curl_multibyte: support Windows paths longer than MAX_PATH #13522
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- Add a helper function for the Windows file wrapper functions that will normalize a long path (or a filename in a long path) and add the prefix `\\?\` so that Windows will access the file. Prior to this change if a filename (when normalized internally by Windows to its full path) or a path was longer than MAX_PATH (260) then Windows would not open the path, unless it was already normalized by the user and had the `\\?\` prefix prepended. The `\\?\` prefix could not be passed to file:// so for example something like file://c:/foo/bar/filename255chars could not be opened prior to this change. There's some code in tool_doswin that will need to be modified as well to further remove MAX_PATH (aka PATH_MAX) limitation. Ref: curl#8361 Ref: curl#13512 Ref: https://learn.microsoft.com/en-us/dotnet/standard/io/file-path-formats Ref: https://learn.microsoft.com/en-us/windows/win32/fileio/maximum-file-path-limitation Closes #xxxx
bagder
reviewed
May 3, 2024
nmoinvaz
reviewed
May 3, 2024
nmoinvaz
reviewed
May 3, 2024
- explain 32767 constant is "approximate" maximum path len, so says MS. - explain GetFullPathNameW returns a normalized full path and what it means to normalize. - fix `\\?\` logic to restrict the times when it is prepended, since it may already be prepended. - skip excessively long path input if it's already prefixed with `\\?\` (likely by the user)
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\\?\so that Windows will access the file.Prior to this change if a filename (when normalized internally by Windows to its full path) or a path was longer than MAX_PATH (260) then Windows would not open the path, unless it was already normalized by the user and had the
\\?\prefix prepended.The
\\?\prefix could not be passed to file:// so for example something like file://c:/foo/bar/filename255chars could not be opened prior to this change.There's some code in tool_doswin that will need to be modified as well to further remove MAX_PATH (aka PATH_MAX) limitation.
Ref: #8361
Ref: #13512
Ref: https://learn.microsoft.com/en-us/dotnet/standard/io/file-path-formats
Ref: https://learn.microsoft.com/en-us/windows/win32/fileio/maximum-file-path-limitation
Closes #xxxx