| readBin | R Documentation |
Read binary data from or write binary data to a connection or raw vector.
readBin(con, what, n = 1L, size = NA_integer_, signed = TRUE,
endian = .Platform$endian)
writeBin(object, con, size = NA_integer_,
endian = .Platform$endian, useBytes = FALSE)
con |
A connection object or a character string naming a file or a raw vector. |
what |
Either an object whose mode will give the mode of the
vector to be read, or a character vector of length one describing
the mode: one of |
n |
numeric. The (maximal) number of records to be
read. You can use an over-estimate here, but not too large as
storage is reserved for |
size |
integer. The number of bytes per element in the byte
stream. The default, |
signed |
logical. Only used for integers of sizes 1 and 2, when it determines if the quantity on file should be regarded as a signed or unsigned integer. |
endian |
The endian-ness ( |
object |
An R object to be written to the connection. |
useBytes |
See |
These functions can only be used with binary-mode connections.
If con is a character string, the functions call
file to obtain a binary-mode file connection which is
opened for the duration of the function call.
If the connection is open it is read/written from its current position. If it is not open, it is opened for the duration of the call in an appropriate mode (binary read or write) and then closed again. An open connection must be in binary mode.
If readBin is called with con a raw vector, the data in
the vector is used as input. If writeBin is called with
con a raw vector, it is just an indication that a raw vector
should be returned.
If size is specified and not the natural size of the object,
each element of the vector is coerced to an appropriate type before
being written or as it is read. Possible sizes are 1, 2, 4 and
possibly 8 for integer or logical vectors, and 4, 8 and possibly 12/16
for numeric vectors. (Note that coercion occurs as signed types
except if signed = FALSE when reading integers of sizes 1 and 2.)
Changing sizes is unlikely to preserve NAs, and the extended
precision sizes are unlikely to be portable across platforms.
readBin and writeBin read and write C-style
zero-terminated character strings. Input strings are limited to 10000
characters. readChar and writeChar can
be used to read and write fixed-length strings. No check is made that
the string is valid in the current locale's encoding.
Handling R's missing and special (Inf, -Inf and
NaN) values is discussed in the ‘R Data Import/Export’ manual.
Only 2^31 - 1 bytes can be written in a single call (and that is the maximum capacity of a raw vector on 32-bit platforms).
‘Endian-ness’ is relevant for size > 1, and should
always be set for portable code (the default is only appropriate when
writing and then reading files on the same platform).
For readBin, a vector of appropriate mode and length the number of
items read (which might be less than n).
For writeBin, a raw vector (if con is a raw vector) or
invisibly NULL.
Integer read/writes of size 8 will be available if either C type
long is of size 8 bytes or C type long long exists and
is of size 8 bytes.
Real read/writes of size sizeof(long double) (usually 12 or 16
bytes) will be available only if that type is available and different
from double.
If readBin(what = character()) is used incorrectly on a file
which does not contain C-style character strings, warnings (usually
many) are given. From a file or connection, the input will be broken
into pieces of length 10000 with any final part being discarded.
The ‘R Data Import/Export’ manual.
readChar to read/write fixed-length strings.
connections, readLines,
writeLines.
.Machine for the sizes of long, long long
and long double.
zzfil <- tempfile("testbin")
zz <- file(zzfil, "wb")
writeBin(1:10, zz)
writeBin(pi, zz, endian = "swap")
writeBin(pi, zz, size = 4)
writeBin(pi^2, zz, size = 4, endian = "swap")
writeBin(pi+3i, zz)
writeBin("A test of a connection", zz)
z <- paste("A very long string", 1:100, collapse = " + ")
writeBin(z, zz)
if(.Machine$sizeof.long == 8 || .Machine$sizeof.longlong == 8)
writeBin(as.integer(5^(1:10)), zz, size = 8)
if((s <- .Machine$sizeof.longdouble) > 8)
writeBin((pi/3)^(1:10), zz, size = s)
close(zz)
zz <- file(zzfil, "rb")
readBin(zz, integer(), 4)
readBin(zz, integer(), 6)
readBin(zz, numeric(), 1, endian = "swap")
readBin(zz, numeric(), size = 4)
readBin(zz, numeric(), size = 4, endian = "swap")
readBin(zz, complex(), 1)
readBin(zz, character(), 1)
z2 <- readBin(zz, character(), 1)
if(.Machine$sizeof.long == 8 || .Machine$sizeof.longlong == 8)
readBin(zz, integer(), 10, size = 8)
if((s <- .Machine$sizeof.longdouble) > 8)
readBin(zz, numeric(), 10, size = s)
close(zz)
unlink(zzfil)
stopifnot(z2 == z)
## signed vs unsigned ints
zzfil <- tempfile("testbin")
zz <- file(zzfil, "wb")
x <- as.integer(seq(0, 255, 32))
writeBin(x, zz, size = 1)
writeBin(x, zz, size = 1)
x <- as.integer(seq(0, 60000, 10000))
writeBin(x, zz, size = 2)
writeBin(x, zz, size = 2)
close(zz)
zz <- file(zzfil, "rb")
readBin(zz, integer(), 8, size = 1)
readBin(zz, integer(), 8, size = 1, signed = FALSE)
readBin(zz, integer(), 7, size = 2)
readBin(zz, integer(), 7, size = 2, signed = FALSE)
close(zz)
unlink(zzfil)
## use of raw
z <- writeBin(pi^{1:5}, raw(), size = 4)
readBin(z, numeric(), 5, size = 4)
z <- writeBin(c("a", "test", "of", "character"), raw())
readBin(z, character(), 4)
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