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+/*****
+ * coder.h
+ * Andy Hammerlindl 2004/11/06
+ *
+ * Handles encoding of syntax into programs.  It's methods are called by
+ * abstract syntax objects during translation to construct the virtual machine
+ * code.
+ *****/
+
+#ifndef CODER_H
+#define CODER_H
+
+#include "errormsg.h"
+#include "entry.h"
+#include "types.h"
+#include "record.h"
+#include "frame.h"
+#include "program.h"
+#include "util.h"
+#include "modifier.h"
+
+namespace trans {
+
+using sym::symbol;
+using types::ty;
+using types::function;
+using types::record;
+
+using vm::bltin;
+using vm::inst;
+using vm::item;
+
+class coder {
+  // The frame of the function we are currently encoding.  This keeps
+  // track of local variables, and parameters with respect to the stack.
+  frame *level;
+
+  // The frame of the enclosing record that the "this" expression yields.  ie.
+  // the highest frame that is a record, not a function. 
+  frame *recordLevel;
+
+  // The type of the enclosing record.  Also needed for the "this" expression.
+  record *recordType;
+  
+  // Are we translating a codelet?
+  bool isCodelet;
+
+  // The lambda being constructed. In some cases, this lambda is needed
+  // before full translation of the function, so it is stored,
+  // incomplete, here.
+  vm::lambda *l;
+
+  // The type of the function being translated.
+  const function *funtype;
+
+  // The enclosing environment.  Null if this is a file-level module.
+  coder *parent;
+
+  // The mode of encoding, either static or dynamic. sord is used as an
+  // acronym for Static OR Dynamic.
+  // Once something is static, no amount of dynamic modifiers can change
+  // that, so once a stack is EXPLICIT_STATIC, additional modifiers will
+  // be pushed on as EXPLICIT_STATIC.
+  modifier sord;
+  std::stack<modifier> sord_stack;
+
+  // What permissions will be given to a new access.
+  // TODO: Ensure private fields don't show up calling lookup for a
+  // record.
+  permission perm;
+  
+  // The function code as its being written.  Code points to next place in
+  // array to write.
+  vm::program *program;
+
+  // Keeps track of labels and writes in memory addresses as they're defined.
+  // This way a label can be used before its address is known.
+  std::map<Int,vm::program::label> defs;
+  std::multimap<Int,vm::program::label> uses;
+  Int numLabels;
+
+  // The loop constructs allocate nested frames, in case variables in an
+  // iteration escape in a closure.  This stack keeps track of where the
+  // variables are allocated, so the size of the frame can be encoded.  At the
+  // start, it just holds the label of the first instruction of the lambda, as
+  // this is where space for the variables of the function is allocated.
+  std::stack<vm::program::label> allocs;
+
+  // Loops need to store labels to where break and continue statements
+  // should pass control to.  Since loops can be nested, this needs to
+  // be stored as a stack.
+  std::stack<Int> breakLabels;
+  std::stack<Int> continueLabels;
+
+  // Current File Position
+  position curPos;
+
+public:
+  // Define a new function coder.  If reframe is true, this gives the function
+  // its own frame, which is the usual (sensible) thing to do.  It is set to
+  // false for a line-at-a-time codelet, where variables should be allocated in
+  // the lower frame.
+  coder(function *t, coder *parent, modifier sord = DEFAULT_DYNAMIC,
+        bool reframe=true);
+
+  // Start encoding the body of the record.  The function being encoded
+  // is the record's initializer.
+  coder(record *t, coder *parent, modifier sord = DEFAULT_DYNAMIC);
+
+  coder(modifier sord = DEFAULT_DYNAMIC);
+  
+  coder(const coder&);
+  
+  /* Add a static or dynamic modifier. */
+  void pushModifier(modifier s)
+  {
+    /* Default setting should only be used in the constructor. */
+    assert(s != DEFAULT_STATIC && s != DEFAULT_DYNAMIC);
+
+    /* Non-default static overrules. */
+    if (sord != EXPLICIT_STATIC)
+      sord = s;
+
+    sord_stack.push(sord);
+  }
+
+  /* Tests if encoding mode is currently static. */
+  bool isStatic()
+  {
+    switch(sord) {
+      case DEFAULT_STATIC:
+      case EXPLICIT_STATIC:
+        return true;
+      case DEFAULT_DYNAMIC:
+      case EXPLICIT_DYNAMIC:
+        return false;
+      default:
+        assert(False);
+        return false;
+    }
+  }
+
+
+  /* Remove a modifier. */
+  void popModifier()
+  {
+    assert(!sord_stack.empty());
+    sord_stack.pop();
+
+    assert(!sord_stack.empty());
+    sord = sord_stack.top();
+  }
+
+  /* Set/get/clear permissions. */
+  void setPermission(permission p)
+  {
+    perm = p;
+  }
+  permission getPermission()
+  {
+    return perm;
+  }
+  void clearPermission()
+  {
+    perm = DEFAULT_PERM;
+  }
+    
+
+  // Says what the return type of the function is.
+  ty *getReturnType() {
+    return funtype->result;
+  }
+
+  bool isRecord();
+  
+  // Creates a new coder to handle the translation of a new function.
+  coder newFunction(function *t, modifier sord=DEFAULT_DYNAMIC);
+
+  // Creates a new record type.
+  record *newRecord(symbol *id);
+
+  // Create a coder for the initializer of the record.
