tests/readBinFragments.R

In R.utils: Various Programming Utilities

library("R.utils")

if ("covr" %in% loadedNamespaces())
  options("R.utils::onNonSeekable"="warning")

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# Create a data file
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data <- 1:255
size <- 2
pathname <- tempfile("exampleReadBinFragments")
writeBin(con=pathname, data, size=size)


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# Read and write using index vectors
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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")


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# Ditto but via a connection
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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)

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# Clean up
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file.remove(pathname)