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

			}
		}

		// Add the current part.
		fi.AddObjectPart(part.Number, part.ETag, part.Size, part.ActualSize, part.ModTime, part.Index, part.Checksums)
	}

	// Calculate full object size.
	var objectSize int64

	// Calculate consolidated actual size.
	var objectActualSize int64

	// Order online disks in accordance with distribution order.

//
//	 e1 := MD5(part-1)
//	 e2 := MD5(part-2)
//	...
//	 eN := MD5(part-N)
//
// Then, the ETag of the object is computed as MD5 of all individual
// part checksums. S3 also encodes the number of parts into the ETag
// by appending a -<number-of-parts> at the end:
//
//	ETag := MD5(e1 || e2 || e3 ... || eN) || -N
//
//	For example: ceb8853ddc5086cc4ab9e149f8f09c88-5
//

   */
  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;
      }
    }

      public String join(Iterable<?> parts) {
        return join(parts.iterator());
      }

      @Override
      public <A extends Appendable> A appendTo(A appendable, Iterator<?> parts) throws IOException {
        checkNotNull(appendable, "appendable");
        checkNotNull(parts, "parts");
        while (parts.hasNext()) {
          Object part = parts.next();
          if (part != null) {

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 a 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

	// Test 4: key = disk index, value = part name with hash mismatch
	erasureDisks = s.getDisks()
	diskFailures := make(map[int]string)
	diskFailures[0] = "part.1"
	diskFailures[3] = "part.1"
	diskFailures[15] = "part.1"

	for diskIndex, partName := range diskFailures {
		for i := range partsMetadata[diskIndex].Parts {
			if fmt.Sprintf("part.%d", i+1) == partName {

		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.

}

// PartInfo - represents individual part metadata.
type PartInfo struct {
	// Part number that identifies the part. This is a positive integer between
	// 1 and 10,000.
	PartNumber int

	// Date and time at which the part was uploaded.
	LastModified time.Time

	// Entity tag returned when the part was initially uploaded.
	ETag string

	// Size in bytes of the part.
	Size int64

        .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 =
      """