如何使用PathCreateFromUrlA API

Question

我需要将像文件：/// C：/ test folder / file.text这样的uri路径转换为windows样式路径C：/ test folder / file.text。为此，我试图使用以下代码使用PathCreatesFromUrlA API，但我只是不明白如何设置API的最后两个参数（在下面的代码中标记为???）。

std::string uri("file:///C:/test folder/file.text");  
char buf[255];  
auto result = ::PathCreateFromUrlA(uri.c_str(), buf, ???, ???); 

PathCreateFromUrlA声明如下。

LWSTDAPI PathCreateFromUrlA(_In_ PCSTR pszUrl, _Out_writes_to_(*pcchPath, *pcchPath) PSTR pszPath, _Inout_ DWORD *pcchPath, DWORD dwFlags);

根据这个，第三个参数是指向DWORD的指针，我不明白目的是什么以及如何使用它。对于某些标志，第四个参数是DWORD。 shlwapi.h声明以下标志

#define URL_UNESCAPE                    0x10000000
#define URL_ESCAPE_UNSAFE               0x20000000
#define URL_PLUGGABLE_PROTOCOL          0x40000000
#define URL_WININET_COMPATIBILITY       0x80000000
#define URL_DONT_ESCAPE_EXTRA_INFO      0x02000000
#define URL_DONT_UNESCAPE_EXTRA_INFO    URL_DONT_ESCAPE_EXTRA_INFO
#define URL_BROWSER_MODE                URL_DONT_ESCAPE_EXTRA_INFO
#define URL_ESCAPE_SPACES_ONLY          0x04000000
#define URL_DONT_SIMPLIFY               0x08000000
#define URL_NO_META                     URL_DONT_SIMPLIFY
#define URL_UNESCAPE_INPLACE            0x00100000
#define URL_CONVERT_IF_DOSPATH          0x00200000
#define URL_UNESCAPE_HIGH_ANSI_ONLY     0x00400000
#define URL_INTERNAL_PATH               0x00800000  // Will escape #'s in paths
#define URL_FILE_USE_PATHURL            0x00010000
#if (_WIN32_IE >= _WIN32_IE_IE60SP2)
#define URL_DONT_UNESCAPE               0x00020000  // Do not unescape the path/url at all
#endif // _WIN32_IE_IE60SP2
#if (NTDDI_VERSION >= NTDDI_WIN7)
#define URL_ESCAPE_AS_UTF8              0x00040000  // Percent-encode all non-ASCII characters as their UTF-8 equivalents.
#endif // (NTDDI_VERSION >= NTDDI_WIN7)
#if (NTDDI_VERSION >= NTDDI_WIN8)
#define URL_UNESCAPE_AS_UTF8            URL_ESCAPE_AS_UTF8
#define URL_ESCAPE_ASCII_URI_COMPONENT  0x00080000  // Percent-encode all ASCII characters outside of the unreserved set from URI RFC 3986 (a-zA-Z0-9-.~_) (i.e.) No need for URL_ESCAPE_PERCENT along with this.
#define URL_ESCAPE_URI_COMPONENT        (URL_ESCAPE_ASCII_URI_COMPONENT | URL_ESCAPE_AS_UTF8)
#define URL_UNESCAPE_URI_COMPONENT      URL_UNESCAPE_AS_UTF8
#endif // (NTDDI_VERSION >= NTDDI_WIN8)
#define URL_ESCAPE_PERCENT              0x00001000
#define URL_ESCAPE_SEGMENT_ONLY         0x00002000  // Treat the entire URL param as one URL segment.

#define URL_PARTFLAG_KEEPSCHEME         0x00000001

#define URL_APPLY_DEFAULT               0x00000001
#define URL_APPLY_GUESSSCHEME           0x00000002
#define URL_APPLY_GUESSFILE             0x00000004
#define URL_APPLY_FORCEAPPLY            0x00000008

我不知道哪个标志对我的用例是正确的。有什么建议？

Answer 1

第三个参数表示缓冲区的大小（很可能包含函数返回后写入或需要的字符数）。 MSDN说第四个参数是保留的，必须为0。

std::string uri("file:///C:/test folder/file.text");  
char buf[MAX_PATH];  
DWORD cch = ARRAYSIZE(buf);
HRESULT hr = ::PathCreateFromUrlA(uri.c_str(), buf, &cch, 0);
if (SUCCEEDED(hr)) ...