在给定名称的情况下，C++中最简单的方法来获取导出的dll函数的序数是什么？
(正在寻找一种不会干扰自己解析IAT的方法...)
最佳答案
我想不出任何非常简单的方法来完成您想要的事情。您至少可以看到几个选择:
我看到的第一个选项的主要问题是，您不知道要尝试多少个序数(序数中可能有空格，因此依靠
GetProcAddress返回NULL表示结束将不起作用)。它也有些效率低下，因为它需要反复进行许多Win32调用，并且基本上相当于对导出地址表进行线性搜索。确实，非常优雅。或者，您可以搜索NPT并将结果索引用于EOT以获取序数。这是一种更优雅的方法，因为它以最直接的方式到达序数(实际上，动态链接程序使用该方法将导出名称解析为其地址)。另外，由于NPT是按词法排序的，因此可以进行二进制搜索，这显然比其他方法的线性搜索更可取。实际上，使用此方法实现的对
GetProcOrdinal的单次调用应比仅对GetProcAddress的单次调用快一点。也许更重要的是，此方法不依赖于任何未知数(即，序数)。这种方法的缺点是它不像其他方法那么简单。您可以使用Debug Help Library来帮助避免对PE文件镜像进行某些解析(这是我最初所做的)，但是事实证明，解析PE镜像的所需部分并不那么困难。我认为避免依赖于Debug Help Library值得在解析PE镜像头时花费最少的额外精力。
谈谈业务，这是C语言中的示例实现:
#include <stdio.h>
#include "windows.h"
/// Efficiently searches a module's name pointer table (NPT) for the named
/// procedure.
///
/// @param[in] npt Address of the NPT to search.
///
/// @param[in] size Number of entries in the NPT.
///
/// @param[in] base Base address of the module containing the NPT. This is
/// used to resolve addresses in the NPT (which are relative
/// to the module's base address).
///
/// @param[in] proc String containing the name of the procedure to search
/// for.
///
/// @return Returns the index into the NPT of the entry matching the named
/// procedure. If no such matching entry exists, the function returns
/// -1.
///
DWORD FindNptProc (PDWORD npt, DWORD size, PBYTE base, LPCSTR proc)
{
INT cmp;
DWORD max;
DWORD mid;
DWORD min;
min = 0;
max = size - 1;
while (min <= max) {
mid = (min + max) >> 1;
cmp = strcmp((LPCSTR)(npt[mid] + base), proc);
if (cmp < 0) {
min = mid + 1;
} else if (cmp > 0) {
max = mid - 1;
} else {
return mid;
}
}
return -1;
}
/// Gets a pointer to a module's export directory table (EDT).
///
/// @param[in] module Handle to the module (as returned by GetModuleHandle).
///
/// @return Returns a pointer to the module's EDT. If there is an error (e.g.
/// if the module handle is invalid or the module has no EDT) the
/// function will return NULL.
///
PIMAGE_EXPORT_DIRECTORY GetExportDirectoryTable (HMODULE module)
{
PBYTE base; // base address of module
PIMAGE_FILE_HEADER cfh; // COFF file header
PIMAGE_EXPORT_DIRECTORY edt; // export directory table (EDT)
DWORD rva; // relative virtual address of EDT
PIMAGE_DOS_HEADER mds; // MS-DOS stub
PIMAGE_OPTIONAL_HEADER oh; // so-called "optional" header
PDWORD sig; // PE signature
// Start at the base of the module. The MS-DOS stub begins there.
base = (PBYTE)module;
mds = (PIMAGE_DOS_HEADER)module;
// Get the PE signature and verify it.
sig = (DWORD *)(base + mds->e_lfanew);
if (IMAGE_NT_SIGNATURE != *sig) {
// Bad signature -- invalid image or module handle
return NULL;
}
// Get the COFF file header.
cfh = (PIMAGE_FILE_HEADER)(sig + 1);
// Get the "optional" header (it's not actually optional for executables).
oh = (PIMAGE_OPTIONAL_HEADER)(cfh + 1);
// Finally, get the export directory table.
if (IMAGE_DIRECTORY_ENTRY_EXPORT >= oh->NumberOfRvaAndSizes) {
// This image doesn't have an export directory table.
return NULL;
}
rva = oh->DataDirectory[IMAGE_DIRECTORY_ENTRY_EXPORT].VirtualAddress;
edt = (PIMAGE_EXPORT_DIRECTORY)(base + rva);
return edt;
}
/// Gets the ordinal of an exported procedure.
///
/// @param[in] module Handle (as returned by GetModuleHandle) of the module
/// that exports the procedure.
///
/// @param[in] proc String containing the name of the procedure.
///
/// @return Returns the procedure's ordinal. If an ordinal for the procedure
/// could not be located (e.g. if the named procedure is not exported
/// by the specified module) then the function will return -1.
///
DWORD GetProcOrdinal (HMODULE module, LPCSTR proc)
{
PBYTE base; // module base address
PIMAGE_EXPORT_DIRECTORY edt; // export directory table (EDT)
PWORD eot; // export ordinal table (EOT)
DWORD i; // index into NPT and/or EOT
PDWORD npt; // name pointer table (NPT)
base = (PBYTE)module;
// Get the export directory table, from which we can find the name pointer
// table and export ordinal table.
edt = GetExportDirectoryTable(module);
// Get the name pointer table and search it for the named procedure.
npt = (DWORD *)(base + edt->AddressOfNames);
i = FindNptProc(npt, edt->NumberOfNames, base, proc);
if (-1 == i) {
// The procedure was not found in the module's name pointer table.
return -1;
}
// Get the export ordinal table.
eot = (WORD *)(base + edt->AddressOfNameOrdinals);
// Actual ordinal is ordinal from EOT plus "ordinal base" from EDT.
return eot[i] + edt->Base;
}
int main (int argc, char *argv [])
{
LPCSTR procName;
HMODULE module = NULL;
LPCSTR moduleName;
DWORD ordinal;
if (argc != 3) {
printf("A DLL name and procedure name must be specified\n");
return EXIT_FAILURE;
}
moduleName = argv[1];
procName = argv[2];
if (NULL == LoadLibrary(moduleName)) {
printf("Could not load library %s\n", moduleName);
return EXIT_FAILURE;
}
module = GetModuleHandle(moduleName);
if (NULL == module) {
printf("Couldn't get a handle to %s\n", moduleName);
return EXIT_FAILURE;
}
ordinal = GetProcOrdinal(module, procName);
if (-1 == ordinal) {
printf("Could not find ordinal for %s in %s\n", procName, moduleName);
} else {
printf("Found %s at ordinal %d\n", procName, ordinal);
}
return EXIT_SUCCESS;
}
GetProcOrdinal是有趣的地方。希望该代码是不言自明的；但是，要完全理解它可能需要一些有关PE文件格式的知识，而我不打算在这里进行介绍(网络上有很多关于它的信息)。 FindNptProc只是一个便捷功能，它可以对NPT进行二进制搜索。 GetExportDirectoryTable是另一个便利功能，用于解析PE header 以定位导出目录表。上面的代码为我在Visual Studio 2008和Windows XP(SP3)下干净地编译，但是为YMMV。我并不是Windows专家，所以这可能不是最干净的代码可移植性(就Windows的不同版本而言)。与往常一样，此代码按“原样”提供，不提供任何形式的保证;)
*是的，如果您想知道的话，在编写所有Microsoft风格的Windows代码后，我仍然感到有些肮脏。
关于c++ - 以编程方式从函数名称获取序数，我们在Stack Overflow上找到一个类似的问题：https://stackoverflow.com/questions/2273603/