readbytes!
readbytes!(stream, b::Vector{UInt8}, nb=length(b); all=true)
Read at most nb bytes from the stream into b, returning the number of bytes read (increasing the size of b as needed).
See readbytes for a description of the all option.
Examples
In the Julia programming language, the function readbytes!(stream, b::Vector{UInt8}, nb=length(b); all=true)
Read at most nb bytes from the stream into b, modifying b in-place, and return the number of bytes read. The size of b will be increased as needed to accommodate the read bytes.
julia> io = IOBuffer("Hello, world!")
IOBuffer(data=UInt8[...], readable=true, writable=false, seekable=true, append=false, size=13, maxsize=Inf, ptr=1, mark=-1)
julia> bytes = Vector{UInt8}(undef, 5)
5-element Array{UInt8,1}:
0x00
0x00
0x00
0x00
0x00
julia> readbytes!(io, bytes, 5)
5
julia> bytes
5-element Array{UInt8,1}:
0x48
0x65
0x6c
0x6c
0x6fHere are some common examples of its use:
-
Read bytes from an
IOStream:julia> io = IOBuffer("Hello, Julia!") IOBuffer(data=UInt8[...], readable=true, writable=false, seekable=true, append=false, size=13, maxsize=Inf, ptr=1, mark=-1) julia> bytes = Vector{UInt8}(undef, 7) 7-element Array{UInt8,1}: 0x00 0x00 0x00 0x00 0x00 0x00 0x00 julia> readbytes!(io, bytes, 7) 7 julia> bytes 7-element Array{UInt8,1}: 0x48 0x65 0x6c 0x6c 0x6f 0x20 0x4a -
Read a specific number of bytes from a file:
julia> file = open("data.bin", "r") IOStream(<file data.bin>) julia> bytes = Vector{UInt8}(undef, 10) 10-element Array{UInt8,1}: 0x00 0x00 0x00 0x00 0x00 0x00 0x00 0x00 0x00 0x00 julia> readbytes!(file, bytes, 10) 10 julia> bytes 10-element Array{UInt8,1}: 0x01 0x02 0x03 0x04 0x05 0x06 0x07 0x08 0x09 0x0a julia> close(file)
Common mistake example:
julia> io = IOBuffer("Hello, Julia!")
IOBuffer(data=UInt8[...], readable=true, writable=false, seekable=true, append=false, size=13, maxsize=Inf, ptr=1, mark=-1)
julia> bytes = Vector{UInt8}(undef, 10)
10-element Array{UInt8,1}:
0x00
0x00
0x00
0x00
0x00
0x00
0x00
0x00
0x00
0x00
julia> readbytes!(io, bytes, 15)
ERROR: MethodError: no method matching readbytes!(::IOBuffer, ::Array{UInt8,1}, ::Int64)In this example, the nb argument is set to a value larger than the available bytes in the stream. It's important to ensure that nb is within the valid range to avoid such errors.
See Also
deserialize, eachline, eof, fd, flush, IOBuffer, ismarked, isopen, isreadonly, mark, nb_available, open, pipeline, position, read, read!, readavailable, readbytes, readbytes!, readline, redirect_stderr, redirect_stdin, reset, seek, seekend, seekstart, serialize, skip, skipchars, TextDisplay, unmark, write, writemime,User Contributed Notes
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