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diff --git a/absl/debugging/internal/decode_rust_punycode.h b/absl/debugging/internal/decode_rust_punycode.h
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+// Copyright 2024 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_DEBUGGING_INTERNAL_DECODE_RUST_PUNYCODE_H_
+#define ABSL_DEBUGGING_INTERNAL_DECODE_RUST_PUNYCODE_H_
+
+#include "absl/base/config.h"
+#include "absl/base/nullability.h"
+
+namespace absl {
+ABSL_NAMESPACE_BEGIN
+namespace debugging_internal {
+
+struct DecodeRustPunycodeOptions {
+  const char* punycode_begin;
+  const char* punycode_end;
+  char* out_begin;
+  char* out_end;
+};
+
+// Given Rust Punycode in `punycode_begin .. punycode_end`, writes the
+// corresponding UTF-8 plaintext into `out_begin .. out_end`, followed by a NUL
+// character, and returns a pointer to that final NUL on success.  On failure
+// returns a null pointer, and the contents of `out_begin .. out_end` are
+// unspecified.
+//
+// Failure occurs in precisely these cases:
+//   - Any input byte does not match [0-9a-zA-Z_].
+//   - The first input byte is an underscore, but no other underscore appears in
+//     the input.
+//   - The delta sequence does not represent a valid sequence of code-point
+//     insertions.
+//   - The plaintext would contain more than 256 code points.
+//
+// DecodeRustPunycode is async-signal-safe with bounded runtime and a small
+// stack footprint, making it suitable for use in demangling Rust symbol names
+// from a signal handler.
+absl::Nullable<char*> DecodeRustPunycode(DecodeRustPunycodeOptions options);
+
+}  // namespace debugging_internal
+ABSL_NAMESPACE_END
+}  // namespace absl
+
+#endif  // ABSL_DEBUGGING_INTERNAL_DECODE_RUST_PUNYCODE_H_