Variable: cache
constcache:Cache
This module deals with Caching of images and volumes The cache has two main components: a volatile portion for images and a non-volatile portion for volumes. Individual 2D images are volatile and will be replaced by new images hitting the cache. When you allocate volumes, these are non-volatile and reserve a block of memory from the cache. Volumes must be released manually. We will have a shared block of memory allocated for the entire cache, e.g. 1GB which will be shared for images and volumes.
When a new image is added: We check if there is enough unallocated + volatile space for the single image
if so
- We allocate the image in image cache, and if necessary oldest images are decached to match the maximumCacheSize criteria
- If a volume contains that imageId, copy it over using TypedArray's set method. If no volumes contain the imageId, the image is fetched by image loaders
If not (cache is mostly/completely full with volumes)
- throw that the cache does not have enough working space to allocate the image
When a new volume is added: Check if there is enough unallocated + volatile space to allocate the volume:
If so:
- Decache oldest images which won't be included in this volume until we have enough free space for the volume
- If not enough space from previous space, decache images that will be included in the volume until we have enough free space (These will need to be re-fetched, but we must do this not to straddle over the given memory limit, even for a short time, as this may crash the app)
- At this point, if any of the frames (indexed by imageId) are present in the volatile image cache, copy these over to the volume now
If not (cache is mostly/completely full with volumes),
- throw that the cache does not have enough working space to allocate the volume.