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man pages section 3: Library Interfaces and Headers

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Updated: Thursday, June 13, 2019
 
 

archives.h(3HEAD)

Name

archives.h, archives - device header

Description

/* Magic numbers */
#define CMN_ASC 0x070701    /* Cpio Magic Number for -c header */
#define CMN_BIN 070707      /* Cpio Magic Number for Binary header */
#define CMN_BBS 0143561     /* Cpio Magic Number for Byte-Swap header */
#define CMN_CRC 0x070702    /* Cpio Magic Number for CRC header */
#define CMS_ASC "070701"    /* Cpio Magic String for -c header */
#define CMS_CHR "070707"    /* Cpio Magic String for odc header */
#define CMS_CRC "070702"    /* Cpio Magic String for CRC header */
#define CMS_LEN 6           /* Cpio Magic String length */
/* Various header and field lengths */
#define CHRSZ   76         /* -H odc size minus filename field */
#define ASCSZ   110        /* -c and CRC hdr size minus filename field */
#define TARSZ   512        /* TAR hdr size */
#define HNAMLEN 256        /* maximum filename length for binary and
                          odc headers */
#define EXPNLEN 1024      /* maximum filename length for -c and
                         CRC headers */
#define HTIMLEN 2         /* length of modification time field */
#define HSIZLEN 2         /* length of file size field */
/* cpio binary header definition */
struct hdr_cpio {
       short   h_magic,           /* magic number field */
               h_dev;             /* file system of file */
       ushort_t  h_ino,           /* inode of file */
               h_mode,            /* modes of file */
               h_uid,             /* uid of file */
               h_gid;             /* gid of file */
       short   h_nlink,           /* number of links to file */
               h_rdev,            /* maj/min numbers for special files */
               h_mtime[HTIMLEN],  /* modification time of file */
               h_namesize,        /* length of filename */
          h_filesize[HSIZLEN];     /* size of file */
     char h_name[HNAMLEN];    /* filename */
} ;
/* cpio -H odc header format */
struct c_hdr {
       char c_magic[CMS_LEN],
            c_dev[6],
            c_ino[6],
            c_mode[6],
            c_uid[6],
            c_gid[6],
            c_nlink[6],
            c_rdev[6],
            c_mtime[11],
            c_namesz[6],
            c_filesz[11],
            c_name[HNAMLEN];
} ;
/* -c and CRC header format */
struct Exp_cpio_hdr {
     char E_magic[CMS_LEN],
          E_ino[8],
          E_mode[8],
          E_uid[8],
          E_gid[8],
          E_nlink[8],
          E_mtime[8],
          E_filesize[8],
          E_maj[8],
          E_min[8],
          E_rmaj[8],
          E_rmin[8],
          E_namesize[8],
          E_chksum[8],
          E_name[EXPNLEN];
} ;
/* Tar header structure and format */
#define TBLOCK 512  /* length of tar header and data blocks */
#define TNAMLEN     100  /* maximum length for tar file names */
#define TMODLEN     8    /* length of mode field */
#define TUIDLEN     8    /* length of uid field */
#define TGIDLEN     8    /* length of gid field */
#define TSIZLEN     12   /* length of size field */
#define TTIMLEN     12   /* length of modification time field */
#define TCRCLEN     8    /* length of header checksum field */
/* tar header definition */
union tblock {
     char dummy[TBLOCK];
     struct header {
         char  t_name[TNAMLEN];     /* name of file */
         char  t_mode[TMODLEN];     /* mode of file */
         char  t_uid[TUIDLEN];      /* uid of file */
         char  t_gid[TGIDLEN];      /* gid of file */
         char  t_size[TSIZLEN];     /* size of file in bytes */
         char  t_mtime[TTIMLEN];    /* modification time of file */
         char  t_chksum[TCRCLEN];   /* checksum of header */
         char  t_typeflag;          /* flag to indicate type of file */
         char  t_linkname[TNAMLEN]; /* file this file is linked with */
         char  t_magic[6];          /* magic string always "ustar" */
         char  t_version[2];        /* version strings always "00" */
         char  t_uname[32];         /* owner of file in ASCII */
         char  t_gname[32];         /* group of file in ASCII */
         char  t_devmajor[8];       /* major number for special files */
         char  t_devminor[8];       /* minor number for special files */
         char  t_prefix[155];       /* pathname prefix */
     } tbuf;
}
/* volcopy tape label format and structure */
#define VMAGLEN 8
#define VVOLLEN     6
#define VFILLEN     464
struct volcopy_label {
     char v_magic[VMAGLEN],
          v_volume[VVOLLEN],
          v_reels,
          v_reel;
     long v_time,
          v_length,
          v_dens,
          v_reelblks,    /* u370 added field */
          v_blksize,     /* u370 added field */
          v_nblocks;     /* u370 added field */
     char v_fill[VFILLEN];
     long v_offset; /* used with -e and -reel options */
     int  v_type;        /* does tape have nblocks field? */
} ;

