♻️ Refactor: use c.app.getString instead of string(...)

[ghost]

Description

I noticed 2 functions (those being GetReqHeaders and GetRespHeaders) use string(...) instead of c.app.getString to convert a byte array to a string

c.Request().Header.VisitAll(func(k, v []byte) {
	headers[string(k)] = c.app.getString(v)
})

c.Response().Header.VisitAll(func(k, v []byte) {
	headers[string(k)] = c.app.getString(v)
})

Using c.app.getString is around 16-19% faster, and allocates less. (See benchmark spreadsheets below. Both c.app.getString, and string(...) was tested on both functions, 100 times.)

Benchmark result for using string(...) on GetReqHeaders: GetReqHeaders.xlsx
(Average 1,756,668 Iterations, 700 ns/op, 357 B/op, 5 allocs/op)

Benchmark result for using c.app.getString on GetReqHeaders: GetReqHeadersNew.xlsx
(Average 2,164,354 Iterations, 567 ns/op, 336 B/op, 2 allocs/op)

Benchmark result for using string(...) on GetRespHeaders: GetRespHeaders.xlsx
(Average 1,823,697 Iterations, 678 ns/op, 357 B/op, 5 allocs/op)

Benchmark result for using c.app.getString on GetRespHeaders: GetRespHeadersNew.xlsx
(Average 2,176,443 Iterations, 564 ns/op, 336 B/op, 2 allocs/op)

Type of change

• Bug fix (non-breaking change which fixes an issue)

Checklist:

• I have performed a self-review of my own code
• New and existing unit tests pass locally with my changes
• I tried to make my code as fast as possible with as few allocations as possible

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[ReneWerner87]

thx, good found

[sadfun]

Hmmm. @ReneWerner87, func (h *RequestHeader) VisitAll(f func(key, value []byte)) literally says:

// f must not retain references to key and/or value after returning.
// Copy key and/or value contents before returning if you need retaining them.

But by calling c.app.getString, which is unsafe.String(unsafe.SliceData(b), len(b)) by default, we are making reference to key's byte slice 💀

[ReneWerner87]

yes i know, that's why the instructions for copying are also in our documentation and methods when they are used

so that one makes a copy for the value, if one would like to use these data over the request/response expiration further