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package chunk_cache
import (
"github.com/karlseguin/ccache/v2"
"time"
)
var (
_ ChunkCache = &ChunkCacheInMemory{}
)
// a global cache for recently accessed file chunks
type ChunkCacheInMemory struct {
cache *ccache.Cache
}
func (c *ChunkCacheInMemory) ReadChunkAt(data []byte, fileId string, offset uint64) (n int, err error) {
return c.readChunkAt(data, fileId, offset)
}
func (c *ChunkCacheInMemory) IsInCache(fileId string, lockNeeded bool) (answer bool) {
item := c.cache.Get(fileId)
if item == nil {
return false
}
return true
}
func (c *ChunkCacheInMemory) GetMaxFilePartSizeInCache() (answer uint64) {
return 8 * 1024 * 1024
}
func NewChunkCacheInMemory(maxEntries int64) *ChunkCacheInMemory {
pruneCount := maxEntries >> 3
if pruneCount <= 0 {
pruneCount = 500
}
return &ChunkCacheInMemory{
cache: ccache.New(ccache.Configure().MaxSize(maxEntries).ItemsToPrune(uint32(pruneCount))),
}
}
func (c *ChunkCacheInMemory) GetChunk(fileId string) []byte {
item := c.cache.Get(fileId)
if item == nil {
return nil
}
data := item.Value().([]byte)
item.Extend(time.Hour)
return data
}
func (c *ChunkCacheInMemory) getChunkSlice(fileId string, offset, length uint64) ([]byte, error) {
item := c.cache.Get(fileId)
if item == nil {
return nil, nil
}
data := item.Value().([]byte)
item.Extend(time.Hour)
wanted := min(int(length), len(data)-int(offset))
if wanted < 0 {
return nil, ErrorOutOfBounds
}
return data[offset : int(offset)+wanted], nil
}
func (c *ChunkCacheInMemory) readChunkAt(buffer []byte, fileId string, offset uint64) (int, error) {
item := c.cache.Get(fileId)
if item == nil {
return 0, nil
}
data := item.Value().([]byte)
item.Extend(time.Hour)
wanted := min(len(buffer), len(data)-int(offset))
if wanted < 0 {
return 0, ErrorOutOfBounds
}
n := copy(buffer, data[offset:int(offset)+wanted])
return n, nil
}
func (c *ChunkCacheInMemory) SetChunk(fileId string, data []byte) {
localCopy := make([]byte, len(data))
copy(localCopy, data)
c.cache.Set(fileId, localCopy, time.Hour)
}
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