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doc: clarify behavior of byteLength with 'base64' #11238

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Feb 9, 2017
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doc: clarify behavior of byteLength with 'base64' #11238

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4 changes: 4 additions & 0 deletions doc/api/buffer.md
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Expand Up @@ -618,6 +618,10 @@ Returns the actual byte length of a string. This is not the same as
[`String.prototype.length`] since that returns the number of *characters* in
a string.

*Note* that for `'base64'` and `'hex'`, this function assumes valid input. For
strings that contain non-Base64/Hex-encoded data (e.g. whitespace), the return
value might be greater than the length of a `Buffer` created from the string.
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The return value could be smaller too (e.g. Buffer.byteLength('1345 4 ', 'hex') === 3, Buffer.from('1345 4 ').byteLength === 7), but then since the data is invalid it's just hard to say. Maybe just say something like the return value is meaningless and should not be used?

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Hmm, wait, I forgot to pass hex to Buffer.from('1345 4 '), that one would just throws TypeError: Invalid hex string, so there is nothing to compare :/

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Yeah, logically there is no way for it to be smaller. That would imply that you can encode more data by using an invalid string than a valid string.

It's not completely meaningless - e.g. if you allocate a Buffer with the size at least Buffer.byteLength, then the actual buffer will fit in it. Although I can't imagine a use case for it.


Example:

```js
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