*/
  private static boolean validateSyntax(List<String> parts) {
    int lastIndex = parts.size() - 1;

    // Validate the last part specially, as it has different syntax rules.

    if (!validatePart(parts.get(lastIndex), true)) {
      return false;
    }

    for (int i = 0; i < lastIndex; i++) {
      String part = parts.get(i);
      if (!validatePart(part, false)) {
        return false;
      }
    }

	binary.LittleEndian.PutUint32(partIDbin[:], uint32(partID)) // marshal part ID

	mac := hmac.New(sha256.New, objectEncryptionKey) // derive part encryption key from part ID and object key
	mac.Write(partIDbin[:])
	partEncryptionKey := mac.Sum(nil)

	// Limit the reader, so the decryptor doesn't receive bytes
	// from the next part (different DARE stream)
	encLenToRead := d.parts[d.partIndex].Size - d.partEncRelOffset

ciphertext  := sealed_chunk_0   ||       sealed_chunk_1   ||       sealed_chunk_2   ||       ...
```

In case of a S3 multi-part operation each part is en/decrypted with the scheme shown in Figure 1. However, for each part an unique secret key is derived from the OEK and the part number using a PRF. So in case of multi-part not the OEK but the output of `PRF(OEK, part_id)` is used as secret key.

#### Cryptographic Primitives

 *   while (true) {
 *     val part = multipartReader.nextPart() ?: break
 *     process(part.headers, part.body)
 *   }
 * }
 * ```
 *
 * Note that [nextPart] will skip any unprocessed data from the preceding part. If the preceding
 * part is particularly large or if the underlying source is particularly slow, the [nextPart] call
 * may be slow!
 *

        .replace("\n", "\r\n")

    val parts =
      MultipartReader(
        boundary = "simple boundary",
        source = Buffer().writeUtf8(multipart),
      )

    val part = parts.nextPart()!!
    assertThat(part.body.readUtf8()).isEqualTo("abcd\r\n--simple boundar\r\n\r\nefgh")

    assertThat(parts.nextPart()).isNull()
  }

  @Test fun `do not need to read entire part`() {
    val multipart =
      """

      return specialCases.get(constantName);
    }
    List<String> parts = Lists.newArrayList();
    for (String part : SPLITTER.split(constantName)) {
      if (!uppercaseAcronyms.contains(part)) {
        part = part.charAt(0) + Ascii.toLowerCase(part.substring(1));
      }
      parts.add(part);
    }
    return JOINER.join(parts);
  }

      return specialCases.get(constantName);
    }
    List<String> parts = Lists.newArrayList();
    for (String part : SPLITTER.split(constantName)) {
      if (!uppercaseAcronyms.contains(part)) {
        part = part.charAt(0) + Ascii.toLowerCase(part.substring(1));
      }
      parts.add(part);
    }
    return JOINER.join(parts);
  }

		Checksums:  checksums,
	}

	// Update part info if it already exists.
	for i, part := range fi.Parts {
		if partNumber == part.Number {
			fi.Parts[i] = partInfo
			return
		}
	}

	// Proceed to include new part info.
	fi.Parts = append(fi.Parts, partInfo)

	// Parts in FileInfo should be in sorted order by part number.

          parts += part
        }

      /** Assemble the specified parts into a request body. */
      fun build(): MultipartBody {
        check(parts.isNotEmpty()) { "Multipart body must have at least one part." }
        return MultipartBody(boundary, type, parts.toImmutableList())
      }
    }

  companion object {
    /**
     * The "mixed" subtype of "multipart" is intended for use when the body parts are independent

		b = b[length:]
		if !typ.Is(ChecksumIncludesMultipart) {
			continue
		}
		parts, n := binary.Uvarint(b)
		if n <= 0 {
			break
		}
		if len(res) == 0 {
			res = make([]map[string]string, parts)
		}
		b = b[n:]
		for part := 0; part < int(parts); part++ {
			if len(b) < length {
				break
			}
			// Read part checksum
			cs := base64.StdEncoding.EncodeToString(b[:length])
			b = b[length:]