R/download_help.R

In ani-ghosh/luna_dev: Satellite Remote Sensing (Earth Observation) data analysis

# Functions to help with downloading data
# Authors: Aniruddha Ghosh, Robert J. Hijmans, Alex Mandel
# July 2019
# Version 0.1
# Licence GPL v3

.download <- function(aurl, filename,...) {
	fn <- paste(tempfile(), ".download", sep="")
	res <- utils::download.file(url=aurl, destfile=fn, method="auto", quiet = FALSE, mode = "wb", cacheOK = TRUE)
	if (res == 0) {
		w <- getOption("warn")
		on.exit(options("warn" = w))
		options("warn"=-1) 
		if (!file.rename(fn, filename) ) { 
			# rename failed, perhaps because fn and filename refer to different devices
			file.copy(fn, filename)
			file.remove(fn)
		}
	} else {
		stop("could not download the file" )
	}
}


.getCleanPath <- function(path) {
	
	if (missing(path)) {
		path <- tempdir()
	} 
  
	if (path == "") {
		path <- tempdir()
	} 
  
	path <- trimws(path)
  
	if (substr(path, nchar(path)-1, nchar(path)) == '//' ) {
		p <- substr(path, 1, nchar(path)-2)		
	} else if (substr(path, nchar(path), nchar(path)) == '/'  | substr(path, nchar(path), nchar(path)) == '\\') {
		p <- substr(path, 1, nchar(path)-1)
	} else {
		p <- path
	}
	if (!file.exists(p) & !file.exists(path)) {
		stop('path does not exist: ', path)
	}
	if (substr(path, nchar(path), nchar(path)) != '/' & substr(path, nchar(path), nchar(path)) != '\\') {
		path <- paste(path, "/", sep="")
	}
	return(path)
}




.getExtent <- function(aoi) {
  # Return the extent of an Area Of Interest in a character format for Web API requests
	if (!is.vector(aoi)) {
		b <- as.vector(bbox(aoi))
	} else {
		b <- as.vector(t(matrix(aoi, ncol=2)))
	}
	paste(b, collapse=",")
}



# Simplified download wrappers
.downloadCurl <- function(u, f, overwrite, ...) {
  if (!overwrite & file.exists(f)) return()
  curl::curl_download(u, destfile = fn, ...)
}

.downloadFile <- function(u, f, overwrite, ...) {
  if (!overwrite & file.exists(f)) return()
  download.file(u, f, ...)
}