fix setSessionHistorySize method on native platforms

android/ffmpeg-kit-android-lib/src/main/java/com/arthenica/ffmpegkit/FFmpegKitConfig.java

@@ -1086,6 +1086,22 @@ public class FFmpegKitConfig {
             throw new IllegalArgumentException("Session history size must not exceed the hard limit!");
         } else if (sessionHistorySize > 0) {
             FFmpegKitConfig.sessionHistorySize = sessionHistorySize;
+            deleteExpiredSessions();
+        }
+    }
+
+    /**
+     * Deletes expired sessions.
+     */
+    private static void deleteExpiredSessions() {
+        while (sessionHistoryList.size() > sessionHistorySize) {
+            try {
+                Session expiredSession = sessionHistoryList.remove(0);
+                if (expiredSession != null) {
+                    sessionHistoryMap.remove(expiredSession.getSessionId());
+                }
+            } catch (final IndexOutOfBoundsException ignored) {
+            }
         }
     }
 
@@ -1099,18 +1115,13 @@ public class FFmpegKitConfig {
 
             /*
              * ASYNC SESSIONS CALL THIS METHOD TWICE
-             * THIS CHECK PREVENTS ADDING THE SAME SESSION TWICE
+             * THIS CHECK PREVENTS ADDING THE SAME SESSION AGAIN
              */
             final boolean sessionAlreadyAdded = sessionHistoryMap.containsKey(session.getSessionId());
             if (!sessionAlreadyAdded) {
                 sessionHistoryMap.put(session.getSessionId(), session);
                 sessionHistoryList.add(session);
-                if (sessionHistoryList.size() > sessionHistorySize) {
-                    try {
-                        sessionHistoryList.remove(0);
-                    } catch (final IndexOutOfBoundsException ignored) {
-                    }
-                }
+                deleteExpiredSessions();
             }
         }
     }

android/ffmpeg-kit-android-lib/src/test/java/com/arthenica/ffmpegkit/FFmpegKitConfigTest.java

@@ -19,6 +19,8 @@
 
 package com.arthenica.ffmpegkit;
 
+import static com.arthenica.ffmpegkit.FFmpegSessionTest.TEST_ARGUMENTS;
+
 import org.junit.Assert;
 import org.junit.Test;
 
@@ -167,6 +169,24 @@ public class FFmpegKitConfigTest {
         Assert.assertEquals("mp4", extension);
     }
 
+    @Test
+    public void setSessionHistorySize() {
+        int newSize = 15;
+        FFmpegKitConfig.setSessionHistorySize(newSize);
+
+        for (int i = 1; i <= (newSize + 5); i++) {
+            new FFmpegSession(TEST_ARGUMENTS);
+            Assert.assertTrue(FFmpegKitConfig.getSessions().size() <= newSize);
+        }
+
+        newSize = 3;
+        FFmpegKitConfig.setSessionHistorySize(newSize);
+        for (int i = 1; i <= (newSize + 5); i++) {
+            new FFmpegSession(TEST_ARGUMENTS);
+            Assert.assertTrue(FFmpegKitConfig.getSessions().size() <= newSize);
+        }
+    }
+
     private String listToPackageName(final List<String> externalLibraryList) {
         boolean speex = externalLibraryList.contains("speex");
         boolean fribidi = externalLibraryList.contains("fribidi");

android/ffmpeg-kit-android-lib/src/test/java/com/arthenica/ffmpegkit/FFmpegSessionTest.java

@@ -26,7 +26,7 @@ import java.util.List;
 
 public class FFmpegSessionTest {
 
-    private static final String[] TEST_ARGUMENTS = new String[]{"argument1", "argument2"};
+    static final String[] TEST_ARGUMENTS = new String[]{"argument1", "argument2"};
 
     @Test
     public void constructorTest() {