Add support for readFully at the S3SeekableInputStream level

input-stream/src/main/java/software/amazon/s3/analyticsaccelerator/S3SeekableInputStream.java

@@ -15,6 +15,7 @@
  */
 package software.amazon.s3.analyticsaccelerator;
 
+import java.io.EOFException;
 import java.io.IOException;
 import java.nio.ByteBuffer;
 import java.util.List;
@@ -234,6 +235,41 @@ public void readVectored(
     logicalIO.readVectored(ranges, allocate);
   }
 
+  /**
+   * Fill the provided buffer with the contents of the input source starting at {@code position} for
+   * the given {@code offset} and {@code length}.
+   *
+   * @param position start position of the read
+   * @param buffer target buffer to copy data
+   * @param offset offset in the buffer to copy the data
+   * @param length size of the read
+   * @throws IOException if an I/O error occurs
+   */
+  public void readFully(long position, byte[] buffer, int offset, int length) throws IOException {
+    throwIfClosed("cannot read from closed stream");
+    validatePositionedReadArgs(position, buffer, offset, length);
+
+    if (length == 0) {
+      return;
+    }
+
+    this.telemetry.measureVerbose(
+        () ->
+            Operation.builder()
+                .name(OPERATION_READ)
+                .attribute(StreamAttributes.uri(this.s3URI))
+                .attribute(StreamAttributes.etag(this.logicalIO.metadata().getEtag()))
+                .attribute(StreamAttributes.range(position, position + length - 1))
+                .build(),
+        () -> {
+          int bytesRead = this.logicalIO.read(buffer, offset, length, position);
+          if (bytesRead < length) {
+            throw new EOFException(
+                "Reached the end of stream with " + (length - bytesRead) + " bytes left to read");
+          }
+        });
+  }
+
   /**
    * Releases all resources associated with the {@link S3SeekableInputStream}.
    *

input-stream/src/main/java/software/amazon/s3/analyticsaccelerator/SeekableInputStream.java

@@ -80,6 +80,19 @@ public abstract void readVectored(
       Consumer<ByteBuffer> release)
       throws IOException;
 
+  /**
+   * Fill the provided buffer with the contents of the input source starting at {@code position} for
+   * the given {@code offset} and {@code length}.
+   *
+   * @param position start position of the read
+   * @param buffer target buffer to copy data
+   * @param offset offset in the buffer to copy the data
+   * @param length size of the read
+   * @throws IOException if an I/O error occurs
+   */
+  public abstract void readFully(long position, byte[] buffer, int offset, int length)
+      throws IOException;
+
   /**
    * Validates the arguments for a read operation. This method is available to use in all subclasses
    * to ensure consistency.

input-stream/src/referenceTest/java/software/amazon/s3/analyticsaccelerator/model/InMemorySeekableStream.java

@@ -15,6 +15,7 @@
  */
 package software.amazon.s3.analyticsaccelerator.model;
 
+import java.io.IOException;
 import java.nio.ByteBuffer;
 import java.util.List;
 import java.util.function.Consumer;
@@ -84,6 +85,28 @@ public void readVectored(
     }
   }
 
+  @Override
+  public void readFully(long position, byte[] buffer, int offset, int length) throws IOException {
+    // Save current position of stream
+    long prevPosition = this.position;
+    if (position >= this.contentLength) {
+      throw new IOException("Position is beyond end of stream");
+    }
+
+    data.position((int) position);
+    int bytesAvailable = this.contentLength - (int) position;
+    int bytesToRead = Math.min(length, bytesAvailable);
+    data.get(buffer, offset, bytesToRead);
+    if (bytesToRead < length) {
+      throw new IOException(
+          "Reached the end of stream with " + (length - bytesToRead) + " bytes left to read");
+    }
+
+    // Restore original position
+    this.position = prevPosition;
+    data.position((int) this.position);
+  }
+
   @Override
   public int read() {
     if (this.position >= this.contentLength) {

input-stream/src/referenceTest/java/software/amazon/s3/analyticsaccelerator/property/InMemoryS3SeekableInputStream.java

@@ -131,6 +131,11 @@ public void readVectored(
     this.delegate.readVectored(ranges, allocate, release);
   }
 
+  @Override
+  public void readFully(long position, byte[] buffer, int offset, int length) throws IOException {
+    this.delegate.readFully(position, buffer, offset, length);
+  }
+
   @Override
   public int read() throws IOException {
     return this.delegate.read();

input-stream/src/test/java/software/amazon/s3/analyticsaccelerator/S3SeekableInputStreamTest.java

