Various DataBufferUtils improvements

- Made sure that takeUntilByteCount is usable in multiple subscriptions.
- Added composite Matcher

spring-core/src/main/java/org/springframework/core/io/buffer/DataBufferUtils.java

@@ -419,19 +419,21 @@ public abstract class DataBufferUtils {
 		Assert.notNull(publisher, "Publisher must not be null");
 		Assert.isTrue(maxByteCount >= 0, "'maxByteCount' must be a positive number");
 
-		AtomicLong countDown = new AtomicLong(maxByteCount);
-		return Flux.from(publisher)
-				.map(buffer -> {
-					long remainder = countDown.addAndGet(-buffer.readableByteCount());
-					if (remainder < 0) {
-						int length = buffer.readableByteCount() + (int) remainder;
-						return buffer.slice(0, length);
-					}
-					else {
-						return buffer;
-					}
-				})
-				.takeUntil(buffer -> countDown.get() <= 0);
+		return Flux.defer(() -> {
+			AtomicLong countDown = new AtomicLong(maxByteCount);
+			return Flux.from(publisher)
+					.map(buffer -> {
+						long remainder = countDown.addAndGet(-buffer.readableByteCount());
+						if (remainder < 0) {
+							int length = buffer.readableByteCount() + (int) remainder;
+							return buffer.slice(0, length);
+						}
+						else {
+							return buffer;
+						}
+					})
+					.takeUntil(buffer -> countDown.get() <= 0);
+		});
 
 		// No doOnDiscard as operators used do not cache (and drop) buffers
 	}
@@ -539,7 +541,7 @@ public abstract class DataBufferUtils {
 	}
 
 	/**
-	 * Return a {@link Matcher} for the given delimiters. The matcher can be used to find the
+	 * Return a {@link Matcher} for the given delimiter. The matcher can be used to find the
 	 * delimiters in data buffers.
 	 * @param delimiter the delimiter bytes to find
 	 * @return the matcher
@@ -550,6 +552,26 @@ public abstract class DataBufferUtils {
 		return new KnuthMorrisPrattMatcher(delimiter);
 	}
 
+	/** Return a {@link Matcher} for the given delimiters.  The matcher can be used to find the
+	 * delimiters in data buffers.
+	 * @param delimiters the delimiters bytes to find
+	 * @return the matcher
+	 * @since 5.2
+	 */
+	public static Matcher matcher(byte[]... delimiters) {
+		Assert.isTrue(delimiters.length > 0, "Delimiters must not be empty");
+		if (delimiters.length == 1) {
+			return matcher(delimiters[0]);
+		}
+		else {
+			Matcher[] matchers = new Matcher[delimiters.length];
+			for (int i = 0; i < delimiters.length; i++) {
+				matchers[i] = matcher(delimiters[i]);
+			}
+			return new CompositeMatcher(matchers);
+		}
+	}
+
 	/**
 	 * Splits the given stream of data buffers around the given delimiter.
 	 * The returned flux contains data buffers that are terminated by the given delimiter,
@@ -1030,6 +1052,62 @@ public abstract class DataBufferUtils {
 		}
 	}
 
+	/**
+	 * Implementation of {@link Matcher} that wraps several other matchers.
+	 */
+	private static class CompositeMatcher implements Matcher {
+
+		private static final byte[] NO_DELIMITER = new byte[0];
+
+		private final Matcher[] matchers;
+
+		byte[] longestDelimiter = NO_DELIMITER;
+
+
+		public CompositeMatcher(Matcher[] matchers) {
+			this.matchers = matchers;
+		}
+
+		@Override
+		public int match(DataBuffer dataBuffer) {
+			this.longestDelimiter = NO_DELIMITER;
+			int bestEndIdx = Integer.MAX_VALUE;
+
+
+			for (Matcher matcher : this.matchers) {
+				int endIdx = matcher.match(dataBuffer);
+				if (endIdx != -1 &&
+						endIdx <= bestEndIdx &&
+						matcher.delimiter().length > this.longestDelimiter.length) {
+					bestEndIdx = endIdx;
+					this.longestDelimiter = matcher.delimiter();
+				}
+			}
+			if (bestEndIdx == Integer.MAX_VALUE) {
+				this.longestDelimiter = NO_DELIMITER;
+				return -1;
+			}
+			else {
+				reset();
+				return bestEndIdx;
+			}
+		}
+
+		@Override
+		public byte[] delimiter() {
+			Assert.state(this.longestDelimiter != NO_DELIMITER, "Illegal state!");
+			return this.longestDelimiter;
+		}
+
+		@Override
+		public void reset() {
+			for (Matcher matcher : this.matchers) {
+				matcher.reset();
+			}
+		}
+	}
+
+
 
 	private static class EndFrameBuffer implements DataBuffer {