[pve-devel] [PATCH installer v2 4/4] assistant: avoid regex for simple prefix matching

[Christoph Heiss]

udev properties are very easy to parse and can be done by doing a
line-based scan and matching the prefix, splitting once for properties.
Avoids the use of regexes and signicantly reduces binary size by about
-38%(!).

Tested by comparing the output of `proxmox-auto-install-assistant
device-info`, running it before and after the changes.

Stripped binary size for release builds:
  before: 3103104 bytes ~ 2.96MiB
  after:  1935744 bytes ~ 1.85MiB

   text    data     bss     dec     hex filename
2906765  187144     537 3094446  2f37ae proxmox-auto-install-assistant-before
1871090   55736     497 1927323  1d689b proxmox-auto-install-assistant-after

No functional changes.

Signed-off-by: Christoph Heiss <c.heiss at proxmox.com>
---
Changes v1 -> v2:
  * rebased on latest master

 proxmox-auto-install-assistant/Cargo.toml  |  1 -
 proxmox-auto-install-assistant/src/main.rs | 57 +++++++++-------------
 2 files changed, 24 insertions(+), 34 deletions(-)

diff --git a/proxmox-auto-install-assistant/Cargo.toml b/proxmox-auto-install-assistant/Cargo.toml
index 0286c80..766b445 100644
--- a/proxmox-auto-install-assistant/Cargo.toml
+++ b/proxmox-auto-install-assistant/Cargo.toml
@@ -15,7 +15,6 @@ anyhow = "1.0"
 clap = { version = "4.0", features = ["derive"] }
 glob = "0.3"
 proxmox-auto-installer = { path = "../proxmox-auto-installer" }
-regex = "1.7"
 serde = { version = "1.0", features = ["derive"] }
 serde_json = "1.0"
 toml = "0.7"
diff --git a/proxmox-auto-install-assistant/src/main.rs b/proxmox-auto-install-assistant/src/main.rs
index 790dbc7..7c0b0c6 100644
--- a/proxmox-auto-install-assistant/src/main.rs
+++ b/proxmox-auto-install-assistant/src/main.rs
@@ -1,7 +1,6 @@
 use anyhow::{bail, format_err, Result};
 use clap::{Args, Parser, Subcommand, ValueEnum};
 use glob::Pattern;
-use regex::Regex;
 use serde::Serialize;
 use std::{
     collections::BTreeMap,
@@ -439,13 +438,9 @@ fn get_disks() -> Result<BTreeMap<String, BTreeMap<String, String>>> {
         Pattern::new("sr[0-9]*")?,
     ];
 
-    // compile Regex here once and not inside the loop
-    let re_disk = Regex::new(r"(?m)^E: DEVTYPE=disk")?;
-    let re_cdrom = Regex::new(r"(?m)^E: ID_CDROM")?;
-    let re_iso9660 = Regex::new(r"(?m)^E: ID_FS_TYPE=iso9660")?;
-
-    let re_name = Regex::new(r"(?m)^N: (.*)$")?;
-    let re_props = Regex::new(r"(?m)^E: ([^=]+)=(.*)$")?;
+    const PROP_DEVTYP_PREFIX: &str = "E: DEVTYPE=";
+    const PROP_CDROM: &str = "E: ID_CDROM";
+    const PROP_ISO9660_FS: &str = "E: ID_FS_TYPE=iso9660";
 
     let mut disks: BTreeMap<String, BTreeMap<String, String>> = BTreeMap::new();
 
@@ -467,30 +462,27 @@ fn get_disks() -> Result<BTreeMap<String, BTreeMap<String, String>>> {
             }
         };
 
-        if !re_disk.is_match(&output) {
-            continue 'outer;
-        };
-        if re_cdrom.is_match(&output) {
-            continue 'outer;
-        };
-        if re_iso9660.is_match(&output) {
-            continue 'outer;
-        };
-
         let mut name = filename;
-        if let Some(cap) = re_name.captures(&output) {
-            if let Some(res) = cap.get(1) {
-                name = String::from(res.as_str());
+        let mut udev_props: BTreeMap<String, String> = BTreeMap::new();
+        for line in output.lines() {
+            if let Some(prop) = line.strip_prefix(PROP_DEVTYP_PREFIX) {
+                if prop != "disk" {
+                    continue 'outer;
+                }
             }
-        }
 
-        let mut udev_props: BTreeMap<String, String> = BTreeMap::new();
+            if line.starts_with(PROP_CDROM) || line.starts_with(PROP_ISO9660_FS) {
+                continue 'outer;
+            }
 
-        for line in output.lines() {
-            if let Some(caps) = re_props.captures(line) {
-                let key = String::from(caps.get(1).unwrap().as_str());
-                let value = String::from(caps.get(2).unwrap().as_str());
-                udev_props.insert(key, value);
+            if let Some(prop) = line.strip_prefix("N: ") {
+                name = prop.to_owned();
+            };
+
+            if let Some(prop) = line.strip_prefix("E: ") {
+                if let Some((key, val)) = prop.split_once('=') {
+                    udev_props.insert(key.to_owned(), val.to_owned());
+                }
             }
         }
 
@@ -500,7 +492,6 @@ fn get_disks() -> Result<BTreeMap<String, BTreeMap<String, String>>> {
 }
 
 fn get_nics() -> Result<BTreeMap<String, BTreeMap<String, String>>> {
-    let re_props = Regex::new(r"(?m)^E: (.*)=(.*)$")?;
     let mut nics: BTreeMap<String, BTreeMap<String, String>> = BTreeMap::new();
 
     let links = get_nic_list()?;
@@ -518,10 +509,10 @@ fn get_nics() -> Result<BTreeMap<String, BTreeMap<String, String>>> {
         let mut udev_props: BTreeMap<String, String> = BTreeMap::new();
 
         for line in output.lines() {
-            if let Some(caps) = re_props.captures(line) {
-                let key = String::from(caps.get(1).unwrap().as_str());
-                let value = String::from(caps.get(2).unwrap().as_str());
-                udev_props.insert(key, value);
+            if let Some(prop) = line.strip_prefix("E: ") {
+                if let Some((key, val)) = prop.split_once('=') {
+                    udev_props.insert(key.to_owned(), val.to_owned());
+                }
             }
         }
 
-- 
2.44.0