idn: clarify null-termination on Windows #19980
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https://learn.microsoft.com/windows/win32/api/stringapiset/nf-stringapiset-multibytetowidechar https://learn.microsoft.com/windows/win32/api/stringapiset/nf-stringapiset-widechartomultibyte https://learn.microsoft.com/windows/win32/api/winnls/nf-winnls-idntoascii https://learn.microsoft.com/windows/win32/api/winnls/nf-winnls-idntounicode WINE source code: https://gitlab.winehq.org/wine/wine/-/blob/wine-10.20/dlls/kernelbase/locale.c https://gitlab.winehq.org/wine/wine/-/blob/wine-10.20/dlls/ntdll/locale.c https://gitlab.winehq.org/wine/wine/-/blob/wine-10.20/dlls/ntdll/locale_private.h Ref: curl#19976 (comment) Follow-up to 6694a42 curl#19798
bagder
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Add comments to clarify that a terminating null is always present in
the buffers returned to the caller.
The curl APIs
win32_idn_to_ascii()orwin32_ascii_to_idn()receivea null-terminated UTF-8 string as input. They first convert it to wide
chars by first asking
MultiByteToWideChar()to calculate the length,by passing -1. This API returns the length with the null char included
(=
strlen() + 1), does the conversion, with the output alsonull-terminated.
IdnTo*()preserve this null character as documented.Then we pass this null-terminated, fixed-length buffer ito
WideCharToMultiByte(), which keeps preserving the null, ending up inthe buffer returned to the caller.
Refs:
https://learn.microsoft.com/windows/win32/api/stringapiset/nf-stringapiset-multibytetowidechar
https://learn.microsoft.com/windows/win32/api/stringapiset/nf-stringapiset-widechartomultibyte
https://learn.microsoft.com/windows/win32/api/winnls/nf-winnls-idntoascii
https://learn.microsoft.com/windows/win32/api/winnls/nf-winnls-idntounicode
WINE source code:
https://gitlab.winehq.org/wine/wine/-/blob/wine-10.20/dlls/kernelbase/locale.c
https://gitlab.winehq.org/wine/wine/-/blob/wine-10.20/dlls/ntdll/locale.c
https://gitlab.winehq.org/wine/wine/-/blob/wine-10.20/dlls/ntdll/locale_private.h
Ref: #19976 (comment)
Follow-up to 6694a42 #19798