R/gdal_abs2rel.R

In pobsteta/theia2r: An R toolbox to find, download and preprocess Sentinel-2 data

#' @title Convert absolute from/to relative paths in a virtual file
#' @description The two functions read the content of a GDAL virtual
#'  file (VRT) and check the presence of paths to linked files.
#'
#'  [gdal_abs2rel] scans the presence of absolute paths: when an
#'  absolute path has a common parent directory with the path in which
#'  the VRT is, this is replaced with a relative. This is useful when
#'  VRT are on a remote driver, which can be mounted to several points.
#' @param in_vrt The path of the VRT to be read.
#' @param out_vrt (optional) The path of the output VRT file (default
#'  is to overwrite `in_vrt`).
#' @return NULL
#' @author Luigi Ranghetti, phD (2017) \email{ranghetti.l@@irea.cnr.it}
#' @note License: GPL 3.0
#' @export
#' @importFrom magrittr '%>%'
#' @name gdal_abs2rel
#' @rdname gdal_abs2rel_rel2abs
#' @examples
#' \dontrun{
#' example_vrt <- '/TODO/example/s2_translate.vrt'
#' rel_vrt <- '/TODO/example/s2_translate_rel.vrt'
#' abs_vrt <- '/TODO/example/s2_translate_abs.vrt'
#' gdal_abs2rel(example_vrt, rel_vrt)
#' gdal_rel2abs(example_vrt, abs_vrt)
#' }
gdal_abs2rel <- function(in_vrt, out_vrt = NA) {
    
    # to avoid NOTE on check
    . <- NULL
    
    if (is.na(out_vrt)) {
        out_vrt <- in_vrt
    }
    
    if (!file.exists(in_vrt)) {
        print_message(type = "error", "Input file (\"", in_vrt, "\") does not exists.")
    }
    
    vrt_text <- readLines(in_vrt)
    
    # path_regex <- '^ *<SourceFilename relativeToVRT=\'0\'>(.*)</SourceFilename> *$'
    path_regex <- "^.* relativeToVRT=\"0\">(.*)</.*"
    
    for (sel_line in grep(path_regex, vrt_text)) {
        abs_path <- gsub(path_regex, "\\1", vrt_text[sel_line])
        rel_path <- suppressWarnings(abs2rel(abs_path, dirname(in_vrt)))
        if (abs_path != rel_path) {
            vrt_text[sel_line] <- vrt_text[sel_line] %>% gsub(abs_path, rel_path, ., fixed = TRUE) %>% gsub("relativeToVRT=\"0\"", "relativeToVRT=\"1\"", ., fixed = TRUE)
        }
    }
    writeLines(vrt_text, out_vrt)
    
}


#' @description [gdal_rel2abs] checks the presence of relative paths,
#'  and replace them with the corresponding absolute path (symbolic
#'  links are followed). This is useful to grant that VRT can be moved
#'  (if the files they link to are not moved).
#' @export
#' @importFrom magrittr '%>%'
#' @name gdal_rel2abs
#' @rdname gdal_abs2rel_rel2abs
gdal_rel2abs <- function(in_vrt, out_vrt = NA) {
    
    # to avoid NOTE on check
    . <- NULL
    
    if (is.na(out_vrt)) {
        out_vrt <- in_vrt
    }
    
    if (!file.exists(in_vrt)) {
        print_message(type = "error", "Input file (\"", in_vrt, "\") does not exists.")
    }
    
    vrt_text <- readLines(in_vrt)
    
    # path_regex <- '^ *<SourceFilename relativeToVRT=\'1\'>(.*)</SourceFilename> *$'
    path_regex <- "^.* relativeToVRT=\"1\">(.*)</.*"
    
    for (sel_line in grep(path_regex, vrt_text)) {
        rel_path <- gsub(path_regex, "\\1", vrt_text[sel_line])
        abs_path <- expand_path(rel_path, dirname(in_vrt), normalize = TRUE)
        vrt_text[sel_line] <- vrt_text[sel_line] %>% gsub(rel_path, abs_path, ., fixed = TRUE) %>% gsub("relativeToVRT=\"1\"", "relativeToVRT=\"0\"", ., fixed = TRUE)
    }
    
    writeLines(vrt_text, out_vrt)
    
}