Multipart.pre.if: def of bend-kit-multipart@0.3.0.0
Import: import bend-kit-multipart@0.3.0.0/multipart.bend as Multipart
Lines 411-422 of bend-kit-multipart@0.3.0.0/multipart.bend: https://jend.leeeet.dev/read.txt?path=bend-kit-multipart@0.3.0.0/multipart.bend&start_line=411&end_line=422

import Base
import bend-kit-bytes@0.3.3.0/bytes.bend as Bytes

# Pre: the preamble is dropped. Keeping dlen - 1 bytes means a delimiter split across chunks is still found.
# A 0/1/2 suffix kind as two flags, since only a parameter can be matched.
def pre.if(delim: Bool, data: Bool, buf: Bytes.Bytes, +i: U32, +dlen: U32, out: List<&1, Item>) -> Step:
  match delim:
    case True{}:
      More{After{}, drop(buf, (i + dlen : U32)), out}
    case False{}:
      match data:
        case True{}:
          More{Pre{}, drop(buf, (i + 1 : U32)), out}
        case False{}:
          Pause{Pre{}, drop(buf, i), out}

Uses (9):
  https://jend.leeeet.dev/definition.txt?path=Base/base.bend&name=Bool
  https://jend.leeeet.dev/definition.txt?path=Base/base.bend&name=List
  https://jend.leeeet.dev/definition.txt?path=Base/base.bend&name=U32
  https://jend.leeeet.dev/definition.txt?path=Base/base.bend&name=U32.add
  https://jend.leeeet.dev/definition.txt?path=bend-kit-bytes@0.3.3.0/bytes.bend&name=Bytes
  https://jend.leeeet.dev/definition.txt?path=bend-kit-multipart@0.3.0.0/multipart.bend&name=Item
  https://jend.leeeet.dev/definition.txt?path=bend-kit-multipart@0.3.0.0/multipart.bend&name=Stage
  https://jend.leeeet.dev/definition.txt?path=bend-kit-multipart@0.3.0.0/multipart.bend&name=Step
  https://jend.leeeet.dev/definition.txt?path=bend-kit-multipart@0.3.0.0/multipart.bend&name=drop