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6 messages in net.java.dev.jna.usersRe: [jna-users] Structure mapping que...| From | Sent On | Attachments |
|---|---|---|
| Steve Newell | Jul 30, 2008 11:05 am | |
| Michael Brewer-Davis | Jul 30, 2008 11:42 am | |
| Timothy Wall | Jul 30, 2008 11:48 am | |
| Steve Newell | Jul 30, 2008 12:34 pm | |
| Timothy Wall | Jul 30, 2008 2:48 pm | |
| Steve Newell | Jul 31, 2008 12:33 pm |
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| Subject: | Re: [jna-users] Structure mapping question | Actions... |
|---|---|---|
| From: | Timothy Wall (twal...@dev.java.net) | |
| Date: | Jul 30, 2008 11:48:04 am | |
| List: | net.java.dev.jna.users | |
On Jul 30, 2008, at 2:06 PM, Steve Newell wrote:
I have the following C structs:
typedef struct ByteSignature { int offset; int length; PBYTE signature; } ByteSignature;
typedef struct FileSignature { char* mimeType; // NULL terminated string int numSignatures; // number of ByteSignatures in the signatures array ByteSignature* signatures; // array of ByteSignatures. There must be at least 1, to be valid. } FileSignature, * PFileSignature, ** PPFileSignature;
FileSignature is allocated and filled by my Java code, and passed to the dll.
I have mapped these two structures as follows:
public class ByteSignature extends Structure { public int offset; public int length; public byte[] signature;
The signature field needs to be a Pointer. Primitive arrays are inlined, which is not what you want.
public ByteSignature() { super(); } public ByteSignature( Pointer p ) { super(); useMemory( p ); read(); } public ByteSignature( int offset, byte... byteValues ) { super(); this.offset = offset; this.length = byteValues.length; signature = new byte[ byteValues.length ];
for( int i = 0; i < byteValues.length; i++ ) { signature[ i ] = byteValues[ i ]; } } }
You probably want to allocate the memory yourself here for "signature", and use Pointer methods to set its contents.
public class FileSignature extends Structure { public String mimeType; public int numSignatures; public ByteSignature[] signatures;
This needs to be a pointer, since nested structures are inlined. You can also make the field implement Structure.ByReference to force the field to be treated as a pointer rather than by value.
e.g.
class ByteSignature extends Structure { class ByReference extends ByteSignature implements Structure.ByReference { } }
ByteSignature[] bsa = new ByteSignature.ByReference().toArray(size); s.signatures = bsa[0];
public FileSignature() { super(); } public FileSignature( Pointer p ) { super(); useMemory( p ); read(); } }
The function I am attempting to call looks like this:
public int FindMatchingDeletedFiles( WString szDirectory, FileSignature[] fileSignatures, int numFileSignatures, PointerByReference fileHandles );
and this is how I am calling it:
public static void main( String[] args ) { Native.setProtected( true );
Undelete undelete = Undelete.INSTANCE;
PointerByReference fileHandles = new PointerByReference();
FileSignature[] signatures = createFileSignatures();
int numFiles = undelete.FindMatchingDeletedFiles( new WString( "C:\ \" ), signatures, signatures.length, fileHandles );
for( int i = 0; i < numFiles; i++ ) { ... } }
However, when I run this, I get the following error:
Exception in thread "main" java.lang.IllegalStateException: Array fields must be initialized
This error should go away once you eliminate primitive array fields as described above.