Remove CordRepRing experiment.

We have no intention to use it instead of the CordRepBtree implementation, so cleanup up and remove all code and references.

PiperOrigin-RevId: 563803813
Change-Id: I95a67318d0f722f3eb7ecdcc7b6c87e28f2e26dd

7 files changed, 5 insertions, 1613 deletions

diff --git a/absl/strings/internal/cord_internal.cc b/absl/strings/internal/cord_internal.cc
index b7874385..57d9d385 100644
--- a/absl/strings/internal/cord_internal.cc
+++ b/absl/strings/internal/cord_internal.cc
@@ -22,15 +22,12 @@
 #include "absl/strings/internal/cord_rep_btree.h"
 #include "absl/strings/internal/cord_rep_crc.h"
 #include "absl/strings/internal/cord_rep_flat.h"
-#include "absl/strings/internal/cord_rep_ring.h"
 #include "absl/strings/str_cat.h"
 
 namespace absl {
 ABSL_NAMESPACE_BEGIN
 namespace cord_internal {
 
-ABSL_CONST_INIT std::atomic<bool> cord_ring_buffer_enabled(
-    kCordEnableRingBufferDefault);
 ABSL_CONST_INIT std::atomic<bool> shallow_subcords_enabled(
     kCordShallowSubcordsDefault);
 
@@ -47,9 +44,6 @@ void CordRep::Destroy(CordRep* rep) {
     if (rep->tag == BTREE) {
       CordRepBtree::Destroy(rep->btree());
       return;
-    } else if (rep->tag == RING) {
-      CordRepRing::Destroy(rep->ring());
-      return;
     } else if (rep->tag == EXTERNAL) {
       CordRepExternal::Delete(rep);
       return;
diff --git a/absl/strings/internal/cord_internal.h b/absl/strings/internal/cord_internal.h
index 9ec6b2a6..a487fd59 100644
--- a/absl/strings/internal/cord_internal.h
+++ b/absl/strings/internal/cord_internal.h
@@ -55,24 +55,15 @@ struct CordRepExternal;
 struct CordRepFlat;
 struct CordRepSubstring;
 struct CordRepCrc;
-class CordRepRing;
 class CordRepBtree;
 
 class CordzInfo;
 
 // Default feature enable states for cord ring buffers
-enum CordFeatureDefaults {
-  kCordEnableRingBufferDefault = false,
-  kCordShallowSubcordsDefault = false
-};
+enum CordFeatureDefaults { kCordShallowSubcordsDefault = false };
 
-extern std::atomic<bool> cord_ring_buffer_enabled;
 extern std::atomic<bool> shallow_subcords_enabled;
 
-inline void enable_cord_ring_buffer(bool enable) {
-  cord_ring_buffer_enabled.store(enable, std::memory_order_relaxed);
-}
-
 inline void enable_shallow_subcords(bool enable) {
   shallow_subcords_enabled.store(enable, std::memory_order_relaxed);
 }
@@ -215,7 +206,7 @@ enum CordRepKind {
   SUBSTRING = 1,
   CRC = 2,
   BTREE = 3,
-  RING = 4,
+  UNUSED_4 = 4,
   EXTERNAL = 5,
 
   // We have different tags for different sized flat arrays,
@@ -234,12 +225,8 @@ enum CordRepKind {
 // There are various locations where we want to check if some rep is a 'plain'
 // data edge, i.e. an external or flat rep. By having FLAT == EXTERNAL + 1, we
 // can perform this check in a single branch as 'tag >= EXTERNAL'
-// Likewise, we have some locations where we check for 'ring or external/flat',
-// so likewise align RING to EXTERNAL.
 // Note that we can leave this optimization to the compiler. The compiler will
 // DTRT when it sees a condition like `tag == EXTERNAL || tag >= FLAT`.
-static_assert(RING == BTREE + 1, "BTREE and RING not consecutive");
-static_assert(EXTERNAL == RING + 1, "BTREE and EXTERNAL not consecutive");
 static_assert(FLAT == EXTERNAL + 1, "EXTERNAL and FLAT not consecutive");
 
 struct CordRep {
@@ -283,15 +270,12 @@ struct CordRep {
   // # LINT.ThenChange(cord_rep_btree.h:copy_raw)
 
   // Returns true if this instance's tag matches the requested type.
-  constexpr bool IsRing() const { return tag == RING; }
   constexpr bool IsSubstring() const { return tag == SUBSTRING; }
   constexpr bool IsCrc() const { return tag == CRC; }
   constexpr bool IsExternal() const { return tag == EXTERNAL; }
   constexpr bool IsFlat() const { return tag >= FLAT; }
   constexpr bool IsBtree() const { return tag == BTREE; }
 
