The unchanged txt2nls.cpp and c_1252.txt come from ReactOS revision dacf2a6c47fa562799f9c8a41ab6d5c558556558, at sdk/tools/txt2nls/main.cpp and media/nls/src/c_1252.txt. The source archive SHA-256 is 5373bbbb60541cb2a49e0acb53360e1218d4f5d56c31f9187b341b9fc16daa69. The tool retains its GPL-2.0-or-later notice and COPYING. ReactOS identifies Microsoft's Windows Supported Code Page Data Files as the text data's origin. The same table is published as Unicode's WindowsBestFit/bestfit1252.txt. Every byte matches after CRLF-to-LF conversion. data-provenance.json records the URLs and hashes; Unicode-3.0.txt preserves the applicable data license. Unicode's Terms of Use cover data files under https://www.unicode.org/Public/ unless a specific exception is indicated. This records the table's terms separately from the GPL converter's license.

The tool runs only during the build. Its generated NLS file must match e2634ee32da7977d762d2d45be2053309ee718572a7d8bb0034180dc1b0b6b76 before the qualified 65536-byte Unicode-to-CP1252 and 256-entry byte-to-Unicode tables are embedded. Raven's conversion uses that immutable data; no upstream loader or process state is adopted. The SBCS mapping passed every UTF-16 code unit against pinned Wine NT and Win32 conversion. Other legacy code pages, DBCS and UTF-8 ACP remain unsupported.

MultiByteToWideChar uses this byte table for the owned ACP profile and explicit CP1252. MB_COMPOSITE uses the selected Unicode canonical decompositions. Explicit UTF-8 conversion uses a separate selected ReactOS decoder; its native adapter and tests preserve the measured status/buffer behavior. This does not extend the process ACP configuration or the existing NT encode_ansi helper to UTF-8.