Usage
## S3 method for class 'default}(con, what, idxs=1, size=NA, ..., verbose=FALSE)':
readBinFragmentsundefined
Reads binary data from disjoint sections of a connection or a file.
- con
{A connection
or the pathname of an existing file.}
- what
{A character
string or an object specifying the the
data type (mode
()) to be read.}
- idxs
{A vector
of (non-duplicated) indices or a Nx2 matrix
of N from-to index intervals specifying the elements to be read.}
- size
{The size of the data type to be read. If NA
, the natural
size of the data type is used.}
- ...
{Additional arguments passed to readBin
().}
- verbose
{A logical
or a Verbose
object.}
Returns a vector
of the requested mode
().
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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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# 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)
# Update every 16:th byte in the file
x0 <- x
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(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))
# Read the complete file
x <- readBin(pathname, what="integer", size=size, signed=FALSE, n=length(data))
stopifnot(identical(x, data))
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# Clean up
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file.remove(pathname)
[object Object]
writeBinFragments
().
IO