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83e4cdf03a4d702b30e69204060de09e462e23c6 by Greg Falcon <gfalcon@google.com>:

Revert the crc addition to RefcountAndFlags, and restore related comments to their original state.

In development, the implementation of SetExpectedCrc() changed, and there is no longer a need to track the CRC status in the refcount.

Since the distinction between IsOne() and IsMutable() is subtle *and unused*, removing it now can help avoid subtle bugs in the future.  This distinction can always be added back later, if it proves necessary.

Keep the reserved bit for now; all it costs is one extra mask instruction in the refcount checks, and space for extra state in Cord is always hard to find.

PiperOrigin-RevId: 408647038

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ee67585cf66954176615271f50f8b278119dd138 by Greg Falcon <gfalcon@google.com>:

Implement Cord::SetExpectedChecksum() and Cord::ExpectedChecksum().

SetExpectedChecksum() will store a uint32_t out-of-band alongside a Cord's data.  This value persists through copies and assignments.  Mutating operations on a Cord cause the value to be forgotten.  ExpectedChecksum() retrieves the stored value, if present.

This API is intended for storing a CRC32C checksum alongside data, allowing checksums to be passed through dataflows and validated at the final step.  However, this API is agnostic to the meaning of the stored value.  No CRC32C validation is performed by these new APIs.

This implementation adds a new CordRep node, CordRepCrc.  A CordRepCrc may (currently) only live at the top of a tree.  This allows traversal logic to be agnostic to these nodes, instead putting the needed branches at the mutation level.    This also implements the property requested from API review, that any mutation is guaranteed to permanently forget the stored CRC.

PiperOrigin-RevId: 408611221

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a86f592402b37c854ebdc77d2b9b425451a7a675 by Martijn Vels <mvels@google.com>:

Move 'ExtractResult' into CordRep

The result of an extract operation is logically identical for any tree implementation, and having a single type makes 'tree independent' implementation in cord.cc more concise.

PiperOrigin-RevId: 408332408

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baa7647e21db59a87f75af9cac62172ce38a0f71 by Abseil Team <absl-team@google.com>:

Replace usages of `assert` macros with `ABSL_HARDENING_ASSERT`.

PiperOrigin-RevId: 408272133

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c7658133d8662c39fa5035fc93a364c7c3d327e0 by Martijn Vels <mvels@google.com>:

Add CordRepBtree::ExtractAppendBuffer

PiperOrigin-RevId: 407944179

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5775100363b5890ebfe710fadebf040445eab991 by Martijn Vels <mvels@google.com>:

Add CordRepConcat::ExtractAppendBuffer

PiperOrigin-RevId: 407932968

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9f520ba1600a93352c78f644a369c7c76195ee86 by Greg Falcon <gfalcon@google.com>:

Add cordz tracking for crc nodes.

This also adds a new kSetExpectedChecksum method to the list of tracked methods.  This is presently unused but will be used soon.

PiperOrigin-RevId: 407884120
GitOrigin-RevId: 83e4cdf03a4d702b30e69204060de09e462e23c6
Change-Id: I134ace2d87215813eaa60a282996a33884676c06