-  inline CordRepRing* ring();
-  inline const CordRepRing* ring() const;
   inline CordRepSubstring* substring();
   inline const CordRepSubstring* substring() const;
   inline CordRepCrc* crc();
diff --git a/absl/strings/internal/cord_rep_ring.cc b/absl/strings/internal/cord_rep_ring.cc
deleted file mode 100644
index af2fc768..00000000
--- a/absl/strings/internal/cord_rep_ring.cc
+++ /dev/null
@@ -1,773 +0,0 @@
-// Copyright 2020 The Abseil Authors
-//
-// Licensed under the Apache License, Version 2.0 (the "License");
-// you may not use this file except in compliance with the License.
-// You may obtain a copy of the License at
-//
-//     https://www.apache.org/licenses/LICENSE-2.0
-//
-// Unless required by applicable law or agreed to in writing, software
-// distributed under the License is distributed on an "AS IS" BASIS,
-// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
-// See the License for the specific language governing permissions and
-// limitations under the License.
-#include "absl/strings/internal/cord_rep_ring.h"
-
-#include <cassert>
-#include <cstddef>
-#include <cstdint>
-#include <iostream>
-#include <limits>
-#include <memory>
-#include <string>
-
-#include "absl/base/internal/raw_logging.h"
-#include "absl/base/internal/throw_delegate.h"
-#include "absl/base/macros.h"
-#include "absl/container/inlined_vector.h"
-#include "absl/strings/internal/cord_internal.h"
-#include "absl/strings/internal/cord_rep_consume.h"
-#include "absl/strings/internal/cord_rep_flat.h"
-
-namespace absl {
-ABSL_NAMESPACE_BEGIN
-namespace cord_internal {
-
-namespace {
-
-using index_type = CordRepRing::index_type;
-
-enum class Direction { kForward, kReversed };
-
-inline bool IsFlatOrExternal(CordRep* rep) {
-  return rep->IsFlat() || rep->IsExternal();
-}
-
-// Verifies that n + extra <= kMaxCapacity: throws std::length_error otherwise.
-inline void CheckCapacity(size_t n, size_t extra) {
-  if (ABSL_PREDICT_FALSE(extra > CordRepRing::kMaxCapacity - n)) {
-    base_internal::ThrowStdLengthError("Maximum capacity exceeded");
-  }
-}
-
-// Creates a flat from the provided string data, allocating up to `extra`
-// capacity in the returned flat depending on kMaxFlatLength limitations.
-// Requires `len` to be less or equal to `kMaxFlatLength`
-CordRepFlat* CreateFlat(const char* s, size_t n, size_t extra = 0) {  // NOLINT
-  assert(n <= kMaxFlatLength);
-  auto* rep = CordRepFlat::New(n + extra);
-  rep->length = n;
-  memcpy(rep->Data(), s, n);
-  return rep;
-}
-
-// Unrefs the entries in `[head, tail)`.
-// Requires all entries to be a FLAT or EXTERNAL node.
-void UnrefEntries(const CordRepRing* rep, index_type head, index_type tail) {
-  rep->ForEach(head, tail, [rep](index_type ix) {
-    CordRep* child = rep->entry_child(ix);
-    if (!child->refcount.Decrement()) {
-      if (child->tag >= FLAT) {
-        CordRepFlat::Delete(child->flat());
-      } else {
-        CordRepExternal::Delete(child->external());
-      }
-    }
-  });
-}
-
-}  // namespace
-
-std::ostream& operator<<(std::ostream& s, const CordRepRing& rep) {
-  // Note: 'pos' values are defined as size_t (for overflow reasons), but that
-  // prints really awkward for small prepended values such as -5. ssize_t is not
-  // portable (POSIX), so we use ptrdiff_t instead to cast to signed values.
-  s << "  CordRepRing(" << &rep << ", length = " << rep.length
-    << ", head = " << rep.head_ << ", tail = " << rep.tail_
-    << ", cap = " << rep.capacity_ << ", rc = " << rep.refcount.Get()
-    << ", begin_pos_ = " << static_cast<ptrdiff_t>(rep.begin_pos_) << ") {\n";
-  CordRepRing::index_type head = rep.head();
-  do {
-    CordRep* child = rep.entry_child(head);
-    s << " entry[" << head << "] length = " << rep.entry_length(head)
-      << ", child " << child << ", clen = " << child->length
-      << ", tag = " << static_cast<int>(child->tag)
-      << ", rc = " << child->refcount.Get()
-      << ", offset = " << rep.entry_data_offset(head)
-      << ", end_pos = " << static_cast<ptrdiff_t>(rep.entry_end_pos(head))
-      << "\n";
-    head = rep.advance(head);
-  } while (head != rep.tail());
-  return s << "}\n";
-}
-
-void CordRepRing::AddDataOffset(index_type index, size_t n) {
-  entry_data_offset()[index] += static_cast<offset_type>(n);
-}
-
-void CordRepRing::SubLength(index_type index, size_t n) {
-  entry_end_pos()[index] -= n;
-}
-
-class CordRepRing::Filler {
- public:
-  Filler(CordRepRing* rep, index_type pos) : rep_(rep), head_(pos), pos_(pos) {}
-
-  index_type head() const { return head_; }
-  index_type pos() const { return pos_; }
-
-  void Add(CordRep* child, size_t offset, pos_type end_pos) {
-    rep_->entry_end_pos()[pos_] = end_pos;
-    rep_->entry_child()[pos_] = child;
-    rep_->entry_data_offset()[pos_] = static_cast<offset_type>(offset);
-    pos_ = rep_->advance(pos_);
-  }
-
- private:
-  CordRepRing* rep_;
-  index_type head_;
-  index_type pos_;
-};
-
-#ifdef ABSL_INTERNAL_NEED_REDUNDANT_CONSTEXPR_DECL
-constexpr size_t CordRepRing::kMaxCapacity;
-#endif
-
-bool CordRepRing::IsValid(std::ostream& output) const {
-  if (capacity_ == 0) {
-    output << "capacity == 0";
-    return false;
-  }
-
-  if (head_ >= capacity_ || tail_ >= capacity_) {
-    output << "head " << head_ << " and/or tail " << tail_ << "exceed capacity "
-           << capacity_;
-    return false;
-  }
-
-  const index_type back = retreat(tail_);
-  size_t pos_length = Distance(begin_pos_, entry_end_pos(back));
-  if (pos_length != length) {
-    output << "length " << length << " does not match positional length "
-           << pos_length << " from begin_pos " << begin_pos_ << " and entry["
-           << back << "].end_pos " << entry_end_pos(back);
-    return false;
-  }
-
-  index_type head = head_;
-  pos_type begin_pos = begin_pos_;
-  do {
-    pos_type end_pos = entry_end_pos(head);
-    size_t entry_length = Distance(begin_pos, end_pos);
-    if (entry_length == 0) {
-      output << "entry[" << head << "] has an invalid length " << entry_length
-             << " from begin_pos " << begin_pos << " and end_pos " << end_pos;
-      return false;
-    }
-
-    CordRep* child = entry_child(head);
-    if (child == nullptr) {
-      output << "entry[" << head << "].child == nullptr";
-      return false;
-    }
-    if (child->tag < FLAT && child->tag != EXTERNAL) {
-      output << "entry[" << head << "].child has an invalid tag "
-             << static_cast<int>(child->tag);
-      return false;
-    }
-
-    size_t offset = entry_data_offset(head);
-    if (offset >= child->length || entry_length > child->length - offset) {
-      output << "entry[" << head << "] has offset " << offset
-             << " and entry length " << entry_length
-             << " which are outside of the child's length of " << child->length;
-      return false;
-    }
-
-    begin_pos = end_pos;
-    head = advance(head);
-  } while (head != tail_);
-
-  return true;
-}
-
-#ifdef EXTRA_CORD_RING_VALIDATION
-CordRepRing* CordRepRing::Validate(CordRepRing* rep, const char* file,
-                                   int line) {
-  if (!rep->IsValid(std::cerr)) {
-    std::cerr << "\nERROR: CordRepRing corrupted";
-    if (line) std::cerr << " at line " << line;
-    if (file) std::cerr << " in file " << file;
-    std::cerr << "\nContent = " << *rep;
-    abort();
-  }
-  return rep;
-}
-#endif  // EXTRA_CORD_RING_VALIDATION
-
-CordRepRing* CordRepRing::New(size_t capacity, size_t extra) {
-  CheckCapacity(capacity, extra);
-
-  size_t size = AllocSize(capacity += extra);
-  void* mem = ::operator new(size);
-  auto* rep = new (mem) CordRepRing(static_cast<index_type>(capacity));
-  rep->tag = RING;
-  rep->capacity_ = static_cast<index_type>(capacity);
-  rep->begin_pos_ = 0;
-  return rep;
-}
-
-void CordRepRing::SetCapacityForTesting(size_t capacity) {
-  // Adjust for the changed layout
-  assert(capacity <= capacity_);
-  assert(head() == 0 || head() < tail());
-  memmove(Layout::Partial(capacity).Pointer<1>(data_) + head(),
-          Layout::Partial(capacity_).Pointer<1>(data_) + head(),
-          entries() * sizeof(Layout::ElementType<1>));
-  memmove(Layout::Partial(capacity, capacity).Pointer<2>(data_) + head(),
-          Layout::Partial(capacity_, capacity_).Pointer<2>(data_) + head(),
-          entries() * sizeof(Layout::ElementType<2>));
-  capacity_ = static_cast<index_type>(capacity);
-}
-
-void CordRepRing::Delete(CordRepRing* rep) {
-  assert(rep != nullptr && rep->IsRing());
-#if defined(__cpp_sized_deallocation)
-  size_t size = AllocSize(rep->capacity_);
-  rep->~CordRepRing();
-  ::operator delete(rep, size);
-#else
-  rep->~CordRepRing();
-  ::operator delete(rep);
-#endif
-}
-
-void CordRepRing::Destroy(CordRepRing* rep) {
-  UnrefEntries(rep, rep->head(), rep->tail());
-  Delete(rep);
-}
-
-template <bool ref>
-void CordRepRing::Fill(const CordRepRing* src, index_type head,
-                       index_type tail) {
-  this->length = src->length;
-  head_ = 0;
-  tail_ = advance(0, src->entries(head, tail));
-  begin_pos_ = src->begin_pos_;
-
-  // TODO(mvels): there may be opportunities here for large buffers.
-  auto* dst_pos = entry_end_pos();
-  auto* dst_child = entry_child();
-  auto* dst_offset = entry_data_offset();
-  src->ForEach(head, tail, [&](index_type index) {
-    *dst_pos++ = src->entry_end_pos(index);
-    CordRep* child = src->entry_child(index);
-    *dst_child++ = ref ? CordRep::Ref(child) : child;
-    *dst_offset++ = src->entry_data_offset(index);
-  });
-}
-
-CordRepRing* CordRepRing::Copy(CordRepRing* rep, index_type head,
-                               index_type tail, size_t extra) {
-  CordRepRing* newrep = CordRepRing::New(rep->entries(head, tail), extra);
-  newrep->Fill<true>(rep, head, tail);
-  CordRep::Unref(rep);
-  return newrep;
-}
-
-CordRepRing* CordRepRing::Mutable(CordRepRing* rep, size_t extra) {
-  // Get current number of entries, and check for max capacity.
-  size_t entries = rep->entries();
-
-  if (!rep->refcount.IsOne()) {
-    return Copy(rep, rep->head(), rep->tail(), extra);
-  } else if (entries + extra > rep->capacity()) {
-    const size_t min_grow = rep->capacity() + rep->capacity() / 2;
-    const size_t min_extra = (std::max)(extra, min_grow - entries);
-    CordRepRing* newrep = CordRepRing::New(entries, min_extra);
-    newrep->Fill<false>(rep, rep->head(), rep->tail());
-    CordRepRing::Delete(rep);
-    return newrep;
-  } else {
-    return rep;
-  }
-}
-
-Span<char> CordRepRing::GetAppendBuffer(size_t size) {
-  assert(refcount.IsOne());
-  index_type back = retreat(tail_);
-  CordRep* child = entry_child(back);
-  if (child->tag >= FLAT && child->refcount.IsOne()) {
-    size_t capacity = child->flat()->Capacity();
-    pos_type end_pos = entry_end_pos(back);
-    size_t data_offset = entry_data_offset(back);
-    size_t entry_length = Distance(entry_begin_pos(back), end_pos);
-    size_t used = data_offset + entry_length;
-    if (size_t n = (std::min)(capacity - used, size)) {
-      child->length = data_offset + entry_length + n;
-      entry_end_pos()[back] = end_pos + n;
-      this->length += n;
-      return {child->flat()->Data() + used, n};
-    }
-  }
-  return {nullptr, 0};
-}
-
-Span<char> CordRepRing::GetPrependBuffer(size_t size) {
-  assert(refcount.IsOne());
-  CordRep* child = entry_child(head_);
-  size_t data_offset = entry_data_offset(head_);
-  if (data_offset && child->refcount.IsOne() && child->tag >= FLAT) {
-    size_t n = (std::min)(data_offset, size);
-    this->length += n;
-    begin_pos_ -= n;
-    data_offset -= n;
-    entry_data_offset()[head_] = static_cast<offset_type>(data_offset);
