poc(compat): squeue output parsing using header

src/job_watcher.rs

@@ -1,3 +1,4 @@
+use std::io::Lines;
 use std::path::PathBuf;
 use std::{io::BufRead, process::Command, thread, time::Duration};
 
@@ -15,6 +16,22 @@ struct JobWatcher {
 
 pub struct JobWatcherHandle {}
 
+fn addr_of(s: &str) -> usize {
+    s.as_ptr() as usize
+}
+
+fn split_whitespace_indices(s: &str) -> impl Iterator<Item = (usize, &str)> {
+    s.split_whitespace()
+        .map(move |sub| (addr_of(sub) - addr_of(s), sub))
+}
+
+fn offsets_of(s: String) -> Vec<usize> {
+    let iter = split_whitespace_indices(&s);
+    let mut indices: Vec<usize> = iter.map(|split| split.0).collect();
+    indices.push(s.len());
+    return indices;
+}
+
 impl JobWatcher {
     fn new(app: Sender<AppMessage>, interval: Duration, squeue_args: Vec<String>) -> Self {
         Self {
@@ -24,45 +41,51 @@ impl JobWatcher {
         }
     }
 
+    /// Run Slurm squeue compatible with legacy Slurm versions
+    ///
+    /// API compatible with `run`. Uses column header index offsets instead of a magic
+    /// string splitter.
     fn run(&mut self) -> Self {
-        let output_separator = "###turm###";
         let fields = [
             "jobid",
             "name",
             "state",
             "username",
             "timeused",
-            "tres-alloc",
+            "tres-alloc:80",
             "partition",
             "nodelist",
-            "stdout",
+            "stdout:80",
             "stderr",
-            "command",
+            "command:80",
             "statecompact",
             "reason",
             "ArrayJobID",  // %A
             "ArrayTaskID", // %a
             "NodeList",    // %N
             "WorkDir",     // for fallback
         ];
-        let output_format = fields
-            .map(|s| s.to_owned() + ":" + output_separator)
-            .join(",");
+        let output_format = fields.map(|s| s.to_owned()).join(",");
 
         loop {
-            let jobs: Vec<Job> = Command::new("squeue")
+            let results = Command::new("squeue")
                 .args(&self.squeue_args)
                 .arg("--array")
-                .arg("--noheader")
                 .arg("--Format")
                 .arg(&output_format)
                 .output()
-                .expect("failed to execute process")
-                .stdout
-                .lines()
+                .expect("failed to execute process");
+            let mut lines: Lines<&[u8]> = results.stdout.lines();
+            let first_line = lines.next().unwrap().unwrap();
+            let offsets = offsets_of(first_line);
+            let jobs: Vec<Job> = lines
                 .map(|l| l.unwrap().trim().to_string())
                 .filter_map(|l| {
-                    let parts: Vec<_> = l.split(output_separator).collect();
+                    let mut parts: Vec<_> = (0..offsets.len() - 1)
+                        .map(|i| l[offsets[i]..offsets[i + 1]].trim())
+                        .collect();
+                    let last_offset: usize = offsets[offsets.len() - 1];
+                    parts.push(&l[last_offset..l.len() - 1]);
 
                     if parts.len() != fields.len() + 1 {
                         return None;
@@ -208,3 +231,20 @@ impl JobWatcherHandle {
         Self {}
     }
 }
+
+#[cfg(test)]
+mod tests {
+    use super::*;
+
+    #[test]
+    fn test_offsets_of() {
+        let s = b"JOBID               NAME                STATE               USER                TIME                TRES_ALLOC          PARTITION           NODELIST            STDOUT                                                                                              STDERR              COMMAND             ST                  REASON              ARRAY_JOB_ID        ARRAY_TASK_ID       NODELIST            WORK_DIR";
+        let mut lines = s.lines();
+        let first_line = lines.next().unwrap().unwrap();
+        let results = offsets_of(first_line);
+        assert_eq!(
+            results,
+            [0, 20, 40, 60, 80, 100, 120, 140, 160, 260, 280, 300, 320, 340, 360, 380, 400, 408]
+        );
+    }
+}