Refine mmap failure log

native/src/nativeMain/kotlin/moe/tarsin/ehviewer/LogUtils.kt

@@ -0,0 +1,10 @@
+package moe.tarsin.ehviewer
+
+import platform.android.ANDROID_LOG_WARN
+import platform.android.__android_log_print
+
+private val KNI_NATIVE_TAG = "KNI"
+
+fun Warn(message: String) {
+    __android_log_print(ANDROID_LOG_WARN.toInt(), KNI_NATIVE_TAG, "%s", message)
+}

native/src/nativeMain/kotlin/moe/tarsin/ehviewer/mmap.kt

@@ -2,6 +2,8 @@ package moe.tarsin.ehviewer
 
 import kotlinx.cinterop.CPointer
 import kotlinx.cinterop.UnsafeNumber
+import kotlinx.cinterop.interpretCPointer
+import kotlinx.cinterop.nativeNullPtr
 import kotlinx.cinterop.value
 import platform.android.JNIEnvVar
 import platform.android.jclass
@@ -11,12 +13,15 @@ import platform.android.jobject
 import platform.posix.MAP_PRIVATE
 import platform.posix.PROT_READ
 import platform.posix.PROT_WRITE
+import platform.posix.errno
 import platform.posix.mmap
+import platform.posix.strerror
 
 @OptIn(UnsafeNumber::class)
 @Suppress("UNUSED_PARAMETER")
 @CName("Java_com_hippo_Native_mapFd")
 fun mapFd(env: CPointer<JNIEnvVar>, clazz: jclass, fd: jint, capability: jlong): jobject {
     val result = mmap(null, capability.tosize_t(), PROT_READ or PROT_WRITE, MAP_PRIVATE, fd, 0)
-    return env.newDirectByteBuffer(result!!, capability)
+    result ?: Warn("mmap call with fd:${fd} capability:${capability} failed!, error:${strerror(errno)}")
+    return result?.let { env.newDirectByteBuffer(result, capability) } ?: interpretCPointer(nativeNullPtr)!!
 }