Support bits wider than 64 bits

[Copilot]

Emboss previously limited bits types to 64 bits, preventing representation of protocols like NovAtel's RANGECMP (192-bit bitfield) and GPS subframes (300-bit sequences).

Changes

Compiler (constraints.py)

• Remove 64-bit size limit for bits types
• Individual fields within bits remain limited to 64 bits via prelude type constraints

C++ Runtime (emboss_memory_util.h)

• Add LittleEndianWideBitBlock / BigEndianWideBitBlock for >64-bit bit blocks
• Add corresponding WideOffsetBitBlock classes for field access
• These read/write bytes individually rather than loading entire bitfield into a single integer
• Add data() to byte orderers for raw buffer access

Code Generator (header_generator.py)

• Use WideBitBlock variants when size > 64 bits

Example

bits WideBits:
  0   [+64]  UInt  first_64
  64  [+64]  UInt  second_64
  128 [+64]  UInt  third_64

struct ContainsWideBits:
  0 [+24]  WideBits  wide_field

auto view = MakeContainsWideBitsView(buffer, 24);
view.wide_field().first_64().Write(0x1122334455667788ULL);
view.wide_field().second_64().Write(0xAABBCCDDEEFF0011ULL);

Original prompt

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This section details on the original issue you should resolve

<issue_title>Support bits wider than 64 bits</issue_title>
<issue_description>This issue was copied from the upstream repository google/emboss.

Original issue: google#40
Original state: open, created at: 2022-04-19T19:37:41Z, updated at: 2024-12-18T23:14:42Z, by @reventlov

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Original description

NovAtel's RANGECMP (pp 842-844) record contains a 192-bit bitfield.

GPS subframes are defined as 300-bit sequences.

RTCM defines some wide bitfields which -- even more problematically -- contain 64-bit integers that are not aligned to byte boundaries.

Emboss should support bits of arbitrary size.

Note: the restriction that individual integers within those fields are no more than 64 bits is a separate feature that should be evaluated and implemented on its own.

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Discussion (copied comments)

Comment by @AaronWebster on 2022-05-14T00:58:18Z:

GMP might be worth looking into, using mpz_import and mpz_import to escrow data.

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</issue_description>

Comments on the Issue (you are @copilot in this section)

• Fixes Support bits wider than 64 bits #83

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