base: Add documentation to flags.hh

Add documentation to the Flags class. Use this opportunity
to rename some arguments to make their intention clearer.

Finally, the constructors have been merged using a default
value of 0.

Change-Id: I924b1d5c20a3e2066be64ab124ae1a5d96d4b3bf
Signed-off-by: Daniel R. Carvalho <odanrc@yahoo.com.br>
Reviewed-on: https://gem5-review.googlesource.com/c/public/gem5/+/38735
Reviewed-by: Jason Lowe-Power <power.jg@gmail.com>
Reviewed-by: Bobby R. Bruce <bbruce@ucdavis.edu>
Maintainer: Bobby R. Bruce <bbruce@ucdavis.edu>
Tested-by: kokoro <noreply+kokoro@google.com>

diff --git a/src/base/flags.hh b/src/base/flags.hh
index 8cefd2d3399a297c9d72fa5f812b12b7b23f876b..170abc544a0dd7c1ff4584c2e9fee3da73d65c5b 100644 (file)
--- a/src/base/flags.hh
+++ b/src/base/flags.hh
@@ -1,4 +1,5 @@
 /*
+ * Copyright (c) 2020 Daniel R. Carvalho
  * Copyright (c) 2008 The Hewlett-Packard Development Company
  * All rights reserved.
  *
@@ -31,12 +32,18 @@
 
 #include <type_traits>
 
+/**
+ * Wrapper that groups a few flag bits under the same undelying container.
+ *
+ * @tparam T The type of the underlying container. Must be an unsigned integer.
+ */
 template <typename T>
 class Flags
 {
   private:
     static_assert(std::is_unsigned<T>::value, "Flag type must be unsigned");
 
+    /** The undelying container of the flags' bits. */
     T _flags;
 
   public:
@@ -46,18 +53,17 @@ class Flags
      * @ingroup api_flags
      * @{
      */
-    Flags() : _flags(0) {}
-    Flags(Type flags) : _flags(flags) {}
-    /** @} */ // end of api_flags
 
     /**
-     * @ingroup api_flags
+     * Initialize flags with a given value. If no value is provided, the
+     * flag bits are initialized cleared.
+     *
+     * @param flags The value to initialize the flags with.
      */
+    Flags(Type flags=0) : _flags(flags) {}
+
     operator const Type() const { return _flags; }
 
-    /**
-     * @ingroup api_flags
-     */
     const Flags<T> &
     operator=(T flags)
     {
@@ -66,19 +72,89 @@ class Flags
     }
 
     /**
-     * @ingroup api_flags
-     * @{
+     * Verifies whether any bit in the flags is set.
+     *
+     * @return True if any flag bit is set; false otherwise.
      */
     bool isSet() const { return _flags; }
-    bool isSet(Type flags) const { return (_flags & flags); }
+
+    /**
+     * Verifies whether any bit matching the given mask is set.
+     *
+     * @param mask The mask containing the bits to verify.
+     * @return True if any matching bit is set; false otherwise.
+     */
+    bool isSet(Type mask) const { return (_flags & mask); }
+
+    /**
+     * Verifies whether all bits in the flags are set.
+     *
+     * @return True if all flag bits are set; false otherwise.
+     */
     bool allSet() const { return !(~_flags); }
-    bool allSet(Type flags) const { return (_flags & flags) == flags; }
+
+    /**
+     * Verifies whether no bits matching the given mask are set.
+     *
+     * @param mask The mask containing the bits to verify.
+     * @return True if matching bits are set; false otherwise.
+     */
+    bool allSet(Type mask) const { return (_flags & mask) == mask; }
+
+    /**
+     * Verifies whether no bits in the flags are set.
+     *
+     * @return True if all flag bits are cleared; false otherwise.
+     */
     bool noneSet() const { return _flags == 0; }
-    bool noneSet(Type flags) const { return (_flags & flags) == 0; }
+
+    /**
+     * Verifies whether no bits matching the given mask are set.
+     *
+     * @param mask The mask containing the bits to verify.
+     * @return True if matching bits are cleared; false otherwise.
+     */
+    bool noneSet(Type mask) const { return (_flags & mask) == 0; }
+
+    /** Clear all flag's bits. */
     void clear() { _flags = 0; }
-    void clear(Type flags) { _flags &= ~flags; }
-    void set(Type flags) { _flags |= flags; }
-    void set(Type f, bool val) { _flags = (_flags & ~f) | (val ? f : 0); }
+
+    /**
+     * Clear all flag's bits matching the given mask.
+     *
+     * @param mask The mask containing the bits to be cleared.
+     */
+    void clear(Type mask) { _flags &= ~mask; }
+
+    /**
+     * Set all flag's bits matching the given mask.
+     *
+     * @param mask The mask containing the bits to be set.
+     */
+    void set(Type mask) { _flags |= mask; }
+
+    /**
+     * Conditionally set or clear some bits of the flag, given a mask.
+     *
+     * @param mask The mask containing the bits to be modified.
+     * @param condition If true, set masked bits; otherwise, clear them.
+     */
+    void
+    set(Type mask, bool condition)
+    {
+        condition ? set(mask) : clear(mask);
+    }
+
+    /**
+     * Replace the contents of the bits matching the mask with the
+     * corresponding bits in the provided flags.
+     *
+     * This is equivalent to:
+     *     flags.clear(mask); flags.set(flags & mask);
+     *
+     * @param flags Flags to extract new bits from.
+     * @param mask Mask used to determine which bits are replaced.
+     */
     void
     update(Type flags, Type mask)
     {