Kotlin/本地:如何修改CArrayPointer？

Question

我正在尝试使用带有libsecret的K/N。它包含以下结构：

typedef struct {
    const gchar *name;
    SecretSchemaFlags flags;
    SecretSchemaAttribute attributes[32];
} SecretSchema;

(从这里：https://developer.gnome.org/libsecret/0.18/libsecret-SecretSchema.html#SecretSchema)

cinterop生成了以下类：

@kotlinx.cinterop.internal.CStruct public final class SecretSchema public constructor(rawPtr: kotlinx.cinterop.NativePtr /* = kotlin.native.internal.NativePtr */) : kotlinx.cinterop.CStructVar {
   @kotlinx.cinterop.internal.CStruct.VarType public companion object : kotlinx.cinterop.CStructVar.Type {
   }

   public final val attributes: kotlinx.cinterop.CArrayPointer<org.libsecret.SecretSchemaAttribute> /* = kotlinx.cinterop.CPointer<org.libsecret.SecretSchemaAttribute> */ /* compiled code */

   public final var flags: org.libsecret.SecretSchemaFlags /* = kotlin.UInt */ /* compiled code */

   public final var name: kotlinx.cinterop.CPointer<org.libsecret.gcharVar /* = kotlinx.cinterop.ByteVarOf<kotlin.Byte> */>? /* compiled code */

   public final var reserved: org.libsecret.gint /* = kotlin.Int */ /* compiled code */

   public final var reserved1: org.libsecret.gpointer? /* = kotlinx.cinterop.CPointer<out kotlinx.cinterop.CPointed>? */ /* compiled code */

   public final var reserved2: org.libsecret.gpointer? /* = kotlinx.cinterop.CPointer<out kotlinx.cinterop.CPointed>? */ /* compiled code */

   public final var reserved3: org.libsecret.gpointer? /* = kotlinx.cinterop.CPointer<out kotlinx.cinterop.CPointed>? */ /* compiled code */

   public final var reserved4: org.libsecret.gpointer? /* = kotlinx.cinterop.CPointer<out kotlinx.cinterop.CPointed>? */ /* compiled code */

   public final var reserved5: org.libsecret.gpointer? /* = kotlinx.cinterop.CPointer<out kotlinx.cinterop.CPointed>? */ /* compiled code */

   public final var reserved6: org.libsecret.gpointer? /* = kotlinx.cinterop.CPointer<out kotlinx.cinterop.CPointed>? */ /* compiled code */

   public final var reserved7: org.libsecret.gpointer? /* = kotlinx.cinterop.CPointer<out kotlinx.cinterop.CPointed>? */ /* compiled code */
}

我试着这样定义它：

alloc<SecretSchema> {
   name = "com.charlag.tuta-bridge".cstr.ptr
   flags = SECRET_SCHEMA_NONE
}

但是，我看不到修改attributes的方法，因为CArrayPointer (CPointer)不公开修改方法。

我还注意到了一些reserved字段。我应该用它们来代替吗？

下面是如何在C：https://developer.gnome.org/libsecret/0.18/c-examples.html#c-schema-example中使用它的示例

Answer 1

似乎默认情况下没有办法，我最终这样做了：

/**
 * This is a version of the function which is missing in standard library. It initializes members
 * of the array.
 * If possible, allocate array of correct elements instead. It might not be possible with C
 * structures.
 */
inline fun <reified T : CVariable> CArrayPointer<T>.setAt(index: Int, value: CValue<T>) {
    value.write(this.rawValue + index * sizeOf<T>())
}

它适用于我，并使用与access相同的指针位置计算

Answer 2

据我所知，这里最直接的选择是使用[]操作符，并将分配的SecretSchemaAttribute分配给这些地址。要了解有关指针类型交互的更多信息，请查看此documentation page。它可能有点过时，但可以在这里或在kotlinlang Slack上提出更多问题。