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1d35d26b48
Re-implements the optional digit-separator and base-prefix parsing (originally PR #369) on top of the current store_spans hot-path architecture, with the goal of zero overhead when the features are not used. Key changes vs. the original PR: - has_separator is now a *compile-time* template parameter on parse_number_string, dispatched once (from_chars_advanced -> parse_number_string_options) based on options.digit_separator. The has_separator==false instantiation that every default caller uses is byte-for-byte the separator-free parser: no separator comparison ever enters a digit loop and the SIMD eight-digit fast path is preserved. The separator-aware code lives only in the cold true instantiation. - The store_spans no-span hot path (added to main after the original PR was branched) is preserved. - parse_options_t fields are ordered so the two new single-byte fields (digit_separator, format_options) fall into the existing padding for UC == char. sizeof(parse_options_t<char>) stays 16 bytes, so the struct is still register-passed and the call boundary is unchanged. Result: for the default (no separator, no prefix) path, the generated assembly of from_chars<double> is identical to main, and benchmarks show no measurable regression (the original PR was 5-10% slower). Adds basictest coverage for digit separators (including the >19-digit overflow re-scan paths) and prefix skipping. |
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