BoltDB（六）元素的插入

// Put sets the value for a key in the bucket.
// If the key exist then its previous value will be overwritten.
// Supplied value must remain valid for the life of the transaction.
// Returns an error if the bucket was created from a read-only transaction,
// if the key is blank, if the key is too large, or if the value is too large.
func (b *Bucket) Put(key []byte, value []byte) error {
    if b.tx.db == nil {
        return ErrTxClosed
    } else if !b.Writable() {
        return ErrTxNotWritable
    } else if len(key) == 0 {
        return ErrKeyRequired
    } else if len(key) > MaxKeySize {
        return ErrKeyTooLarge
    } else if int64(len(value)) > MaxValueSize {
        return ErrValueTooLarge
    }
    // Move cursor to correct position.
    c := b.Cursor()
    k, _, flags := c.seek(key)
    // Return an error if there is an existing key with a bucket value.
    if bytes.Equal(key, k) && (flags&bucketLeafFlag) != 0 {
        return ErrIncompatibleValue
    }
    // Insert into node.
    key = cloneBytes(key)
    c.node().put(key, key, value, 0, 0)
    return nil
}

c.seek在前文已经描述，这里只看看

// c.node()已经定位到要插入的page对应的内存数据结构node

func (n *node) put(oldKey, newKey, value []byte, pgid pgid, flags uint32) {
    if pgid >= n.bucket.tx.meta.pgid {
        panic(fmt.Sprintf("pgid (%d) above high water mark (%d)", pgid, n.bucket.tx.meta.pgid))
    } else if len(oldKey) <= 0 {
        panic("put: zero-length old key")
    } else if len(newKey) <= 0 {
        panic("put: zero-length new key")
    }

    // Find insertion index.
    index := sort.Search(len(n.inodes), func(i int) bool { return bytes.Compare(n.inodes[i].key, oldKey) != -1 })

    // Add capacity and shift nodes if we don't have an exact match and need to insert.
    exact := (len(n.inodes) > 0 && index < len(n.inodes) && bytes.Equal(n.inodes[index].key, oldKey))
    if !exact {
        n.inodes = append(n.inodes, inode{})
        copy(n.inodes[index+1:], n.inodes[index:])
    }

    inode := &n.inodes[index]
    inode.flags = flags
    inode.key = newKey
    inode.value = value
    inode.pgid = pgid
    _assert(len(inode.key) > 0, "put: zero-length inode key")
}