将字符串转换为JNA的指针

我正在尝试使用JNA来查询Windows中文件的有效权限。 最后，我计划使用GetEffectiveRightsFromAcl函数 ，但为此，我需要提供一个指向填充的TRUSTEE结构的指针。 JNA平台（platform.jar）似乎没有定义这个结构，所以我试图自己定义它。 这是我到目前为止所拥有的：

public static class TRUSTEE extends Structure { public TRUSTEE() { super(); } public TRUSTEE(Pointer p) { super(p); read(); } public Pointer pMultipleTrustee; public int MultipleTrusteeOperation; public int TrusteeForm; public int TrusteeType; public Pointer ptstrName; } 

我正在尝试填充这样的结构：

 private TRUSTEE createTrusteeForCurrentUser() { TRUSTEE result = new TRUSTEE(); result.TrusteeForm = TRUSTEE_FORM.TRUSTEE_IS_NAME; result.TrusteeType = TRUSTEE_TYPE.TRUSTEE_IS_USER; String strName = "CURRENT_USER"; // How can I set result.ptstrName using strName? } 

此Google Groups主题建议在调用char *时在结构中使用String字段。 但是，我不认为这在我的情况下是合适的，考虑到ptstrName字段可以指向不同类型的事物，具体取决于TrusteeForm的值。 所以，我想我不知何故需要从String转换为Pointer 。 我在JNA中找到了NativeString类，它可以工作，除了它是一个包私有类。

将Java String转换为本机格式并获取Pointer它的Pointer的推荐方法是什么？ 我甚至为TRUSTEE结构使用正确的数据类型？ 我对JNA有些新意，所以如果我错过了一些明显的东西，请原谅。

更新

我找到了解决问题的方法，但如果有人有更好的解决方案，我仍然希望听到它。

Answer 1

假设您希望在本机端使用char * （如果字符串包含非ascii字符，则可能需要更多内存分配），

 String myString = "CURRENT_USER"; Pointer m = new Memory(myString.length() + 1); // WARNING: assumes ascii-only string m.setString(0, myString); 

然后，您可以在需要的地方使用m来引用“本机”字符串。

对于宽字符串（ wchar_t * ），

 String myString = "CURRENT_USER"; Pointer m = new Memory(Native.WCHAR_SIZE * (myString.length() + 1)); m.setWideString(0, myString); 

Answer 2

我通过复制package-private NativeString类的源代码并在我的项目中创建公共副本来解决了这个问题。 由于在构造函数中使用了package-private方法，我不得不进行一次小的更改。

更新：正如@fragorl在评论中指出的那样，下面显示的NativeString的实现到现在已经过时了。

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用法：

 private static TRUSTEE createTrusteeForCurrentUser() { TRUSTEE result = new TRUSTEE(); result.TrusteeForm = TRUSTEE_FORM.TRUSTEE_IS_NAME; result.TrusteeType = TRUSTEE_TYPE.TRUSTEE_IS_USER; result.ptstrName = new NativeString("CURRENT_USER",true).getPointer(); result.write(); return result; } 

NativeString.java：

 /** Provides a temporary allocation of an immutable C string * (const char* or const wchar_t*) for use when * converting a Java String into a native memory function argument. * * @author Todd Fast, [e-mail] * @author [e-mail] */ public class NativeString implements CharSequence, Comparable { private Pointer pointer; private boolean wide; /** Create a native string (NUL-terminated array of char).
 * If the system property jna.encoding is set, its value will * be used to encode the native string. If not set or if the encoding * is unavailable, the default platform encoding will be used. */ public NativeString(String string) { this(string, false); } /** Create a native string as a NUL-terminated array of wchar_t * (if wide is true) or char.
 * If the system property jna.encoding is set, its value will * be used to encode the native charstring. * If not set or if the encoding is unavailable, the default platform * encoding will be used. * * @param string value to write to native memory * @param wide whether to store the String as wchar_t */ public NativeString(String string, boolean wide) { if (string == null) { throw new NullPointerException("String must not be null"); } // Allocate the memory to hold the string. Note, we have to // make this 1 element longer in order to accommodate the terminating // NUL (which is generated in Pointer.setString()). this.wide = wide; if (wide) { int len = (string.length() + 1 ) * Native.WCHAR_SIZE; pointer = new Memory(len); pointer.setString(0, string, true); } else { byte[] data = Native.toByteArray(string); pointer = new Memory(data.length + 1); pointer.write(0, data, 0, data.length); pointer.setByte(data.length, (byte)0); } } public int hashCode() { return toString().hashCode(); } public boolean equals(Object other) { if (other instanceof CharSequence) { return compareTo(other) == 0; } return false; } public String toString() { String s = wide ? "const wchar_t*" : "const char*"; s += "(" + pointer.getString(0, wide) + ")"; return s; } public Pointer getPointer() { return pointer; } public char charAt(int index) { return toString().charAt(index); } public int length() { return toString().length(); } public CharSequence subSequence(int start, int end) { return CharBuffer.wrap(toString()).subSequence(start, end); } public int compareTo(Object other) { if (other == null) return 1; return toString().compareTo(other.toString()); } } 

Answer 3

尝试在http://jna.java.net/javadoc/com/sun/jna/Pointer.html中使用Pointer类。