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/*-------------------------------------------------------------------------
*
* walmethods.h
*
* Portions Copyright (c) 1996-2021, PostgreSQL Global Development Group
*
* IDENTIFICATION
* src/bin/pg_basebackup/walmethods.h
*-------------------------------------------------------------------------
*/
typedef void *Walfile;
typedef enum
{
CLOSE_NORMAL,
CLOSE_UNLINK,
CLOSE_NO_RENAME
} WalCloseMethod;
/*
* A WalWriteMethod structure represents the different methods used
* to write the streaming WAL as it's received.
*
* All methods that have a failure return indicator will set state
* allowing the getlasterror() method to return a suitable message.
* Commonly, errno is this state (or part of it); so callers must take
* care not to clobber errno between a failed method call and use of
* getlasterror() to retrieve the message.
*/
typedef struct WalWriteMethod WalWriteMethod;
struct WalWriteMethod
{
/*
* Open a target file. Returns Walfile, or NULL if open failed. If a temp
* suffix is specified, a file with that name will be opened, and then
* automatically renamed in close(). If pad_to_size is specified, the file
* will be padded with NUL up to that size, if supported by the Walmethod.
*/
Walfile (*open_for_write) (const char *pathname, const char *temp_suffix, size_t pad_to_size);
/*
* Close an open Walfile, using one or more methods for handling automatic
* unlinking etc. Returns 0 on success, other values for error.
*/
int (*close) (Walfile f, WalCloseMethod method);
/* Check if a file exist */
bool (*existsfile) (const char *pathname);
/* Return the size of a file, or -1 on failure. */
ssize_t (*get_file_size) (const char *pathname);
/*
* Return the name of the current file to work on in pg_malloc()'d string,
* without the base directory. This is useful for logging.
*/
char *(*get_file_name) (const char *pathname, const char *temp_suffix);
/* Return the level of compression */
int (*compression) (void);
/*
* Write count number of bytes to the file, and return the number of bytes
* actually written or -1 for error.
*/
ssize_t (*write) (Walfile f, const void *buf, size_t count);
/* Return the current position in a file or -1 on error */
off_t (*get_current_pos) (Walfile f);
/*
* fsync the contents of the specified file. Returns 0 on success.
*/
int (*sync) (Walfile f);
/*
* Clean up the Walmethod, closing any shared resources. For methods like
* tar, this includes writing updated headers. Returns true if the
* close/write/sync of shared resources succeeded, otherwise returns false
* (but the resources are still closed).
*/
bool (*finish) (void);
/* Return a text for the last error in this Walfile */
const char *(*getlasterror) (void);
};
/*
* Available WAL methods:
* - WalDirectoryMethod - write WAL to regular files in a standard pg_wal
* - WalTarMethod - write WAL to a tarfile corresponding to pg_wal
* (only implements the methods required for pg_basebackup,
* not all those required for pg_receivewal)
*/
WalWriteMethod *CreateWalDirectoryMethod(const char *basedir,
int compression, bool sync);
WalWriteMethod *CreateWalTarMethod(const char *tarbase, int compression, bool sync);
/* Cleanup routines for previously-created methods */
void FreeWalDirectoryMethod(void);
void FreeWalTarMethod(void);
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