From fafb9048750be670f7eb9706567865f44fd1ae6b Mon Sep 17 00:00:00 2001
From: Lachlan Sneff <lachlan.sneff@gmail.com>
Date: Mon, 17 Dec 2018 18:57:44 -0500
Subject: [PATCH] Initial additional modules

---
 src/webassembly/mod.rs       |   2 +
 src/webassembly/vmcontext.rs | 153 +++++++++++++++++++++++++++++++++++
 src/webassembly/vmoffsets.rs |  12 +++
 3 files changed, 167 insertions(+)
 create mode 100644 src/webassembly/vmcontext.rs
 create mode 100644 src/webassembly/vmoffsets.rs

diff --git a/src/webassembly/mod.rs b/src/webassembly/mod.rs
index 5c679ba48..d285582d9 100644
--- a/src/webassembly/mod.rs
+++ b/src/webassembly/mod.rs
@@ -6,6 +6,8 @@ pub mod memory;
 pub mod module;
 pub mod relocation;
 pub mod utils;
+pub mod vmcontext;
+pub mod vmoffsets;
 
 use cranelift_codegen::{
     isa,
diff --git a/src/webassembly/vmcontext.rs b/src/webassembly/vmcontext.rs
new file mode 100644
index 000000000..5efc7c62b
--- /dev/null
+++ b/src/webassembly/vmcontext.rs
@@ -0,0 +1,153 @@
+
+use cranelift_wasm::{
+    TableIndex, FuncIndex, MemoryIndex, GlobalIndex,
+    DefinedTableIndex, DefinedFuncIndex, DefinedMemoryIndex, DefinedGlobalIndex,
+    SignatureIndex,
+};
+use crate::webassembly::vmoffsets::VMOffsets;
+
+#[repr(C)]
+pub struct VMContext {
+    /// A pointer to an array of imported functions, indexed by `FuncIndex`.
+    imported_functions: *const *const VMFunctionBody,
+
+    /// A pointer to an array of imported tables, indexed by `TableIndex`.
+    imported_tables: *mut VMTableImport,
+
+    /// A pointer to an array of imported memories, indexed by `MemoryIndex,
+    imported_memories: *mut VMMemoryImport,
+
+    /// A pointer to an array of imported globals, indexed by `GlobalIndex`.
+    imported_globals: *mut VMGlobalImport,
+
+    /// A pointer to an array of locally-defined tables, indexed by `DefinedTableIndex`.
+    tables: *mut VMTableDefinition,
+
+    /// A pointer to an array of locally-defined memories, indexed by `DefinedMemoryIndex`.
+    memories: *mut VMMemoryDefinition,
+
+    /// A pointer to an array of locally-defined globals, indexed by ``DefinedGlobalIndex`.
+    globals: *mut VMGlobalDefinition,
+
+    /// Signature identifiers for signature-checked indirect calls.
+    signature_ids: *mut VMSharedSigIndex,
+}
+
+/// Used to provide type safety for passing around function pointers.
+/// The typesystem ensures this cannot be dereferenced.
+pub enum VMFunctionBody { }
+
+/// Definition of a table used by the VM. (obviously)
+#[repr(C)]
+pub struct VMTableDefinition {
+    /// pointer to the elements in the table.
+    pub base: *mut u8,
+    /// Number of elements in the table (NOT necessarily the size of the table in bytes!).
+    pub current_elements: usize,
+}
+
+impl VMTableDefinition {
+    pub fn offset_base(offsets: &VMOffsets) -> u8 {
+        0 * offsets.ptr_size
+    }
+
+    pub fn offset_current_elements(offsets: &VMOffsets) -> u8 {
+        1 * offsets.ptr_size
+    }
+}
+
+#[repr(C)]
+pub struct VMTableImport {
+    /// A pointer to the table definition.
+    pub table: *mut VMTableDefinition,
+    /// A pointer to the vmcontext that owns this table definition.
+    pub vmctx: *mut VMContext,
+}
+
+impl VMTableImport {
+    pub fn offset_table(offsets: &VMOffsets) -> u8 {
+        0 * offsets.ptr_size
+    }
+
+    pub fn offset_vmctx(offsets: &VMOffsets) -> u8 {
+        1 * offsets.ptr_size
+    }
+}
+
+/// Definition of a memory used by the VM.
+#[repr(C)]
+pub struct VMMemoryDefinition {
+    /// Pointer to the bottom of linear memory.
+    pub base: *mut u8,
+    /// Current logical size of this linear memory in bytes.
+    pub size: usize,
+}
+
+impl VMMemoryDefinition {
+    pub fn offset_base(offsets: &VMOffsets) -> u8 {
+        0 * offsets.ptr_size
+    }
+
+    pub fn offset_size(offsets: &VMOffsets) -> u8 {
+        1 * offsets.ptr_size
+    }
+}
+
+#[repr(C)]
+pub struct VMMemoryImport {
+    /// A pointer to the memory definition.
+    pub memory: *mut VMMemoryDefinition,
+    /// A pointer to the vmcontext that owns this memory definition.
+    pub vmctx: *mut VMContext,
+}
+
+impl VMMemoryImport {
+    pub fn offset_memory(offsets: &VMOffsets) -> u8 {
+        0 * offsets.ptr_size
+    }
+
+    pub fn offset_vmctx(offsets: &VMOffsets) -> u8 {
+        1 * offsets.ptr_size
+    }
+}
+
+/// Definition of a global used by the VM.
+#[repr(C, align(8))]
+pub struct VMGlobalDefinition {
+    pub data: [u8; 8],
+}
+
+#[repr(C)]
+pub struct VMGlobalImport {
+    pub globals: *mut VMGlobalDefinition,
+}
+
+impl VMGlobalImport {
+    pub fn offset_globals(offsets: &VMOffsets) -> u8 {
+        0 * offsets.ptr_size
+    }
+}
+
+#[repr(C)]
+pub struct VMSharedSigIndex(u32);
+
+#[repr(C)]
+pub struct VMCallerCheckedAnyfunc {
+    pub func: *const VMFunctionBody,
+    pub type_index: VMSharedSigIndex,
+    pub vmctx: *mut VMContext,
+}
+
+impl VMCallerCheckedAnyfunc {
+    pub fn offset_func(offsets: &VMOffsets) -> u8 {
+        0 * offsets.ptr_size
+    }
+
+    pub fn offset_type_index(offsets: &VMOffsets) -> u8 {
+        1 * offsets.ptr_size
+    }
+
+    pub fn offset_vmctx(offsets: &VMOffsets) -> u8 {
+        2 * offsets.ptr_size
+    }
+}
\ No newline at end of file
diff --git a/src/webassembly/vmoffsets.rs b/src/webassembly/vmoffsets.rs
new file mode 100644
index 000000000..bfe7af3d5
--- /dev/null
+++ b/src/webassembly/vmoffsets.rs
@@ -0,0 +1,12 @@
+
+pub struct VMOffsets {
+    pub(in crate::webassembly) ptr_size: u8,
+}
+
+impl VMOffsets {
+    pub fn new(ptr_size: u8) -> Self {
+        Self {
+            ptr_size,
+        }
+    }
+}
\ No newline at end of file