start work on binary format, per v8 spec

1 files changed, 200 insertions, 0 deletions

diff --git a/src/wasm-binary.h b/src/wasm-binary.h
new file mode 100644
index 000000000..9b81cffe8
--- /dev/null
+++ b/src/wasm-binary.h
@@ -0,0 +1,200 @@
+/*
+ * Copyright 2015 WebAssembly Community Group participants
+ *
+ * Licensed under the Apache License, Version 2.0 (the "License");
+ * you may not use this file except in compliance with the License.
+ * You may obtain a copy of the License at
+ *
+ *     http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ */
+
+//
+// Parses and emits WebAssembly binary code
+//
+
+#ifndef wasm_wasm_binary_h
+#define wasm_wasm_binary_h
+
+#include <ostream>
+
+#include "wasm.h"
+#include "shared-constants.h"
+
+namespace wasm {
+
+enum Section {
+  Memory = 0,
+  Signatures = 1,
+  Functions = 2,
+  DataSegments = 4,
+  FunctionTable = 5,
+  End = 6
+};
+
+enum FunctionEntry {
+  Named = 1,
+  Import = 2,
+  Locals = 4,
+  Export = 8
+};
+
+char binaryWasmType(WasmType type) {
+  switch (type) {
+    case none: return 0;
+    case i32: return 1;
+    case i64: return 2;
+    case f32: return 3;
+    case f64: return 4;
+    default: abort();
+  }
+}
+
+class WasmBinaryWriter : public WasmVisitor<void> {
+  Module* wasm;
+  ostream& o;
+
+public:
+  WasmBinaryWriter(Module* wasm, ostream& o) : wasm(wasm), o(o) {}
+
+  void write() {
+    writeMemory();
+    writeSignatures();
+    writeFunctions();
+    writeDataSegments();
+    writeFunctionTable();
+    writeEnd();
+  }
+
+  writeMemory() {
+    o << Section::Memory << char(log2(wasm.memory.initial)) <<
+                            char(log2(wasm.memory.max)) <<
+                            char(1); // export memory
+  }
+
+  writeSignatures() {
+    o << Section::Signatures << LEB128(wasm.functionTypes.size());
+    for (auto type : wasm.functionTypes) {
+      o << char(type->params.size());
+      o << binaryWasmType(type->result);
+      for (auto param : type->params) {
+        o << binaryWasmType(param);
+      }
+    }
+  }
+
+  int16_t functionTypeIndex(Name type) {
+    // TODO: optimize
+    for (size_t i = 0; i < wasm.functionTypes.size(); i++) {
+      if (wasm.functionTypes[i].name == type) return i;
+    }
+    abort();
+  }
+
+  std::map<Name, size_t> mappedLocals; // local name => index in compact form of [all int32s][all int64s]etc
+  std::map<WasmType, size_t> numLocalsByType; // type => number of locals of that type in the compact form
+
+  void mapLocals(Function* function) {
+    for (auto& local : function->locals) {
+      numLocalsByType[local.type]++;
+    }
+    std::map<WasmType, size_t> currLocalsByType;
+    for (auto& local : function->locals) {
+      size_t index = 0;
+      Name name = local.name;
+      WasmType type = local.type;
+      currLocalsByType[type]++; // increment now for simplicity, must decremebt it in returns
+      if (type == i32) {
+        mappedLocals[name] = index + currLocalsByType[i32] - 1;
+        break;
+      }
+      index += numLocalsByType[i32];
+      if (type == i64) {
+        mappedLocals[name] = index + currLocalsByType[i64] - 1;
+        break;
+      }
+      index += numLocalsByType[i64];
+      if (type == f32) {
+        mappedLocals[name] = index + currLocalsByType[f32] - 1;
+        break;
+      }
+      index += numLocalsByType[f32];
+      if (type == f64) {
+        mappedLocals[name] = index + currLocalsByType[f64] - 1;
+        break;
+      }
+    }
+  }
+
+  std::vector<char> encodeAST(Function* function) {
+  }
+
+  writeFunctions() {
+    size_t total = wasm.imports.size() + wasm.functions.size();
+    o << Section::Functions << LEB128(total);
+    for (size_t i = 0; i < total; i++) {
+      Import* import = i < wasm.imports.size() ? wasm.imports[i] : nullptr;
+      Function* function = i >= wasm.imports.size() ? wasm.functions[i - wasm.imports.size()] : nullptr;
+      Name name, type;
+      if (import) {
+        name = import->name;
+        type = import->type.name;
+      } else {
+        name = function->name;
+        type = function->type;
+      }
+      o << functionTypeIndex(type);
+      o << char(FunctionEntry::Named |
+                (FunctionEntry::Import * !!import) |
+                (FunctionEntry::Locals * (function && function->locals.size() > 0) |
+                (FunctionEntry::Export) * (wasm.exportsMap[name].count(name) > 0)));
+      // TODO: name. how can we do an offset? into what section? and how do we know it now?
+      if (function && function->locals.size() > 0) {
+        mapLocals(function);
+        o << uint16_t(numLocalsByType[i32])
+          << uint16_t(numLocalsByType[i64])
+          << uint16_t(numLocalsByType[f32])
+          << uint16_t(numLocalsByType[f64]);
+      }
+      if (function) {
+        auto ast = encodeAST(function);
+        o << uint16_t(ast.size());
+        for (auto c : ast) {
+          o << c;
+        }
+      }
+    }
+  }
+
+  writeDataSegments() {
+  }
+
+  writeFunctionTable() {
+  }
+
+  writeEnd() {
+    o << Section::End;
+  }
+};
+
+class WasmBinaryBuilder {
+  AllocatingModule& wasm;
+  MixedArena& allocator;
+  istream& i;
+public:
+  WasmBinaryBuilder(AllocatingModule& wasm, istream& i) : wasm(wasm), allocator(wasm.allocator), i(i) {}
+
+  void read() {
+    //
+  }
+};
+
+} // namespace wasm
+
+#endif // wasm_wasm_binary_h
+