IO::Buffer#copy
static VALUE
io_buffer_copy(int argc, VALUE *argv, VALUE self)
{
rb_check_arity(argc, 1, 4);
struct rb_io_buffer *buffer = NULL;
TypedData_Get_Struct(self, struct rb_io_buffer, &rb_io_buffer_type, buffer);
VALUE source = argv[0];
const void *source_base;
size_t source_size;
rb_io_buffer_get_bytes_for_reading(source, &source_base, &source_size);
VALUE result = io_buffer_copy_from(buffer, source_base, source_size, argc-1, argv+1);
RB_GC_GUARD(source);
return result;
}
Efficiently copy from a source IO::Buffer into the buffer, at offset using memmove. For copying String instances, see set_string.
buffer = IO::Buffer.new(32) # => # #<IO::Buffer 0x0000555f5ca22520+32 INTERNAL> # 0x00000000 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 ................ # 0x00000010 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 ................ * buffer.copy(IO::Buffer.for("test"), 8) # => 4 -- size of buffer copied buffer # => # #<IO::Buffer 0x0000555f5cf8fe40+32 INTERNAL> # 0x00000000 00 00 00 00 00 00 00 00 74 65 73 74 00 00 00 00 ........test.... # 0x00000010 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 ................ *
copy can be used to put buffer into strings associated with buffer:
string = "data: " # => "data: " buffer = IO::Buffer.for(string) do |buffer| buffer.copy(IO::Buffer.for("test"), 5) end # => 4 string # => "data:test"
Attempt to copy into a read-only buffer will fail:
File.write('test.txt', 'test') buffer = IO::Buffer.map(File.open('test.txt'), nil, 0, IO::Buffer::READONLY) buffer.copy(IO::Buffer.for("test"), 8) # in `copy': Buffer is not writable! (IO::Buffer::AccessError)
See ::map for details of creation of mutable file mappings, this will work:
buffer = IO::Buffer.map(File.open('test.txt', 'r+')) buffer.copy(IO::Buffer.for("boom"), 0) # => 4 File.read('test.txt') # => "boom"
Attempt to copy the buffer which will need place outside of buffer’s bounds will fail:
buffer = IO::Buffer.new(2) buffer.copy(IO::Buffer.for('test'), 0) # in `copy': Specified offset+length is bigger than the buffer size! (ArgumentError)
It is safe to copy between memory regions that overlaps each other. In such case, the data is copied as if the data was first copied from the source buffer to a temporary buffer, and then copied from the temporary buffer to the destination buffer.
buffer = IO::Buffer.new(10) buffer.set_string("0123456789") buffer.copy(buffer, 3, 7) # => 7 buffer # => # #<IO::Buffer 0x000056494f8ce440+10 INTERNAL> # 0x00000000 30 31 32 30 31 32 33 34 35 36 0120123456
Ruby version changes
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3.4
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IO::Buffer#copycan release the GVL, allowing other threads to run while copying data. [Feature #20902]
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