buffer copy with overlapping regions

[redchair123]

The documentation merely says:

The source and target regions can be overlapped.

What is the expected behavior in this case? Experimentally, the line buf.copy(buf, targetStart, sourceStart, sourceEnd) appears to be roughly equivalent to for(var i = sourceEnd - sourceStart; i > 0; --i) buf[targetStart + i - 1] = buf[sourceStart + i - 1];, but the documentation is unclear.

[jasnell]

Unfortunately looking at the source doesn't make this one any clearer. Definitely appears to be a straightforward documentation bug. The expected behavior is just that buf1[sourceStart...sourceEnd] is copied to buf1[targetStart...n], where n depends on a number of factors. The sentence about regions being overlapped just adds unnecessary confusion.

[bjouhier]

buffer.copy is implemented with memmove rather than memcpy. See https://github.com/joyent/node/blob/master/src/node_buffer.cc#L336 and http://stackoverflow.com/questions/1201319/what-is-the-difference-between-memmove-and-memcpy

[jasnell]

Ah yes... completely overlooked that one the first time through. It would definitely be a good thing to call that out a bit more explicitly in the docs then.