// Clear the entire file and resize it to initial size.
func (file *DataFile) Clear() (err error) {
if err = file.Close(); err != nil {
return
} else if err = os.Truncate(file.Path, 0); err != nil {
return
} else if file.Fh, err = os.OpenFile(file.Path, os.O_CREATE|os.O_RDWR, 0600); err != nil {
return
} else if err = file.overwriteWithZero(0, file.Growth); err != nil {
return
} else if file.Buf, err = gommap.Map(file.Fh); err != nil {
return
}
file.Used, file.Size = 0, file.Growth
tdlog.Infof("%s cleared: %d of %d bytes in-use", file.Path, file.Used, file.Size)
return
}
// Ensure there is enough room for that many bytes of data.
func (file *DataFile) EnsureSize(more int) (err error) {
if file.Used+more <= file.Size {
return
} else if file.Buf != nil {
if err = file.Buf.Unmap(); err != nil {
return
}
}
if err = file.overwriteWithZero(file.Size, file.Growth); err != nil {
return
} else if file.Buf, err = gommap.Map(file.Fh); err != nil {
return
}
file.Size += file.Growth
tdlog.Infof("%s grown: %d -> %d bytes (%d bytes in-use)", file.Path, file.Size-file.Growth, file.Size, file.Used)
return file.EnsureSize(more)
}
// Follow the longest bucket chain to calculate total number of buckets, hence the "used size" of hash table file.
func (ht *HashTable) calculateNumBuckets() {
ht.numBuckets = ht.Size / BUCKET_SIZE
largestBucketNum := INITIAL_BUCKETS - 1
for i := 0; i < INITIAL_BUCKETS; i++ {
lastBucket := ht.lastBucket(i)
if lastBucket > largestBucketNum && lastBucket < ht.numBuckets {
largestBucketNum = lastBucket
}
}
ht.numBuckets = largestBucketNum + 1
usedSize := ht.numBuckets * BUCKET_SIZE
if usedSize > ht.Size {
ht.Used = ht.Size
ht.EnsureSize(usedSize - ht.Used)
}
ht.Used = usedSize
tdlog.Infof("%s: calculated used size is %d", ht.Path, usedSize)
}
// Open a data file that grows by the specified size.
func OpenDataFile(path string, growth int) (file *DataFile, err error) {
file = &DataFile{Path: path, Growth: growth}
if file.Fh, err = os.OpenFile(file.Path, os.O_CREATE|os.O_RDWR, 0600); err != nil {
return
}
var size int64
if size, err = file.Fh.Seek(0, os.SEEK_END); err != nil {
return
}
// Ensure the file is not smaller than file growth
if file.Size = int(size); file.Size < file.Growth {
if err = file.EnsureSize(file.Growth); err != nil {
return
}
}
if file.Buf == nil {
file.Buf, err = gommap.Map(file.Fh)
}
defer tdlog.Infof("%s opened: %d of %d bytes in-use", file.Path, file.Used, file.Size)
// Bi-sect file buffer to find out how much space is in-use
for low, mid, high := 0, file.Size/2, file.Size; ; {
switch {
case high-mid == 1:
if LooksEmpty(file.Buf[mid:]) {
if mid > 0 && LooksEmpty(file.Buf[mid-1:]) {
file.Used = mid - 1
} else {
file.Used = mid
}
return
}
file.Used = high
return
case LooksEmpty(file.Buf[mid:]):
high = mid
mid = low + (mid-low)/2
default:
low = mid
mid = mid + (high-mid)/2
}
}
return
}