Fixing StringReader to support skipping negative distances. This bizarre behaviour is required by the spec.
git-svn-id: https://svn.apache.org/repos/asf/harmony/enhanced/classlib/trunk@881092 13f79535-47bb-0310-9956-ffa450edef68
diff --git a/modules/luni/src/main/java/java/io/StringReader.java b/modules/luni/src/main/java/java/io/StringReader.java
index c700b78..30561b0 100644
--- a/modules/luni/src/main/java/java/io/StringReader.java
+++ b/modules/luni/src/main/java/java/io/StringReader.java
@@ -221,13 +221,19 @@
}
/**
- * Skips {@code amount} characters in the source string. Subsequent calls of
- * {@code read} methods will not return these characters unless {@code
- * reset()} is used.
- *
+ * Moves {@code ns} characters in the source string. Unlike the {@link
+ * Reader#skip(long) overridden method}, this method may skip negative skip
+ * distances: this rewinds the input so that characters may be read again.
+ * When the end of the source string has been reached, the input cannot be
+ * rewound.
+ *
* @param ns
- * the maximum number of characters to skip.
- * @return the number of characters actually skipped or 0 if {@code ns < 0}.
+ * the maximum number of characters to skip. Positive values skip
+ * forward; negative values skip backward.
+ * @return the number of characters actually skipped. This is bounded below
+ * by the number of characters already read and above by the
+ * number of characters remaining:<br> {@code -(num chars already
+ * read) <= distance skipped <= num chars remaining}.
* @throws IOException
* if this reader is closed.
* @see #mark(int)
@@ -240,18 +246,18 @@
if (isClosed()) {
throw new IOException(Msg.getString("K0083")); //$NON-NLS-1$
}
- if (ns <= 0) {
- return 0;
+
+ int minSkip = -pos;
+ int maxSkip = count - pos;
+
+ if (maxSkip == 0 || ns > maxSkip) {
+ ns = maxSkip; // no rewinding if we're at the end
+ } else if (ns < minSkip) {
+ ns = minSkip;
}
- long skipped = 0;
- if (ns < this.count - pos) {
- pos = pos + (int) ns;
- skipped = ns;
- } else {
- skipped = this.count - pos;
- pos = this.count;
- }
- return skipped;
+
+ pos += ns;
+ return ns;
}
}
}
