[vedchaudhari]

On buffers bigger than 2 GiB, indexOf(), lastIndexOf() and includes() change any byteOffset above 2 ** 31 - 1 to 2 ** 31 - 1, so the search starts in the wrong place:

const G = 2 ** 30;
const buf = Buffer.alloc(3 * G);
buf[2.25 * G] = 0x0a;
buf[2.75 * G] = 0x0a;

buf.indexOf(0x0a, 2.5 * G);     // main: 2415919104 (before the offset), this PR: 2952790016
buf.includes(0x0a, 2.9 * G);    // main: true, this PR: false
buf.lastIndexOf(0x0a, 2.6 * G); // main: -1, this PR: 2415919104

The int32 limit was added in 2016 (6c1e5ad), when buffers couldn't be bigger than 2 GiB. MAX_LENGTH has grown a lot since v14, but the limit was never updated. The C++ side already uses 64-bit offsets, so I raised the limit to Number.MAX_SAFE_INTEGER, which still keeps values like Infinity out. The negative return values from the issue were already fixed by #66325.

The new cases in test/pummel/test-buffer-indexof-large.js fail on main and pass with this change. Results on normal-size buffers are unchanged.

Tested on macOS arm64.

Note: #66590 edits the same comment, so whichever lands second will need a small rebase.

Fixes: #67008

Assisted-by: Claude. I reproduced the bug, reviewed the change and ran the tests myself.

[codecov]

Codecov Report

✅ All modified and coverable lines are covered by tests.
✅ Project coverage is 90.66%. Comparing base (3983092) to head (4fb3d72).

Additional details and impacted files

@@            Coverage Diff             @@
##             main   #67009      +/-   ##
==========================================
- Coverage   92.96%   90.66%   -2.30%     
==========================================
  Files         428      797     +369     
  Lines      195232   278262   +83030     
  Branches    30184    53512   +23328     
==========================================
+ Hits       181492   252286   +70794     
- Misses      13413    16340    +2927     
- Partials      327     9636    +9309     

Files with missing lines	Coverage Δ
lib/buffer.js	99.74% <100.00%> (+2.90%)	⬆️

... and 500 files with indirect coverage changes

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