@@ -448,6 +448,99 @@ public void testInsufficientBuffer() throws IOException {
         IndexOutOfBoundsException.class, () -> seekableInputStream.readTail(new byte[0], 0, 8), -1);
     SpotBugsLambdaWorkaround.assertReadResult(
         IndexOutOfBoundsException.class, () -> seekableInputStream.readTail(new byte[0], 0, 8), -1);
+    assertThrows(
+        IndexOutOfBoundsException.class, () -> seekableInputStream.readFully(0, new byte[0], 0, 8));
+  }
+
+  @Test
+  void testReadFullyWithInvalidArgument() throws IOException {
+    // Given: seekable stream
+    try (S3SeekableInputStream stream = getTestStream()) {
+      // When & Then: reading with invalid arguments, exception is thrown
+      // -1 is invalid position
+      assertThrows(IllegalArgumentException.class, () -> stream.readFully(-1, new byte[10], 0, 5));
+      // -1 is invalid length
+      assertThrows(IllegalArgumentException.class, () -> stream.readFully(0, new byte[10], 0, -1));
+      // Requesting more data than byte buffer size
+      assertThrows(IndexOutOfBoundsException.class, () -> stream.readFully(0, new byte[5], 0, 10));
+    }
+  }
+
+  @Test
+  void testReadFullyHappyCase() throws IOException {
+    // Given: seekable stream
+    try (S3SeekableInputStream stream = getTestStream()) {
+      // When: reading 5 bytes from position 3
+      byte[] buf = new byte[5];
+      stream.readFully(3, buf, 0, 5);
+
+      // Then: buffer contains the expected 5 bytes from position 3
+      byte[] expected = TEST_DATA.substring(3, 8).getBytes(StandardCharsets.UTF_8);
+      assertArrayEquals(expected, buf);
+
+      // Position should remain unchanged after readFully
+      assertEquals(0, stream.getPos());
+    }
+  }
+
+  @Test
+  void testReadFullyDoesNotAlterPosition() throws IOException {
+    // Given: seekable stream with data "test-data12345678910"
+    try (S3SeekableInputStream stream = getTestStream()) {
+      // When:
+      // 1) Reading first 5 bytes from position 0 (should be "test-")
+      // 2) Reading 5 bytes from position 10 using readFully (should be "23456")
+      // 3) Reading next 5 bytes from current position (should be "data1")
+      byte[] one = new byte[5];
+      byte[] two = new byte[5];
+      byte[] three = new byte[5];
+
+      int numBytesRead1 = stream.read(one, 0, one.length);
+      stream.readFully(10, two, 0, two.length);
+      int numBytesRead3 = stream.read(three, 0, three.length);
+
+      // Then: readFully did not alter the position and reads #1 and #3 return subsequent bytes
+      // First read should return 5 bytes
+      assertEquals(5, numBytesRead1);
+      // Third read should also return 5 bytes, continuing from where first read left off
+      assertEquals(5, numBytesRead3);
+
+      // Verify the actual content of each buffer
+      assertEquals("test-", new String(one, StandardCharsets.UTF_8));
+      assertEquals("data1", new String(three, StandardCharsets.UTF_8));
+      assertEquals("23456", new String(two, StandardCharsets.UTF_8));
+
+      // Verify the stream position is at 10 (5 + 5) after all reads
+      assertEquals(10, stream.getPos());
+    }
+  }
+
+  @Test
+  public void testReadFullyOnClosedStream() throws IOException {
+    S3SeekableInputStream seekableInputStream = getTestStream();
+    seekableInputStream.close();
+    assertThrows(IOException.class, () -> seekableInputStream.readFully(0, new byte[8], 0, 8));
+  }
+
+  @Test
+  public void testZeroLengthReadFully() throws IOException {
+    S3SeekableInputStream seekableInputStream = getTestStream();
+    assertDoesNotThrow(() -> seekableInputStream.readFully(0, new byte[0], 0, 0));
+  }
+
+  @Test
+  void testReadFullyThrowsWhenInsufficientBytes() throws IOException {
+    // Given: seekable stream with TEST_DATA (20 bytes)
+    try (S3SeekableInputStream stream = getTestStream()) {
+      // When & Then: trying to read beyond available data should throw IOException
+      byte[] buffer = new byte[10];
+
+      // Try to read 10 bytes starting at position 15 (only 5 bytes available)
+      assertThrows(IOException.class, () -> stream.readFully(15, buffer, 0, 10));
+
+      // Verify stream position remains unchanged after failed readFully
+      assertEquals(0, stream.getPos());
+    }
   }
 
   private S3SeekableInputStream getTestStream() {