First iteration of wasmer-reborn

lib/compiler/src/jump_table.rs

@@ -0,0 +1,33 @@
+//! A jump table is a method of transferring program control (branching)
+//! to another part of a program (or a different program that may have
+//! been dynamically loaded) using a table of branch or jump instructions.
+//!
+//! Source: https://en.wikipedia.org/wiki/Branch_table
+
+use super::CodeOffset;
+use serde::{Deserialize, Serialize};
+use wasm_common::entity::{entity_impl, SecondaryMap};
+
+/// An opaque reference to a [jump table](https://en.wikipedia.org/wiki/Branch_table).
+///
+/// `JumpTable`s are used for indirect branching and are specialized for dense,
+/// 0-based jump offsets.
+#[derive(Copy, Clone, PartialEq, Eq, Hash, PartialOrd, Ord, Serialize, Deserialize)]
+pub struct JumpTable(u32);
+entity_impl!(JumpTable, "jt");
+
+impl JumpTable {
+    /// Create a new jump table reference from its number.
+    ///
+    /// This method is for use by the parser.
+    pub fn with_number(n: u32) -> Option<Self> {
+        if n < u32::max_value() {
+            Some(Self(n))
+        } else {
+            None
+        }
+    }
+}
+
+/// Code offsets for Jump Tables.
+pub type JumpTableOffsets = SecondaryMap<JumpTable, CodeOffset>;