Method ComposeObject

api-compose-object.go:417–572

ComposeObject - creates an object using server-side copying of existing objects. It takes a list of source objects (with optional offsets) and concatenates them into a new object using only server-side copying operations. Optionally takes progress reader hook for applications to look at current prog

(ctx context.Context, dst CopyDestOptions, srcs ...CopySrcOptions)

// operations. Optionally takes progress reader hook for applications to
// look at current progress.
func (c *Client) ComposeObject(ctx context.Context, dst CopyDestOptions, srcs ...CopySrcOptions) (UploadInfo, error) {
	if len(srcs) < 1 || len(srcs) > maxPartsCount {
		return UploadInfo{}, errInvalidArgument("There must be as least one and up to 10000 source objects.")
	}

	for _, src := range srcs {
		if err := src.validate(); err != nil {
			return UploadInfo{}, err
		}
	}

	if err := dst.validate(); err != nil {
		return UploadInfo{}, err
	}

	srcObjectInfos := make([]ObjectInfo, len(srcs))
	srcObjectSizes := make([]int64, len(srcs))
	var totalSize, totalParts int64
	var err error
	for i, src := range srcs {
		opts := StatObjectOptions{ServerSideEncryption: encrypt.SSE(src.Encryption), VersionID: src.VersionID}
		srcObjectInfos[i], err = c.StatObject(context.Background(), src.Bucket, src.Object, opts)
		if err != nil {
			return UploadInfo{}, err
		}

		srcCopySize := srcObjectInfos[i].Size
		// Check if a segment is specified, and if so, is the
		// segment within object bounds?
		if src.MatchRange {
			// Since range is specified,
			//    0 <= src.start <= src.end
			// so only invalid case to check is:
			if src.End >= srcCopySize || src.Start < 0 {
				return UploadInfo{}, errInvalidArgument(
					fmt.Sprintf("CopySrcOptions %d has invalid segment-to-copy [%d, %d] (size is %d)",
						i, src.Start, src.End, srcCopySize))
			}
			srcCopySize = src.End - src.Start + 1
		}

		// Only the last source may be less than `absMinPartSize`
		if srcCopySize < absMinPartSize && i < len(srcs)-1 {
			return UploadInfo{}, errInvalidArgument(
				fmt.Sprintf("CopySrcOptions %d is too small (%d) and it is not the last part", i, srcCopySize))
		}

		// Is data to copy too large?
		totalSize += srcCopySize
		if totalSize > maxObjectSize {
			return UploadInfo{}, errInvalidArgument(fmt.Sprintf("Cannot compose an object of size %d (> 5GiB * 10000)", totalSize))
		}

		// record source size
		srcObjectSizes[i] = srcCopySize

		// calculate parts needed for current source
		totalParts += partsRequired(srcCopySize, int64(dst.PartSize))