purescript-parsing-dataview
Primitive parsers for parsing
DataViews on Javascript ArrayBuffers with the package
purescript-parsing.
With this package, the input stream support of purescript-parsing roughly matches the built-in stream support of Megaparsec:
| Stream type | purescript-parsing | Megaparsec |
|---|---|---|
| UTF-16 strings | String | Text |
| Listy strings | Token | String |
| Binary blobs | DataView | ByteString |
Usage examples
Parse values out of a dataview :: Data.ArrayBuffer.Types.DataView. All
DataView parsing must be done in an Effect context. The result will be
Either a parse error or the parsed value.
Parse two numbers
Parse two big-endian IEEE 754 double-precision floats.
do
result <- Text.Parsing.Parser.runParserT dataview $ do
float1 <- anyFloat64be
float2 <- anyFloat64be
pure $ Tuple float1 float2Parse an array
Parse an array of n 32-bit signed integers.
do
result <- Text.Parsing.Parser.runParserT dataview $ replicateA n anyInt32beParse UTF8
Parse a String as UTF8 with a length prefix.
We give this as an example, rather than supporting it in the library, because
it depends on
Data.TextDecoding.decodeUtf8.
mkTypedArray :: Data.ArrayBuffer.Types.DataView -> Effect Data.ArrayBuffer.Types.Uint8Array
mkTypedArray dv = do
let buffer = Data.ArrayBuffer.DataView.buffer dv
byteOffset = Data.ArrayBuffer.DataView.byteOffset dv
byteLength = Data.ArrayBuffer.DataView.byteLength dv
Data.ArrayBuffer.Typed.part buffer byteOffset byteLength
do
result <- Text.Parsing.Parser.runParserT dataview $ do
-- Parse a 32-bit big-endian length prefix for the length of the utf8 string,
-- in bytes.
length <- anyUint32be
stringview <- takeN $ UInt.toInt length
stringarray <- liftEffect $ mkTypedArray stringview
case Data.TextDecoding.decodeUtf8 stringarray of
Left err -> Data.Parsing.Parser.fail $ show err
Right s -> pure sSerialization
This package is for reading (DataViews on) ArrayBuffers, not writing
them. See the package
purescript-arraybuffer-builder
for a way to
serialize and build ArrayBuffers.
References
Notes
Perhaps some day this package can be merged into purescript-parsing, but for now it has too many non-purescript-contrib dependencies.
![dependabot[bot]](https://avatars.githubusercontent.com/u/49699333?size=120)