FFDB-008: Implement RandomAccessLog.getSegment (#16)

godcrampy · Jan 6, 2024 · 478b435 · 478b435
1 parent c7615c1
commit 478b435
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Showing 5 changed files with 114 additions and 4 deletions.
diff --git a/src/main/java/com/sahilbondre/firefly/filetable/SerializedPersistableFileTable.java b/src/main/java/com/sahilbondre/firefly/filetable/SerializedPersistableFileTable.java
@@ -5,7 +5,10 @@
 import com.esotericsoftware.kryo.io.Input;
 import com.esotericsoftware.kryo.io.Output;
 
-import java.io.*;
+import java.io.FileInputStream;
+import java.io.FileNotFoundException;
+import java.io.FileOutputStream;
+import java.io.Serializable;
 import java.util.HashMap;
 import java.util.Map;
 

diff --git a/src/main/java/com/sahilbondre/firefly/log/FileChannelRandomAccessLog.java b/src/main/java/com/sahilbondre/firefly/log/FileChannelRandomAccessLog.java
@@ -1,6 +1,7 @@
 package com.sahilbondre.firefly.log;
 
 import com.sahilbondre.firefly.filetable.FilePointer;
+import com.sahilbondre.firefly.model.Segment;
 
 import java.io.IOException;
 import java.io.RandomAccessFile;
@@ -51,6 +52,46 @@ public byte[] read(long offset, long length) throws IOException, InvalidRangeExc
         return buffer.array();
     }
 
+    @Override
+    public Segment readSegment(long offset) throws IOException, InvalidRangeException {
+        long fileSize = fileChannel.size();
+
+        if (offset < 0 || offset >= fileSize) {
+            throw new InvalidRangeException("Invalid offset");
+        }
+
+        // Read Key Size
+        byte[] keySizeBytes = new byte[Segment.KEY_SIZE_LENGTH];
+        fileChannel.read(ByteBuffer.wrap(keySizeBytes), offset + Segment.KEY_SIZE_LENGTH);
+
+        // Read Value Size
+        byte[] valueSizeBytes = new byte[Segment.VALUE_SIZE_LENGTH];
+        fileChannel.read(ByteBuffer.wrap(valueSizeBytes),
+            offset + Segment.KEY_SIZE_LENGTH + Segment.VALUE_SIZE_LENGTH);
+
+        // Total Size
+        int totalSize = Segment.CRC_LENGTH + Segment.KEY_SIZE_LENGTH +
+            Segment.VALUE_SIZE_LENGTH + byteArrayToInt(keySizeBytes) + byteArrayToInt(valueSizeBytes);
+
+        // Read entire segment
+        byte[] segmentBytes = new byte[totalSize];
+        fileChannel.read(ByteBuffer.wrap(segmentBytes), offset);
+
+
+        Segment segment = Segment.fromByteArray(segmentBytes);
+
+        // Validate CRC
+        if (!segment.isSegmentValid()) {
+            throw new InvalidRangeException("Segment is invalid");
+        }
+
+        return segment;
+    }
+
+    private int byteArrayToInt(byte[] bytes) {
+        return (bytes[0] << 8) | (bytes[1] & 0xFF);
+    }
+
     public void close() throws IOException {
         fileChannel.close();
         randomAccessFile.close();

diff --git a/src/main/java/com/sahilbondre/firefly/log/RandomAccessLog.java b/src/main/java/com/sahilbondre/firefly/log/RandomAccessLog.java
@@ -1,6 +1,7 @@
 package com.sahilbondre.firefly.log;
 
 import com.sahilbondre.firefly.filetable.FilePointer;
+import com.sahilbondre.firefly.model.Segment;
 
 import java.io.IOException;
 
@@ -13,5 +14,7 @@ public interface RandomAccessLog {
 
     byte[] read(long offset, long length) throws IOException, InvalidRangeException;
 
