80 lines
2.7 KiB
Nim
80 lines
2.7 KiB
Nim
# SPDX-FileCopyrightText: ☭ Emery Hemingway
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# SPDX-License-Identifier: Unlicense
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import std/[endians, options, streams, strutils]
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import bigints
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import ./decoding, ./parsing, ./values
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type BufferedDecoder* = object
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## Type for buffering binary Preserves before decoding.
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stream: StringStream
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appendPosition, decodePosition, maxSize: int
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proc newBufferedDecoder*(maxSize = 4096): BufferedDecoder =
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## Create a new `newBufferedDecoder`.
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runnableExamples:
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var
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buf = newBufferedDecoder()
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bin = encode(parsePreserves("<foobar>"))
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buf.feed(bin[0..2])
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buf.feed(bin[3..bin.high])
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var (success, pr) = decode(buf)
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assert success
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assert $pr == "<foobar>"
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BufferedDecoder(
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stream: newStringStream(newStringOfCap(maxSize)),
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maxSize: maxSize,
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)
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proc feed*(dec: var BufferedDecoder; buf: pointer; len: int) =
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assert len > 0
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if dec.maxSize > 0 and dec.maxSize < (dec.appendPosition + len):
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raise newException(IOError, "BufferedDecoder at maximum buffer size")
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dec.stream.setPosition(dec.appendPosition)
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dec.stream.writeData(buf, len)
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inc(dec.appendPosition, len)
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assert dec.appendPosition == dec.stream.getPosition()
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proc feed*[T: byte|char](dec: var BufferedDecoder; data: openarray[T]) =
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if data.len > 0:
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dec.feed(addr data[0], data.len)
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proc feed*[T: byte|char](dec: var BufferedDecoder; data: openarray[T]; slice: Slice[int]) =
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let n = slice.b + 1 - slice.a
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if n > 0:
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dec.feed(addr data[slice.a], n)
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proc decode*(dec: var BufferedDecoder): Option[Value] =
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## Decode from `dec`. If decoding fails the internal position of the
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## decoder does not advance.
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if dec.appendPosition > 0:
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assert(dec.decodePosition < dec.appendPosition)
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dec.stream.setPosition(dec.decodePosition)
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try:
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result = dec.stream.decodePreserves.some
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dec.decodePosition = dec.stream.getPosition()
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if dec.decodePosition == dec.appendPosition:
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dec.stream.setPosition(0)
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dec.stream.data.setLen(0)
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dec.appendPosition = 0
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dec.decodePosition = 0
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except IOError:
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discard
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proc parse*(dec: var BufferedDecoder): Option[Value] =
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## Parse from `dec`. If parsing fails the internal position of the
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## decoder does not advance.
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if dec.appendPosition > 0:
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assert(dec.decodePosition < dec.appendPosition)
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dec.stream.setPosition(dec.decodePosition)
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try:
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result = dec.stream.readAll.parsePreserves.some
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dec.decodePosition = dec.stream.getPosition()
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if dec.decodePosition == dec.appendPosition:
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dec.stream.setPosition(0)
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dec.stream.data.setLen(0)
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dec.appendPosition = 0
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dec.decodePosition = 0
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except IOError, ValueError:
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discard
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