LBMC » CacheCache

get_content = structure( function(## Get content from cached 

### Access to the cached content of a file via the global variable CACHE_CACHE. Load content in CACHE_CACHE if needed.

filename, ##<< The path to the file that contain dataset

class=NULL, ##<< The class of dataset

# FORCE_RELOAD=FALSE, ##<< Force cachecache to reload the value

... ##<< Parameters that will be passed to my_read

) {

  if (inherits(try(CACHE_CACHE,TRUE), "try-error") || is.null(CACHE_CACHE)) {

    CACHE_CACHE <<- list()

  }

  obj = list(filename=filename)

  class(obj) = class

  FORCE_RELOAD = FALSE

  if (is.null(CACHE_CACHE[[obj$filename]]) | FORCE_RELOAD) {

    print(paste("Loading file ",obj$filename, sep=""))

		tmp_content = my_read(obj, ...)

    print("affect it...")

    CACHE_CACHE[[obj$filename]] <<- tmp_content

    print("done.")

  }  

  return(CACHE_CACHE[[obj$filename]])

### Returns the cached content of the current object. 

}, ex=function(){

	# Create a dataframe

	df = data.frame(list(key1 = "value1", key2 = "value2"), stringsAsFactors=FALSE)

	df = rbind(df, list(key1 = "value1'", key2 = "value3'"))

	# Dump it into tmp file

	write.table(df, file="/tmp/tmp.dump.table.tmp")

	# Load it into cache using feature.

	# First time it will be load into cache

	print(get_content("/tmp/tmp.dump.table.tmp", "table", stringsAsFactors=FALSE))

	# Second time not

	print(get_content("/tmp/tmp.dump.table.tmp", "table", stringsAsFactors=FALSE))

})

my_read = function(

### Abstract my_read function.	

	obj, ...) {

  UseMethod("my_read", obj)

}

my_read.default = function(

### Default my_read function.	

	obj, ...){

  stop(paste("ERROR, my_read is not defined for any Objects (file ", obj$filename," )", sep=""))			

}

my_read.table = function(

### my_read function for table files.	

	obj, ...){

	if (rev(unlist(strsplit(obj$filename, ".", fixed=TRUE)))[1] == "gz") {

	  return(read.table(file=gzfile(obj$filename), ...))			

	} else { 

	  return(read.table(file=obj$filename, ...))

	}

}	

my_read.csv = function(

### my_read function for cvs files.	

	obj, ...){

  return(read.csv(file=obj$filename, ...))

}