Accidentally re-added caching_paged_reader

low/caching_paged_reader.go

@@ -1,72 +0,0 @@
-package squashfslow
-
-import (
-	"errors"
-	"math"
-)
-
-var errOutOfBounds = errors.New("out of bounds")
-var errUnexpectedOutOfBounds = errors.New("unexpected out of bounds")
-var errNilCollection = errors.New("nil collection")
-
-// readPagedItems calls readBLockOrPartial the correct number of times to cache
-// requestedItemIndex in currentItems, and then returns currentItems[requestedItemIndex].
-// Parameters:
-// - requestedItemIndex: The index of the item to be retrieved.
-// - blockSize: The number of items per block.
-// - currentItems: A slice of already-read items to manage in-memory storage. Must not be nil.
-// - readBlockOrPartial: A callback function that reads the next block. It takes the index of the block
-// to be read, and the number of items to read. It is normally passed block size, but if the last
-// block is incomplete, it will be passed the number of items in the last block.
-// Returns:
-//   - the T at requestedItemIndex
-//   - a non-nil error and the zero value of T if an error was encountered.
-func readPagedItems[T any](
-	requestedItemIndex int,
-	blockSize int,
-	currentItems *[]T,
-	totalItems int,
-	readBlockOrPartial func(idxBlock, numItems int) ([]T, error),
-) (T, error) {
-	var zero T // Zero value for the item type, used for default return in error cases.
-	if currentItems == nil {
-		return zero, errNilCollection
-	}
-
-	if requestedItemIndex < 0 || requestedItemIndex >= totalItems {
-		return zero, errOutOfBounds
-	}
-
-	if len(*currentItems) > requestedItemIndex {
-		return (*currentItems)[requestedItemIndex], nil
-	}
-
-	// Calculate which block contains the requested item
-	blockNum := int(math.Ceil(float64(requestedItemIndex+1)/float64(blockSize))) - 1
-
-	// Calculate blocks to read
-	blocksRead := len(*currentItems) / blockSize
-	blocksToRead := blockNum - blocksRead + 1
-
-	// Read and append new blocks
-	for i := 0; i < blocksToRead; i++ {
-		startBlock := blocksRead + i
-		itemsLeft := totalItems - len(*currentItems)
-		itemsToRead := blockSize
-		if itemsToRead > itemsLeft {
-			itemsToRead = itemsLeft
-		}
-		items, err := readBlockOrPartial(startBlock, itemsToRead)
-		if err != nil {
-			return zero, err
-		}
-		*currentItems = append(*currentItems, items...)
-	}
-
-	// Ensure the slice contains the requested index after reading
-	if len(*currentItems) <= requestedItemIndex {
-		return zero, errUnexpectedOutOfBounds
-	}
-
-	return (*currentItems)[requestedItemIndex], nil
-}