How to pass strings to FFI | Bun | Page 1

slate hamlet Oct 25, 2023, 7:07 PM

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Do I have to manually allocate an ArrayBuffer and encode as utf-8 with TextEncoder? Seems odd to me that you can't construct a CString from a regular js string and use that.
Either way, would be nice to have some examples of this in the docs :)

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Oh, guess I forgot how TextEncoder works, it allocates the buffer for you. That makes it nicer :)

urban spear Oct 25, 2023, 7:11 PM

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yeah you convert it to format expected by function and pass it as pointer

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the only important thing is to make sure buffer stays alive while ptr is in use

slate hamlet Oct 25, 2023, 7:13 PM

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Since there's a few footguns here (ensuring null-termination, keeping the buffer alive if C retains the pointer, etc.) I think it'd be worth having a section in the docs

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I'll make an issue for that

urban spear Oct 25, 2023, 7:14 PM

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null termination is only needed if you use it as c string

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which is not recommended if possible

slate hamlet Oct 25, 2023, 7:14 PM

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ofc, but some APIs require null termination

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It's common enough to be worth mentioning

urban spear Oct 25, 2023, 7:15 PM

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yeah that’s the if possible part

crisp dragon Oct 26, 2023, 3:57 AM

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i agree the docs should clarify this

also kinda wish string handling could be better in general

urban spear Oct 26, 2023, 4:43 AM

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there is no better way to do it than make user hardcode behavior they need

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it’s cheaper to add zero to rope in js than make whole ffi pad every string after turning rope into string

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not to mention currently utf8 simd doesn’t return zero padded strings

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one qol thing we could add is TextEncoder() that returns managed pointers

#How to pass strings to FFI