ksud_overlayfs: ability to specify custom sparse image size

userspace/ksud_overlayfs/src/module.rs

@@ -13,6 +13,8 @@ use java_properties::PropertiesIter;
 use log::{info, warn};
 
 use std::fs::OpenOptions;
+use std::fs;
+use std::io;
 use std::{
     collections::HashMap,
     env::var as env_var,
@@ -376,7 +378,39 @@ fn _install_module(zip: &str) -> Result<()> {
         humansize::format_size(zip_uncompressed_size, humansize::DECIMAL)
     );
 
-    let sparse_image_size = 6 << 30; // 6GB
+    fn parse_size(size_str: &str) -> io::Result<u64> {
+        let size_str = size_str.trim();
+        if size_str.is_empty() {
+            return Err(io::Error::new(io::ErrorKind::InvalidData, "Empty size string"));
+        }
+    
+        let (num, unit) = size_str.split_at(size_str.len().saturating_sub(1));
+        let num = u64::from_str(num.trim()).map_err(|_| io::Error::new(io::ErrorKind::InvalidData, "Invalid number"))?;
+    
+        let multiplier = match unit.to_ascii_uppercase().as_str() {
+            "G" => 1 << 30,
+            "M" => 1 << 20,
+            "K" => 1 << 10,
+            _ => 1, // Default to bytes if no unit is specified
+        };
+    
+        Ok(num * multiplier)
+    }
+    
+    fn get_sparse_image_size() -> u64 {
+        let default_size = 6 << 30; // 6GB
+        let custom_size_file = "/data/adb/ksu/custom_sparse_size.txt";
+    
+        match fs::read_to_string(custom_size_file) {
+            Ok(contents) => match parse_size(&contents) {
+                Ok(size) => size,
+                Err(_) => default_size, // Fallback on error
+            },
+            Err(_) => default_size, // Fallback if file is missing
+        }
+    }
+
+    let sparse_image_size = get_sparse_image_size();
     if !modules_img_exist && !modules_update_img_exist {
         // if no modules and modules_update, it is brand new installation, we should create a new img
         // create a tmp module img and mount it to modules_update