optimization: use mcopy in String() and Bytes()

[snissn]

Optimize String and Bytes Handling with MCOPY

Summary:
This PR introduces an optimization for the String() and Bytes operations by leveraging the MCOPY opcode, resulting in reduced gas costs.

Details:
I've been working on MCOPY support for the Filecoin EVM as part of the FIL-Builders team. I noticed that the current implementation of String() and Bytes in this repo can benefit from MCOPY to achieve better gas efficiency.

Gas Comparison:
This optimization was validated by running the Forge test suite. Below is a summary of the key results:

With Optimization (This PR):

Ran 8 tests for test/comparison/CborDecode_ReadCbor.t.sol:ComparisonTest
[PASS] test_decodeArrayU8_ReadCbor()             (gas: 2334)
[PASS] test_decodeFalse_ReadCbor()               (gas: 437)
[PASS] test_decodeFixedArray_ReadCbor()          (gas: 4402)
[PASS] test_decodeInteger_ReadCbor()             (gas: 554)
[PASS] test_decodeNull_ReadCbor()                (gas: 240)
[PASS] test_decodeStringWithWeirdChar_ReadCbor() (gas: 1052)
[PASS] test_decodeString_ReadCbor()              (gas: 1125)
[PASS] test_decodeTrue_ReadCbor()                (gas: 495)

Current main Branch:

Ran 8 tests for test/comparison/CborDecode_ReadCbor.t.sol:ComparisonTest
[PASS] test_decodeArrayU8_ReadCbor()             (gas: 2334)
[PASS] test_decodeFalse_ReadCbor()               (gas: 437)
[PASS] test_decodeFixedArray_ReadCbor()          (gas: 4472)
[PASS] test_decodeInteger_ReadCbor()             (gas: 554)
[PASS] test_decodeNull_ReadCbor()                (gas: 240)
[PASS] test_decodeStringWithWeirdChar_ReadCbor() (gas: 1122)
[PASS] test_decodeString_ReadCbor()              (gas: 1195)
[PASS] test_decodeTrue_ReadCbor()                (gas: 495)

Improvements

• Reduced Gas Costs:
  • test_decodeFixedArray_ReadCbor(): 4472 → 4402
  • test_decodeStringWithWeirdChar_ReadCbor(): 1122 → 1052
  • test_decodeString_ReadCbor(): 1195 → 1125

Notes

This PR improves efficiency without changing the core logic or functionality.

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Let me know if there's anything you'd like to add or modify!

[turbocrime]

thanks for the pr!

i wasn't aware of mcopy, it's definitely preferable to the loop.

[snissn]

@turbocrime Thanks for merging the PR! I’m glad this was helpful — I appreciate the opportunity to contribute!