autocommit 2022-01-02 20:11:25 CET

src/utils/buffd/parser.rs

@@ -0,0 +1,93 @@
+use crate::globals::GlobalName;
+use crate::object::ObjectId;
+use crate::utils::buffd::BufFdIn;
+use thiserror::Error;
+use uapi::OwnedFd;
+
+#[derive(Debug, Error)]
+pub enum MsgParserError {
+    #[error("The message ended unexpectedly")]
+    UnexpectedEof,
+    #[error("The message contained a non-utf8 string")]
+    NonUtf8,
+    #[error("The message contained a string of size 0")]
+    EmptyString,
+    #[error("Message is missing a required file descriptor")]
+    MissingFd,
+    #[error("There is trailing data after the message")]
+    TrailingData,
+}
+
+pub struct MsgParser<'a, 'b> {
+    buf: &'a mut BufFdIn,
+    pos: usize,
+    data: &'b [u8],
+}
+
+impl<'a, 'b> MsgParser<'a, 'b> {
+    pub fn new(buf: &'a mut BufFdIn, data: &'b [u32]) -> Self {
+        Self {
+            buf,
+            pos: 0,
+            data: unsafe { std::slice::from_raw_parts(data.as_ptr() as *const u8, data.len() * 4) },
+        }
+    }
+
+    pub fn int(&mut self) -> Result<i32, MsgParserError> {
+        if self.data.len() - self.pos < 4 {
+            return Err(MsgParserError::UnexpectedEof);
+        }
+        let res = unsafe { *(self.data.as_ptr().add(self.pos) as *const i32) };
+        self.pos += 4;
+        Ok(res)
+    }
+
+    pub fn uint(&mut self) -> Result<u32, MsgParserError> {
+        self.int().map(|i| i as u32)
+    }
+
+    pub fn object(&mut self) -> Result<ObjectId, MsgParserError> {
+        self.int().map(|i| ObjectId::from_raw(i as u32))
+    }
+
+    pub fn global(&mut self) -> Result<GlobalName, MsgParserError> {
+        self.int().map(|i| GlobalName::from_raw(i as u32))
+    }
+
+    pub fn fixed(&mut self) -> Result<f64, MsgParserError> {
+        self.int().map(|i| i as f64 / 256.0)
+    }
+
+    pub fn string(&mut self) -> Result<&'b str, MsgParserError> {
+        let len = self.uint()? as usize;
+        if len == 0 {
+            return Err(MsgParserError::EmptyString);
+        }
+        let cap = (len + 3) & !3;
+        if cap > self.data.len() - self.pos {
+            return Err(MsgParserError::UnexpectedEof);
+        }
+        let s = &self.data[self.pos..self.pos + len - 1];
+        let s = match std::str::from_utf8(s) {
+            Ok(s) => s,
+            _ => return Err(MsgParserError::NonUtf8),
+        };
+        self.pos += cap;
+        Ok(s)
+    }
+
+    pub fn fd(&mut self) -> Result<OwnedFd, MsgParserError> {
+        match self.buf.get_fd() {
+            Ok(fd) => Ok(fd),
+            _ => Err(MsgParserError::MissingFd),
+        }
+    }
+
+    pub fn eof(&self) -> Result<(), MsgParserError> {
+        if self.pos == self.data.len() {
+            Ok(())
+        } else {
+            Err(MsgParserError::TrailingData)
+        }
+    }
+}