instance method
IO::Buffer#pread
(untyped, untyped, untyped) -> untyped
pread(io, from, [length, [offset]]) → read length or -errno
io_buffer.c
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static VALUE
io_buffer_pread(int argc, VALUE *argv, VALUE self)
{
rb_check_arity(argc, 2, 4);
VALUE io = argv[0];
rb_off_t from = NUM2OFFT(argv[1]);
size_t length, offset;
io_buffer_extract_length_offset(self, argc-2, argv+2, &length, &offset);
return rb_io_buffer_pread(self, io, from, length, offset);
}
Read at least length bytes from the io starting at the specified from position, into the buffer starting at offset. If an error occurs, return -errno.
If length is not given or nil, it defaults to the size of the buffer minus the offset, i.e. the entire buffer.
If length is zero, exactly one pread operation will occur.
If offset is not given, it defaults to zero, i.e. the beginning of the buffer.
Example
IO::Buffer.for('test') do |buffer| p buffer # => # <IO::Buffer 0x00007fca40087c38+4 SLICE> # 0x00000000 74 65 73 74 test # take 2 bytes from the beginning of urandom, # put them in buffer starting from position 2 buffer.pread(File.open('/dev/urandom', 'rb'), 0, 2, 2) p buffer # => # <IO::Buffer 0x00007f3bc65f2a58+4 EXTERNAL SLICE> # 0x00000000 05 35 73 74 te.5 end