thin-provisioning-tools/functional-tests/persistent-data/btree.scm

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(library
(btree)
(export btree-value-type
btree-bcache
btree-root
btree-open
btree-lookup
btree-each
le64-vt
BTreeNodeHeader)
(import (bcache block-manager)
(chezscheme)
(list-utils)
(utils))
(define-ftype BTreeNodeHeader
(packed
(endian little
(struct
(csum unsigned-32)
(flags unsigned-32)
(blocknr unsigned-64)
(nr-entries unsigned-32)
(max-entries unsigned-32)
(value-size unsigned-32)
(padding unsigned-32)))))
(define-ftype LittleEndian64
(endian little unsigned-64))
;; The metadata block is made up of:
;; | node header | keys | values |
(define (block->header b)
(make-ftype-pointer BTreeNodeHeader b))
(define (block->keys b)
(make-ftype-pointer LittleEndian64
(+ b (ftype-sizeof BTreeNodeHeader))))
;;; Value-types are dlambdas with these methods:
;;; (vt 'mk-ptr <raw-ptr>)
;;; (vt 'ref <vt-ptr> index)
;;; (vt 'set <vt-ptr> index val)
;;; (vt 'size)
(define le64-vt
(dlambda
(mk-ptr (p) (make-ftype-pointer LittleEndian64 p))
(ref (fp index) (ftype-ref LittleEndian64 () fp index))
(set (fp index val) (ftype-set! LittleEndian64 () fp index val))
(size () (ftype-sizeof LittleEndian64))))
(define (block->values b vt)
(vt
(+ b (ftype-sizeof BTreeNodeHeader)
(* (ftype-ref BTreeNodeHeader (max-entries) (block->header b))
(ftype-sizeof LittleEndian64)))))
(define (key-at keys index)
(ftype-ref LittleEndian64 () keys index))
(define (value-at vt vals index)
(vt 'ref vals index))
#|
(define (max-entries vt)
(/ (- metadata-block-size (ftype-sizeof BTreeNodeHeader))
(+ (ftype-sizeof LittleEndian64)
(vt 'size))))
|#
(define-record-type btree
(fields value-type bcache root))
(define (btree-open vt bcache root)
(make-btree vt bcache root))
;;; (ftype-pointer BTreeNodeHeader) -> bool
(define (internal-node? header)
(bitwise-bit-set? (ftype-ref BTreeNodeHeader (flags) header) 0))
;;; (ftype-pointer BTreeNodeHeader) -> bool
(define (leaf-node? header)
(bitwise-bit-set? (ftype-ref BTreeNodeHeader (flags) header) 1))
;;; void* BTreeNodeHeader u64 -> integer
;;; Performs a binary search looking for the key and returns the index of the
;;; lower bound.
(define (lower-bound b header key)
(let ((keys (block->keys b)))
(let loop ((lo 0)
(hi (ftype-ref BTreeNodeHeader (nr-entries) header)))
(if (<= (- hi lo) 1)
lo
(let* ((mid (+ lo (/ (- hi lo) 2)))
(k (key-at b mid)))
(cond
((= key k) mid)
((< k key) (loop mid hi))
(else (loop lo mid))))))))
;;;;----------------------------------------------
;;;; Lookup
;;;;----------------------------------------------
;; FIXME: this holds more blocks than we need as we recurse, use a fixed
;; size block queue.
(define (btree-lookup tree key default)
(let ((cache (btree-bcache tree))
(vt (btree-value-type tree)))
(let loop ((root (btree-root tree)))
(with-block (b cache root (get-flags))
(let* ((header (block->header b))
(keys (block->keys b))
(vals (block->values b vt))
(index (lower-bound b header key)))
(if (internal-node? header)
(loop (value-at le64-vt vals index))
(if (= key (key-at keys index))
(value-at vt vals index)
default)))))))
;;;;----------------------------------------------
;;;; Walking the btree
;;;;----------------------------------------------
;;; Calls (fn key value) on every entry of the btree.
(define (btree-each tree fn)
(let ((vt (btree-value-type tree))
(cache (btree-bcache tree)))
(define (visit-leaf nr-entries keys vals)
(let loop ((index 0))
(when (< index nr-entries)
(fn (key-at keys index) (value-at vt vals index))
(loop (+ 1 index)))))
(define (visit-internal nr-entries keys vals)
(let loop ((index 0))
(when (< index nr-entries)
(visit-node (value-at le64-vt vals index))
(loop (+ 1 index)))))
(define (visit-node root)
(with-block (b cache root (get-flags))
(let* ((header (block->header b))
(nr-entries (ftype-ref BTreeNodeHeader (nr-entries) header))
(keys (block->keys b))
(vals (block->values b vt)))
((if (internal-node? header)
visit-internal
visit-leaf) nr-entries keys vals))))
(visit-node (btree-root tree)))))