/*
 * Define archive formats for extended attributes.
 *
 * Extended attributes are stored in two pieces.
 * 1. An attribute header which has information about
 *    what file the attribute is for and what the attribute
 *    is named.
 * 2. The attribute record itself.  Stored as a normal file type
 *    of entry.
 * Both the header and attribute record have special modes/typeflags
 * associated with them.
 *
 * The names of the header in the archive look like:
 * /dev/null/attr.hdr
 *
 * The name of the attribute looks like:
 * /dev/null/attr.
 *
 * This is done so that an archiver that doesn't understand these formats
 * can just dispose of the attribute records unless the user chooses to
 * rename them via cpio -r or pax -i
 *
 * The format is composed of a fixed size header followed
 * by a variable sized xattr_buf. If the attribute is a hard link
 * to another attribute, then another xattr_buf section is included
 * for the link.
 *
 * The xattr_buf is used to define the necessary "pathing" steps
 * to get to the extended attribute.  This is necessary to support
 * a fully recursive attribute model where an attribute may itself
 * have an attribute.
 *
 * The basic layout looks like this.
 *
 *     --------------------------------
 *     |                              |
 *     |         xattr_hdr            |
 *     |                              |
 *     --------------------------------
 *     --------------------------------
 *     |                              |
 *     |        xattr_buf             |
 *     |                              |
 *     --------------------------------
 *     --------------------------------
 *     |                              |
 *     |      (optional link info)    |
 *     |                              |
 *     --------------------------------
 *     --------------------------------
 *     |                              |
 *     |      attribute itself        |
 *     |      stored as normal tar    |
 *     |      or cpio data with       |
 *     |      special mode or         |
 *     |      typeflag                |
 *     |                              |
 *     --------------------------------
 *
 */
#define XATTR_ARCH_VERS "1.0"

/*
 * extended attribute fixed header
 *
 * h_version            format version.
 * h_size               size of header + variable sized data sections.
 * h_component_len      Length of entire pathing section.
 * h_link_component_len Length of link component section.  Again same 
 *                      definition as h_component_len.
 */
struct xattr_hdr {
        char    h_version[7];
        char    h_size[10];
        char    h_component_len[10]; /* total length of path component */
        char    h_link_component_len[10];
};

/*
 * The name is encoded like this:
 * filepathNULattrpathNUL[attrpathNULL]...
 */
struct xattr_buf {
        char    h_namesz[7];  /* length of h_names */
        char    h_typeflag;   /* actual typeflag of file being archived */
        char    h_names[1];   /* filepathNULattrpathNUL... */
};

/*
 * Special values for tar archives
 */

/*
 * typeflag for tar archives.
 */

/*
 * Attribute hdr and attribute files have the following typeflag
 */
#define _XATTR_HDRTYPE          'E'

/*
 * For cpio archives the header and attribute have
 * _XATTR_CPIO_MODE ORED into the mode field in both
 * character and binary versions of the archive format
 */
#define _XATTR_CPIO_MODE        0xB000