-    return {child->flat()->Data() + data_offset, n};
-  }
-  return {nullptr, 0};
-}
-
-CordRepRing* CordRepRing::CreateFromLeaf(CordRep* child, size_t offset,
-                                         size_t len, size_t extra) {
-  CordRepRing* rep = CordRepRing::New(1, extra);
-  rep->head_ = 0;
-  rep->tail_ = rep->advance(0);
-  rep->length = len;
-  rep->entry_end_pos()[0] = len;
-  rep->entry_child()[0] = child;
-  rep->entry_data_offset()[0] = static_cast<offset_type>(offset);
-  return Validate(rep);
-}
-
-CordRepRing* CordRepRing::CreateSlow(CordRep* child, size_t extra) {
-  CordRepRing* rep = nullptr;
-  Consume(child, [&](CordRep* child_arg, size_t offset, size_t len) {
-    if (IsFlatOrExternal(child_arg)) {
-      rep = rep ? AppendLeaf(rep, child_arg, offset, len)
-                : CreateFromLeaf(child_arg, offset, len, extra);
-    } else if (rep) {
-      rep = AddRing<AddMode::kAppend>(rep, child_arg->ring(), offset, len);
-    } else if (offset == 0 && child_arg->length == len) {
-      rep = Mutable(child_arg->ring(), extra);
-    } else {
-      rep = SubRing(child_arg->ring(), offset, len, extra);
-    }
-  });
-  return Validate(rep, nullptr, __LINE__);
-}
-
-CordRepRing* CordRepRing::Create(CordRep* child, size_t extra) {
-  size_t length = child->length;
-  if (IsFlatOrExternal(child)) {
-    return CreateFromLeaf(child, 0, length, extra);
-  }
-  if (child->IsRing()) {
-    return Mutable(child->ring(), extra);
-  }
-  return CreateSlow(child, extra);
-}
-
-template <CordRepRing::AddMode mode>
-CordRepRing* CordRepRing::AddRing(CordRepRing* rep, CordRepRing* ring,
-                                  size_t offset, size_t len) {
-  assert(offset < ring->length);
-  constexpr bool append = mode == AddMode::kAppend;
-  Position head = ring->Find(offset);
-  Position tail = ring->FindTail(head.index, offset + len);
-  const index_type entries = ring->entries(head.index, tail.index);
-
-  rep = Mutable(rep, entries);
-
-  // The delta for making ring[head].end_pos into 'len - offset'
-  const pos_type delta_length =
-      (append ? rep->begin_pos_ + rep->length : rep->begin_pos_ - len) -
-      ring->entry_begin_pos(head.index) - head.offset;
-
-  // Start filling at `tail`, or `entries` before `head`
-  Filler filler(rep, append ? rep->tail_ : rep->retreat(rep->head_, entries));
-
-  if (ring->refcount.IsOne()) {
-    // Copy entries from source stealing the ref and adjusting the end position.
-    // Commit the filler as this is no-op.
-    ring->ForEach(head.index, tail.index, [&](index_type ix) {
-      filler.Add(ring->entry_child(ix), ring->entry_data_offset(ix),
-                 ring->entry_end_pos(ix) + delta_length);
-    });
-
-    // Unref entries we did not copy over, and delete source.
-    if (head.index != ring->head_) UnrefEntries(ring, ring->head_, head.index);
-    if (tail.index != ring->tail_) UnrefEntries(ring, tail.index, ring->tail_);
-    CordRepRing::Delete(ring);
-  } else {
-    ring->ForEach(head.index, tail.index, [&](index_type ix) {
-      CordRep* child = ring->entry_child(ix);
-      filler.Add(child, ring->entry_data_offset(ix),
-                 ring->entry_end_pos(ix) + delta_length);
-      CordRep::Ref(child);
-    });
-    CordRepRing::Unref(ring);
-  }
-
-  if (head.offset) {
-    // Increase offset of first 'source' entry appended or prepended.
-    // This is always the entry in `filler.head()`
-    rep->AddDataOffset(filler.head(), head.offset);
-  }
-
-  if (tail.offset) {
-    // Reduce length of last 'source' entry appended or prepended.
-    // This is always the entry tailed by `filler.pos()`
-    rep->SubLength(rep->retreat(filler.pos()), tail.offset);
-  }
-
-  // Commit changes
-  rep->length += len;
-  if (append) {
-    rep->tail_ = filler.pos();
-  } else {
-    rep->head_ = filler.head();
-    rep->begin_pos_ -= len;
-  }
-
-  return Validate(rep);
-}
-
-CordRepRing* CordRepRing::AppendSlow(CordRepRing* rep, CordRep* child) {
-  Consume(child, [&rep](CordRep* child_arg, size_t offset, size_t len) {
-    if (child_arg->IsRing()) {
-      rep = AddRing<AddMode::kAppend>(rep, child_arg->ring(), offset, len);
-    } else {
-      rep = AppendLeaf(rep, child_arg, offset, len);
-    }
-  });
-  return rep;
-}
-
-CordRepRing* CordRepRing::AppendLeaf(CordRepRing* rep, CordRep* child,
-                                     size_t offset, size_t len) {
-  rep = Mutable(rep, 1);
-  index_type back = rep->tail_;
-  const pos_type begin_pos = rep->begin_pos_ + rep->length;
-  rep->tail_ = rep->advance(rep->tail_);
-  rep->length += len;
-  rep->entry_end_pos()[back] = begin_pos + len;
-  rep->entry_child()[back] = child;
-  rep->entry_data_offset()[back] = static_cast<offset_type>(offset);
-  return Validate(rep, nullptr, __LINE__);
-}
-
-CordRepRing* CordRepRing::Append(CordRepRing* rep, CordRep* child) {
-  size_t length = child->length;
-  if (IsFlatOrExternal(child)) {
-    return AppendLeaf(rep, child, 0, length);
-  }
-  if (child->IsRing()) {
-    return AddRing<AddMode::kAppend>(rep, child->ring(), 0, length);
-  }
-  return AppendSlow(rep, child);
-}
-
-CordRepRing* CordRepRing::PrependSlow(CordRepRing* rep, CordRep* child) {
-  ReverseConsume(child, [&](CordRep* child_arg, size_t offset, size_t len) {
-    if (IsFlatOrExternal(child_arg)) {
-      rep = PrependLeaf(rep, child_arg, offset, len);
-    } else {
-      rep = AddRing<AddMode::kPrepend>(rep, child_arg->ring(), offset, len);
-    }
-  });
-  return Validate(rep);
-}
-
-CordRepRing* CordRepRing::PrependLeaf(CordRepRing* rep, CordRep* child,
-                                      size_t offset, size_t len) {
-  rep = Mutable(rep, 1);
-  index_type head = rep->retreat(rep->head_);
-  pos_type end_pos = rep->begin_pos_;
-  rep->head_ = head;
-  rep->length += len;
-  rep->begin_pos_ -= len;
-  rep->entry_end_pos()[head] = end_pos;
-  rep->entry_child()[head] = child;
-  rep->entry_data_offset()[head] = static_cast<offset_type>(offset);
-  return Validate(rep);
-}
-
-CordRepRing* CordRepRing::Prepend(CordRepRing* rep, CordRep* child) {
-  size_t length = child->length;
-  if (IsFlatOrExternal(child)) {
-    return PrependLeaf(rep, child, 0, length);
-  }
-  if (child->IsRing()) {
-    return AddRing<AddMode::kPrepend>(rep, child->ring(), 0, length);
-  }
-  return PrependSlow(rep, child);
-}
-
-CordRepRing* CordRepRing::Append(CordRepRing* rep, absl::string_view data,
-                                 size_t extra) {
-  if (rep->refcount.IsOne()) {
-    Span<char> avail = rep->GetAppendBuffer(data.length());
-    if (!avail.empty()) {
-      memcpy(avail.data(), data.data(), avail.length());
-      data.remove_prefix(avail.length());
-    }
-  }
-  if (data.empty()) return Validate(rep);
-
-  const size_t flats = (data.length() - 1) / kMaxFlatLength + 1;
-  rep = Mutable(rep, flats);
-
-  Filler filler(rep, rep->tail_);
-  pos_type pos = rep->begin_pos_ + rep->length;
-
-  while (data.length() >= kMaxFlatLength) {
-    auto* flat = CreateFlat(data.data(), kMaxFlatLength);
-    filler.Add(flat, 0, pos += kMaxFlatLength);
-    data.remove_prefix(kMaxFlatLength);
-  }
-
-  if (data.length()) {
-    auto* flat = CreateFlat(data.data(), data.length(), extra);
-    filler.Add(flat, 0, pos += data.length());
-  }
-
-  rep->length = pos - rep->begin_pos_;
-  rep->tail_ = filler.pos();
-
-  return Validate(rep);
-}
-
-CordRepRing* CordRepRing::Prepend(CordRepRing* rep, absl::string_view data,
-                                  size_t extra) {
-  if (rep->refcount.IsOne()) {
-    Span<char> avail = rep->GetPrependBuffer(data.length());
-    if (!avail.empty()) {
-      const char* tail = data.data() + data.length() - avail.length();
-      memcpy(avail.data(), tail, avail.length());
-      data.remove_suffix(avail.length());
-    }
-  }
-  if (data.empty()) return rep;
-
-  const size_t flats = (data.length() - 1) / kMaxFlatLength + 1;
-  rep = Mutable(rep, flats);
-  pos_type pos = rep->begin_pos_;
-  Filler filler(rep, rep->retreat(rep->head_, static_cast<index_type>(flats)));
-
-  size_t first_size = data.size() - (flats - 1) * kMaxFlatLength;
-  CordRepFlat* flat = CordRepFlat::New(first_size + extra);
-  flat->length = first_size + extra;
-  memcpy(flat->Data() + extra, data.data(), first_size);
-  data.remove_prefix(first_size);
-  filler.Add(flat, extra, pos);
-  pos -= first_size;
-
-  while (!data.empty()) {
-    assert(data.size() >= kMaxFlatLength);
-    flat = CreateFlat(data.data(), kMaxFlatLength);
-    filler.Add(flat, 0, pos);
-    pos -= kMaxFlatLength;
-    data.remove_prefix(kMaxFlatLength);
-  }
-
-  rep->head_ = filler.head();
-  rep->length += rep->begin_pos_ - pos;
-  rep->begin_pos_ = pos;
-
-  return Validate(rep);
-}
-
-// 32 entries is 32 * sizeof(pos_type) = 4 cache lines on x86
-static constexpr index_type kBinarySearchThreshold = 32;
-static constexpr index_type kBinarySearchEndCount = 8;
-
-template <bool wrap>
-CordRepRing::index_type CordRepRing::FindBinary(index_type head,
-                                                index_type tail,
-                                                size_t offset) const {
-  index_type count = tail + (wrap ? capacity_ : 0) - head;
-  do {
-    count = (count - 1) / 2;
-    assert(count < entries(head, tail_));
-    index_type mid = wrap ? advance(head, count) : head + count;
-    index_type after_mid = wrap ? advance(mid) : mid + 1;
-    bool larger = (offset >= entry_end_offset(mid));
-    head = larger ? after_mid : head;
-    tail = larger ? tail : mid;
-    assert(head != tail);
-  } while (ABSL_PREDICT_TRUE(count > kBinarySearchEndCount));
-  return head;
-}
-
-CordRepRing::Position CordRepRing::FindSlow(index_type head,
-                                            size_t offset) const {
-  index_type tail = tail_;
-
-  // Binary search until we are good for linear search
-  // Optimize for branchless / non wrapping ops
-  if (tail > head) {
-    index_type count = tail - head;
-    if (count > kBinarySearchThreshold) {
-      head = FindBinary<false>(head, tail, offset);
-    }
-  } else {
-    index_type count = capacity_ + tail - head;
-    if (count > kBinarySearchThreshold) {
-      head = FindBinary<true>(head, tail, offset);
-    }
-  }
-
-  pos_type pos = entry_begin_pos(head);
-  pos_type end_pos = entry_end_pos(head);
-  while (offset >= Distance(begin_pos_, end_pos)) {
-    head = advance(head);
-    pos = end_pos;
-    end_pos = entry_end_pos(head);
-  }
-
-  return {head, offset - Distance(begin_pos_, pos)};
-}
-
-CordRepRing::Position CordRepRing::FindTailSlow(index_type head,
-                                                size_t offset) const {
-  index_type tail = tail_;
-  const size_t tail_offset = offset - 1;
-
-  // Binary search until we are good for linear search
-  // Optimize for branchless / non wrapping ops
-  if (tail > head) {
-    index_type count = tail - head;
-    if (count > kBinarySearchThreshold) {
-      head = FindBinary<false>(head, tail, tail_offset);
-    }
-  } else {
-    index_type count = capacity_ + tail - head;
-    if (count > kBinarySearchThreshold) {
-      head = FindBinary<true>(head, tail, tail_offset);
-    }
-  }
-
-  size_t end_offset = entry_end_offset(head);
-  while (tail_offset >= end_offset) {
-    head = advance(head);
-    end_offset = entry_end_offset(head);
-  }
-
-  return {advance(head), end_offset - offset};
-}
-
-char CordRepRing::GetCharacter(size_t offset) const {
-  assert(offset < length);
-
-  Position pos = Find(offset);
-  size_t data_offset = entry_data_offset(pos.index) + pos.offset;
-  return GetRepData(entry_child(pos.index))[data_offset];
-}
-
-CordRepRing* CordRepRing::SubRing(CordRepRing* rep, size_t offset,
