kernel, ksud: collect binaries into /data/adb/ksu (#161)

userspace/ksud/src/utils.rs

@@ -1,7 +1,11 @@
-use std::path::Path;
-
-use anyhow::{ensure, Context, Result};
+use anyhow::{bail, ensure, Context, Error, Ok, Result};
 use retry::delay::NoDelay;
+use std::{
+    fs::{create_dir_all, set_permissions, write, File, Permissions},
+    io::ErrorKind::AlreadyExists,
+    os::unix::prelude::PermissionsExt,
+    path::Path,
+};
 use sys_mount::{unmount, FilesystemType, Mount, UnmountFlags};
 
 fn do_mount_image(src: &str, target: &str) -> Result<()> {
@@ -33,6 +37,52 @@ pub fn ensure_clean_dir(dir: &str) -> Result<()> {
     Ok(std::fs::create_dir_all(path)?)
 }
 
+pub fn ensure_file_exists<T: AsRef<Path>>(file: T) -> Result<()> {
+    match File::options().write(true).create_new(true).open(&file) {
+        std::result::Result::Ok(_) => Ok(()),
+        Err(err) => {
+            if err.kind() == AlreadyExists && file.as_ref().is_file() {
+                Ok(())
+            } else {
+                Err(Error::from(err)).with_context(|| {
+                    format!("{} is not a regular file", file.as_ref().to_str().unwrap())
+                })
+            }
+        }
+    }
+}
+
+pub fn ensure_dir_exists<T: AsRef<Path>>(dir: T) -> Result<()> {
+    let result = create_dir_all(&dir).map_err(Error::from);
+    if dir.as_ref().is_dir() {
+        result
+    } else if result.is_ok() {
+        bail!(
+            "{} is not a regular directory",
+            dir.as_ref().to_str().unwrap()
+        )
+    } else {
+        result
+    }
+}
+
+pub fn ensure_binary<T: AsRef<Path>>(path: T, contents: &[u8]) -> Result<()> {
+    if path.as_ref().exists() {
+        return Ok(());
+    }
+
+    ensure_dir_exists(path.as_ref().parent().ok_or_else(|| {
+        anyhow::anyhow!(
+            "{} does not have parent directory",
+            path.as_ref().to_string_lossy()
+        )
+    })?)?;
+
+    write(&path, contents)?;
+    set_permissions(&path, Permissions::from_mode(0o755))?;
+    Ok(())
+}
+
 pub fn getprop(prop: &str) -> Option<String> {
     android_properties::getprop(prop).value()
 }