ei: add support for libei

src/utils/buffd/ei_formatter.rs

@@ -0,0 +1,106 @@
+use {
+    crate::{
+        ei::ei_object::EiObjectId,
+        utils::buffd::buf_out::{MsgFds, OutBuffer, OutBufferMeta, OUT_BUF_SIZE},
+    },
+    std::{mem, rc::Rc},
+    uapi::OwnedFd,
+};
+
+pub struct EiMsgFormatter<'a> {
+    buf: &'a mut [u8],
+    meta: &'a mut OutBufferMeta,
+    pos: usize,
+    fds: &'a mut Vec<Rc<OwnedFd>>,
+}
+
+impl<'a> EiMsgFormatter<'a> {
+    pub fn new(buf: &'a mut OutBuffer, fds: &'a mut Vec<Rc<OwnedFd>>) -> Self {
+        Self {
+            pos: buf.meta.write_pos,
+            buf: &mut buf.buf[..],
+            fds,
+            meta: &mut buf.meta,
+        }
+    }
+
+    fn write(&mut self, bytes: &[u8]) {
+        if bytes.len() > OUT_BUF_SIZE - self.meta.write_pos {
+            panic!("Out buffer overflow");
+        }
+        self.buf[self.meta.write_pos..self.meta.write_pos + bytes.len()].copy_from_slice(bytes);
+        self.meta.write_pos += bytes.len();
+    }
+
+    pub fn int(&mut self, int: i32) -> &mut Self {
+        self.write(uapi::as_bytes(&int));
+        self
+    }
+
+    pub fn uint(&mut self, int: u32) -> &mut Self {
+        self.write(uapi::as_bytes(&int));
+        self
+    }
+
+    #[allow(dead_code)]
+    pub fn long(&mut self, int: i64) -> &mut Self {
+        self.write(uapi::as_bytes(&int));
+        self
+    }
+
+    pub fn ulong(&mut self, int: u64) -> &mut Self {
+        self.write(uapi::as_bytes(&int));
+        self
+    }
+
+    pub fn float(&mut self, f: f32) -> &mut Self {
+        self.write(uapi::as_bytes(&f));
+        self
+    }
+
+    pub fn optstr<S: AsRef<[u8]> + ?Sized>(&mut self, s: Option<&S>) -> &mut Self {
+        match s {
+            Some(s) => self.string(s),
+            _ => self.uint(0),
+        }
+    }
+
+    pub fn string<S: AsRef<[u8]> + ?Sized>(&mut self, s: &S) -> &mut Self {
+        let s = s.as_ref();
+        let len = s.len() + 1;
+        let cap = (len + 3) & !3;
+        self.uint(len as u32);
+        self.write(uapi::as_bytes(s));
+        let none = [0; 4];
+        self.write(&none[..cap - len + 1]);
+        self
+    }
+
+    pub fn fd(&mut self, fd: Rc<OwnedFd>) -> &mut Self {
+        self.fds.push(fd);
+        self
+    }
+
+    pub fn object<T: Into<EiObjectId>>(&mut self, obj: T) -> &mut Self {
+        self.ulong(obj.into().raw())
+    }
+
+    pub fn header<T: Into<EiObjectId>>(&mut self, obj: T, event: u32) -> &mut Self {
+        self.object(obj).uint(0).uint(event)
+    }
+
+    pub fn write_len(self) {
+        assert!(self.meta.write_pos - self.pos >= 16);
+        assert_eq!(self.pos % 4, 0);
+        unsafe {
+            let second_ptr = self.buf.as_ptr().add(self.pos + 8) as *mut u32;
+            *second_ptr = (self.meta.write_pos - self.pos) as u32;
+        }
+        if self.fds.len() > 0 {
+            self.meta.fds.push_back(MsgFds {
+                pos: self.pos,
+                fds: mem::take(self.fds),
+            })
+        }
+    }
+}