Cleanup: Move BitwiseCompare() to InlineData, and make it layout independent.

This removes layout specific details from InlineData from cord.h, making future platform specific internal layout changes easier to land.

PiperOrigin-RevId: 477869206
Change-Id: I1d417af47d7f04e34a98ba7b93ae591ece8f9151

absl/strings/cord.h

@@ -876,20 +876,6 @@ class Cord {
     bool IsSame(const InlineRep& other) const {
       return memcmp(&data_, &other.data_, sizeof(data_)) == 0;
     }
-    int BitwiseCompare(const InlineRep& other) const {
-      uint64_t x, y;
-      // Use memcpy to avoid aliasing issues.
-      memcpy(&x, &data_, sizeof(x));
-      memcpy(&y, &other.data_, sizeof(y));
-      if (x == y) {
-        memcpy(&x, reinterpret_cast<const char*>(&data_) + 8, sizeof(x));
-        memcpy(&y, reinterpret_cast<const char*>(&other.data_) + 8, sizeof(y));
-        if (x == y) return 0;
-      }
-      return absl::big_endian::FromHost64(x) < absl::big_endian::FromHost64(y)
-                 ? -1
-                 : 1;
-    }
     void CopyTo(std::string* dst) const {
       // memcpy is much faster when operating on a known size. On most supported
       // platforms, the small string optimization is large enough that resizing
@@ -1387,7 +1373,7 @@ extern template void Cord::Prepend(std::string&& src);
 
 inline int Cord::Compare(const Cord& rhs) const {
   if (!contents_.is_tree() && !rhs.contents_.is_tree()) {
-    return contents_.BitwiseCompare(rhs.contents_);
+    return contents_.data_.Compare(rhs.contents_.data_);
   }
 
   return CompareImpl(rhs);

absl/strings/internal/cord_internal.h

@@ -582,6 +582,29 @@ class InlineData {
     tag() = static_cast<char>(size << 1);
   }
 
+  // Compares 'this' inlined data  with rhs. The comparison is a straightforward
+  // lexicographic comparison. `Compare()` returns values as follows:
+  //
+  //   -1  'this' InlineData instance is smaller
+  //    0  the InlineData instances are equal
+  //    1  'this' InlineData instance larger
+  int Compare(const InlineData& rhs) const {
+    uint64_t x, y;
+    memcpy(&x, as_chars(), sizeof(x));
+    memcpy(&y, rhs.as_chars(), sizeof(y));
+    if (x == y) {
+      memcpy(&x, as_chars() + 7, sizeof(x));
+      memcpy(&y, rhs.as_chars() + 7, sizeof(y));
+      if (x == y) {
+        if (inline_size() == rhs.inline_size()) return 0;
+        return inline_size() < rhs.inline_size() ? -1 : 1;
+      }
+    }
+    x = absl::big_endian::FromHost64(x);
+    y = absl::big_endian::FromHost64(y);
+    return x < y ? -1 : 1;
+  }
+
  private:
   // See cordz_info_t for forced alignment and size of `cordz_info` details.
   struct AsTree {