zstream: consolidate shared code

[GarthSnyder]

zstream currently contains three identical copies of dump_record(), which ultimately appear to all have been drawn from libzfs_sendrecv.c. The original is marked internal and so can't be referenced directly, although exposing that API might be a good idea. (At least in theory...)

This PR adds zstream_util.[hc] and puts the shared code there along with a couple of other items in common.

No functional changes.

Notes

I used the libzfs version of dump_record() as the shared code. It is identical to the zstream versions except that the payload length is a size_t rather than an int and it uses the uppercase assertion macros.

How Has This Been Tested?

Compiles and runs with no errors.

Types of changes

• Bug fix (non-breaking change which fixes an issue)
• New feature (non-breaking change which adds functionality)
• Performance enhancement (non-breaking change which improves efficiency)
• Code cleanup (non-breaking change which makes code smaller or more readable)
• Quality assurance (non-breaking change which makes the code more robust against bugs)
• Breaking change (fix or feature that would cause existing functionality to change)
• Library ABI change (libzfs, libzfs_core, libnvpair, libuutil and libzfsbootenv)
• Documentation (a change to man pages or other documentation)

Checklist:

• My code follows the OpenZFS code style requirements.
• I have updated the documentation accordingly.
• I have read the contributing document.
• I have added tests to cover my changes.
• I have run the ZFS Test Suite with this change applied.
• All commit messages are properly formatted and contain Signed-off-by.

[Copilot]

Pull request overview

This PR refactors cmd/zstream to remove duplicated helper implementations by introducing a shared zstream_util.[ch] module, intended to centralize common helpers (notably dump_record() plus “safe_” helpers) used across multiple zstream subcommands.

Changes:

• Add new zstream_util.c/.h containing shared helpers (e.g., dump_record(), safe_malloc(), safe_calloc(), sfread()).
• Replace per-file copies of these helpers in zstream_{redup,recompress,decompress,dump}.c with calls to the shared module.
• Update build inputs (Makefile.am) and exported declarations (zstream.h) accordingly.

Reviewed changes

Copilot reviewed 8 out of 8 changed files in this pull request and generated 6 comments.

Show a summary per file

File	Description
cmd/zstream/zstream_util.h	New shared header for zstream utility helpers.
cmd/zstream/zstream_util.c	New shared implementation of dump_record() and “safe_” IO/allocation helpers.
cmd/zstream/zstream_redup.c	Removes local helper copies; uses zstream_util.h.
cmd/zstream/zstream_recompress.c	Removes local dump_record(); uses shared implementation.
cmd/zstream/zstream_decompress.c	Removes local dump_record(); uses shared implementation.
cmd/zstream/zstream_dump.c	Removes local safe_malloc(); uses shared implementation.
cmd/zstream/zstream.h	Stops exporting utility helper prototypes from the main zstream header.
cmd/zstream/Makefile.am	Builds/ships the new shared utility module.

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[Copilot]

Pull request overview

Copilot reviewed 8 out of 8 changed files in this pull request and generated 3 comments.

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[behlendorf]

Good find, and thanks for the cleanup. I'd prefer not to add another symbol to the libzfs ABI for now, even if zstream already links against libzfs, so your approach here makes good sense to me.