file_modification_time_cache: Create function for operating on disk files with caching

In zzawadz/rawk: Utils for Text Manipulation.

Description

Create function which cache result based on file. If file will be changed, function will also be recalculated, otherwise cached value will be returned

Usage

file_modification_time_cache(fnc)

Arguments

fnc	function that operates on file (first argument must be path to file).

Value

Return new function with caching functionality

Examples

fnc <- function(file) {
   n <- as.numeric(readLines(file, warn = FALSE))
   rnorm(n)
}

file <- tempfile()
cat(5, file = file)
all.equal(fnc(file), fnc(file))

fcached <- file_modification_time_cache(fnc)

all.equal(fcached(file), fcached(file))

x <- fcached(file)

cat(5, file = file)
y <- fcached(file)
all.equal(x, y)

fnc2 <- function(file, k = 2) {
   n <- as.numeric(readLines(file, warn = FALSE))
   rnorm(n * k)
}

fcached2 <- file_modification_time_cache(fnc2)
all.equal(fcached2(file,1), fcached2(file,1))
all.equal(fcached2(file,1), fcached2(file,2))

zzawadz/rawk documentation built on May 5, 2019, 3:48 a.m.