R/files.R

In stringi: Fast and Portable Character String Processing Facilities

# kate: default-dictionary en_US

## This file is part of the 'stringi' package for R.
## Copyright (c) 2013-2023, Marek Gagolewski <https://www.gagolewski.com/>
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#' @title
#' Read Text File as Raw
#'
#' @description
#' Reads a text file as-is, with no conversion or text line splitting.
#'
#' @details
#' Once a text file is read into memory,
#' encoding detection (see \code{\link{stri_enc_detect}}),
#' conversion (see \code{\link{stri_encode}}), and/or
#' splitting of text into lines (see \code{\link{stri_split_lines1}})
#' can be performed.
#'
#' @param con name of the output file or a connection object
#'        (opened in the binary mode)
#' @param fname [DEPRECATED] alias of \code{con}
#'
#' @return
#' Returns a vector of type \code{raw}.
#'
#' @family files
#' @export
stri_read_raw <- function(con, fname = con)
{
    if (!missing(fname) && missing(con)) { # DEPRECATED
        warning("The 'fname' argument in stri_read_raw is a deprecated alias of 'con' and will be removed in a future release of 'stringi'.")
        con <- fname
    }

    if (is.character(con)) {
        con <- file(con, "rb")
        on.exit(close(con))
    }

    bufsize <- 4194304L
    data <- list()
    n <- 1L
    repeat {
        buf <- readBin(con, what = "raw", size = 1L, n = bufsize)
        data[[n]] <- buf
        n <- n + 1L
        if (length(buf) < bufsize)
            break
    }
    do.call(c, data)
}


#' @title
#' Read Text Lines from a Text File
#'
#' @description
#' Reads a text file in ins entirety, re-encodes it, and splits it into text lines.
#'
#' @details
#' This aims to be a substitute for the \code{\link{readLines}} function,
#' with the ability to re-encode the input file in a much more robust way,
#' and split the text into lines with \code{\link{stri_split_lines1}}
#' (which conforms with the Unicode guidelines for newline markers).
#'
#' The function calls \code{\link{stri_read_raw}},
#' \code{\link{stri_encode}}, and \code{\link{stri_split_lines1}},
#' in this order.
#'
#' Because of the way this function is currently implemented,
#' maximal file size cannot exceed ~0.67 GB.
#'
#' @param con name of the output file or a connection object
#'        (opened in the binary mode)
#' @param encoding single string; input encoding;
#' \code{NULL} or \code{''} for the current default encoding.
#' @param fname [DEPRECATED] alias of \code{con}
#'
#' @return
#' Returns a character vector, each text line is a separate string.
#' The output is always marked as UTF-8.
#'
#' @family files
#' @export
stri_read_lines <- function(con, encoding = NULL,
    fname = con)
{
    if (!missing(fname) && missing(con)) { # DEPRECATED
        warning("The 'fname' argument in stri_read_lines is a deprecated alias of 'con' and will be removed in a future release of 'stringi'.")
        con <- fname
    }

    stopifnot(is.null(encoding) || is.character(encoding))

    if (is.null(encoding) || encoding == "")
        encoding <- stri_enc_get()  # this need to be done manually, see ?stri_encode

    if (encoding == "auto")
        stop("encoding `auto` is no longer supported")  # TODO: remove in the future

    txt <- stri_read_raw(con)
    txt <- stri_encode(txt, encoding, "UTF-8")
    stri_split_lines1(txt)
}


#' @title
#' Write Text Lines to a Text File
#'
#' @description
#' Writes a text file is such a way that each element of a given
#' character vector becomes a separate text line.
#'
#'
#' @details
#' It is a substitute for the \R \code{\link{writeLines}} function,
#' with the ability to easily re-encode the output.
#'
#' We suggest using the UTF-8 encoding for all text files:
#' thus, it is the default one for the output.
#'
#' @param str character vector with data to write
#' @param con name of the output file or a connection object
#'        (opened in the binary mode)
#' @param encoding output encoding, \code{NULL} or \code{''} for
#' the current default one
#' @param sep newline separator
#' @param fname [DEPRECATED] alias of \code{con}
#'
#' @return
#' This function returns nothing noteworthy.
#'
#' @family files
#' @export
stri_write_lines <- function(str, con,
    encoding = "UTF-8",
    sep = ifelse(.Platform$OS.type == "windows", "\r\n", "\n"),
    fname = con)
{
    if (!missing(fname) && missing(con)) { # DEPRECATED
        warning("The 'fname' argument in stri_write_lines is a deprecated alias of 'con' and will be removed in a future release of 'stringi'.")
        con <- fname
    }

    stopifnot(is.character(sep), length(sep) == 1)
    str <- stri_join(str, sep, collapse = "")
    str <- stri_encode(str, "", encoding, to_raw = TRUE)[[1]]
    writeBin(str, con, useBytes = TRUE)
    invisible(NULL)
}