pgtar.h

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/*-------------------------------------------------------------------------
 *
 * pgtar.h
 *    Functions for manipulating tarfile datastructures (src/port/tar.c)
 *
 *
 * Portions Copyright (c) 1996-2025, PostgreSQL Global Development Group
 * Portions Copyright (c) 1994, Regents of the University of California
 *
 * src/include/pgtar.h
 *
 *-------------------------------------------------------------------------
 */
#ifndef PG_TAR_H
#define PG_TAR_H
 
#define     TAR_BLOCK_SIZE  512
 
enum tarError
{
    TAR_OK = 0,
    TAR_NAME_TOO_LONG,
    TAR_SYMLINK_TOO_LONG,
};
 
/*
 * Offsets of fields within a 512-byte tar header.
 *
 * "tar number" values should be generated using print_tar_number() and can be
 * read using read_tar_number(). Fields that contain strings are generally
 * both filled and read using strlcpy().
 *
 * The value for the checksum field can be computed using tarChecksum().
 *
 * Some fields are not used by PostgreSQL; see tarCreateHeader().
 */
enum tarHeaderOffset
{
    TAR_OFFSET_NAME = 0,        /* 100 byte string */
    TAR_OFFSET_MODE = 100,      /* 8 byte tar number, excludes S_IFMT */
    TAR_OFFSET_UID = 108,       /* 8 byte tar number */
    TAR_OFFSET_GID = 116,       /* 8 byte tar number */
    TAR_OFFSET_SIZE = 124,      /* 8 byte tar number */
    TAR_OFFSET_MTIME = 136,     /* 12 byte tar number */
    TAR_OFFSET_CHECKSUM = 148,  /* 8 byte tar number */
    TAR_OFFSET_TYPEFLAG = 156,  /* 1 byte file type, see TAR_FILETYPE_* */
    TAR_OFFSET_LINKNAME = 157,  /* 100 byte string */
    TAR_OFFSET_MAGIC = 257,     /* "ustar" with terminating zero byte */
    TAR_OFFSET_VERSION = 263,   /* "00" */
    TAR_OFFSET_UNAME = 265,     /* 32 byte string */
    TAR_OFFSET_GNAME = 297,     /* 32 byte string */
    TAR_OFFSET_DEVMAJOR = 329,  /* 8 byte tar number */
    TAR_OFFSET_DEVMINOR = 337,  /* 8 byte tar number */
    TAR_OFFSET_PREFIX = 345,    /* 155 byte string */
    /* last 12 bytes of the 512-byte block are unassigned */
};
 
enum tarFileType
{
    TAR_FILETYPE_PLAIN = '0',
    TAR_FILETYPE_SYMLINK = '2',
    TAR_FILETYPE_DIRECTORY = '5',
};
 
extern enum tarError tarCreateHeader(char *h, const char *filename,
                                     const char *linktarget, pgoff_t size,
                                     mode_t mode, uid_t uid, gid_t gid,
                                     time_t mtime);
extern uint64 read_tar_number(const char *s, int len);
extern void print_tar_number(char *s, int len, uint64 val);
extern int  tarChecksum(char *header);
 
/*
 * Compute the number of padding bytes required for an entry in a tar
 * archive. We must pad out to a multiple of TAR_BLOCK_SIZE. Since that's
 * a power of 2, we can use TYPEALIGN().
 */
static inline size_t
tarPaddingBytesRequired(size_t len)
{
    return TYPEALIGN(TAR_BLOCK_SIZE, len) - len;
}
 
#endif