src/include/storage/buf.h

   1 /*-------------------------------------------------------------------------
   2  *
   3  * buf.h
   4  *        Basic buffer manager data types.
   5  *
   6  *
   7  * Portions Copyright (c) 1996-2021, PostgreSQL Global Development Group
   8  * Portions Copyright (c) 1994, Regents of the University of California
   9  *
  10  * src/include/storage/buf.h
  11  *
  12  *-------------------------------------------------------------------------
  13  */
  14 #ifndef BUF_H
  15 #define BUF_H
  16
  17 /*
  18  * Buffer identifiers.
  19  *
  20  * Zero is invalid, positive is the index of a shared buffer (1..NBuffers),
  21  * negative is the index of a local buffer (-1 .. -NLocBuffer).
  22  */
  23 typedef int Buffer;
  24
  25 #define InvalidBuffer   0
  26
  27 /*
  28  * BufferIsInvalid
  29  *              True iff the buffer is invalid.
  30  */
  31 #define BufferIsInvalid(buffer) ((buffer) == InvalidBuffer)
  32
  33 /*
  34  * BufferIsLocal
  35  *              True iff the buffer is local (not visible to other backends).
  36  */
  37 #define BufferIsLocal(buffer)   ((buffer) < 0)
  38
  39 /*
  40  * Buffer access strategy objects.
  41  *
  42  * BufferAccessStrategyData is private to freelist.c
  43  */
  44 typedef struct BufferAccessStrategyData *BufferAccessStrategy;
  45
  46 #endif                                                  /* BUF_H */