wasi-c2: rewrite wasi-common in terms of system-interface

crates/wasi-c2/src/file.rs

@@ -0,0 +1,53 @@
+use crate::Error;
+use std::ops::Deref;
+use system_interface::fs::FileIoExt;
+
+pub trait WasiFile: FileIoExt {}
+
+pub(crate) struct FileEntry {
+    pub(crate) base_caps: FileCaps,
+    pub(crate) inheriting_caps: FileCaps,
+    pub(crate) file: Box<dyn WasiFile>,
+}
+
+impl FileEntry {
+    pub fn get_cap(&self, caps: FileCaps) -> Result<&dyn WasiFile, Error> {
+        if self.base_caps.contains(&caps) && self.inheriting_caps.contains(&caps) {
+            Ok(self.file.deref())
+        } else {
+            Err(Error::FileNotCapable(caps))
+        }
+    }
+}
+
+#[derive(Debug, Clone, Copy)]
+pub struct FileCaps {
+    flags: u32,
+}
+
+impl FileCaps {
+    pub fn empty() -> Self {
+        FileCaps { flags: 0 }
+    }
+
+    /// Checks if `other` is a subset of those capabilties:
+    pub fn contains(&self, other: &Self) -> bool {
+        self.flags & other.flags == other.flags
+    }
+
+    pub const DATASYNC: Self = FileCaps { flags: 1 };
+    pub const READ: Self = FileCaps { flags: 2 };
+    pub const SEEK: Self = FileCaps { flags: 4 };
+    pub const FDSTAT_SET_FLAGS: Self = FileCaps { flags: 8 };
+    pub const SYNC: Self = FileCaps { flags: 16 };
+    pub const TELL: Self = FileCaps { flags: 32 };
+    pub const WRITE: Self = FileCaps { flags: 64 };
+    pub const ADVISE: Self = FileCaps { flags: 128 };
+    pub const ALLOCATE: Self = FileCaps { flags: 256 };
+}
+
+impl std::fmt::Display for FileCaps {
+    fn fmt(&self, _f: &mut std::fmt::Formatter) -> std::fmt::Result {
+        todo!()
+    }
+}