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# Feature name
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# buffer.swap(b: buffer, x: number, y: number, range: number?)
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## Summary
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One paragraph explanation of the feature.
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`buffer.swap(b, x, y, range?)` swaps a variable `range(?=1)` of bytes stored at offsets `x` and `y` of buffer `b`
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## Motivation
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Why are we doing this? What use cases does it support? What is the expected outcome?
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The absence of a byte-range-swap function implies that for any variable range of bytes that need to be swapped, these bytes would have to be normalized as strings (see *Design*), *then* written back into the buffer. Although the implementation works, it would make more sense to have a buffer function that interally manipulates the desired offsets/range of bytes instead of the provided method where the byte ranges are interpreted as strings to achieve the same result
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In short, the current swap implementation has a string "layer" (unneccessary complexity/operations/conversions? (conjecture)), whereas the proposal for `buffer.swap( ... )` internally manipulates the byte ranges without any string interpretations etc.
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## Design
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This is the bulk of the proposal. Explain the design in enough detail for somebody familiar with the language to understand, and include examples of how the feature is used.
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An example of a `buffer.swap( ... )` implementation for any `range` range of bytes:
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```lua
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--- swaps range of bytes stored at offsets `x` and `y` \
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--- `range (?=1)` range of bytes to swap
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local function swap(b: buffer, x: number, y: number, range: number?)
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local z = buffer.readstring(b, x, range or 1)
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buffer.writestring(b, x, buffer.readstring(b, y, range or 1))
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buffer.writestring(b, y, z)
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end
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local b = buffer.create(8) --- create 8-width buffer
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buffer.writef32(b, 0, math.pi) --- store 3.14... at 0
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buffer.writef32(b, 4, 2*math.pi) --- store 6.28... at 4
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swap(b, 0, 4, 4) --- buffer.swap(b, 0, 4, 4)
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print(buffer.readf32(b, 0)) --- 6.28... is now at 0
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print(buffer.readf32(b, 4)) --- 3.14... is now at 4
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```
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## Drawbacks
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Why should we *not* do this?
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Real use-cases may be sparse, where this rfc could be interpreted as having added bloat to the buffer library
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## Alternatives
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What other designs have been considered? What is the impact of not doing this?
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`is:pr is:open buffer.swap` search query on `/luau-lang/rfcs/pulls` returns no results
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`buffer.swap[u/i/f/string/...][8/16/32/64/...](b, x, y, range?)` (a case for each buffer type) was initially considered but that would very quickly become a nightmare for managing code. The provided working implementation is shown because (despite normalizing bytes as strings) it most-closely represents the goal of this rfc
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