Replace manual string converter to readText method.

Change-Id: If8cc6c27bd399fcdf8446ec411626f13d39e707c

Author: Jaehwa-Noh

core/network/src/main/kotlin/com/google/samples/apps/nowinandroid/core/network/demo/DemoNiaNetworkDataSource.kt

@@ -29,11 +29,7 @@ import kotlinx.coroutines.withContext
 import kotlinx.serialization.ExperimentalSerializationApi
 import kotlinx.serialization.json.Json
 import kotlinx.serialization.json.decodeFromStream
-import java.io.ByteArrayOutputStream
-import java.io.InputStream
-import java.nio.charset.StandardCharsets
 import javax.inject.Inject
-import kotlin.coroutines.coroutineContext
 
 /**
  * [NiaNetworkDataSource] implementation that provides static news resources to aid development
@@ -52,7 +48,7 @@ class DemoNiaNetworkDataSource @Inject constructor(
             } else {
                 // Use decodeFromString to capability with API 24 below.
                 // https://github.com/Kotlin/kotlinx.serialization/issues/2457#issuecomment-1786923342
-                val topicsJsonString = convertStreamToString(assets.open(TOPICS_ASSET))
+                val topicsJsonString = assets.readText(TOPICS_ASSET)
                 networkJson.decodeFromString(topicsJsonString)
             }
         }
@@ -65,7 +61,7 @@ class DemoNiaNetworkDataSource @Inject constructor(
             } else {
                 // Use decodeFromString to capability with API 24 below.
                 // https://github.com/Kotlin/kotlinx.serialization/issues/2457#issuecomment-1786923342
-                val newsJsonString = convertStreamToString(assets.open(NEWS_ASSET))
+                val newsJsonString = assets.readText(NEWS_ASSET)
                 networkJson.decodeFromString(newsJsonString)
             }
         }
@@ -76,24 +72,6 @@ class DemoNiaNetworkDataSource @Inject constructor(
     override suspend fun getNewsResourceChangeList(after: Int?): List<NetworkChangeList> =
         getNewsResources().mapToChangeList(NetworkNewsResource::id)
 
-    /**
-     * Convert [InputStream] to [String].
-     */
-    private suspend fun convertStreamToString(inputStream: InputStream): String = withContext(
-        coroutineContext,
-    ) {
-        val result = ByteArrayOutputStream()
-        val buffer = ByteArray(1024)
-        var length: Int
-        while (true) {
-            length = inputStream.read(buffer)
-            if (length == -1) break
-            result.write(buffer, 0, length)
-        }
-
-        result.toString(StandardCharsets.UTF_8.name())
-    }
-
     companion object {
         private const val NEWS_ASSET = "news.json"
         private const val TOPICS_ASSET = "topics.json"