Get StringBuilder capacity again after decompress

StringBuilder's capicity field is updated after a decompress()
call is made. StringBuilder methods that store the capacity in
a local variable before a call to decompress() should update this
stored value again after the call. This applies only to StringBuilder
methods that use the stored capacity value after a decompress() call.

As an example, if this value is not updated again after decompress(),
the old value will be used as a check on whether or not to run
ensureCapacityImpl(), leading to additional array copies.

decompress() now returns the new capacity, for which the sharedBit
need not be masked off since decompress() creates a new array.

Signed-off-by: Mansoor Saqib <[email protected]>

jcl/src/java.base/share/classes/java/lang/StringBuilder.java

@@ -78,8 +78,8 @@ public final class StringBuilder extends AbstractStringBuilder implements Serial
 	private transient int count;
 	private transient char[] value;
 	private transient int capacity;
-	
-	private void decompress(int min) {
+
+	private int decompress(int min) {
 		int currentLength = lengthInternal();
 		int currentCapacity = capacityInternal();
 
@@ -100,6 +100,7 @@ private void decompress(int min) {
 		capacity = newValue.length;
 
 		String.initCompressionFlag();
+		return capacity;
 	}
 
 /**
@@ -208,7 +209,7 @@ public StringBuilder append (char[] chars) {
 		} else {
 			// Check if the StringBuilder is compressed
 			if (count >= 0) {
-				decompress(newLength);
+				currentCapacity = decompress(newLength);
 			}
 
 			if (newLength > currentCapacity) {
@@ -265,7 +266,7 @@ public StringBuilder append (char chars[], int start, int length) {
 			} else {
 				// Check if the StringBuilder is compressed
 				if (count >= 0) {
-					decompress(newLength);					
+					currentCapacity = decompress(newLength);
 				}
 
 				if (newLength > currentCapacity) {
@@ -311,7 +312,7 @@ StringBuilder append (char[] chars, int start, int length, boolean compressed) {
 		} else {
 			// Check if the StringBuilder is compressed
 			if (count >= 0) {
-				decompress(newLength);				
+				currentCapacity = decompress(newLength);
 			}
 
 			if (newLength > currentCapacity) {
@@ -369,7 +370,7 @@ public StringBuilder append(char ch) {
 		} else {
 			// Check if the StringBuilder is compressed
 			if (count >= 0) {
-				decompress(newLength);
+				currentCapacity = decompress(newLength);
 			}
 
 			if (newLength > currentCapacity) {
@@ -547,7 +548,7 @@ public StringBuilder append (String string) {
 		} else {
 			// Check if the StringBuilder is compressed
 			if (count >= 0) {
-				decompress(newLength);
+				currentCapacity = decompress(newLength);
 			}
 
 			if (newLength > currentCapacity) {
@@ -2217,7 +2218,7 @@ public StringBuilder append(CharSequence sequence) {
 			} else {
 				// Check if the StringBuilder is compressed
 				if (count >= 0) {
-					decompress(newLength);
+					currentCapacity = decompress(newLength);
 				}
 
 				if (newLength > currentCapacity) {
@@ -2281,8 +2282,7 @@ public StringBuilder append(CharSequence sequence, int start, int end) {
 				} else {
 					// Check if the StringBuilder is compressed
 					if (count >= 0) {
-						decompress(newLength);
-						currentCapacity = capacityInternal();
+						currentCapacity = decompress(newLength);
 					}
 
 					if (newLength > currentCapacity) {
@@ -2359,7 +2359,7 @@ public StringBuilder append(CharSequence sequence, int start, int end) {
 				} else {
 					// Check if the StringBuilder is compressed
 					if (count >= 0) {
-						decompress(newLength);
+						currentCapacity = decompress(newLength);
 					}
 
 					if (newLength > currentCapacity) {