Abstract getting unique status result into a single method

Removes a possibly failing assertion and some unnecessary code
duplication.

Signed-off-by: mulhern <amulhern@redhat.com>

Author: mulkieran

src/cachedev.rs

@@ -11,7 +11,7 @@ use crate::core::{DevId, Device, DeviceInfo, DmName, DmOptions, DmUuid, DM};
 use crate::lineardev::{LinearDev, LinearDevTargetParams};
 use crate::result::{DmError, DmResult, ErrorEnum};
 use crate::shared::{
-    device_create, device_exists, device_match, get_status_line_fields,
+    device_create, device_exists, device_match, get_status, get_status_line_fields,
     make_unexpected_value_error, parse_device, parse_value, DmDevice, TargetLine, TargetParams,
     TargetTable, TargetTypeBuf,
 };
@@ -713,14 +713,7 @@ impl CacheDev {
     /// Get the current status of the cache device.
     pub fn status(&self, dm: &DM) -> DmResult<CacheDevStatus> {
         let (_, status) = dm.table_status(&DevId::Name(self.name()), &DmOptions::new())?;
-
-        assert_eq!(
-            status.len(),
-            1,
-            "Kernel must return 1 line from cache dev status"
-        );
-
-        status.first().expect("assertion above holds").3.parse()
+        get_status(&status)?.parse()
     }
 }
 

src/shared.rs

@@ -245,6 +245,27 @@ pub fn get_status_line_fields<'a>(
     Ok(status_vals)
 }
 
+/// Get unique status element from a status result.
+/// Return an error if an incorrect number of lines is obtained.
+pub fn get_status(status_lines: &[(u64, u64, String, String)]) -> DmResult<String> {
+    let length = status_lines.len();
+    if length != 1 {
+        return Err(DmError::Dm(
+            ErrorEnum::Invalid,
+            format!(
+                "Incorrect number of lines for status; expected 1, found {} in status result \"{}\"",
+                length,
+                status_lines.iter().map(|(s, l, t, v)| format!("{} {} {} {}", s, l, t, v)).collect::<Vec<String>>().join(", ")
+            ),
+        ));
+    }
+    Ok(status_lines
+        .first()
+        .expect("if length != 1, already returned")
+        .3
+        .to_owned())
+}
+
 /// Construct an error when parsing yields an unexpected value.
 /// Indicate the location of the unexpected value, 1-indexed, its actual
 /// value, and the name of the expected thing.

src/thindev.rs

@@ -9,8 +9,8 @@ use std::str::FromStr;
 use crate::core::{DevId, Device, DeviceInfo, DmCookie, DmFlags, DmName, DmOptions, DmUuid, DM};
 use crate::result::{DmError, DmResult, ErrorEnum};
 use crate::shared::{
-    device_create, device_exists, device_match, get_status_line_fields, message, parse_device,
-    parse_value, DmDevice, TargetLine, TargetParams, TargetTable, TargetTypeBuf,
+    device_create, device_exists, device_match, get_status, get_status_line_fields, message,
+    parse_device, parse_value, DmDevice, TargetLine, TargetParams, TargetTable, TargetTypeBuf,
 };
 use crate::thindevid::ThinDevId;
 use crate::thinpooldev::ThinPoolDev;
@@ -379,14 +379,7 @@ impl ThinDev {
     /// Get the current status of the thin device.
     pub fn status(&self, dm: &DM) -> DmResult<ThinStatus> {
         let (_, table) = dm.table_status(&DevId::Name(self.name()), &DmOptions::new())?;
-
-        assert_eq!(
-            table.len(),
-            1,
-            "Kernel must return 1 line table for thin status"
-        );
-
-        table.first().expect("assertion above holds").3.parse()
+        get_status(&table)?.parse()
     }
 
     /// Set the table for the thin device's target

src/thinpooldev.rs

@@ -11,7 +11,7 @@ use crate::core::{DevId, Device, DeviceInfo, DmName, DmOptions, DmUuid, DM};
 use crate::lineardev::{LinearDev, LinearDevTargetParams};
 use crate::result::{DmError, DmResult, ErrorEnum};
 use crate::shared::{
-    device_create, device_exists, device_match, get_status_line_fields,
+    device_create, device_exists, device_match, get_status, get_status_line_fields,
     make_unexpected_value_error, parse_device, parse_value, DmDevice, TargetLine, TargetParams,
     TargetTable, TargetTypeBuf,
 };
@@ -547,14 +547,7 @@ impl ThinPoolDev {
     /// Returns an error if there was an error getting the status value.
     pub fn status(&self, dm: &DM) -> DmResult<ThinPoolStatus> {
         let (_, status) = dm.table_status(&DevId::Name(self.name()), &DmOptions::new())?;
-
-        assert_eq!(
-            status.len(),
-            1,
-            "Kernel must return 1 line from thin pool status"
-        );
-
-        status.first().expect("assertion above holds").3.parse()
+        get_status(&status)?.parse()
     }
 
     /// Set the table for the existing metadata device.