diff options
Diffstat (limited to 'src/include/c.h')
| -rw-r--r-- | src/include/c.h | 20 |
1 files changed, 14 insertions, 6 deletions
diff --git a/src/include/c.h b/src/include/c.h index 9daa9e4c0eb..0774ec7cc1e 100644 --- a/src/include/c.h +++ b/src/include/c.h @@ -12,7 +12,7 @@ * Portions Copyright (c) 1996-2007, PostgreSQL Global Development Group * Portions Copyright (c) 1994, Regents of the University of California * - * $PostgreSQL: pgsql/src/include/c.h,v 1.217 2007/01/25 03:30:43 momjian Exp $ + * $PostgreSQL: pgsql/src/include/c.h,v 1.218 2007/02/05 04:22:18 tgl Exp $ * *------------------------------------------------------------------------- */ @@ -537,12 +537,12 @@ typedef NameData *Name; /* ---------------- * Alignment macros: align a length or address appropriately for a given type. + * The fooALIGN() macros round up to a multiple of the required alignment, + * while the fooALIGN_DOWN() macros round down. The latter are more useful + * for problems like "how many X-sized structures will fit in a page?". * - * There used to be some incredibly crufty platform-dependent hackery here, - * but now we rely on the configure script to get the info for us. Much nicer. - * - * NOTE: TYPEALIGN will not work if ALIGNVAL is not a power of 2. - * That case seems extremely unlikely to occur in practice, however. + * NOTE: TYPEALIGN[_DOWN] will not work if ALIGNVAL is not a power of 2. + * That case seems extremely unlikely to be needed in practice, however. * ---------------- */ @@ -557,6 +557,14 @@ typedef NameData *Name; /* MAXALIGN covers only built-in types, not buffers */ #define BUFFERALIGN(LEN) TYPEALIGN(ALIGNOF_BUFFER, (LEN)) +#define TYPEALIGN_DOWN(ALIGNVAL,LEN) \ + (((long) (LEN)) & ~((long) ((ALIGNVAL) - 1))) + +#define SHORTALIGN_DOWN(LEN) TYPEALIGN_DOWN(ALIGNOF_SHORT, (LEN)) +#define INTALIGN_DOWN(LEN) TYPEALIGN_DOWN(ALIGNOF_INT, (LEN)) +#define LONGALIGN_DOWN(LEN) TYPEALIGN_DOWN(ALIGNOF_LONG, (LEN)) +#define DOUBLEALIGN_DOWN(LEN) TYPEALIGN_DOWN(ALIGNOF_DOUBLE, (LEN)) +#define MAXALIGN_DOWN(LEN) TYPEALIGN_DOWN(MAXIMUM_ALIGNOF, (LEN)) /* ---------------------------------------------------------------- * Section 6: widely useful macros |