Replace hard coded constant with generated bindings

Cargo.toml

@@ -16,6 +16,9 @@ travis-ci = { repository = "serde-rs/serde" }
 errno = "0.2"
 libc = "0.2"
 
+[build-dependencies]
+bindgen = "0.58.1"
+
 [dev-dependencies]
 tempfile = "3.1.0"
 lazy_static = "1.3.0"

build.rs

@@ -0,0 +1,18 @@
+extern crate bindgen;
+
+use bindgen::Builder;
+use std::{env::var, path::PathBuf};
+
+fn main() {
+    let bindings = Builder::default()
+        .header_contents("wrapper.h", "#include <linux/loop.h>")
+        .derive_default(true)
+        .generate()
+        .expect("Could not generate bindings");
+
+    let mut bindings_path = PathBuf::from(var("OUT_DIR").unwrap());
+    bindings_path.push("bindings.rs");
+    bindings
+        .write_to_file(&bindings_path)
+        .expect("Could not write bindings to file");
+}

src/lib.rs

@@ -18,27 +18,29 @@
 
 extern crate libc;
 
-use std::fs::File;
-use std::fs::OpenOptions;
-
+use bindings::{
+    loop_info64, LOOP_CLR_FD, LOOP_CTL_GET_FREE, LOOP_SET_CAPACITY, LOOP_SET_FD, LOOP_SET_STATUS64,
+};
 use libc::{c_int, ioctl};
-use std::default::Default;
-use std::io;
-use std::os::unix::prelude::*;
-use std::path::{Path, PathBuf};
-
-// TODO support missing operations
-const LOOP_SET_FD: u16 = 0x4C00;
-const LOOP_CLR_FD: u16 = 0x4C01;
-const LOOP_SET_STATUS64: u16 = 0x4C04;
-//const LOOP_GET_STATUS64: u16 = 0x4C05;
-const LOOP_SET_CAPACITY: u16 = 0x4C07;
-//const LOOP_SET_DIRECT_IO: u16 = 0x4C08;
-//const LOOP_SET_BLOCK_SIZE: u16 = 0x4C09;
-
-//const LOOP_CTL_ADD: u16 = 0x4C80;
-//const LOOP_CTL_REMOVE: u16 = 0x4C81;
-const LOOP_CTL_GET_FREE: u16 = 0x4C82;
+use std::fs::{File, OpenOptions};
+use std::{
+    default::Default,
+    io,
+    os::unix::prelude::*,
+    path::{Path, PathBuf},
+};
+
+#[allow(non_camel_case_types)]
+#[allow(dead_code)]
+#[allow(non_snake_case)]
+mod bindings {
+    include!(concat!(env!("OUT_DIR"), "/bindings.rs"));
+}
+
+#[cfg(not(target_os = "android"))]
+type IoctlRequest = libc::c_ulong;
+#[cfg(target_os = "android")]
+type IoctlRequest = libc::c_int;
 
 const LOOP_CONTROL: &str = "/dev/loop-control";
 const LOOP_PREFIX: &str = "/dev/loop";
@@ -72,7 +74,10 @@ impl LoopControl {
     /// ```
     pub fn next_free(&self) -> io::Result<LoopDevice> {
         let dev_num = ioctl_to_error(unsafe {
-            ioctl(self.dev_file.as_raw_fd() as c_int, LOOP_CTL_GET_FREE.into())
+            ioctl(
+                self.dev_file.as_raw_fd() as c_int,
+                LOOP_CTL_GET_FREE as IoctlRequest,
+            )
         })?;
         LoopDevice::open(&format!("{}{}", LOOP_PREFIX, dev_num))
     }
@@ -124,7 +129,7 @@ impl LoopDevice {
         note = "use `loop.with().offset(offset).attach(file)` instead"
     )]
     pub fn attach<P: AsRef<Path>>(&self, backing_file: P, offset: u64) -> io::Result<()> {
-        let info = LoopInfo64 {
+        let info = loop_info64 {
             lo_offset: offset,
             ..Default::default()
         };
@@ -145,7 +150,7 @@ impl LoopDevice {
     /// # ld.detach().unwrap();
     /// ```
     pub fn attach_file<P: AsRef<Path>>(&self, backing_file: P) -> io::Result<()> {
-        let info = LoopInfo64 {
+        let info = loop_info64 {
             ..Default::default()
         };
 
@@ -162,7 +167,7 @@ impl LoopDevice {
         backing_file: P,
         offset: u64,
     ) -> io::Result<()> {
-        let info = LoopInfo64 {
+        let info = loop_info64 {
             lo_offset: offset,
             ..Default::default()
         };
@@ -181,7 +186,7 @@ impl LoopDevice {
         offset: u64,
         size_limit: u64,
     ) -> io::Result<()> {
-        let info = LoopInfo64 {
+        let info = loop_info64 {
             lo_offset: offset,
             lo_sizelimit: size_limit,
             ..Default::default()
@@ -190,11 +195,11 @@ impl LoopDevice {
         Self::attach_with_loop_info(self, backing_file, info)
     }
 
