[EGIT PATCH 09/10] Hash ObjectId faster.
From: Robin Rosenberg <hidden>
Date: 2016-06-15 22:42:59
Subsystem:
the rest · Maintainer:
Linus Torvalds
ObjectId's are well distributed so we can grab the first four bytes as the hash code. The assumption makes hashing faster. Signed-off-by: Robin Rosenberg <redacted> --- .../src/org/spearce/jgit/lib/ObjectId.java | 13 +++++++------ 1 files changed, 7 insertions(+), 6 deletions(-)
diff --git a/org.spearce.jgit/src/org/spearce/jgit/lib/ObjectId.java b/org.spearce.jgit/src/org/spearce/jgit/lib/ObjectId.java
index 9e62424..45e23e6 100644
--- a/org.spearce.jgit/src/org/spearce/jgit/lib/ObjectId.java
+++ b/org.spearce.jgit/src/org/spearce/jgit/lib/ObjectId.java@@ -163,12 +163,13 @@ public class ObjectId implements Comparable { } public int hashCode() { - int r = 0; - for (int k = id.length - 1; k >= 0; k--) { - r *= 31; - r += id[k]; - } - return r; + // Object Id' are well distributed so grab the first four bytes + int b0 = id[0] & 0xff; + int b1 = id[1] & 0xff; + int b2 = id[2] & 0xff; + int b3 = id[3] & 0xff; + int h = (b0 << 24) | (b1 << 16) | (b2 << 8) | b3; + return h; } public boolean equals(final ObjectId o) {