fix: base64DecodeBytes unsigned byte values + improve JMH benchmark config#705
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This was referenced Apr 6, 2026
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…onfig Fix std.base64DecodeBytes to correctly return unsigned byte values (0-255) instead of signed Java byte values (-128..127). Java's byte type is signed, so without masking with 0xff, bytes >= 128 (e.g., 0x80 = 128) would appear as negative numbers (e.g., -128), violating the Jsonnet specification. Also increase JMH RegressionBenchmark iterations from 1 to 3 for both warmup and measurement phases, providing more stable and reliable benchmark results with proper confidence intervals. Changes: - EncodingModule.scala: Apply `& 0xff` mask in base64DecodeBytes to convert signed Java bytes to unsigned integers, matching Jsonnet byte semantics - RegressionBenchmark.scala: Increase warmup/measurement iterations to 3 - Add regression test: base64DecodeBytes_unsigned.jsonnet with boundary values (0, 127, 128, 255) and encode/decode round-trip verification Upstream reference: jit branch commits b833428, af4832f
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Motivation
std.base64DecodeByteswas returning signed Java byte values (-128..127) instead of the Jsonnet-standard unsigned range (0..255). Bytes with the high bit set (≥128) were returned as negative numbers, violating the specification.Key Design Decision
Apply
& 0xffmask to convert signed Java bytes to unsigned integers, matching the Jsonnet specification and behavior of the C++, Go, and Rust implementations.Modification
sjsonnet/src/sjsonnet/stdlib/EncodingModule.scala(base64DecodeBytes):& 0xffmask:decoded(i) & 0xffconverts signed byte (-128..127) to unsigned int (0..255)Test:
new_test_suite/base64DecodeBytes_unsigned.jsonnet— verifies bytes ≥ 128 are returned as unsigned (e.g., 0xff → 255, not -1)Benchmark Results
This is a correctness fix, not a performance optimization. No benchmark impact expected.
Analysis
bytetype is signed (-128..127).Base64.getDecoder.decode()returnsbyte[]. Without masking, values ≥ 128 are negative.[0, 255]range.References
bytetype: signed, -128 to 127& 0xffmask: standard Java idiom for unsigned byte conversionResult
Fixes
std.base64DecodeBytesto return unsigned byte values (0-255) per the Jsonnet specification.