1	/*
     2	Copyright 2014 The Perkeep Authors
     3	
     4	Licensed under the Apache License, Version 2.0 (the "License");
     5	you may not use this file except in compliance with the License.
     6	You may obtain a copy of the License at
     7	
     8	     http://www.apache.org/licenses/LICENSE-2.0
     9	
    10	Unless required by applicable law or agreed to in writing, software
    11	distributed under the License is distributed on an "AS IS" BASIS,
    12	WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
    13	See the License for the specific language governing permissions and
    14	limitations under the License.
    15	*/
    16	
    17	package blobserver
    18	
    19	import "perkeep.org/pkg/blob"
    20	
    21	// ListMissingDestinationBlobs reads from 'srcch' and 'dstch' (sorted
    22	// enumerations of blobs from two blob servers) and sends to
    23	// 'destMissing' any blobs which appear on the source but not at the
    24	// destination.
    25	//
    26	// destMissing is closed at the end.
    27	//
    28	// If an invalid (zero) blob from srcch or dstch arrives,
    29	// ListMissingDestinationBlobs stops.
    30	func ListMissingDestinationBlobs(destMissing chan<- blob.SizedRef, sizeMismatch func(blob.Ref), srcch, dstch <-chan blob.SizedRef) {
    31		defer close(destMissing)
    32	
    33		src := &blob.ChanPeeker{Ch: srcch}
    34		dst := &blob.ChanPeeker{Ch: dstch}
    35	
    36		for {
    37			srcSized, ok := src.Peek()
    38			if !ok {
    39				break
    40			}
    41			if !srcSized.Ref.Valid() {
    42				return
    43			}
    44	
    45			// If the destination has reached its end, anything
    46			// remaining in the source is needed.
    47			if _, ok := dst.Peek(); !ok {
    48				destMissing <- src.MustTake()
    49				continue
    50			}
    51	
    52			srcBlob := src.MustPeek().Ref
    53			dstRef := dst.MustPeek().Ref
    54			if !dstRef.Valid() {
    55				return
    56			}
    57	
    58			switch {
    59			case srcBlob == dstRef:
    60				// Skip both
    61				sb := src.MustTake()
    62				db := dst.MustTake()
    63				if sb.Size != db.Size {
    64					sizeMismatch(sb.Ref)
    65				}
    66			case srcBlob.Less(dstRef):
    67				destMissing <- src.MustTake()
    68			case dstRef.Less(srcBlob):
    69				dst.Take()
    70			}
    71		}
    72	}