-                                  size_t len, size_t extra) {
-  assert(offset <= rep->length);
-  assert(offset <= rep->length - len);
-
-  if (len == 0) {
-    CordRep::Unref(rep);
-    return nullptr;
-  }
-
-  // Find position of first byte
-  Position head = rep->Find(offset);
-  Position tail = rep->FindTail(head.index, offset + len);
-  const size_t new_entries = rep->entries(head.index, tail.index);
-
-  if (rep->refcount.IsOne() && extra <= (rep->capacity() - new_entries)) {
-    // We adopt a privately owned rep and no extra entries needed.
-    if (head.index != rep->head_) UnrefEntries(rep, rep->head_, head.index);
-    if (tail.index != rep->tail_) UnrefEntries(rep, tail.index, rep->tail_);
-    rep->head_ = head.index;
-    rep->tail_ = tail.index;
-  } else {
-    // Copy subset to new rep
-    rep = Copy(rep, head.index, tail.index, extra);
-    head.index = rep->head_;
-    tail.index = rep->tail_;
-  }
-
-  // Adjust begin_pos and length
-  rep->length = len;
-  rep->begin_pos_ += offset;
-
-  // Adjust head and tail blocks
-  if (head.offset) {
-    rep->AddDataOffset(head.index, head.offset);
-  }
-  if (tail.offset) {
-    rep->SubLength(rep->retreat(tail.index), tail.offset);
-  }
-
-  return Validate(rep);
-}
-
-CordRepRing* CordRepRing::RemovePrefix(CordRepRing* rep, size_t len,
-                                       size_t extra) {
-  assert(len <= rep->length);
-  if (len == rep->length) {
-    CordRep::Unref(rep);
-    return nullptr;
-  }
-
-  Position head = rep->Find(len);
-  if (rep->refcount.IsOne()) {
-    if (head.index != rep->head_) UnrefEntries(rep, rep->head_, head.index);
-    rep->head_ = head.index;
-  } else {
-    rep = Copy(rep, head.index, rep->tail_, extra);
-    head.index = rep->head_;
-  }
-
-  // Adjust begin_pos and length
-  rep->length -= len;
-  rep->begin_pos_ += len;
-
-  // Adjust head block
-  if (head.offset) {
-    rep->AddDataOffset(head.index, head.offset);
-  }
-
-  return Validate(rep);
-}
-
-CordRepRing* CordRepRing::RemoveSuffix(CordRepRing* rep, size_t len,
-                                       size_t extra) {
-  assert(len <= rep->length);
-
-  if (len == rep->length) {
-    CordRep::Unref(rep);
-    return nullptr;
-  }
-
-  Position tail = rep->FindTail(rep->length - len);
-  if (rep->refcount.IsOne()) {
-    // We adopt a privately owned rep, scrub.
-    if (tail.index != rep->tail_) UnrefEntries(rep, tail.index, rep->tail_);
-    rep->tail_ = tail.index;
-  } else {
-    // Copy subset to new rep
-    rep = Copy(rep, rep->head_, tail.index, extra);
-    tail.index = rep->tail_;
-  }
-
-  // Adjust length
-  rep->length -= len;
-
-  // Adjust tail block
-  if (tail.offset) {
-    rep->SubLength(rep->retreat(tail.index), tail.offset);
-  }
-
-  return Validate(rep);
-}
-
-}  // namespace cord_internal
-ABSL_NAMESPACE_END
-}  // namespace absl
diff --git a/absl/strings/internal/cord_rep_ring.h b/absl/strings/internal/cord_rep_ring.h
deleted file mode 100644
index 79a2fdb1..00000000
--- a/absl/strings/internal/cord_rep_ring.h
+++ /dev/null
@@ -1,607 +0,0 @@
-// Copyright 2020 The Abseil Authors
-//
-// Licensed under the Apache License, Version 2.0 (the "License");
-// you may not use this file except in compliance with the License.
-// You may obtain a copy of the License at
-//
-//     https://www.apache.org/licenses/LICENSE-2.0
-//
-// Unless required by applicable law or agreed to in writing, software
-// distributed under the License is distributed on an "AS IS" BASIS,
-// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
-// See the License for the specific language governing permissions and
-// limitations under the License.
-
-#ifndef ABSL_STRINGS_INTERNAL_CORD_REP_RING_H_
-#define ABSL_STRINGS_INTERNAL_CORD_REP_RING_H_
-
-#include <cassert>
-#include <cstddef>
-#include <cstdint>
-#include <iosfwd>
-#include <limits>
-#include <memory>
-
-#include "absl/container/internal/layout.h"
-#include "absl/strings/internal/cord_internal.h"
-#include "absl/strings/internal/cord_rep_flat.h"
-
-namespace absl {
-ABSL_NAMESPACE_BEGIN
-namespace cord_internal {
-
-// All operations modifying a ring buffer are implemented as static methods
-// requiring a CordRepRing instance with a reference adopted by the method.
-//
-// The methods return the modified ring buffer, which may be equal to the input
-// if the input was not shared, and having large enough capacity to accommodate
-// any newly added node(s). Otherwise, a copy of the input rep with the new
-// node(s) added is returned.
-//
-// Any modification on non shared ring buffers with enough capacity will then
-// require minimum atomic operations. Caller should where possible provide
-// reasonable `extra` hints for both anticipated extra `flat` byte space, as
-// well as anticipated extra nodes required for complex operations.
-//
-// Example of code creating a ring buffer, adding some data to it,
-// and discarding the buffer when done:
-//
-//   void FunWithRings() {
-//     // Create ring with 3 flats
-//     CordRep* flat = CreateFlat("Hello");
-//     CordRepRing* ring = CordRepRing::Create(flat, 2);
-//     ring = CordRepRing::Append(ring, CreateFlat(" "));
-//     ring = CordRepRing::Append(ring, CreateFlat("world"));
-//     DoSomethingWithRing(ring);
-//     CordRep::Unref(ring);
-//   }
-//
-// Example of code Copying an existing ring buffer and modifying it:
-//
-//   void MoreFunWithRings(CordRepRing* src) {
-//     CordRepRing* ring = CordRep::Ref(src)->ring();
-//     ring = CordRepRing::Append(ring, CreateFlat("Hello"));
-//     ring = CordRepRing::Append(ring, CreateFlat(" "));
-//     ring = CordRepRing::Append(ring, CreateFlat("world"));
-//     DoSomethingWithRing(ring);
-//     CordRep::Unref(ring);
-//   }
-//
-class CordRepRing : public CordRep {
- public:
-  // `pos_type` represents a 'logical position'. A CordRepRing instance has a
-  // `begin_pos` (default 0), and each node inside the buffer will have an
-  // `end_pos` which is the `end_pos` of the previous node (or `begin_pos`) plus
-  // this node's length. The purpose is to allow for a binary search on this
-  // position, while allowing O(1) prepend and append operations.
-  using pos_type = size_t;
-
-  // `index_type` is the type for the `head`, `tail` and `capacity` indexes.
-  // Ring buffers are limited to having no more than four billion entries.
-  using index_type = uint32_t;
-
-  // `offset_type` is the type for the data offset inside a child rep's data.
-  using offset_type = uint32_t;
-
-  // Position holds the node index and relative offset into the node for
-  // some physical offset in the contained data as returned by the Find()
-  // and FindTail() methods.
-  struct Position {
-    index_type index;
-    size_t offset;
-  };
-
-  // The maximum # of child nodes that can be hosted inside a CordRepRing.
-  static constexpr size_t kMaxCapacity = (std::numeric_limits<uint32_t>::max)();
-
-  // CordRepring can not be default constructed, moved, copied or assigned.
-  CordRepRing() = delete;
-  CordRepRing(const CordRepRing&) = delete;
-  CordRepRing& operator=(const CordRepRing&) = delete;
-
-  // Returns true if this instance is valid, false if some or all of the
-  // invariants are broken. Intended for debug purposes only.
-  // `output` receives an explanation of the broken invariants.
-  bool IsValid(std::ostream& output) const;
-
-  // Returns the size in bytes for a CordRepRing with `capacity' entries.
-  static constexpr size_t AllocSize(size_t capacity);
-
-  // Returns the distance in bytes from `pos` to `end_pos`.
-  static constexpr size_t Distance(pos_type pos, pos_type end_pos);
-
-  // Creates a new ring buffer from the provided `rep`. Adopts a reference
-  // on `rep`. The returned ring buffer has a capacity of at least `extra + 1`
-  static CordRepRing* Create(CordRep* child, size_t extra = 0);
-
-  // `head`, `tail` and `capacity` indexes defining the ring buffer boundaries.
-  index_type head() const { return head_; }
-  index_type tail() const { return tail_; }
-  index_type capacity() const { return capacity_; }
-
-  // Returns the number of entries in this instance.
-  index_type entries() const { return entries(head_, tail_); }
-
-  // Returns the logical begin position of this instance.
-  pos_type begin_pos() const { return begin_pos_; }
-
-  // Returns the number of entries for a given head-tail range.
-  // Requires `head` and `tail` values to be less than `capacity()`.
-  index_type entries(index_type head, index_type tail) const {
-    assert(head < capacity_ && tail < capacity_);
-    return tail - head + ((tail > head) ? 0 : capacity_);
-  }
-
-  // Returns the logical end position of entry `index`.
-  pos_type const& entry_end_pos(index_type index) const {
-    assert(IsValidIndex(index));
-    return Layout::Partial().Pointer<0>(data_)[index];
-  }
-
-  // Returns the child pointer of entry `index`.
-  CordRep* const& entry_child(index_type index) const {
-    assert(IsValidIndex(index));
-    return Layout::Partial(capacity()).Pointer<1>(data_)[index];
-  }
-
-  // Returns the data offset of entry `index`
-  offset_type const& entry_data_offset(index_type index) const {
-    assert(IsValidIndex(index));
-    return Layout::Partial(capacity(), capacity()).Pointer<2>(data_)[index];
-  }
-
-  // Appends the provided child node to the `rep` instance.
-  // Adopts a reference from `rep` and `child` which may not be null.
-  // If the provided child is a FLAT or EXTERNAL node, or a SUBSTRING node
-  // containing a FLAT or EXTERNAL node, then flat or external the node is added
-  // 'as is', with an offset added for the SUBSTRING case.
-  // If the provided child is a RING or CONCAT tree, or a SUBSTRING of a RING or
-  // CONCAT tree, then all child nodes not excluded by any start offset or
-  // length values are added recursively.
-  static CordRepRing* Append(CordRepRing* rep, CordRep* child);
-
-  // Appends the provided string data to the `rep` instance.
-  // This function will attempt to utilize any remaining capacity in the last
-  // node of the input if that node is not shared (directly or indirectly), and
-  // of type FLAT. Remaining data will be added as one or more FLAT nodes.
-  // Any last node added to the ring buffer will be allocated with up to
-  // `extra` bytes of capacity for (anticipated) subsequent append actions.
-  static CordRepRing* Append(CordRepRing* rep, string_view data,
-                             size_t extra = 0);
-
-  // Prepends the provided child node to the `rep` instance.
-  // Adopts a reference from `rep` and `child` which may not be null.
-  // If the provided child is a FLAT or EXTERNAL node, or a SUBSTRING node
-  // containing a FLAT or EXTERNAL node, then flat or external the node is
-  // prepended 'as is', with an optional offset added for the SUBSTRING case.
-  // If the provided child is a RING or CONCAT tree, or a SUBSTRING of a RING
-  // or CONCAT tree, then all child nodes not excluded by any start offset or
-  // length values are added recursively.
-  static CordRepRing* Prepend(CordRepRing* rep, CordRep* child);
-
-  // Prepends the provided string data to the `rep` instance.
-  // This function will attempt to utilize any remaining capacity in the first
-  // node of the input if that node is not shared (directly or indirectly), and
-  // of type FLAT. Remaining data will be added as one or more FLAT nodes.
-  // Any first node prepnded to the ring buffer will be allocated with up to
-  // `extra` bytes of capacity for (anticipated) subsequent prepend actions.
-  static CordRepRing* Prepend(CordRepRing* rep, string_view data,
-                              size_t extra = 0);
-
