GHC.Data.StringBuffer

ghc-lib-parser-9.14.1.20251220: The GHC API, decoupled from GHC versions

Safe Haskell | Ignore
Language | GHC2021

GHC.Data.StringBuffer

Contents

- Creation/destruction
- Inspection
- Moving and comparison
- Conversion
- Parsing integers
- Checking for bi-directional format characters

Synopsis

- data StringBuffer = StringBuffer {
  - buf :: !(ForeignPtr Word8)
  - len :: !Int
  - cur :: !Int
  }
- hGetStringBuffer :: FilePath -> IO StringBuffer
- hGetStringBufferBlock :: Handle -> Int -> IO StringBuffer
- hPutStringBuffer :: Handle -> StringBuffer -> IO ()
- appendStringBuffers :: StringBuffer -> StringBuffer -> IO StringBuffer
- stringToStringBuffer :: String -> StringBuffer
- stringBufferFromByteString :: ByteString -> StringBuffer
- nextChar :: StringBuffer -> (Char, StringBuffer)
- currentChar :: StringBuffer -> Char
- prevChar :: StringBuffer -> Char -> Char
- atEnd :: StringBuffer -> Bool
- fingerprintStringBuffer :: StringBuffer -> Fingerprint
- stepOn :: StringBuffer -> StringBuffer
- offsetBytes :: Int -> StringBuffer -> StringBuffer
- byteDiff :: StringBuffer -> StringBuffer -> Int
- atLine :: Int -> StringBuffer -> Maybe StringBuffer
- lexemeToString :: StringBuffer -> Int -> String
- lexemeToFastString :: StringBuffer -> Int -> FastString
- decodePrevNChars :: Int -> StringBuffer -> String
- parseUnsignedInteger :: StringBuffer -> Int -> Integer -> (Char -> Int) -> Integer
- findHashOffset :: StringBuffer -> Int
- containsBidirectionalFormatChar :: StringBuffer -> Bool
- bidirectionalFormatChars :: [(Char, String)]

# Documentation

data StringBuffer #

A StringBuffer is an internal pointer to a sized chunk of bytes. The bytes are intended to be *immutable*. There are pure operations to read the contents of a StringBuffer.

A StringBuffer may have a finalizer, depending on how it was obtained.

Constructors

StringBuffer |
Fields buf :: !(ForeignPtr Word8) len :: !Int cur :: !Int

#### Instances

Instances details

Show StringBuffer # |
Instance details Defined in GHC.Data.StringBuffer Methods showsPrec :: Int -> StringBuffer -> ShowS # show :: StringBuffer -> String # showList :: [StringBuffer] -> ShowS #

# Creation/destruction

hGetStringBuffer :: FilePath -> IO StringBuffer #

Read a file into a `StringBuffer`. The resulting buffer is automatically managed by the garbage collector.

hGetStringBufferBlock :: Handle -> Int -> IO StringBuffer #

hPutStringBuffer :: Handle -> StringBuffer -> IO () #

appendStringBuffers :: StringBuffer -> StringBuffer -> IO StringBuffer #

stringToStringBuffer :: String -> StringBuffer #

Encode a `String` into a `StringBuffer` as UTF-8. The resulting buffer is automatically managed by the garbage collector.

stringBufferFromByteString :: ByteString -> StringBuffer #

Convert a UTF-8 encoded `ByteString` into a 'StringBuffer. This really relies on the internals of both `ByteString` and `StringBuffer`.

O(n) (but optimized into a `memcpy` by `bytestring` under the hood)

# Inspection

nextChar :: StringBuffer -> (Char, StringBuffer) #

Return the first UTF-8 character of a nonempty `StringBuffer` and as well the remaining portion (analogous to `uncons`). Warning: The behavior is undefined if the `StringBuffer` is empty. The result shares the same buffer as the original. Similar to `utf8DecodeChar`, if the character cannot be decoded as UTF-8, `'\0'` is returned.

currentChar :: StringBuffer -> Char #

Return the first UTF-8 character of a nonempty `StringBuffer` (analogous to `head`). Warning: The behavior is undefined if the `StringBuffer` is empty. Similar to `utf8DecodeChar`, if the character cannot be decoded as UTF-8, `'\0'` is returned.

prevChar :: StringBuffer -> Char -> Char #

atEnd :: StringBuffer -> Bool #

Check whether a `StringBuffer` is empty (analogous to `null`).

fingerprintStringBuffer :: StringBuffer -> Fingerprint #

Computes a hash of the contents of a `StringBuffer`.

# Moving and comparison

stepOn :: StringBuffer -> StringBuffer #

Return a `StringBuffer` with the first UTF-8 character removed (analogous to `tail`). Warning: The behavior is undefined if the `StringBuffer` is empty. The result shares the same buffer as the original.

offsetBytes #

Arguments

:: Int | `n`, the number of bytes
-> StringBuffer |
-> StringBuffer |

Return a `StringBuffer` with the first `n` bytes removed. Warning: If there aren't enough characters, the returned `StringBuffer` will be invalid and any use of it may lead to undefined behavior. The result shares the same buffer as the original.

byteDiff :: StringBuffer -> StringBuffer -> Int #

Compute the difference in offset between two `StringBuffer`s that share the same buffer. Warning: The behavior is undefined if the `StringBuffer`s use separate buffers.

atLine :: Int -> StringBuffer -> Maybe StringBuffer #

Computes a `StringBuffer` which points to the first character of the wanted line. Lines begin at 1.

# Conversion

lexemeToString #

Arguments

:: StringBuffer |
-> Int | `n`, the number of bytes
-> String |

Decode the first `n` bytes of a `StringBuffer` as UTF-8 into a `String`. Similar to `utf8DecodeChar`, if the character cannot be decoded as UTF-8, they will be replaced with `'\0'`.

lexemeToFastString #

Arguments

:: StringBuffer |
-> Int | `n`, the number of bytes
-> FastString |

decodePrevNChars :: Int -> StringBuffer -> String #

Return the previous `n` characters (or fewer if we are less than `n` characters into the buffer.

# Parsing integers

parseUnsignedInteger :: StringBuffer -> Int -> Integer -> (Char -> Int) -> Integer #

findHashOffset :: StringBuffer -> Int #

Find the offset of the `#` character in the StringBuffer.

Make sure that it contains one before calling this function!

# Checking for bi-directional format characters

containsBidirectionalFormatChar :: StringBuffer -> Bool #

Returns true if the buffer contains Unicode bi-directional formatting characters.

https://www.unicode.org/reports/tr9/#Bidirectional_Character_Types

Bidirectional format characters are one of 'x202a' : "U+202A LEFT-TO-RIGHT EMBEDDING (LRE)" 'x202b' : "U+202B RIGHT-TO-LEFT EMBEDDING (RLE)" 'x202c' : "U+202C POP DIRECTIONAL FORMATTING (PDF)" 'x202d' : "U+202D LEFT-TO-RIGHT OVERRIDE (LRO)" 'x202e' : "U+202E RIGHT-TO-LEFT OVERRIDE (RLO)" 'x2066' : "U+2066 LEFT-TO-RIGHT ISOLATE (LRI)" 'x2067' : "U+2067 RIGHT-TO-LEFT ISOLATE (RLI)" 'x2068' : "U+2068 FIRST STRONG ISOLATE (FSI)" 'x2069' : "U+2069 POP DIRECTIONAL ISOLATE (PDI)"

This list is encoded in `bidirectionalFormatChars`

bidirectionalFormatChars :: [(Char, String)] #