-    /// Attach the loop device to a file with loop_info.
+    /// Attach the loop device to a file with loop_info64.
     fn attach_with_loop_info(
         &self, // TODO should be mut? - but changing it is a breaking change
         backing_file: impl AsRef<Path>,
-        info: LoopInfo64,
+        info: loop_info64,
     ) -> io::Result<()> {
         let bf = OpenOptions::new()
             .read(true)
@@ -205,15 +210,15 @@ impl LoopDevice {
         ioctl_to_error(unsafe {
             ioctl(
                 self.device.as_raw_fd() as c_int,
-                LOOP_SET_FD.into(),
+                LOOP_SET_FD as IoctlRequest,
                 bf.as_raw_fd() as c_int,
             )
         })?;
 
         if let Err(err) = ioctl_to_error(unsafe {
             ioctl(
                 self.device.as_raw_fd() as c_int,
-                LOOP_SET_STATUS64.into(),
+                LOOP_SET_STATUS64 as IoctlRequest,
                 &info,
             )
         }) {
@@ -252,7 +257,13 @@ impl LoopDevice {
     /// ld.detach().unwrap();
     /// ```
     pub fn detach(&self) -> io::Result<()> {
-        ioctl_to_error(unsafe { ioctl(self.device.as_raw_fd() as c_int, LOOP_CLR_FD.into(), 0) })?;
+        ioctl_to_error(unsafe {
+            ioctl(
+                self.device.as_raw_fd() as c_int,
+                LOOP_CLR_FD as IoctlRequest,
+                0,
+            )
+        })?;
         Ok(())
     }
 
@@ -262,7 +273,7 @@ impl LoopDevice {
         ioctl_to_error(unsafe {
             ioctl(
                 self.device.as_raw_fd() as c_int,
-                LOOP_SET_CAPACITY.into(),
+                LOOP_SET_CAPACITY as IoctlRequest,
                 0,
             )
         })?;
@@ -300,7 +311,7 @@ impl LoopDevice {
 /// ```
 pub struct AttachOptions<'d> {
     device: &'d mut LoopDevice,
-    info: LoopInfo64,
+    info: loop_info64,
 }
 
 impl AttachOptions<'_> {
@@ -333,44 +344,6 @@ impl AttachOptions<'_> {
     }
 }
 
-// https://man7.org/linux/man-pages/man4/loop.4.html
-#[repr(C)]
-struct LoopInfo64 {
-    pub lo_device: u64,           // ioctl r/o
-    pub lo_inode: u64,            // ioctl r/o
-    pub lo_rdevice: u64,          // ioctl r/o
-    pub lo_offset: u64,           //
-    pub lo_sizelimit: u64,        // bytes, 0 == max available
-    pub lo_number: u32,           // ioctl r/o
-    pub lo_encrypt_type: u32,     //
-    pub lo_encrypt_key_size: u32, // ioctl w/o
-    pub lo_flags: u32,            // ioctl r/w (r/o before Linux 2.6.25)
-    pub lo_file_name: [u8; 64],   //
-    pub lo_crypt_name: [u8; 64],  //
-    pub lo_encrypt_key: [u8; 32], // ioctl w/o
-    pub lo_init: [u64; 2],        //
-}
-
-impl Default for LoopInfo64 {
-    fn default() -> Self {
-        Self {
-            lo_device: 0,
-            lo_inode: 0,
-            lo_rdevice: 0,
-            lo_offset: 0,
-            lo_sizelimit: 0,
-            lo_number: 0,
-            lo_encrypt_type: 0,
-            lo_encrypt_key_size: 0,
-            lo_flags: 0,
-            lo_file_name: [0; 64],
-            lo_crypt_name: [0; 64],
-            lo_encrypt_key: [0; 32],
-            lo_init: [0; 2],
-        }
-    }
-}
-
 fn ioctl_to_error(ret: i32) -> io::Result<i32> {
     if ret < 0 {
         Err(io::Error::last_os_error())

tests/util/mod.rs

@@ -1,9 +1,11 @@
 use libc::fallocate;
 use serde::{Deserialize, Deserializer};
-use std::io;
-use std::os::unix::io::AsRawFd;
-use std::process::Command;
-use std::sync::{Arc, Mutex, MutexGuard};
+use std::{
+    io,
+    os::unix::io::AsRawFd,
+    process::Command,
+    sync::{Arc, Mutex, MutexGuard},
+};
 
 use tempfile::{NamedTempFile, TempPath};