sk0x50 commented on a change in pull request #9177:
URL: https://github.com/apache/ignite/pull/9177#discussion_r661363591
##########
File path:
modules/core/src/main/java/org/apache/ignite/internal/util/IgniteUtils.java
##########
@@ -12106,4 +12106,33 @@ public static long uncompressedSize(File zip) throws
IOException {
return size;
}
}
+
+ /**
+ * Map object hash to some index between 0 and specified size via modulo
operation.
+ *
+ * @param hash Object hash.
+ * @param size Size greater than 0.
+ * @return Calculated index in range [0..size).
+ */
+ public static int hashToIndex(int hash, int size) {
+ return safeAbs(hash % size);
+ }
+
+ /**
+ * Map object hash to some index between 0 and specified size using
+ * approach similar to {@link HashMap#hash(Object)}. In case
+ * <code>size</code> is not a power of 2 we fallback to modulo operation.
+ *
+ * @param hash Object hash.
+ * @param size Size greater than 0.
+ * @return Calculated index in range [0..size).
+ */
+ public static int hashToIndexOpt(int hash, int size, boolean isSizePow2) {
+ int h = (hash ^ (hash >>> 16));
+
+ return isSizePow2
Review comment:
Well, this implementation relies on the user input and does not
explicitly check the fact that the size variable is a power of two.
It seems to me, it is easy to write a code as follows: hashToIndex(hash, 9,
true) that leads to that only two results can be returned in this case - 0 and
8.
##########
File path:
modules/core/src/main/java/org/apache/ignite/internal/util/IgniteUtils.java
##########
@@ -12106,4 +12106,33 @@ public static long uncompressedSize(File zip) throws
IOException {
return size;
}
}
+
+ /**
+ * Map object hash to some index between 0 and specified size via modulo
operation.
+ *
+ * @param hash Object hash.
+ * @param size Size greater than 0.
+ * @return Calculated index in range [0..size).
+ */
+ public static int hashToIndex(int hash, int size) {
+ return safeAbs(hash % size);
+ }
+
+ /**
+ * Map object hash to some index between 0 and specified size using
+ * approach similar to {@link HashMap#hash(Object)}. In case
+ * <code>size</code> is not a power of 2 we fallback to modulo operation.
+ *
+ * @param hash Object hash.
+ * @param size Size greater than 0.
+ * @return Calculated index in range [0..size).
+ */
+ public static int hashToIndexOpt(int hash, int size, boolean isSizePow2) {
Review comment:
Well, I don't think that you need to provide a unique name here,
overloading is enough.
##########
File path:
modules/core/src/main/java/org/apache/ignite/internal/util/IgniteUtils.java
##########
@@ -12106,4 +12106,33 @@ public static long uncompressedSize(File zip) throws
IOException {
return size;
}
}
+
+ /**
+ * Map object hash to some index between 0 and specified size via modulo
operation.
+ *
+ * @param hash Object hash.
+ * @param size Size greater than 0.
+ * @return Calculated index in range [0..size).
+ */
+ public static int hashToIndex(int hash, int size) {
+ return safeAbs(hash % size);
+ }
+
+ /**
+ * Map object hash to some index between 0 and specified size using
+ * approach similar to {@link HashMap#hash(Object)}. In case
+ * <code>size</code> is not a power of 2 we fallback to modulo operation.
+ *
+ * @param hash Object hash.
+ * @param size Size greater than 0.
+ * @return Calculated index in range [0..size).
Review comment:
Please add to Javadoc a new parameter which is `isSizePow2`.
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