[PJK]

Summary

• Adds cbor_structurally_equal(const cbor_item_t*, const cbor_item_t*) to common.h/common.c
• 36 test cases in test/structurally_equal_test.c covering all eight CBOR major types
• RST documentation in doc/source/api/item_types.rst

Design rationale

PR #96 proposed a cbor_equal function but left the semantics underspecified. RFC 8949 defines two distinct notions of equality:

• Data-model equality (RFC 8949 §2.1, §5.6.1): encoding width is invisible; maps are unordered sets of key-value pairs; uint8(1) and uint64(1) are the same integer.
• Structural equality: every byte of the encoding counts; uint8(1) ≠ uint16(1).

This PR implements structural equality under the name cbor_structurally_equal, which makes the semantics explicit and avoids surprising callers who might expect data-model behaviour from a function named cbor_equal. The function is extensively documented to explain what it does and does not compare, and to point callers toward the value accessors (cbor_get_uint64 etc.) for data-model comparisons.

Notable structural rules that differ from data-model equality:

Case	cbor_structurally_equal
uint8(1) vs uint16(1)	false — encoding width differs
float2(1.5) vs float4(1.5)	false — float width differs
Definite array vs indefinite array (same elements)	false
Indefinite bytestring, same bytes, different chunk split	false
Maps with same pairs in different order	false — positional comparison
Two NaN with different bit patterns	false — bitwise float comparison

NULL inputs are programming errors; assertions fire in debug builds (consistent with the rest of the libcbor API).

Test plan

• ctest -R structurally_equal_test passes (36/36)
• bash clang-format.sh produces no diff
• CI green

🤖 Generated with Claude Code

[codecov]

Codecov Report

❌ Patch coverage is 88.23529% with 8 lines in your changes missing coverage. Please review.
✅ Project coverage is 99.42%. Comparing base (dfe2297) to head (8aaabe6).
⚠️ Report is 16 commits behind head on master.

Files with missing lines	Patch %	Lines
src/cbor/common.c	88.23%	8 Missing ⚠️

Additional details and impacted files

@@             Coverage Diff             @@
##            master     #408      +/-   ##
===========================================
- Coverage   100.00%   99.42%   -0.58%     
===========================================
  Files           20       20              
  Lines         1663     1731      +68     
===========================================
+ Hits          1663     1721      +58     
- Misses           0       10      +10     

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