-  // Returns a span referencing potentially unused capacity in the last node.
-  // The returned span may be empty if no such capacity is available, or if the
-  // current instance is shared. Else, a span of size `n <= size` is returned.
-  // If non empty, the ring buffer is adjusted to the new length, with the newly
-  // added capacity left uninitialized. Callers should assign a value to the
-  // entire span before any other operations on this instance.
-  Span<char> GetAppendBuffer(size_t size);
-
-  // Returns a span referencing potentially unused capacity in the first node.
-  // This function is identical to GetAppendBuffer except that it returns a span
-  // referencing up to `size` capacity directly before the existing data.
-  Span<char> GetPrependBuffer(size_t size);
-
-  // Returns a cord ring buffer containing `len` bytes of data starting at
-  // `offset`. If the input is not shared, this function will remove all head
-  // and tail child nodes outside of the requested range, and adjust the new
-  // head and tail nodes as required. If the input is shared, this function
-  // returns a new instance sharing some or all of the nodes from the input.
-  static CordRepRing* SubRing(CordRepRing* r, size_t offset, size_t len,
-                              size_t extra = 0);
-
-  // Returns a cord ring buffer with the first `len` bytes removed.
-  // If the input is not shared, this function will remove all head child nodes
-  // fully inside the first `length` bytes, and adjust the new head as required.
-  // If the input is shared, this function returns a new instance sharing some
-  // or all of the nodes from the input.
-  static CordRepRing* RemoveSuffix(CordRepRing* r, size_t len,
-                                   size_t extra = 0);
-
-  // Returns a cord ring buffer with the last `len` bytes removed.
-  // If the input is not shared, this function will remove all head child nodes
-  // fully inside the first `length` bytes, and adjust the new head as required.
-  // If the input is shared, this function returns a new instance sharing some
-  // or all of the nodes from the input.
-  static CordRepRing* RemovePrefix(CordRepRing* r, size_t len,
-                                   size_t extra = 0);
-
-  // Returns the character at `offset`. Requires that `offset < length`.
-  char GetCharacter(size_t offset) const;
-
-  // Returns true if this instance manages a single contiguous buffer, in which
-  // case the (optional) output parameter `fragment` is set. Otherwise, the
-  // function returns false, and `fragment` is left unchanged.
-  bool IsFlat(absl::string_view* fragment) const;
-
-  // Returns true if the data starting at `offset` with length `len` is
-  // managed by this instance inside a single contiguous buffer, in which case
-  // the (optional) output parameter `fragment` is set to the contiguous memory
-  // starting at offset `offset` with length `length`. Otherwise, the function
-  // returns false, and `fragment` is left unchanged.
-  bool IsFlat(size_t offset, size_t len, absl::string_view* fragment) const;
-
-  // Testing only: set capacity to requested capacity.
-  void SetCapacityForTesting(size_t capacity);
-
-  // Returns the CordRep data pointer for the provided CordRep.
-  // Requires that the provided `rep` is either a FLAT or EXTERNAL CordRep.
-  static const char* GetLeafData(const CordRep* rep);
-
-  // Returns the CordRep data pointer for the provided CordRep.
-  // Requires that `rep` is either a FLAT, EXTERNAL, or SUBSTRING CordRep.
-  static const char* GetRepData(const CordRep* rep);
-
-  // Advances the provided position, wrapping around capacity as needed.
-  // Requires `index` < capacity()
-  inline index_type advance(index_type index) const;
-
-  // Advances the provided position by 'n`, wrapping around capacity as needed.
-  // Requires `index` < capacity() and `n` <= capacity.
-  inline index_type advance(index_type index, index_type n) const;
-
-  // Retreats the provided position, wrapping around 0 as needed.
-  // Requires `index` < capacity()
-  inline index_type retreat(index_type index) const;
-
-  // Retreats the provided position by 'n', wrapping around 0 as needed.
-  // Requires `index` < capacity()
-  inline index_type retreat(index_type index, index_type n) const;
-
-  // Returns the logical begin position of entry `index`
-  pos_type const& entry_begin_pos(index_type index) const {
-    return (index == head_) ? begin_pos_ : entry_end_pos(retreat(index));
-  }
-
-  // Returns the physical start offset of entry `index`
-  size_t entry_start_offset(index_type index) const {
-    return Distance(begin_pos_, entry_begin_pos(index));
-  }
-
-  // Returns the physical end offset of entry `index`
-  size_t entry_end_offset(index_type index) const {
-    return Distance(begin_pos_, entry_end_pos(index));
-  }
-
-  // Returns the data length for entry `index`
-  size_t entry_length(index_type index) const {
-    return Distance(entry_begin_pos(index), entry_end_pos(index));
-  }
-
-  // Returns the data for entry `index`
-  absl::string_view entry_data(index_type index) const;
-
-  // Returns the position for `offset` as {index, prefix}. `index` holds the
-  // index of the entry at the specified offset and `prefix` holds the relative
-  // offset inside that entry.
-  // Requires `offset` < length.
-  //
-  // For example we can implement GetCharacter(offset) as:
-  //   char GetCharacter(size_t offset) {
-  //     Position pos = this->Find(offset);
-  //     return this->entry_data(pos.pos)[pos.offset];
-  //   }
-  inline Position Find(size_t offset) const;
-
-  // Find starting at `head`
-  inline Position Find(index_type head, size_t offset) const;
-
-  // Returns the tail position for `offset` as {tail index, suffix}.
-  // `tail index` holds holds the index of the entry holding the offset directly
-  // before 'offset` advanced by one. 'suffix` holds the relative offset from
-  // that relative offset in the entry to the end of the entry.
-  // For example, FindTail(length) will return {tail(), 0}, FindTail(length - 5)
-  // will return {retreat(tail), 5)} provided the preceding entry contains at
-  // least 5 bytes of data.
-  // Requires offset >= 1 && offset <= length.
-  //
-  // This function is very useful in functions that need to clip the end of some
-  // ring buffer such as 'RemovePrefix'.
-  // For example, we could implement RemovePrefix for non shared instances as:
-  //   void RemoveSuffix(size_t n) {
-  //     Position pos = FindTail(length - n);
-  //     UnrefEntries(pos.pos, this->tail_);
-  //     this->tail_ = pos.pos;
-  //     entry(retreat(pos.pos)).end_pos -= pos.offset;
-  //   }
-  inline Position FindTail(size_t offset) const;
-
-  // Find tail starting at `head`
-  inline Position FindTail(index_type head, size_t offset) const;
-
-  // Invokes f(index_type index) for each entry inside the range [head, tail>
-  template <typename F>
-  void ForEach(index_type head, index_type tail, F&& f) const {
-    index_type n1 = (tail > head) ? tail : capacity_;
-    for (index_type i = head; i < n1; ++i) f(i);
-    if (tail <= head) {
-      for (index_type i = 0; i < tail; ++i) f(i);
-    }
-  }
-
-  // Invokes f(index_type index) for each entry inside this instance.
-  template <typename F>
-  void ForEach(F&& f) const {
-    ForEach(head_, tail_, std::forward<F>(f));
-  }
-
-  // Dump this instance's data tp stream `s` in human readable format, excluding
-  // the actual data content itself. Intended for debug purposes only.
-  friend std::ostream& operator<<(std::ostream& s, const CordRepRing& rep);
-
- private:
-  enum class AddMode { kAppend, kPrepend };
-
-  using Layout = container_internal::Layout<pos_type, CordRep*, offset_type>;
-
-  class Filler;
-  class Transaction;
-  class CreateTransaction;
-
-  static constexpr size_t kLayoutAlignment = Layout::Partial().Alignment();
-
-  // Creates a new CordRepRing.
-  explicit CordRepRing(index_type capacity) : capacity_(capacity) {}
-
-  // Returns true if `index` is a valid index into this instance.
-  bool IsValidIndex(index_type index) const;
-
-  // Debug use only: validates the provided CordRepRing invariants.
-  // Verification of all CordRepRing methods can be enabled by defining
-  // EXTRA_CORD_RING_VALIDATION, i.e.: `--copts=-DEXTRA_CORD_RING_VALIDATION`
-  // Verification is VERY expensive, so only do it for debugging purposes.
-  static CordRepRing* Validate(CordRepRing* rep, const char* file = nullptr,
-                               int line = 0);
-
-  // Allocates a CordRepRing large enough to hold `capacity + extra' entries.
-  // The returned capacity may be larger if the allocated memory allows for it.
-  // The maximum capacity of a CordRepRing is capped at kMaxCapacity.
-  // Throws `std::length_error` if `capacity + extra' exceeds kMaxCapacity.
-  static CordRepRing* New(size_t capacity, size_t extra);
-
-  // Deallocates (but does not destroy) the provided ring buffer.
-  static void Delete(CordRepRing* rep);
-
-  // Destroys the provided ring buffer, decrementing the reference count of all
-  // contained child CordReps. The provided 1\`rep` should have a ref count of
-  // one (pre decrement destroy call observing `refcount.IsOne()`) or zero
-  // (post decrement destroy call observing `!refcount.Decrement()`).
-  static void Destroy(CordRepRing* rep);
-
-  // Returns a mutable reference to the logical end position array.
-  pos_type* entry_end_pos() {
-    return Layout::Partial().Pointer<0>(data_);
-  }
-
-  // Returns a mutable reference to the child pointer array.
-  CordRep** entry_child() {
-    return Layout::Partial(capacity()).Pointer<1>(data_);
-  }
-
-  // Returns a mutable reference to the data offset array.
-  offset_type* entry_data_offset() {
-    return Layout::Partial(capacity(), capacity()).Pointer<2>(data_);
-  }
-
-  // Find implementations for the non fast path 0 / length cases.
-  Position FindSlow(index_type head, size_t offset) const;
-  Position FindTailSlow(index_type head, size_t offset) const;
-
-  // Finds the index of the first node that is inside a reasonable distance
-  // of the node at `offset` from which we can continue with a linear search.
-  template <bool wrap>
-  index_type FindBinary(index_type head, index_type tail, size_t offset) const;
-
-  // Fills the current (initialized) instance from the provided source, copying
-  // entries [head, tail). Adds a reference to copied entries if `ref` is true.
-  template <bool ref>
-  void Fill(const CordRepRing* src, index_type head, index_type tail);
-
-  // Create a copy of 'rep', copying all entries [head, tail), allocating room
-  // for `extra` entries. Adds a reference on all copied entries.
-  static CordRepRing* Copy(CordRepRing* rep, index_type head, index_type tail,
-                           size_t extra = 0);
-
-  // Returns a Mutable CordRepRing reference from `rep` with room for at least
-  // `extra` additional nodes. Adopts a reference count from `rep`.
-  // This function will return `rep` if, and only if:
-  // - rep.entries + extra <= rep.capacity
-  // - rep.refcount == 1
-  // Otherwise, this function will create a new copy of `rep` with additional
-  // capacity to satisfy `extra` extra nodes, and unref the old `rep` instance.
-  //
-  // If a new CordRepRing can not be allocated, or the new capacity would exceed
-  // the maximum capacity, then the input is consumed only, and an exception is
-  // thrown.
-  static CordRepRing* Mutable(CordRepRing* rep, size_t extra);
-
-  // Slow path for Append(CordRepRing* rep, CordRep* child). This function is
-  // exercised if the provided `child` in Append() is not a leaf node, i.e., a
