
+    pub blocks: u64,
+    /// Device name
+    pub name: String
+}
+
+impl super::FromBufRead for Vec<PartitionEntry> {
+    fn from_buf_read<R: BufRead>(r: R) -> ProcResult<Self> {
+        let mut vec = Vec::new();
+
+        for line in r.lines().skip(2) {
+            let line = expect!(line);
+
+            let mut s = line.split_whitespace();
+
+            let major = expect!(u16::from_str(expect!(s.next())));
+            let minor = expect!(u16::from_str(expect!(s.next())));
+            let blocks = expect!(u64::from_str(expect!(s.next())));
+            let name = expect!(s.next()).to_string();
+
+            let partition_entry = PartitionEntry {
+                major,
+		minor,
+		blocks,
+		name
+            };
+
+            vec.push(partition_entry);
+        }
+
+        Ok(vec)
+    }
+}
+
+
+#[test]
+fn test_partitions() {
+    use crate::FromBufRead;
+    use std::io::Cursor;
+
+    let s = "major minor  #blocks  name
+
+ 259        0 1000204632 nvme0n1
+ 259        1    1048576 nvme0n1p1
+ 259        2    1048576 nvme0n1p2
+ 259        3  104857600 nvme0n1p3
+ 259        4  893248512 nvme0n1p4
+ 253        0  104841216 dm-0
+ 252        0    8388608 zram0
+ 253        1  893232128 dm-1
+   8        0    3953664 sda
+   8        1    2097152 sda1
+   8        2    1855488 sda2
+ 253        2    1853440 dm-2
+";
+
+    let cursor = Cursor::new(s);
+    let partitions = Vec::<PartitionEntry>::from_buf_read(cursor).unwrap();
+    assert_eq!(partitions.len(), 12);
+
+    assert_eq!(partitions[3].major, 259);
+    assert_eq!(partitions[3].minor, 3);
+    assert_eq!(partitions[3].blocks, 104857600);
+    assert_eq!(partitions[3].name, "nvme0n1p3");
+
+    assert_eq!(partitions[11].major, 253);
+    assert_eq!(partitions[11].minor, 2);
+    assert_eq!(partitions[11].blocks, 1853440);
+    assert_eq!(partitions[11].name, "dm-2");
+}

procfs/examples/partitions.rs

@@ -0,0 +1,7 @@
+// List partitions listed in /proc/partitions
+
+fn main() {
+    for part_entry in procfs::partitions().unwrap() {
+        println!("{part_entry:?}");
+    }
+}

procfs/src/lib.rs

@@ -472,6 +472,15 @@ pub fn mounts() -> ProcResult<Vec<MountEntry>> {
     Vec::<MountEntry>::current()
 }
 
+impl Current for Vec<PartitionEntry> {
+    const PATH: &'static str = "/proc/partitions";
+}
+
+/// Get a list of partitions from `/proc/partitions`
+pub fn partitions() -> ProcResult<Vec<PartitionEntry>> {
+    Vec::<PartitionEntry>::current()
+}
+
 impl Current for Locks {
     const PATH: &'static str = "/proc/locks";
 }

support.md

@@ -115,7 +115,7 @@ This is an approximate list of all the files under the `/proc` mount, and an ind
   * [x] `/proc/net/udp`
   * [x] `/proc/net/unix`
   * [ ] `/proc/net/netfilter/nfnetlink_queue`
-* [ ] `/proc/partitions`
+* [x] `/proc/partitions`
 * [ ] `/proc/pci`
 * [x] `/proc/pressure`
   * [x] `/proc/pressure/cpu`