JNA and ZBar(library for bar code reader)

I'm creating Java Interface with JNA for ZBar(library for bar code reader).

In JNA, structures in C are needed to declare. For example::

// In C
typedef struct {
    char* id;
    char* name;开发者_JAVA技巧
    int age;
    char* sectionId
} EMPLOYEE;

to

// In Java with JNA
public static class Employee extends Structure {  // com.sun.jna.Structure
    String id;
    String name;
    int age;
    String sectionId;
}

But in ZBar, structures have no members. For example::

// zbar-0.10/include/zbar.h
// line:1009-1011
struct zbar_image_scanner_s;
/** opaque image scanner object. */
typedef struct zbar_image_scanner_s zbar_image_scanner_t;

That doesn't declare size or members of the structures.

How can I write interfaces for these structures in JNA?

---

the struct zbar_image_scanner_s is declared in img_scanner.c as:

/* image scanner state */
struct zbar_image_scanner_s {
    zbar_scanner_t *scn;        /* associated linear intensity scanner */
    zbar_decoder_t *dcode;      /* associated symbol decoder */
#ifdef ENABLE_QRCODE
    qr_reader *qr;              /* QR Code 2D reader */
#endif

    const void *userdata;       /* application data */
    /* user result callback */
    zbar_image_data_handler_t *handler;

    unsigned long time;         /* scan start time */
    zbar_image_t *img;          /* currently scanning image *root* */
    int dx, dy, du, umin, v;    /* current scan direction */
    zbar_symbol_set_t *syms;    /* previous decode results */
    /* recycled symbols in 4^n size buckets */
    recycle_bucket_t recycle[RECYCLE_BUCKETS];

    int enable_cache;           /* current result cache state */
    zbar_symbol_t *cache;       /* inter-image result cache entries */

    /* configuration settings */
    unsigned config;            /* config flags */
    int configs[NUM_SCN_CFGS];  /* int valued configurations */

#ifndef NO_STATS
    int stat_syms_new;
    int stat_iscn_syms_inuse, stat_iscn_syms_recycle;
    int stat_img_syms_inuse, stat_img_syms_recycle;
    int stat_sym_new;
    int stat_sym_recycle[RECYCLE_BUCKETS];
#endif
};

not knowing what your setup (ie: ENABLE_QRCODE, NO_STATS, etc) for compilation is; I will leave the c to jna structure conversion to you, but the mapping rules as desccribe in https://jna.dev.java.net/javadoc/overview-summary.html should apply to it.

---

Since the structures are opaque, the API can not require any knowledge of their contents, and so you don't need to worry about them.

Just use Pointer whenever you see a reference to "zbar_image_scanner_t *".