slru_io.h

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/*
 * slru_io.h
 *
 * Copyright (c) 2025-2026, PostgreSQL Global Development Group
 * src/bin/pg_upgrade/slru_io.h
 */
 
#ifndef SLRU_IO_H
#define SLRU_IO_H
 
/*
 * State for reading or writing an SLRU, with a one page buffer.
 */
typedef struct SlruSegState
{
    bool        writing;
    bool        long_segment_names;
 
    char       *dir;
    char       *fn;
    int         fd;
    int64       segno;
    uint64      pageno;
 
    PGAlignedBlock buf;
} SlruSegState;
 
extern SlruSegState *AllocSlruRead(const char *dir, bool long_segment_names);
extern char *SlruReadSwitchPageSlow(SlruSegState *state, uint64 pageno);
extern void FreeSlruRead(SlruSegState *state);
 
static inline char *
SlruReadSwitchPage(SlruSegState *state, uint64 pageno)
{
    if (state->segno != -1 && pageno == state->pageno)
        return state->buf.data;
    return SlruReadSwitchPageSlow(state, pageno);
}
 
extern SlruSegState *AllocSlruWrite(const char *dir, bool long_segment_names);
extern char *SlruWriteSwitchPageSlow(SlruSegState *state, uint64 pageno);
extern void FreeSlruWrite(SlruSegState *state);
 
static inline char *
SlruWriteSwitchPage(SlruSegState *state, uint64 pageno)
{
    if (state->segno != -1 && pageno == state->pageno)
        return state->buf.data;
    return SlruWriteSwitchPageSlow(state, pageno);
}
 
#endif                          /* SLRU_IO_H */