JCLOUDS-1606: JCLOUDS-1608: Fix MPU off-by-one

Previously GCS could not upload large objects due to its 32 part
limit.

blobstore/src/main/java/org/jclouds/blobstore/strategy/internal/MultipartUploadSlicingAlgorithm.java

@@ -72,6 +72,7 @@ public MultipartUploadSlicingAlgorithm(long minimumPartSize, long maximumPartSiz
       this.maximumNumberOfParts = maximumNumberOfParts;
    }
 
+   // TODO: This algorithm is needlessly complicated.
    public long calculateChunkSize(long length) {
       long unitPartSize = defaultPartSize; // first try with default part size
       int parts = (int)(length / unitPartSize);
@@ -112,6 +113,10 @@ public long calculateChunkSize(long length) {
       if (remainder == 0 && parts > 0) {
          parts -= 1;
       }
+      if (remainder > 0 && parts == maximumNumberOfParts) {
+          parts -= 1;
+          partSize = length / parts;
+      }
       this.chunkSize = partSize;
       this.parts = parts;
       this.remaining = length - partSize * parts;

blobstore/src/test/java/org/jclouds/blobstore/strategy/internal/MpuPartitioningAlgorithmTest.java

@@ -137,9 +137,9 @@ public void testWhenPartsExceedsMaxNumberOfParts() {
       // then the number of parts is increasing
       length += 1;
       chunkSize = strategy.calculateChunkSize(length);
-      assertEquals(chunkSize, MAX_PART_SIZE);
-      assertEquals(strategy.getParts(), MAX_NUMBER_OF_PARTS);
-      assertEquals(strategy.getRemaining(), 1);
+      assertEquals(chunkSize, 5369246044L);
+      assertEquals(strategy.getParts(), MAX_NUMBER_OF_PARTS - 1);
+      assertEquals(strategy.getRemaining(), 6045);
       assertEquals(chunkSize * strategy.getParts() + strategy.getRemaining(), length);
    }
 }