Move pg_crc.c to src/common, and remove pg_crc_tables.h

To get CRC functionality in a client program, you now need to link with
libpgcommon instead of libpgport. The CRC code has nothing to do with
portability, so libpgcommon is a better home. (libpgcommon didn't exist
when pg_crc.c was originally moved to src/port.)

Remove the possibility to get CRC functionality by just #including
pg_crc_tables.h. I'm not aware of any extensions that actually did that and
couldn't simply link with libpgcommon.

This also moves the pg_crc.h header file from src/include/utils to
src/include/common, which will require changes to any external programs
that currently does #include "utils/pg_crc.h". That seems acceptable, as
include/common is clearly the right home for it now, and the change needed
to any such programs is trivial.

1 files changed, 121 insertions, 0 deletions

diff --git a/src/include/common/pg_crc.h b/src/include/common/pg_crc.h
new file mode 100644
index 00000000000..ea03dbf8403
--- /dev/null
+++ b/src/include/common/pg_crc.h
@@ -0,0 +1,121 @@
+/*
+ * pg_crc.h
+ *
+ * PostgreSQL CRC support
+ *
+ * See Ross Williams' excellent introduction
+ * A PAINLESS GUIDE TO CRC ERROR DETECTION ALGORITHMS, available from
+ * http://www.ross.net/crc/ or several other net sites.
+ *
+ * We have three slightly different variants of a 32-bit CRC calculation:
+ * CRC-32C (Castagnoli polynomial), CRC-32 (Ethernet polynomial), and a legacy
+ * CRC-32 version that uses the lookup table in a funny way. They all consist
+ * of four macros:
+ *
+ * INIT_<variant>(crc)
+ *		Initialize a CRC accumulator
+ *
+ * COMP_<variant>(crc, data, len)
+ *		Accumulate some (more) bytes into a CRC
+ *
+ * FIN_<variant>(crc)
+ *		Finish a CRC calculation
+ *
+ * EQ_<variant>(c1, c2)
+ *		Check for equality of two CRCs.
+ *
+ * Portions Copyright (c) 1996-2015, PostgreSQL Global Development Group
+ * Portions Copyright (c) 1994, Regents of the University of California
+ *
+ * src/include/common/pg_crc.h
+ */
+#ifndef PG_CRC_H
+#define PG_CRC_H
+
+/* ugly hack to let this be used in frontend and backend code on Cygwin */
+#ifdef FRONTEND
+#define CRCDLLIMPORT
+#else
+#define CRCDLLIMPORT PGDLLIMPORT
+#endif
+
+typedef uint32 pg_crc32;
+
+/*
+ * CRC calculation using the CRC-32C (Castagnoli) polynomial.
+ *
+ * We use all-ones as the initial register contents and final bit inversion.
+ * This is the same algorithm used e.g. in iSCSI. See RFC 3385 for more
+ * details on the choice of polynomial.
+ */
+#define INIT_CRC32C(crc) ((crc) = 0xFFFFFFFF)
+#define FIN_CRC32C(crc)	((crc) ^= 0xFFFFFFFF)
+#define COMP_CRC32C(crc, data, len)	\
+	COMP_CRC32_NORMAL_TABLE(crc, data, len, pg_crc32c_table)
+#define EQ_CRC32C(c1, c2) ((c1) == (c2))
+
+/*
+ * CRC-32, the same used e.g. in Ethernet.
+ *
+ * This is currently only used in ltree and hstore contrib modules. It uses
+ * the same lookup table as the legacy algorithm below. New code should
+ * use the Castagnoli version instead.
+ */
+#define INIT_TRADITIONAL_CRC32(crc) ((crc) = 0xFFFFFFFF)
+#define FIN_TRADITIONAL_CRC32(crc)	((crc) ^= 0xFFFFFFFF)
+#define COMP_TRADITIONAL_CRC32(crc, data, len)	\
+	COMP_CRC32_NORMAL_TABLE(crc, data, len, pg_crc32_table)
+#define EQ_TRADITIONAL_CRC32(c1, c2) ((c1) == (c2))
+
+/*
+ * The CRC algorithm used for WAL et al in pre-9.5 versions.
+ *
+ * This closely resembles the normal CRC-32 algorithm, but is subtly
+ * different. Using Williams' terms, we use the "normal" table, but with
+ * "reflected" code. That's bogus, but it was like that for years before
+ * anyone noticed. It does not correspond to any polynomial in a normal CRC
+ * algorithm, so it's not clear what the error-detection properties of this
+ * algorithm actually are.
+ *
+ * We still need to carry this around because it is used in a few on-disk
+ * structures that need to be pg_upgradeable. It should not be used in new
+ * code.
+ */
+#define INIT_LEGACY_CRC32(crc) ((crc) = 0xFFFFFFFF)
+#define FIN_LEGACY_CRC32(crc)	((crc) ^= 0xFFFFFFFF)
+#define COMP_LEGACY_CRC32(crc, data, len)	\
+	COMP_CRC32_REFLECTED_TABLE(crc, data, len, pg_crc32_table)
+#define EQ_LEGACY_CRC32(c1, c2) ((c1) == (c2))
+
+/*
+ * Common code for CRC computation using a lookup table.
+ */
+#define COMP_CRC32_NORMAL_TABLE(crc, data, len, table)			  \
+do {															  \
+	const unsigned char *__data = (const unsigned char *) (data); \
+	uint32		__len = (len); \
+\
+	while (__len-- > 0) \
+	{ \
+		int		__tab_index = ((int) (crc) ^ *__data++) & 0xFF; \
+		(crc) = table[__tab_index] ^ ((crc) >> 8); \
+	} \
+} while (0)
+
+#define COMP_CRC32_REFLECTED_TABLE(crc, data, len, table) \
+do {															  \
+	const unsigned char *__data = (const unsigned char *) (data); \
+	uint32		__len = (len); \
+\
+	while (__len-- > 0) \
+	{ \
+		int		__tab_index = ((int) ((crc) >> 24) ^ *__data++) & 0xFF;	\
+		(crc) = table[__tab_index] ^ ((crc) << 8); \
+	} \
+} while (0)
+
+/* Constant tables for CRC-32C and CRC-32 polynomials */
+extern CRCDLLIMPORT const uint32 pg_crc32c_table[];
+extern CRCDLLIMPORT const uint32 pg_crc32_table[];
+
+#endif   /* PG_CRC_H */