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Bug #15210

Updated by nobu (Nobuyoshi Nakada) 6 months ago

Hi everyone working on the ruby trunk,

I encountered a problem with a BOM (Byte Order Mark) at the front of UTF-8 string data.

We import some CSV from paypal.
They now include a BOM in front of their UTF-8 encoded CSV data.
This BOM is making some troubles.

I believe this to be a bug in how byte data is converted to the ruby internal String representation.

There is a workaround, but this needs to be documented:
```ruby
IO.read(mode:'r:BOM|UTF-8')
```

`IO.read(mode:'r:BOM|UTF-8')`


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But I'm asking for to improve the UTF-BOM handling:
- The BOM is only used for transfer encoding at the byte stream level.
- The BOM MUST NOT be part of the String in internal representation.

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BTW: stdlib::CSV chokes on the BOM

I'd like to add some code for a workaround:

```ruby
class
`class String

# delete UTF Byte Order Mark from string
# returns self (even if no bom was found, contrary to delete_prefix!)
# NOTE: use with care: better remove the bom when reading the file
def delete_bom!
raise 'encoding is not UTF-8' unless self.encoding == Encoding::UTF_8
delete_prefix!("\xEF\xBB\xBF")
return self
end

# returns a copy of string with UTF Byte Order Mark deleted from string
def delete_bom
dup.delete_bom!
end

end
```


`


---
~eike

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