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db2f7c48cb
Dynamic loading of DLL functions is duplicated in several places in Git
for Windows' source code.
This patch adds a pair of macros to simplify the process: the
DECLARE_PROC_ADDR(<dll>, <return-type>, <function-name>,
...<function-parameter-types>...) macro to be used at the beginning of a
code block, and the INIT_PROC_ADDR(<function-name>) macro to call before
using the declared function. The return value of the INIT_PROC_ADDR()
call has to be checked; If it is NULL, the function was not found in the
specified DLL.
Example:
DECLARE_PROC_ADDR(kernel32.dll, BOOL, CreateHardLinkW,
LPCWSTR, LPCWSTR, LPSECURITY_ATTRIBUTES);
if (!INIT_PROC_ADDR(CreateHardLinkW))
return error("Could not find CreateHardLinkW() function";
if (!CreateHardLinkW(source, target, NULL))
return error("could not create hardlink from %S to %S",
source, target);
return 0;
Signed-off-by: Karsten Blees <blees@dcon.de>
Signed-off-by: Johannes Schindelin <johannes.schindelin@gmx.de>
Reviewed-by: Jonathan Nieder <jrnieder@gmail.com>
Signed-off-by: Johannes Schindelin <johannes.schindelin@gmx.de>
Signed-off-by: Junio C Hamano <gitster@pobox.com>
57 lines
1.6 KiB
C
57 lines
1.6 KiB
C
#ifndef LAZYLOAD_H
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#define LAZYLOAD_H
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/*
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* A pair of macros to simplify loading of DLL functions. Example:
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*
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* DECLARE_PROC_ADDR(kernel32.dll, BOOL, CreateHardLinkW,
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* LPCWSTR, LPCWSTR, LPSECURITY_ATTRIBUTES);
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*
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* if (!INIT_PROC_ADDR(CreateHardLinkW))
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* return error("Could not find CreateHardLinkW() function";
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*
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* if (!CreateHardLinkW(source, target, NULL))
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* return error("could not create hardlink from %S to %S",
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* source, target);
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*/
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struct proc_addr {
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const char *const dll;
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const char *const function;
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FARPROC pfunction;
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unsigned initialized : 1;
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};
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/* Declares a function to be loaded dynamically from a DLL. */
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#define DECLARE_PROC_ADDR(dll, rettype, function, ...) \
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static struct proc_addr proc_addr_##function = \
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{ #dll, #function, NULL, 0 }; \
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static rettype (WINAPI *function)(__VA_ARGS__)
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/*
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* Loads a function from a DLL (once-only).
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* Returns non-NULL function pointer on success.
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* Returns NULL + errno == ENOSYS on failure.
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* This function is not thread-safe.
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*/
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#define INIT_PROC_ADDR(function) \
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(function = get_proc_addr(&proc_addr_##function))
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static inline void *get_proc_addr(struct proc_addr *proc)
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{
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/* only do this once */
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if (!proc->initialized) {
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HANDLE hnd;
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proc->initialized = 1;
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hnd = LoadLibraryExA(proc->dll, NULL,
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LOAD_LIBRARY_SEARCH_SYSTEM32);
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if (hnd)
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proc->pfunction = GetProcAddress(hnd, proc->function);
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}
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/* set ENOSYS if DLL or function was not found */
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if (!proc->pfunction)
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errno = ENOSYS;
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return proc->pfunction;
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}
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#endif
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