Merge pull request #3 from benbjohnson/spill

Spill to dirty pages, write to disk

1 files changed, 95 insertions, 0 deletions

diff --git a/sys.go b/sys.go
new file mode 100644
index 0000000..657c973
--- /dev/null
+++ b/sys.go
@@ -0,0 +1,95 @@
+package bolt
+
+import (
+	"sort"
+	"unsafe"
+)
+
+// sys represents a in-memory system page.
+type sys struct {
+	pgid    pgid
+	buckets map[string]*bucket
+}
+
+// size returns the size of the page after serialization.
+func (s *sys) size() int {
+	var size int = pageHeaderSize
+	for key, _ := range s.buckets {
+		size += int(unsafe.Sizeof(bucket{})) + len(key)
+	}
+	return size
+}
+
+// get retrieves a bucket by name.
+func (s *sys) get(key string) *bucket {
+	return s.buckets[key]
+}
+
+// put sets a new value for a bucket.
+func (s *sys) put(key string, b *bucket) {
+	s.buckets[key] = b
+}
+
+// del deletes a bucket by name.
+func (s *sys) del(key string) {
+	delete(s.buckets, key)
+}
+
+// read initializes the data from an on-disk page.
+func (s *sys) read(p *page) {
+	s.pgid = p.id
+	s.buckets = make(map[string]*bucket)
+
+	var buckets []*bucket
+	var keys []string
+
+	// Read buckets.
+	nodes := (*[maxNodesPerPage]bucket)(unsafe.Pointer(&p.ptr))
+	for i := 0; i < int(p.count); i++ {
+		node := &nodes[i]
+		buckets = append(buckets, node)
+	}
+
+	// Read keys.
+	buf := (*[maxAllocSize]byte)(unsafe.Pointer(&nodes[p.count]))[:]
+	for i := 0; i < int(p.count); i++ {
+		size := int(buf[0])
+		buf = buf[1:]
+		keys = append(keys, string(buf[:size]))
+		buf = buf[size:]
+	}
+
+	// Associate keys and buckets.
+	for index, key := range keys {
+		s.buckets[key] = buckets[index]
+	}
+}
+
+// write writes the items onto a page.
+func (s *sys) write(p *page) {
+	// Initialize page.
+	p.flags |= p_sys
+	p.count = uint16(len(s.buckets))
+
+	// Sort keys.
+	var keys []string
+	for key, _ := range s.buckets {
+		keys = append(keys, key)
+	}
+	sort.StringSlice(keys).Sort()
+
+	// Write each bucket to the page.
+	buckets := (*[maxNodesPerPage]bucket)(unsafe.Pointer(&p.ptr))
+	for index, key := range keys {
+		buckets[index] = *s.buckets[key]
+	}
+
+	// Write each key to the page.
+	buf := (*[maxAllocSize]byte)(unsafe.Pointer(&buckets[p.count]))[:]
+	for _, key := range keys {
+		buf[0] = byte(len(key))
+		buf = buf[1:]
+		copy(buf, []byte(key))
+		buf = buf[len(key):]
+	}
+}