[libc-commits] [PATCH] D136881: [libc] add features to bitset

[Michael Jones via Phabricator via libc-commits]

michaelrj created this revision.
michaelrj added reviewers: sivachandra, lntue.
Herald added subscribers: libc-commits, ecnelises, tschuett.
Herald added projects: libc-project, All.
michaelrj requested review of this revision.

This patch adds the flip, set_range, and operator== functions to bitset.
These will be used in scanf.


Repository:
  rG LLVM Github Monorepo

https://reviews.llvm.org/D136881

Files:
  libc/src/__support/CPP/bitset.h


Index: libc/src/__support/CPP/bitset.h
===================================================================
--- libc/src/__support/CPP/bitset.h
+++ libc/src/__support/CPP/bitset.h
@@ -25,14 +25,53 @@
     return Data[Index / BITS_PER_UNIT] & mask(Index);
   }
 
+  constexpr void flip() {
+    for (size_t i = 0; i < NUMBER_OF_UNITS; ++i)
+      Data[i] = ~Data[i];
+  }
+
+  // This function sets all bits in the range from Start to End (inclusive) to
+  // true. It assumes that Start < End.
+  constexpr void set_range(size_t Start, size_t End) {
+    size_t start_index = Start / BITS_PER_UNIT;
+    size_t end_index = End / BITS_PER_UNIT;
+
+    if (start_index == end_index) {
+      size_t bit_mask = ((size_t(1) << (1 + End - Start)) - 1)
+                        << (Start - (start_index * BITS_PER_UNIT));
+      Data[start_index] |= bit_mask;
+    } else {
+      size_t low_bit_mask =
+          ~((size_t(1) << (1 + Start - (start_index * BITS_PER_UNIT))) - 1);
+      Data[start_index] |= low_bit_mask;
+
+      for (size_t i = start_index + 1; i < end_index; ++i)
+        Data[i] = ~size_t(0);
+
+      size_t high_bit_mask =
+          (size_t(1) << (1 + End - (end_index * BITS_PER_UNIT))) - 1;
+      Data[end_index] |= high_bit_mask;
+    }
+  }
+
+  constexpr bool operator==(const bitset<NumberOfBits> &other) {
+    for (size_t i = 0; i < NUMBER_OF_UNITS; ++i) {
+      if (Data[i] != other.Data[i])
+        return false;
+    }
+    return true;
+  }
+
 private:
   static constexpr size_t BITS_PER_BYTE = 8;
   static constexpr size_t BITS_PER_UNIT = BITS_PER_BYTE * sizeof(size_t);
+  static constexpr size_t NUMBER_OF_UNITS =
+      (NumberOfBits + BITS_PER_UNIT - 1) / BITS_PER_UNIT;
 
   static inline size_t mask(size_t Index) {
     return size_t{1} << (Index % BITS_PER_UNIT);
   }
-  size_t Data[(NumberOfBits + BITS_PER_UNIT - 1) / BITS_PER_UNIT] = {0};
+  size_t Data[NUMBER_OF_UNITS] = {0};
 };
 
 } // namespace __llvm_libc::cpp


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