-  // ring buffer or old (concat) cord tree.
-  static CordRepRing* AppendSlow(CordRepRing* rep, CordRep* child);
-
-  // Appends the provided leaf node. Requires `child` to be FLAT or EXTERNAL.
-  static CordRepRing* AppendLeaf(CordRepRing* rep, CordRep* child,
-                                 size_t offset, size_t length);
-
-  // Prepends the provided leaf node. Requires `child` to be FLAT or EXTERNAL.
-  static CordRepRing* PrependLeaf(CordRepRing* rep, CordRep* child,
-                                  size_t offset, size_t length);
-
-  // Slow path for Prepend(CordRepRing* rep, CordRep* child). This function is
-  // exercised if the provided `child` in Prepend() is not a leaf node, i.e., a
-  // ring buffer or old (concat) cord tree.
-  static CordRepRing* PrependSlow(CordRepRing* rep, CordRep* child);
-
-  // Slow path for Create(CordRep* child, size_t extra). This function is
-  // exercised if the provided `child` in Prepend() is not a leaf node, i.e., a
-  // ring buffer or old (concat) cord tree.
-  static CordRepRing* CreateSlow(CordRep* child, size_t extra);
-
-  // Creates a new ring buffer from the provided `child` leaf node. Requires
-  // `child` to be FLAT or EXTERNAL. on `rep`.
-  // The returned ring buffer has a capacity of at least `1 + extra`
-  static CordRepRing* CreateFromLeaf(CordRep* child, size_t offset,
-                                     size_t length, size_t extra);
-
-  // Appends or prepends (depending on AddMode) the ring buffer in `ring' to
-  // `rep` starting at `offset` with length `len`.
-  template <AddMode mode>
-  static CordRepRing* AddRing(CordRepRing* rep, CordRepRing* ring,
-                              size_t offset, size_t len);
-
-  // Increases the data offset for entry `index` by `n`.
-  void AddDataOffset(index_type index, size_t n);
-
-  // Decreases the length for entry `index` by `n`.
-  void SubLength(index_type index, size_t n);
-
-  index_type head_;
-  index_type tail_;
-  index_type capacity_;
-  pos_type begin_pos_;
-
-  alignas(kLayoutAlignment) char data_[kLayoutAlignment];
-
-  friend struct CordRep;
-};
-
-constexpr size_t CordRepRing::AllocSize(size_t capacity) {
-  return sizeof(CordRepRing) - sizeof(data_) +
-         Layout(capacity, capacity, capacity).AllocSize();
-}
-
-inline constexpr size_t CordRepRing::Distance(pos_type pos, pos_type end_pos) {
-  return (end_pos - pos);
-}
-
-inline const char* CordRepRing::GetLeafData(const CordRep* rep) {
-  return rep->tag != EXTERNAL ? rep->flat()->Data() : rep->external()->base;
-}
-
-inline const char* CordRepRing::GetRepData(const CordRep* rep) {
-  if (rep->tag >= FLAT) return rep->flat()->Data();
-  if (rep->tag == EXTERNAL) return rep->external()->base;
-  return GetLeafData(rep->substring()->child) + rep->substring()->start;
-}
-
-inline CordRepRing::index_type CordRepRing::advance(index_type index) const {
-  assert(index < capacity_);
-  return ++index == capacity_ ? 0 : index;
-}
-
-inline CordRepRing::index_type CordRepRing::advance(index_type index,
-                                                    index_type n) const {
-  assert(index < capacity_ && n <= capacity_);
-  return (index += n) >= capacity_ ? index - capacity_ : index;
-}
-
-inline CordRepRing::index_type CordRepRing::retreat(index_type index) const {
-  assert(index < capacity_);
-  return (index > 0 ? index : capacity_) - 1;
-}
-
-inline CordRepRing::index_type CordRepRing::retreat(index_type index,
-                                                    index_type n) const {
-  assert(index < capacity_ && n <= capacity_);
-  return index >= n ? index - n : capacity_ - n + index;
-}
-
-inline absl::string_view CordRepRing::entry_data(index_type index) const {
-  size_t data_offset = entry_data_offset(index);
-  return {GetRepData(entry_child(index)) + data_offset, entry_length(index)};
-}
-
-inline bool CordRepRing::IsValidIndex(index_type index) const {
-  if (index >= capacity_) return false;
-  return (tail_ > head_) ? (index >= head_ && index < tail_)
-                         : (index >= head_ || index < tail_);
-}
-
-#ifndef EXTRA_CORD_RING_VALIDATION
-inline CordRepRing* CordRepRing::Validate(CordRepRing* rep,
-                                          const char* /*file*/, int /*line*/) {
-  return rep;
-}
-#endif
-
-inline CordRepRing::Position CordRepRing::Find(size_t offset) const {
-  assert(offset < length);
-  return (offset == 0) ? Position{head_, 0} : FindSlow(head_, offset);
-}
-
-inline CordRepRing::Position CordRepRing::Find(index_type head,
-                                               size_t offset) const {
-  assert(offset < length);
-  assert(IsValidIndex(head) && offset >= entry_start_offset(head));
-  return (offset == 0) ? Position{head_, 0} : FindSlow(head, offset);
-}
-
-inline CordRepRing::Position CordRepRing::FindTail(size_t offset) const {
-  assert(offset > 0 && offset <= length);
-  return (offset == length) ? Position{tail_, 0} : FindTailSlow(head_, offset);
-}
-
-inline CordRepRing::Position CordRepRing::FindTail(index_type head,
-                                                   size_t offset) const {
-  assert(offset > 0 && offset <= length);
-  assert(IsValidIndex(head) && offset >= entry_start_offset(head) + 1);
-  return (offset == length) ? Position{tail_, 0} : FindTailSlow(head, offset);
-}
-
-// Now that CordRepRing is defined, we can define CordRep's helper casts:
-inline CordRepRing* CordRep::ring() {
-  assert(IsRing());
-  return static_cast<CordRepRing*>(this);
-}
-
-inline const CordRepRing* CordRep::ring() const {
-  assert(IsRing());
-  return static_cast<const CordRepRing*>(this);
-}
-
-inline bool CordRepRing::IsFlat(absl::string_view* fragment) const {
-  if (entries() == 1) {
-    if (fragment) *fragment = entry_data(head());
-    return true;
-  }
-  return false;
-}
-
-inline bool CordRepRing::IsFlat(size_t offset, size_t len,
-                                absl::string_view* fragment) const {
-  const Position pos = Find(offset);
-  const absl::string_view data = entry_data(pos.index);
-  if (data.length() >= len && data.length() - len >= pos.offset) {
-    if (fragment) *fragment = data.substr(pos.offset, len);
-    return true;
-  }
-  return false;
-}
-
-std::ostream& operator<<(std::ostream& s, const CordRepRing& rep);
-
-}  // namespace cord_internal
-ABSL_NAMESPACE_END
-}  // namespace absl
-
-#endif  // ABSL_STRINGS_INTERNAL_CORD_REP_RING_H_
diff --git a/absl/strings/internal/cord_rep_ring_reader.h b/absl/strings/internal/cord_rep_ring_reader.h
deleted file mode 100644
index 7ceeaa00..00000000
--- a/absl/strings/internal/cord_rep_ring_reader.h
+++ /dev/null
@@ -1,118 +0,0 @@
-// Copyright 2021 The Abseil Authors
-//
-// Licensed under the Apache License, Version 2.0 (the "License");
-// you may not use this file except in compliance with the License.
-// You may obtain a copy of the License at
-//
-//     https://www.apache.org/licenses/LICENSE-2.0
-//
-// Unless required by applicable law or agreed to in writing, software
-// distributed under the License is distributed on an "AS IS" BASIS,
-// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
-// See the License for the specific language governing permissions and
-// limitations under the License.
-
-#ifndef ABSL_STRINGS_INTERNAL_CORD_REP_RING_READER_H_
-#define ABSL_STRINGS_INTERNAL_CORD_REP_RING_READER_H_
-
-#include <cassert>
-#include <cstddef>
-#include <cstdint>
-
-#include "absl/strings/internal/cord_internal.h"
-#include "absl/strings/internal/cord_rep_ring.h"
-#include "absl/strings/string_view.h"
-
-namespace absl {
-ABSL_NAMESPACE_BEGIN
-namespace cord_internal {
-
-// CordRepRingReader provides basic navigation over CordRepRing data.
-class CordRepRingReader {
- public:
-  // Returns true if this instance is not empty.
-  explicit operator bool() const { return ring_ != nullptr; }
-
-  // Returns the ring buffer reference for this instance, or nullptr if empty.
-  CordRepRing* ring() const { return ring_; }
-
-  // Returns the current node index inside the ring buffer for this instance.
-  // The returned value is undefined if this instance is empty.
-  CordRepRing::index_type index() const { return index_; }
-
-  // Returns the current node inside the ring buffer for this instance.
-  // The returned value is undefined if this instance is empty.
-  CordRep* node() const { return ring_->entry_child(index_); }
-
-  // Returns the length of the referenced ring buffer.
-  // Requires the current instance to be non empty.
-  size_t length() const {
-    assert(ring_);
-    return ring_->length;
-  }
-
-  // Returns the end offset of the last navigated-to chunk, which represents the
-  // total bytes 'consumed' relative to the start of the ring. The returned
-  // value is never zero. For example, initializing a reader with a ring buffer
-  // with a first chunk of 19 bytes will return consumed() = 19.
-  // Requires the current instance to be non empty.
-  size_t consumed() const {
-    assert(ring_);
-    return ring_->entry_end_offset(index_);
-  }
-
-  // Returns the number of bytes remaining beyond the last navigated-to chunk.
-  // Requires the current instance to be non empty.
-  size_t remaining() const {
-    assert(ring_);
-    return length() - consumed();
-  }
-
-  // Resets this instance to an empty value
-  void Reset() { ring_ = nullptr; }
-
-  // Resets this instance to the start of `ring`. `ring` must not be null.
-  // Returns a reference into the first chunk of the provided ring.
-  absl::string_view Reset(CordRepRing* ring) {
-    assert(ring);
-    ring_ = ring;
-    index_ = ring_->head();
-    return ring_->entry_data(index_);
-  }
-
-  // Navigates to the next chunk inside the reference ring buffer.
-  // Returns a reference into the navigated-to chunk.
-  // Requires remaining() to be non zero.
-  absl::string_view Next() {
-    assert(remaining());
-    index_ = ring_->advance(index_);
-    return ring_->entry_data(index_);
-  }
-
-  // Navigates to the chunk at offset `offset`.
-  // Returns a reference into the navigated-to chunk, adjusted for the relative
-  // position of `offset` into that chunk. For example, calling Seek(13) on a
-  // ring buffer containing 2 chunks of 10 and 20 bytes respectively will return
-  // a string view into the second chunk starting at offset 3 with a size of 17.
-  // Requires `offset` to be less than `length()`
-  absl::string_view Seek(size_t offset) {
-    assert(offset < length());
-    size_t current = ring_->entry_end_offset(index_);
-    CordRepRing::index_type hint = (offset >= current) ? index_ : ring_->head();
-    const CordRepRing::Position head = ring_->Find(hint, offset);
-    index_ = head.index;
-    auto data = ring_->entry_data(head.index);
-    data.remove_prefix(head.offset);
-    return data;
-  }
-
- private:
-  CordRepRing* ring_ = nullptr;
-  CordRepRing::index_type index_;
-};
-
-}  // namespace cord_internal
-ABSL_NAMESPACE_END
-}  // namespace absl
-
-#endif  // ABSL_STRINGS_INTERNAL_CORD_REP_RING_READER_H_
diff --git a/absl/strings/internal/cordz_info.cc b/absl/strings/internal/cordz_info.cc
index b830c25c..b24c3da7 100644
--- a/absl/strings/internal/cordz_info.cc
+++ b/absl/strings/internal/cordz_info.cc
@@ -21,7 +21,6 @@
 #include "absl/strings/internal/cord_internal.h"
 #include "absl/strings/internal/cord_rep_btree.h"
 #include "absl/strings/internal/cord_rep_crc.h"
-#include "absl/strings/internal/cord_rep_ring.h"
 #include "absl/strings/internal/cordz_handle.h"
 #include "absl/strings/internal/cordz_statistics.h"
 #include "absl/strings/internal/cordz_update_tracker.h"
@@ -97,14 +96,11 @@ class CordRepAnalyzer {
     repref = CountLinearReps(repref, memory_usage_);
 
