start work on shell and sexpr parser

2 files changed, 154 insertions, 0 deletions

diff --git a/src/wasm-sexpr-parser.h b/src/wasm-sexpr-parser.h
new file mode 100644
index 000000000..c36311797
--- /dev/null
+++ b/src/wasm-sexpr-parser.h
@@ -0,0 +1,149 @@
+
+//
+// Parses WebAssembly code in S-Expression format, as in .wast files.
+//
+
+#include "wasm.h"
+#include "mixed_arena.h"
+
+namespace wasm {
+
+// Globals
+
+IString MODULE("module"),
+        FUNC("func");
+
+//
+// Generic S-Expression parsing into lists
+//
+
+class SExpressionParser {
+  char* input;
+
+  MixedArena allocator;
+
+public:
+  // Assumes control of and modifies the input.
+  SExpressionParser(char* input) : input(input) {}
+
+  struct List;
+
+  // A list of Elements, or a string
+  class Element {
+    bool isList;
+    union {
+      List list_;
+      IString str_;
+    };
+
+  public:
+    Element() : isList(true) {}
+
+    // list methods
+
+    List& list() {
+      assert(isList);
+      return list_;
+    }
+
+    // string methods
+
+    IString str() {
+      assert(!isList);
+      return str_;
+    }
+
+    Element* setString(IString str__) {
+      isList = false;
+      str_ = str__;
+      return this;
+    }
+
+  };
+
+  typedef std::vector<Element*> List;
+
+  Element* parseEverything() {
+    return parseInnerList();
+  }
+
+private:
+  // parses the internal part of a list, inside the parens.
+  Element* parseInnerList() {
+    if (input[0] == ';') {
+      // comment
+      input++;
+      input = strchr(input, ";)");
+      assert(input);
+      return nullptr;
+    }
+    auto ret = allocator.alloc<Element>()->setList();
+    while (1) {
+      Element* curr = parse();
+      if (!curr) return ret;
+      curr->list().push_back(curr);
+    }
+  }
+
+  Element* parse() {
+    skipWhitespace(input);
+    if (!input) return nullptr;
+    if (input[0] == '(') {
+      // a list
+      input++;
+      auto ret = parseInnerList();
+      skipWhitespace(input);
+      assert(input[0] == ')';
+      input++;
+      return ret;
+    }
+    return parseString();
+  }
+
+  void skipWhitespace() {
+    while (isspace(input[0])) input++;
+  }
+
+  Element* parseString() {
+    char *start = input;
+    while (isalnum(input[0]) || input[0] == '_' || input[0] == '$') input++;
+    return allocator.alloc<Element>()->setString(IString(start, false)); // TODO: reuse the string here, carefully
+  }
+};
+
+//
+// SExpressions => WebAssembly module
+//
+
+class SExpressionWasmBuilder {
+  Module& wasm;
+
+  MixedArena allocator;
+  SExpressionParser parser;
+
+public:
+  // Assumes control of and modifies the input.
+  SExpressionWasmBuilder(Module& wasm, char* input) : wasm(wasm), parser(input) {}
+
+  void parse() {
+    Element* root = parser.parseEverything();
+    assert(root);
+    assert(root->list()[0]->str() == MODULE);
+    for (unsigned i = 1; i < root->list().size(); i++) {
+      parseModuleElement(root->list()[i]);
+    }
+  }
+
+  void parseModuleElement(Element* curr) {
+    IString id = curr->list()[0]->str();
+    if (id == FUNC) return parseFunction(curr);
+    std::cerr << "bad module element " << id.str << '\n';
+    abort();
+  }
+
+  void parseFunction(Element* curr) {
+  }
+};
+
+} // namespace wasm
+
diff --git a/src/wasm-shell.cpp b/src/wasm-shell.cpp
new file mode 100644
index 000000000..6b5bb942c
--- /dev/null
+++ b/src/wasm-shell.cpp
@@ -0,0 +1,5 @@
+
+//
+// A WebAssembly shell, loads a .wast file (WebAssembly in S-Expression format) and executes it.
+//
+