library("R.utils") if ("covr" %in% loadedNamespaces()) options("R.utils::onNonSeekable"="warning") # - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - # Create a data file # - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - data <- 1:255 size <- 2 pathname <- tempfile("exampleReadBinFragments") writeBin(con=pathname, data, size=size) # - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - # Read and write using index vectors # - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - cat("Read file...\n") # Read every 16:th byte in the file idxs <- seq(from=1, to=255, by=16) x <- readBinFragments(pathname, what="integer", size=size, signed=FALSE, idxs=idxs) stopifnot(identical(x, data[idxs])) print(x) # Read every 16:th byte in a connection starting with the 6th. idxs <- idxs + 5L x <- readBinFragments(pathname, what="integer", size=size, signed=FALSE, idxs=idxs) stopifnot(identical(x, data[idxs])) print(x) cat("Read file...done\n") cat("Write file...\n") # Update every 16:th byte in the file idxs <- seq(from=1, to=255, by=16) x0 <- data[idxs] writeBinFragments(pathname, idxs=idxs, rev(x0), size=size) x <- readBinFragments(pathname, what="integer", size=size, signed=FALSE, idxs=idxs) print(x) stopifnot(identical(rev(x0), x)) # Update every 16:th byte in the file idxs <- seq(from=1, to=255, by=16) writeBinFragments(pathname, idxs=idxs, rev(x), size=size) x <- readBinFragments(pathname, what="integer", size=size, signed=FALSE, idxs=idxs) print(x) stopifnot(identical(x0, x)) # Assert everything is as expected # Read the complete file x <- readBin(pathname, what="integer", size=size, signed=FALSE, n=length(data)) stopifnot(identical(x, data)) cat("Write file...done\n") # - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - # Ditto but via a connection # - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - cat("Read connection...\n") # Read every 16:th byte in a connection con <- file(pathname, open="rb") idxs <- seq(from=1, to=255, by=16) x <- readBinFragments(con, what="integer", size=size, signed=FALSE, idxs=idxs) stopifnot(identical(x, data[idxs])) print(x) # Read every 16:th byte in a connection starting with the 6th. idxs <- idxs + 5L x <- readBinFragments(con, what="integer", size=size, signed=FALSE, idxs=idxs, origin="start") stopifnot(identical(x, data[idxs])) print(x) close(con) cat("Read connection...done\n") # Update every 16:th byte in a connection cat("Write connection...\n") con <- file(pathname, open="r+b") idxs <- seq(from=1, to=255, by=16) x0 <- data[idxs] writeBinFragments(pathname, idxs=idxs, rev(x0), size=size) x <- readBinFragments(pathname, what="integer", size=size, signed=FALSE, idxs=idxs) print(x) stopifnot(identical(rev(x0), x)) # Update every 16:th byte in the file idxs <- seq(from=1, to=255, by=16) writeBinFragments(pathname, idxs=idxs, rev(x), size=size) x <- readBinFragments(pathname, what="integer", size=size, signed=FALSE, idxs=idxs, origin="start") print(x) stopifnot(identical(x0, x)) close(con) # Assert everything is as expected # Read the complete file x <- readBin(pathname, what=integer(), size=size, signed=FALSE, n=length(data)) stopifnot(identical(x, data)) cat("Write connection...done\n") # Read bytes 1-4, 11-14, 21-24, ... idxs <- seq(from=1, to=255, by=10) idxs <- cbind(idxs, idxs+3) x <- readBinFragments(pathname, what="integer", size=size, signed=FALSE, idxs=idxs, verbose=TRUE) idxsX <- intervalsToSeq(idxs) stopifnot(identical(x, data[idxsX])) print(x) # - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - # Clean up # - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - file.remove(pathname)