     switch (repref.tag()) {
-      case CordRepKind::RING:
-        AnalyzeRing(repref);
-        break;
       case CordRepKind::BTREE:
         AnalyzeBtree(repref);
         break;
       default:
-        // We should have either a btree or ring node if not null.
+        // We should have a btree node if not null.
         ABSL_ASSERT(repref.tag() == CordRepKind::UNUSED_0);
         break;
     }
@@ -204,17 +200,6 @@ class CordRepAnalyzer {
     return rep;
   }
 
-  // Analyzes the provided ring.
-  void AnalyzeRing(RepRef rep) {
-    statistics_.node_count++;
-    statistics_.node_counts.ring++;
-    const CordRepRing* ring = rep.rep->ring();
-    memory_usage_.Add(CordRepRing::AllocSize(ring->capacity()), rep.refcount);
-    ring->ForEach([&](CordRepRing::index_type pos) {
-      CountLinearReps(rep.Child(ring->entry_child(pos)), memory_usage_);
-    });
-  }
-
   // Analyzes the provided btree.
   void AnalyzeBtree(RepRef rep) {
     statistics_.node_count++;
diff --git a/absl/strings/internal/cordz_info_statistics_test.cc b/absl/strings/internal/cordz_info_statistics_test.cc
index aad3b1ec..d55773f2 100644
--- a/absl/strings/internal/cordz_info_statistics_test.cc
+++ b/absl/strings/internal/cordz_info_statistics_test.cc
@@ -25,7 +25,6 @@
 #include "absl/strings/internal/cord_rep_btree.h"
 #include "absl/strings/internal/cord_rep_crc.h"
 #include "absl/strings/internal/cord_rep_flat.h"
-#include "absl/strings/internal/cord_rep_ring.h"
 #include "absl/strings/internal/cordz_info.h"
 #include "absl/strings/internal/cordz_sample_token.h"
 #include "absl/strings/internal/cordz_statistics.h"
@@ -123,11 +122,6 @@ size_t SizeOf(const CordRepExternal* rep) {
   return sizeof(CordRepExternalImpl<intptr_t>) + rep->length;
 }
 
