[lib] str_stack: A string allocation library

str_stack is a string allocation library for allocating many temporally correlated write-once strings. This is useful when you need to e.g. read a set of small files into strings but don't want to allocate a new string per file. Additionally, this library provides great cache locality.

Currently, the performance (on my laptop) is as follows:

  • Allocation: ~2.5x speedup (for 1000 strings) (~42ns per string)
  • Indexing: 0.73x speedup (slower) (~1.7ns per index)
  • Iterate: 0.35x speedup (much slower) (~1ns per iteration)

It should be possible to further speedup allocation (see the open issue) but speeding up indexing/iteration are beyond me.

I'll put it on crates.io if people find it useful but, for now, I don't even know if this is the right approach.

You're the first one I see to use the ducktypiness of the write!() macro, and that explains why I was so confused when I saw it used on a string stack. It's a cute experiment, only experience will tell if it's a good idea.

You can use format_args!() to do kind of the same thing without punning the write_fmt method name. Maybe that's just as cryptic though:

stack.write(format_args!("Hello {}", "World"));

You can do that now:

stack.write_fmt(format_args!("Hello {}", "World"));

(that's literally all the write macro does)

However, I hate format_args!() with a burning passion. It puts stuff on the stack which has given me endless grief before.

Interesting! Have you considered inlining the lens using the XOR linked list trick? In this case you can just use addition instead of xor.

So your array would look like:

[a.len, a, a.len + b.len, b, b.len + c.len, c, c.len]



where the numbers between take up a usize of bytes.

Easy to add/remove to the end, and no need for multiple allocations!

Also, double-ended iteration!

But really slow indexing. My current plan is to use two inward growing stacks:

[a, b, c, d, ............, d_end, c_end, b_end, a_end, a_start (0)]

(including a_start makes some of the indexing/iteration logic simpler)