Data.Text.Internal.Encoding

Warning: this is an internal module, and does not have a stable API or name. Functions in this module may not check or enforce preconditions expected by public modules. Use at your own risk!

Internals of Data.Text.Encoding.

Since: 2.0.2

Documentation

validateUtf8Chunk :: ByteString -> (Int, Maybe Utf8State)

Validate a ByteString as UTF-8-encoded text. To be continued using validateUtf8More.

See also validateUtf8More for details on the result of this function.

validateUtf8Chunk = validateUtf8More startUtf8State

Properties

Given:

validateUtf8Chunk chunk = (n, ms)

• The prefix is valid UTF-8. In particular, it should be accepted by this validation:

  validateUtf8Chunk (take n chunk) = (n, Just startUtf8State)
  

validateUtf8More :: Utf8State -> ByteString -> (Int, Maybe Utf8State)

Validate another ByteString chunk in an ongoing stream of UTF-8-encoded text.

Returns a pair:

1. The first component n is the end position, relative to the current chunk, of the longest prefix of the accumulated bytestring which is valid UTF-8. n may be negative: that happens when an incomplete code point started in a previous chunk and is not completed by the current chunk (either that code point is still incomplete, or it is broken by an invalid byte).

2. The second component ms indicates the following:

   • if ms = Nothing, the remainder of the chunk contains an invalid byte, within four bytes from position n;
   • if ms = Just s', you can carry on validating another chunk by calling validateUtf8More with the new state s'.

Properties

Given:

validateUtf8More s chunk = (n, ms)

• If the chunk is invalid, it cannot be extended to be valid.

  ms = Nothing
  ==> validateUtf8More s (chunk <> more) = (n, Nothing)
  

• Validating two chunks sequentially is the same as validating them together at once:

  ms = Just s'
  ==> validateUtf8More s (chunk <> more) = first (length chunk +) (validateUtf8More s' more)
  

decodeUtf8Chunk :: ByteString -> (StrictBuilder, ByteString, Maybe Utf8State)

Decode a chunk of UTF-8 text. To be continued with decodeUtf8More.

See decodeUtf8More for details on the result.

Properties

decodeUtf8Chunk = decodeUtf8More startUtf8State

Given:

decodeUtf8Chunk chunk = (builder, rest, ms)

builder is a prefix and rest is a suffix of chunk.

encodeUtf8 (strictBuilderToText builder) <> rest = chunk

Since: 2.0.2

decodeUtf8More :: Utf8State -> ByteString -> (StrictBuilder, ByteString, Maybe Utf8State)

Decode another chunk in an ongoing UTF-8 stream.

Returns a triple:

1. A StrictBuilder for the decoded chunk of text. You can accumulate chunks with (<>) or output them with toText.
2. The undecoded remainder of the given chunk, for diagnosing errors and resuming (presumably after skipping some bytes).
3. Just the new state, or Nothing if an invalid byte was encountered (it will be within the first 4 bytes of the undecoded remainder).

Properties

Given:

(pre, suf, ms) = decodeUtf8More s chunk

1. If the output pre is nonempty (alternatively, if length chunk > length suf)

   s2b pre `append` suf = p2b s `append` chunk
   

   where

   s2b = encodeUtf8 . toText
   p2b = partUtf8ToByteString
   

2. If the output pre is empty (alternatively, if length chunk = length suf)

   suf = chunk

3. Decoding chunks separately is equivalent to decoding their concatenation.

   Given:

   (pre1, suf1, Just s1) = decodeUtf8More s chunk1
   (pre2, suf2,     ms2) = decodeUtf8More s1 chunk2
   (pre3, suf3,     ms3) = decodeUtf8More s (chunk1 `B.append` chunk2)
   

   we have:

   s2b (pre1 <> pre2) = s2b pre3
   ms2 = ms3
   

decodeUtf8With1 :: OnDecodeError -> String -> ByteString -> Text

Helper for decodeUtf8With.

Since: 2.0.2

decodeUtf8With2 :: OnDecodeError -> String -> Utf8State -> ByteString -> (StrictBuilder, ByteString, Utf8State)

Helper for decodeUtf8With, streamDecodeUtf8With, and lazy decodeUtf8With, which use an OnDecodeError to process bad bytes.

See decodeUtf8Chunk for a more flexible alternative.

Since: 2.0.2

data Utf8State

State of decoding a ByteString in UTF-8. Enables incremental decoding (validateUtf8Chunk, validateUtf8More, decodeUtf8Chunk, decodeUtf8More).

Since: 2.0.2

Instances

Show Utf8State

Defined in Data.Text.Internal.Encoding

Methods

showsPrec :: Int -> Utf8State -> ShowS

show :: Utf8State -> String

showList :: [Utf8State] -> ShowS

Eq Utf8State

Defined in Data.Text.Internal.Encoding

Methods

(==) :: Utf8State -> Utf8State -> Bool

(/=) :: Utf8State -> Utf8State -> Bool

startUtf8State :: Utf8State

Initial Utf8State.

Since: 2.0.2

data StrictBuilder

A delayed representation of strict Text.

Since: 2.0.2

Instances

Monoid StrictBuilder

Defined in Data.Text.Internal.StrictBuilder

Methods

mempty :: StrictBuilder

mappend :: StrictBuilder -> StrictBuilder -> StrictBuilder

mconcat :: [StrictBuilder] -> StrictBuilder

Semigroup StrictBuilder

Concatenation of StrictBuilder is right-biased: the right builder will be run first. This allows a builder to run tail-recursively when it was accumulated left-to-right.

Defined in Data.Text.Internal.StrictBuilder

Methods

(<>) :: StrictBuilder -> StrictBuilder -> StrictBuilder

sconcat :: NonEmpty StrictBuilder -> StrictBuilder

stimes :: Integral b => b -> StrictBuilder -> StrictBuilder

strictBuilderToText :: StrictBuilder -> Text

Use StrictBuilder to build Text.

Since: 2.0.2

textToStrictBuilder :: Text -> StrictBuilder

Copy Text in a StrictBuilder

Since: 2.0.2

Internal

skipIncomplete :: OnDecodeError -> String -> Utf8State -> StrictBuilder

Call the error handler on each byte of the partial code point stored in Utf8State and append the results.

Exported for use in lazy decodeUtf8With.

Since: 2.0.2

getCompleteLen :: Utf8State -> Int

Exported for testing.

getPartialUtf8 :: Utf8State -> ByteString

Exported for testing.