-template <>
-size_t SizeOf(const CordRepRing* rep) {
-  return CordRepRing::AllocSize(rep->capacity());
-}
-
 // Computes fair share memory used in a naive 'we dare to recurse' way.
 double FairShareImpl(CordRep* rep, size_t ref) {
   double self = 0.0, children = 0.0;
@@ -144,11 +138,6 @@ double FairShareImpl(CordRep* rep, size_t ref) {
     for (CordRep*edge : rep->btree()->Edges()) {
       children += FairShareImpl(edge, ref);
     }
-  } else if (rep->tag == RING) {
-    self = SizeOf(rep->ring());
-    rep->ring()->ForEach([&](CordRepRing::index_type i) {
-      self += FairShareImpl(rep->ring()->entry_child(i), 1);
-    });
   } else {
     assert(false);
   }
@@ -294,64 +283,6 @@ TEST(CordzInfoStatisticsTest, SharedSubstring) {
   EXPECT_THAT(SampleCord(substring), EqStatistics(expected));
 }
 
-
-TEST(CordzInfoStatisticsTest, Ring) {
-  RefHelper ref;
-  auto* flat1 = Flat(240);
-  auto* flat2 = Flat(2000);
-  auto* flat3 = Flat(70);
-  auto* external = External(3000);
-  CordRepRing* ring = CordRepRing::Create(flat1);
-  ring = CordRepRing::Append(ring, flat2);
-  ring = CordRepRing::Append(ring, flat3);
-  ring = ref.NeedsUnref(CordRepRing::Append(ring, external));
-
-  CordzStatistics expected;
-  expected.size = ring->length;
-  expected.estimated_memory_usage = SizeOf(ring) + SizeOf(flat1) +
-                                    SizeOf(flat2) + SizeOf(flat3) +
-                                    SizeOf(external);
-  expected.estimated_fair_share_memory_usage = expected.estimated_memory_usage;
-  expected.node_count = 5;
-  expected.node_counts.flat = 3;
-  expected.node_counts.flat_128 = 1;
-  expected.node_counts.flat_256 = 1;
-  expected.node_counts.external = 1;
-  expected.node_counts.ring = 1;
-
-  EXPECT_THAT(SampleCord(ring), EqStatistics(expected));
-}
-
-TEST(CordzInfoStatisticsTest, SharedSubstringRing) {
-  RefHelper ref;
-  auto* flat1 = ref.Ref(Flat(240));
-  auto* flat2 = Flat(200);
-  auto* flat3 = Flat(70);
-  auto* external = ref.Ref(External(3000), 5);
-  CordRepRing* ring = CordRepRing::Create(flat1);
-  ring = CordRepRing::Append(ring, flat2);
-  ring = CordRepRing::Append(ring, flat3);
-  ring = ref.Ref(CordRepRing::Append(ring, external), 4);
-  auto* substring = ref.Ref(ref.NeedsUnref(Substring(ring)));
-
-
-  CordzStatistics expected;
-  expected.size = substring->length;
-  expected.estimated_memory_usage = SizeOf(ring) + SizeOf(flat1) +
-                                    SizeOf(flat2) + SizeOf(flat3) +
-                                    SizeOf(external) + SizeOf(substring);
-  expected.estimated_fair_share_memory_usage = FairShare(substring);
-  expected.node_count = 6;
-  expected.node_counts.flat = 3;
-  expected.node_counts.flat_128 = 1;
-  expected.node_counts.flat_256 = 2;
-  expected.node_counts.external = 1;
-  expected.node_counts.ring = 1;
-  expected.node_counts.substring = 1;
-
-  EXPECT_THAT(SampleCord(substring), EqStatistics(expected));
-}
-
 TEST(CordzInfoStatisticsTest, BtreeLeaf) {
   ASSERT_THAT(CordRepBtree::kMaxCapacity, Ge(3u));
   RefHelper ref;
@@ -528,14 +459,10 @@ TEST(CordzInfoStatisticsTest, ThreadSafety) {
                 CordRep::Unref(cord.as_tree());
                 cord.set_inline_size(0);
               } else {
-                // Coin toss to 25% ring, 25% btree, and 50% flat.
+                // Coin toss to 50% btree, and 50% flat.
                 CordRep* rep = Flat(256);
                 if (coin_toss(gen) != 0) {
-                  if (coin_toss(gen) != 0) {
-                    rep = CordRepRing::Create(rep);
-                  } else {
-                    rep = CordRepBtree::Create(rep);
-                  }
+                  rep = CordRepBtree::Create(rep);
                 }
 
                 // Maybe CRC this cord