Merge pull request #29295 from Gnaily

* gh-29295:
  Polish "Override available() in RandomAccessDataFile's InputStream"
  Override available() in RandomAccessDataFile's InputStream

Closes gh-29295

spring-boot-project/spring-boot-tools/spring-boot-loader/src/main/java/org/springframework/boot/loader/data/RandomAccessDataFile.java

@@ -1,5 +1,5 @@
 /*
- * Copyright 2012-2019 the original author or authors.
+ * Copyright 2012-2022 the original author or authors.
  *
  * Licensed under the Apache License, Version 2.0 (the "License");
  * you may not use this file except in compliance with the License.
@@ -180,6 +180,11 @@ public class RandomAccessDataFile implements RandomAccessData {
 			return (n <= 0) ? 0 : moveOn(cap(n));
 		}
 
+		@Override
+		public int available() throws IOException {
+			return (int) RandomAccessDataFile.this.length - this.position;
+		}
+
 		/**
 		 * Cap the specified value such that it cannot exceed the number of bytes
 		 * remaining.

spring-boot-project/spring-boot-tools/spring-boot-loader/src/test/java/org/springframework/boot/loader/data/RandomAccessDataFileTests.java

@@ -1,5 +1,5 @@
 /*
- * Copyright 2012-2021 the original author or authors.
+ * Copyright 2012-2022 the original author or authors.
  *
  * Licensed under the Apache License, Version 2.0 (the "License");
  * you may not use this file except in compliance with the License.
@@ -199,6 +199,15 @@ class RandomAccessDataFileTests {
 		assertThat(amountSkipped).isEqualTo(0L);
 	}
 
+	@Test
+	void inputStreamAvailable() throws Exception {
+		assertThat(this.inputStream.available()).isEqualTo(256);
+		this.inputStream.skip(56);
+		assertThat(this.inputStream.available()).isEqualTo(200);
+		this.inputStream.skip(200);
+		assertThat(this.inputStream.available()).isEqualTo(0);
+	}
+
 	@Test
 	void subsectionNegativeOffset() {
 		assertThatExceptionOfType(IndexOutOfBoundsException.class).isThrownBy(() -> this.file.getSubsection(-1, 1));