From 1d9ea30b7254a11232acfb265fe25954345333e6 Mon Sep 17 00:00:00 2001
From: Chris Lu <chris.lu@gmail.com>
Date: Sun, 16 Aug 2020 00:49:26 -0700
Subject: [PATCH] fix ViewFromVisibleIntervals

---
 weed/filer2/filechunks.go      | 19 ++++++++++++++-----
 weed/filer2/filechunks_test.go | 31 +++++++++++++++++++++++++++++++
 2 files changed, 45 insertions(+), 5 deletions(-)

diff --git a/weed/filer2/filechunks.go b/weed/filer2/filechunks.go
index 9de888d50..1d546bad0 100644
--- a/weed/filer2/filechunks.go
+++ b/weed/filer2/filechunks.go
@@ -7,6 +7,7 @@ import (
 	"sort"
 	"sync"
 
+	"github.com/chrislusf/seaweedfs/weed/glog"
 	"github.com/chrislusf/seaweedfs/weed/pb/filer_pb"
 )
 
@@ -134,17 +135,19 @@ func ViewFromVisibleIntervals(visibles []VisibleInterval, offset int64, size int
 
 	for _, chunk := range visibles {
 
-		if chunk.start <= offset && offset < chunk.stop && offset < stop {
+		glog.V(1).Infof("visible [%d,%d)", chunk.start, chunk.stop)
+		chunkStart, chunkStop := max(offset, chunk.start), min(stop, chunk.stop)
+
+		if chunkStart < chunkStop {
 			views = append(views, &ChunkView{
 				FileId:      chunk.fileId,
-				Offset:      offset - chunk.start, // offset is the data starting location in this file id
-				Size:        uint64(min(chunk.stop, stop) - offset),
-				LogicOffset: offset,
+				Offset:      chunkStart-chunk.start,
+				Size:        uint64(chunkStop - chunkStart),
+				LogicOffset: chunk.start,
 				ChunkSize:   chunk.chunkSize,
 				CipherKey:   chunk.cipherKey,
 				IsGzipped:   chunk.isGzipped,
 			})
-			offset = min(chunk.stop, stop)
 		}
 	}
 
@@ -266,3 +269,9 @@ func min(x, y int64) int64 {
 	}
 	return y
 }
+func max(x, y int64) int64 {
+	if x <= y {
+		return y
+	}
+	return x
+}
diff --git a/weed/filer2/filechunks_test.go b/weed/filer2/filechunks_test.go
index bfee59198..c1b0427a4 100644
--- a/weed/filer2/filechunks_test.go
+++ b/weed/filer2/filechunks_test.go
@@ -2,9 +2,13 @@ package filer2
 
 import (
 	"log"
+	"math"
 	"testing"
 
 	"fmt"
+
+	"github.com/stretchr/testify/assert"
+
 	"github.com/chrislusf/seaweedfs/weed/pb/filer_pb"
 )
 
@@ -418,3 +422,30 @@ func BenchmarkCompactFileChunks(b *testing.B) {
 		CompactFileChunks(nil, chunks)
 	}
 }
+
+func TestViewFromVisibleIntervals(t *testing.T) {
+	visibles := []VisibleInterval{
+		{
+			start: 0,
+			stop: 25,
+			fileId: "fid1",
+		},
+		{
+			start: 4096,
+			stop: 8192,
+			fileId: "fid2",
+		},
+		{
+			start: 16384,
+			stop: 18551,
+			fileId: "fid3",
+		},
+	}
+
+	views := ViewFromVisibleIntervals(visibles, 0, math.MaxInt32)
+
+	if len(views) != len(visibles) {
+		assert.Equal(t, len(visibles), len(views), "ViewFromVisibleIntervals error")
+	}
+
+}
\ No newline at end of file