[File] File magic for R's RDS and RData file formats

[Gert Hulselmans]

File magic for R's RDS and RData file formats:

$ cat magic/Magdir/r
#------------------------------------------------------------------------------
# $File: r,v 1.0 2025/02/04 12:12:52 christos Exp $
#    file(1) magic for R's RDS and RData file formats
#    Copyright (C) 2025 Gert Hulselmans <hulselmansgert at gmail.com>
#
#    URLS:
#      https://cran.r-project.org/doc/manuals/r-release/R-ints.html#Serialization-Formats
#      https://rdata.readthedocs.io/en/latest/_modules/rdata/parser/_parser.html
#
#    Example files:
#      https://github.com/vnmabus/rdata/tree/develop/rdata/tests/data
#
###############################################################################


###############################################################################
# RDS format
###############################################################################

0    name    RDS
# Check for RDS ASCII formats.
>0    string    A\n2\n    R RDS (ASCII format v2)
>0    string    A\n3\n    R RDS (ASCII format v3)
>0    string    A\r\n2\r\n    R RDS (ASCII CRLF format v2)
>0    string    A\r\n3\r\n    R RDS (ASCII CRLF format v3)
# Check for RDS binary formats with native word order.
>0    string    B\n\0\0\0    R RDS (Native (big-endian) word order format
>>0    use RDS_binary_version_info
>0    string    B\n\2\0\0    R RDS (Native (little-endian) word order format
>>0    use ^RDS_binary_version_info
>0    string    B\n\3\0\0    R RDS (Native (little-endian) word order format
>>0    use ^RDS_binary_version_info
# Check for RDS XDR binary save format.
>0    string    X\n\0\0\0    R RDS (XDR binary save format
>>0    use RDS_binary_version_info


# Parse version numbers from RDS if it was one of the binary versions.
0    name    RDS_binary_version_info
>2    belong    >-1    v%d)
>6    beshort    >-1    \b, written by R v%d.
>8    byte    >-1    \b%d.
>9    byte    >-1    \b%d
>10    beshort    >-1    \b, readable from R v%d.
>12    byte    >-1    \b%d.
>13    byte    >-1    \b%d
>2    belong    >2
>>14    pstring/L    x    \b, %s encoded


# Check if file is one of the RDS ASCII formats.
0    string    A
>0    use RDS    not_printed
!:ext    rds

# Check if file is RDS binary native format.
0    string    B
>0    use RDS    not_printed
!:ext    rds

# Check if file is RDS XDR binary save format.
0    string    X
>0    use RDS    not_printed
!:ext    rds


###############################################################################
# RData file formats: magic bytes followed by RDS container.
###############################################################################

0    string    RDA2\n    R RData version 2 (ASCII),
!:ext    rda/rdata
>5    use    RDS

0    string    RDA3\n    R RData version 3 (ASCII),
!:ext    rda/rdata
>5    use    RDS

0    string    RDX2\n    R RData version 2 (binary),
!:ext    rda/rdata
>5    use    RDS

0    string    RDX3\n    R RData version 3 (binary),
!:ext    rda/rdata
>5    use    RDS


Base64-encoded versions to preserve TABs.
$ cat magic/Magdir/r | base64
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Cheers,
Gert