read_dbc(engine = "native") decodes DBC records directly into R columns
without DBF or CSV temporary files. In engine = "auto", this native path
is selected for files up to 50 MiB by default; set native_threshold to
control the cutoff.
dbc_to_csv() now writes CSV rows directly from the decompression stream,
removing the full-sized temporary DBF previously required during conversion.
dbc_batch_to_csv() gains cols for field selection and workers for
file-level parallel conversion on macOS and Linux.
dbc_batch_to_csv() converts every DBC file in a directory, optionally
recursively, while preserving the input subdirectory layout.
dbc_to_csv() and read_dbc() gain a cols parameter to select fields in
the C writer, avoiding creation of unselected columns in the temporary CSV.
read_dbc() gains engine = "auto" | "data.table" | "base" so users can
choose the CSV reader explicitly for large files.
read_dbc() gains a coerce_types = TRUE parameter that automatically
converts columns to their native R types based on the DBF field metadata:
D (date) fields → Date (DBF format YYYYMMDD)N fields with decimals > 0 → numericN fields with decimals == 0 → integer when values fit in R integers,
otherwise numericL (logical) fields → logicalC (character) fields → character (unchanged)
Blank or zero-filled values become NA of the appropriate type.