+  coder newRecordInit(record *r, modifier sord=DEFAULT_DYNAMIC);
+
+  // Create a coder for translating a small piece of code.  Used for
+  // line-at-a-time mode.
+  coder newCodelet();
+
+  frame *getFrame()
+  {
+    if (isStatic() && !isTopLevel()) {
+      assert(parent->getFrame());
+      return parent->getFrame();
+    }
+    else
+      return level;
+  }
+
+  // Tests if the function or record with the given frame is currently under
+  // translation (either by this coder or an ancestor).
+  bool inTranslation(frame *f) {
+    frame *level=this->level;
+    while (level) {
+      if (f==level)
+        return true;
+      level=level->getParent();
+    }
+    return parent && parent->inTranslation(f);
+  }
+
+  // Allocates space in the function or record frame for a new local variable.
+  access *allocLocal()
+  {
+    return getFrame()->allocLocal();
+  }
+
+  // Get the access in the frame for a specified formal parameter.
+  access *accessFormal(Int index)
+  {
+    // NOTE: This hasn't been extended to handle frames for loops, but is
+    // currently only called when starting to translate a function, where there
+    // can be no loops.
+    return level->accessFormal(index);
+  }
+
+  // Checks if we are at the top level, which is true for a file-level module or
+  // a codelet.
+  bool isTopLevel() {
+    return parent==0 || isCodelet;
+  }
+
+  // The encode functions add instructions and operands on to the code array.
+private:
+  void encode(inst i)
+  {
+    i.pos = curPos;
+    // Static code is put into the enclosing coder, unless we are translating a
+    // codelet.
+    if (isStatic() && !isTopLevel()) {
+      assert(parent);
+      parent->encode(i);
+    }
+    else {
+      program->encode(i);
+    }
+  }
+
+public:
+  void encode(inst::opcode op)
+  {
+    inst i; i.op = op; i.pos = nullPos;
+    encode(i);
+  }
+  void encode(inst::opcode op, item it)
+  {
+    inst i; i.op = op; i.pos = nullPos; i.ref = it;
+    encode(i);
+  }
+
+  // Puts the requested frame on the stack.  If the frame is not that of
+  // this coder or its ancestors, false is returned.
+  bool encode(frame *f);
+
+  // Puts the frame corresponding to the expression "this" on the stack.
+  bool encodeThis()
+  {
+    assert(recordLevel);
+    return encode(recordLevel);
+  }
+
+  // An access that encodes the frame corresponding to "this".
+  access *thisLocation()
+  {
+    assert(recordLevel);
+    return new frameAccess(recordLevel);
+  }
+
+  // Returns the type of the enclosing record.
+  record *thisType()
+  {
+    return recordType;
+  }
+
+  // Puts the 'dest' frame on the stack, assuming the frame 'top' is on
+  // top of the stack.  If 'dest' is not an ancestor frame of 'top',
+  // false is returned.
+  bool encode(frame *dest, frame *top);
+
+
+  // Assigns a handle to the current point in the list of stack
+  // instructions and returns that handle.
+  Int defLabel();
+
+  // Sets the handle given by label to the current point in the list of
+  // instructions.
+  Int defLabel(Int label);
+
+  // Encodes the address pointed to by the handle label into the
+  // sequence of instructions.  This is useful for a jump instruction to
+  // jump to where a label was defined.
+  void useLabel(inst::opcode op, Int label);
+
+  // If an address has to be used for a jump instruction before it is
+  // actually encoded, a handle can be given to it by this function.
+  // When that handle's label is later defined, the proper address will
+  // be inserted into the code where the handle was used. 
+  Int fwdLabel();
+
+  void pushBreak(Int label) {
+    breakLabels.push(label);
+  }
+  void pushContinue(Int label) {
+    continueLabels.push(label);
+  }
+  void popBreak() {
+    breakLabels.pop();
+  }
+  void popContinue() {
+    continueLabels.pop();
+  }
+  bool encodeBreak() {
+    if (breakLabels.empty())
+      return false;
+    else {
+      useLabel(inst::jmp,breakLabels.top());
+      return true;
+    }
+  }
+  bool encodeContinue() {
+    if (continueLabels.empty())
+      return false;
+    else {
+      useLabel(inst::jmp,continueLabels.top());
+      return true;
+    }
+  }
+  
+private:
+  void encodeAllocInstruction() {
+    encode(inst::alloc, 0);
+    allocs.push(--program->end());
+  }
+
+  void finishAlloc() {
+    allocs.top()->ref = level->size();
+    allocs.pop();
+  }
+
+public:
+  void encodePushFrame() {
+    encode(inst::pushframe);
+    level = new frame(level, 0);
+
+    encodeAllocInstruction();
+  }
+
+  void encodePopFrame() {
+    finishAlloc();
+
+    encode(inst::popframe);
+    level = level->getParent();
+  }
+
+  // Adds an entry into the position list, linking the given point in the
+  // source code to the current position in the virtual machine code.  This is
+  // used to print positions at runtime.
+  void markPos(position pos);
+
+  // When translation of the function is finished, this ties up loose ends
+  // and returns the lambda.
+  vm::lambda *close();
+
+  // Finishes translating the initializer of a record.
+  void closeRecord();
+
+private: // Non-copyable
+  void operator=(const coder&);
+};
+
+} // namespace trans
+
+#endif