Function parseRange

packages/effect/src/unstable/http/HttpStaticServer.ts:313–375

(
  header: string,
  fileSize: number
)

}

const parseRange = (
  header: string,
  fileSize: number
):
  | { readonly start: number; readonly end: number }
  | "unsatisfiable"
  | undefined =>
{
  const value = header.trim()
  if (!value.toLowerCase().startsWith("bytes=")) {
    return undefined
  }
  const rangeValue = value.slice(6).trim()
  if (rangeValue.length === 0 || rangeValue.includes(",")) {
    return undefined
  }
  const separatorIndex = rangeValue.indexOf("-")
  if (separatorIndex === -1) {
    return undefined
  }
  const startPart = rangeValue.slice(0, separatorIndex).trim()
  const endPart = rangeValue.slice(separatorIndex + 1).trim()
  if (startPart === "" && endPart === "") {
    return undefined
  }
  if (startPart === "") {
    const suffixLength = parseInteger(endPart)
    if (suffixLength === undefined) {
      return undefined
    }
    if (suffixLength === 0 || fileSize === 0) {
      return "unsatisfiable"
    }
    return {
      start: Math.max(fileSize - suffixLength, 0),
      end: fileSize - 1
    }
  }
  const start = parseInteger(startPart)
  if (start === undefined) {
    return undefined
  }
  if (endPart === "") {
    if (start >= fileSize) {
      return "unsatisfiable"
    }
    return {
      start,
      end: fileSize - 1
    }
  }
  const end = parseInteger(endPart)
  if (end === undefined) {
    return undefined
  }
  if (start > end || start >= fileSize) {
    return "unsatisfiable"
  }