feat: sdk source readRemaining (#1454)

Author: 0marperez

runtime/runtime-core/api/runtime-core.api

@@ -1101,6 +1101,7 @@ public abstract interface class aws/smithy/kotlin/runtime/io/SdkSource : java/io
 
 public final class aws/smithy/kotlin/runtime/io/SdkSourceKt {
 	public static final fun readFully (Laws/smithy/kotlin/runtime/io/SdkSource;Laws/smithy/kotlin/runtime/io/SdkBuffer;J)V
+	public static final fun readRemaining (Laws/smithy/kotlin/runtime/io/SdkSource;Laws/smithy/kotlin/runtime/io/SdkBuffer;)J
 	public static final fun readToByteArray (Laws/smithy/kotlin/runtime/io/SdkSource;Lkotlin/coroutines/Continuation;)Ljava/lang/Object;
 	public static final fun toSdkByteReadChannel (Laws/smithy/kotlin/runtime/io/SdkSource;Lkotlinx/coroutines/CoroutineScope;)Laws/smithy/kotlin/runtime/io/SdkByteReadChannel;
 	public static synthetic fun toSdkByteReadChannel$default (Laws/smithy/kotlin/runtime/io/SdkSource;Lkotlinx/coroutines/CoroutineScope;ILjava/lang/Object;)Laws/smithy/kotlin/runtime/io/SdkByteReadChannel;

runtime/runtime-core/common/src/aws/smithy/kotlin/runtime/io/SdkSource.kt

@@ -110,3 +110,22 @@ public fun SdkSource.readFully(sink: SdkBuffer, byteCount: Long) {
         totalBytesRead += rc
     }
 }
+
+/**
+ * **Caution** Reads the entire contents of the source into [sink].
+ * This function will read until the source is exhausted and no bytes remain
+ *
+ * @param sink the buffer that data read from the source will be appended to
+ */
+@InternalApi
+public fun SdkSource.readRemaining(sink: SdkBuffer): Long {
+    var totalBytesRead: Long = 0
+    var bytesRead = read(sink, Long.MAX_VALUE)
+
+    while (bytesRead != -1L) {
+        totalBytesRead += bytesRead
+        bytesRead = read(sink, Long.MAX_VALUE)
+    }
+
+    return totalBytesRead
+}

runtime/runtime-core/common/test/aws/smithy/kotlin/runtime/io/SdkSourceTest.kt

@@ -0,0 +1,57 @@
+/*
+ * Copyright Amazon.com, Inc. or its affiliates. All Rights Reserved.
+ * SPDX-License-Identifier: Apache-2.0
+ */
+
+package aws.smithy.kotlin.runtime.io
+
+import kotlin.test.Test
+import kotlin.test.assertEquals
+
+class SdkSourceTest {
+    @Test
+    fun readRemaining() {
+        val data = "Hello world"
+        val dataLength = data.length.toLong()
+        val readCycles = 100
+        val totalDataLength = dataLength * readCycles
+
+        // Manual and readRemaining
+        val source = createTestSource(data, dataLength, readCycles)
+        val buffer = SdkBuffer()
+        val manualReads = 10
+        repeat(manualReads) {
+            source.read(buffer, dataLength)
+        }
+        var readByReadRemaining = source.readRemaining(buffer)
+        assertEquals(readByReadRemaining, totalDataLength - manualReads * dataLength)
+        assertEquals(buffer.size, totalDataLength)
+
+        // Only readRemaining
+        buffer.skip(totalDataLength)
+        readByReadRemaining = createTestSource(data, dataLength, readCycles).readRemaining(buffer)
+        assertEquals(readByReadRemaining, totalDataLength)
+        assertEquals(buffer.size, totalDataLength)
+    }
+}
+
+private fun createTestSource(
+    data: String,
+    dataLength: Long,
+    readCycles: Int,
+) =
+    object : SdkSource {
+        var remainingReadCycles = readCycles
+
+        override fun read(sink: SdkBuffer, limit: Long): Long {
+            if (remainingReadCycles == 0) {
+                return -1L
+            }
+
+            sink.writeUtf8(data)
+            remainingReadCycles--
+            return dataLength
+        }
+
+        override fun close() {}
+    }