Data.Text.Internal.Encoding

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)
  

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)
  

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 (Data.Text.Encoding.strictBuilderToText builder) <> rest = chunk

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
   

Helper for decodeUtf8With.

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

See decodeUtf8Chunk for a more flexible alternative.

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

Initial Utf8State.

A delayed representation of strict Text.

A delayed representation of strict Text.

Use StrictBuilder to build Text.

Copy Text in a 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.

Exported for testing.

Exported for testing.