[dicroce]

At least in the implementation I wrote the default way to provide the body was a string... which has a length. For binary data I believe the API could accept either a std::vector<uint8_t> (which has a size) or a pointer and a size. If you needed chunked transfer encoding you had to ask for it and then make repeated calls to write chunks (that each have a fixed length).

To me the more interesting question is how web server receive an incoming request. You want to be able to read the whole thing into a single buffer, but you don't know how long its going to be until you actually read some of it. I learned recently that libc has a way to "peek" at some data without removing it from the recv buffer..... I'm curious if this is ever used to optimize the receive process?

[mikepurvis]

Not sure about Linux, but for LwIP on embedded, the buffer isn’t continuous; it’s a linked list of preallocated pbuf objects. So you can either read directly from those if you play by their rules or if you really do need it in contiguous memory you call a function to copy from LwIP’s buffers to one you supply.