+    Segment readSegment(long offset) throws IOException, InvalidRangeException;
+
     void close() throws IOException;
 }
diff --git a/src/main/java/com/sahilbondre/firefly/model/Segment.java b/src/main/java/com/sahilbondre/firefly/model/Segment.java
@@ -2,9 +2,9 @@
 
 public class Segment {
 
-    private static final int CRC_LENGTH = 2;
-    private static final int KEY_SIZE_LENGTH = 2;
-    private static final int VALUE_SIZE_LENGTH = 4;
+    public static final int CRC_LENGTH = 2;
+    public static final int KEY_SIZE_LENGTH = 2;
+    public static final int VALUE_SIZE_LENGTH = 4;
     /**
      * Class representing a segment of the log file.
      * <p>

diff --git a/src/test/java/com/sahilbondre/firefly/log/FileChannelRandomAccessLogTest.java b/src/test/java/com/sahilbondre/firefly/log/FileChannelRandomAccessLogTest.java
@@ -1,5 +1,7 @@
 package com.sahilbondre.firefly.log;
 
+import com.sahilbondre.firefly.filetable.FilePointer;
+import com.sahilbondre.firefly.model.Segment;
 import org.junit.jupiter.api.AfterEach;
 import org.junit.jupiter.api.BeforeEach;
 import org.junit.jupiter.api.Test;
@@ -121,4 +123,65 @@ void givenLog_whenClose_thenFileIsNotAccessible() throws IOException {
         assertTrue(Files.exists(TEST_FILE_PATH));
         assertThrows(IOException.class, () -> randomAccessLog.append("NewContent".getBytes()));
     }
+
+    @Test
+    void givenLogWithContent_whenReadSegment_thenReturnsCorrectSegment() throws IOException, InvalidRangeException {
+        // Given
+        // A log with existing content
+        Segment firstSegment = Segment.fromKeyValuePair("Hello".getBytes(), "World".getBytes());
+        Segment secondSegment = Segment.fromKeyValuePair("Foo".getBytes(), "Bar".getBytes());
+        FilePointer firstFilePointer = randomAccessLog.append(firstSegment.getBytes());
+        FilePointer secondFilePointer = randomAccessLog.append(secondSegment.getBytes());
+
+        // When
+        Segment firstReadSegment = randomAccessLog.readSegment(firstFilePointer.getOffset());
+        Segment secondReadSegment = randomAccessLog.readSegment(secondFilePointer.getOffset());
+
+        // Then
+        assertArrayEquals(firstSegment.getBytes(), firstReadSegment.getBytes());
+        assertArrayEquals(secondSegment.getBytes(), secondReadSegment.getBytes());
+        assertEquals("Hello", new String(firstReadSegment.getKey()));
+        assertEquals("World", new String(firstReadSegment.getValue()));
+        assertEquals("Foo", new String(secondReadSegment.getKey()));
+        assertEquals("Bar", new String(secondReadSegment.getValue()));
+    }
+
+    @Test
+    void givenLogWithContent_whenReadSegmentWithInvalidOffset_thenThrowsInvalidRangeException() throws IOException {
+        // Given
+        // A log with existing content
+        Segment firstSegment = Segment.fromKeyValuePair("Hello".getBytes(), "World".getBytes());
+        Segment secondSegment = Segment.fromKeyValuePair("Foo".getBytes(), "Bar".getBytes());
+        randomAccessLog.append(firstSegment.getBytes());
+        randomAccessLog.append(secondSegment.getBytes());
+
+        // When/Then
+        assertThrows(InvalidRangeException.class, () -> randomAccessLog.readSegment(-1));
+        assertThrows(InvalidRangeException.class, () -> randomAccessLog.readSegment(100));
+    }
+
+    @Test
+    void givenEmptyLog_whenReadSegment_thenThrowsInvalidRangeException() {
+        // Given
+        // An empty log
+
+        // When/Then
+        assertThrows(InvalidRangeException.class, () -> randomAccessLog.readSegment(0));
+    }
+
+    @Test
+    void givenLogWithContent_whenAppend_thenReturnsCorrectFilePointer() throws IOException {
+        // Given
+        // A log with existing content
+
+        // When
+        FilePointer fp1 = randomAccessLog.append("Hello".getBytes());
+        FilePointer fp2 = randomAccessLog.append("World".getBytes());
+
+        // Then
+        assertEquals(TEST_FILE_NAME, fp1.getFileName());
+        assertEquals(0, fp1.getOffset());
+        assertEquals(TEST_FILE_NAME, fp2.getFileName());
+        assertEquals(5, fp2.getOffset());
+    }
 }