[PATCH] Add FilteredArgList to represent filtered arglist

[Rui Ueyama]

With this patch we can write a loop for command line options like this

  for (const auto &arg : args->filter(OPT_SOMETHING)
    ...

instead of

  for (auto it = args->filtered_begin(OPT_SOMETHING),
         ie = args->filtered_end(); it != ie; ++it) {
    ...

I plan to use this in lld in where range-based for loop is allowed.

http://llvm-reviews.chandlerc.com/D867

Files:
  include/llvm/Option/ArgList.h
  lib/Option/ArgList.cpp

Index: include/llvm/Option/ArgList.h
===================================================================
--- include/llvm/Option/ArgList.h
+++ include/llvm/Option/ArgList.h
@@ -22,6 +22,7 @@
 namespace opt {
 class Arg;
 class ArgList;
+class FilteredArgList;
 class Option;
 
 /// arg_iterator - Iterates through arguments stored inside an ArgList.
@@ -137,10 +138,14 @@
   const_reverse_iterator rbegin() const { return Args.rbegin(); }
   const_reverse_iterator rend() const { return Args.rend(); }
 
+  FilteredArgList filter(OptSpecifier Id0 = 0U, OptSpecifier Id1 = 0U,
+                         OptSpecifier Id2 = 0U) const;
+
   arg_iterator filtered_begin(OptSpecifier Id0 = 0U, OptSpecifier Id1 = 0U,
                               OptSpecifier Id2 = 0U) const {
     return arg_iterator(Args.begin(), *this, Id0, Id1, Id2);
   }
+
   arg_iterator filtered_end() const {
     return arg_iterator(Args.end(), *this);
   }
@@ -275,6 +280,31 @@
   /// @}
 };
 
+/// FilteredArgList - ArgList with filters. Useful to be used in
+/// range-based for loop to iterate over filtered arguments.
+class FilteredArgList {
+private:
+  FilteredArgList(const ArgList &) LLVM_DELETED_FUNCTION;
+  void operator=(const ArgList &) LLVM_DELETED_FUNCTION;
+
+public:
+  FilteredArgList(const ArgList &_Args, OptSpecifier _Id0 = 0U,
+                  OptSpecifier _Id1 = 0U, OptSpecifier _Id2 = 0U)
+    : Args(_Args), Id0(_Id0), Id1(_Id1), Id2(_Id2) {}
+
+  arg_iterator begin() {
+    return Args.filtered_begin(Id0, Id1, Id2);
+  }
+
+  arg_iterator end() {
+    return Args.filtered_end();
+  }
+
+private:
+  const ArgList &Args;
+  OptSpecifier Id0, Id1, Id2;
+};
+
 class InputArgList : public ArgList  {
 private:
   /// List of argument strings used by the contained Args.
Index: lib/Option/ArgList.cpp
===================================================================
--- lib/Option/ArgList.cpp
+++ lib/Option/ArgList.cpp
@@ -44,6 +44,11 @@
   Args.push_back(A);
 }
 
+FilteredArgList ArgList::filter(OptSpecifier Id0, OptSpecifier Id1,
+                                OptSpecifier Id2) const {
+  return FilteredArgList(*this, Id0, Id1, Id2);
+}
+
 void ArgList::eraseArg(OptSpecifier Id) {
   for (iterator it = begin(), ie = end(); it != ie; ) {
     if ((*it)->getOption().matches(Id)) {
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