Good C code will try to avoid allocations as much as possible in the first place. You absolutely don’t need to copy strings around when handling a request. You can read data from the socket in a fixed-size buffer, do all the processing in-place, and then process the next chunk in-place too. You get predictable performance and the thing will work like precise clockwork. Reading the entire thing just to copy the body o…
Can you do parsing of JSON and XML without allocating?
Yes, you can first validate the buffer, to know it contains valid JSON, and then you can work with pointers to beginings of individual syntactic parts of JSON, and have functions that decide what type of the current element is, or move to the next element, etc. Even string work (comparisons with other escaped or unescaped strings, etc.) can be done on escaped strings directly without unescaping them to a buffer first.
Ergonomically, it's pretty much the same as parsing the JSON into some AST first, and then working on the AST. And it can be much faster than dumb parsers that use malloc for individual AST elements.
You can even do JSON path queries on top of this, without allocations.