Move hash_any prototype from access/hash.h to utils/hashutils.h

... as well as its implementation from backend/access/hash/hashfunc.c to
backend/utils/hash/hashfn.c.

access/hash is the place for the hash index AM, not really appropriate
for generic facilities, which is what hash_any is; having things the old
way meant that anything using hash_any had to include the AM's include
file, pointlessly polluting its namespace with unrelated, unnecessary
cruft.

Also move the HTEqual strategy number to access/stratnum.h from
access/hash.h.

To avoid breaking third-party extension code, add an #include
"utils/hashutils.h" to access/hash.h.  (An easily removed line by
committers who enjoy their asbestos suits to protect them from angry
extension authors.)

Discussion: https://postgr.es/m/201901251935.ser5e4h6djt2@alvherre.pgsql

1 files changed, 19 insertions, 0 deletions

diff --git a/src/include/utils/hashutils.h b/src/include/utils/hashutils.h
index 58bacbf19f1..aa90d4195ad 100644
--- a/src/include/utils/hashutils.h
+++ b/src/include/utils/hashutils.h
@@ -7,6 +7,25 @@
 #ifndef HASHUTILS_H
 #define HASHUTILS_H
 
+
+/*
+ * Rotate the high 32 bits and the low 32 bits separately.  The standard
+ * hash function sometimes rotates the low 32 bits by one bit when
+ * combining elements.  We want extended hash functions to be compatible with
+ * that algorithm when the seed is 0, so we can't just do a normal rotation.
+ * This works, though.
+ */
+#define ROTATE_HIGH_AND_LOW_32BITS(v) \
+	((((v) << 1) & UINT64CONST(0xfffffffefffffffe)) | \
+	(((v) >> 31) & UINT64CONST(0x100000001)))
+
+
+extern Datum hash_any(register const unsigned char *k, register int keylen);
+extern Datum hash_any_extended(register const unsigned char *k,
+				  register int keylen, uint64 seed);
+extern Datum hash_uint32(uint32 k);
+extern Datum hash_uint32_extended(uint32 k, uint64 seed);
+
 /*
  * Combine two 32-bit hash values, resulting in another hash value, with
  * decent bit mixing.