nut 0.1.4

Bolt DB Port in Rust
Documentation 
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use std::ops::AddAssign;

#[derive(Default, Debug)]
/// Records statistics about resources used by a bucket.
pub struct BucketStats {
    // Page count statistics.
    pub branch_page_n: usize,     // number of logical branch pages
    pub branch_overflow_n: usize, // number of physical branch overflow pages
    pub leaf_page_n: usize,       // number of logical leaf pages
    pub leaf_overflow_n: usize,   // number of physical leaf overflow pages

    // Tree statistics.
    pub key_n: usize, // number of keys/value pairs
    pub depth: usize, // number of levels in B+tree

    // Page size utilization.
    pub branch_alloc: usize,  // bytes allocated for physical branch pages
    pub branch_in_use: usize, // bytes actually used for branch data
    pub leaf_alloc: usize,    // bytes allocated for physical leaf pages
    pub leaf_in_use: usize,   // bytes actually used for leaf data

    // Bucket statistics
    pub bucket_n: usize, // total number of buckets including the top bucket
    pub inline_bucket_n: usize, // total number on inlined buckets
    pub inline_bucket_in_use: usize, // bytes used for inlined buckets (also accounted for in LeafInuse)
}

impl AddAssign for BucketStats {
    fn add_assign(&mut self, other: BucketStats) {
        self.branch_page_n += other.branch_page_n;
        self.branch_overflow_n += other.branch_overflow_n;
        self.leaf_page_n += other.leaf_page_n;
        self.leaf_overflow_n += other.leaf_overflow_n;
        self.key_n += other.key_n;
        if self.depth < other.depth {
            self.depth = other.depth;
        };
        self.branch_alloc += other.branch_alloc;
        self.branch_in_use += other.branch_in_use;
        self.leaf_alloc += other.leaf_alloc;
        self.leaf_in_use += other.leaf_in_use;

        self.bucket_n += other.bucket_n;
        self.inline_bucket_n += other.inline_bucket_n;
        self.inline_bucket_in_use += other.inline_bucket_in_use;
    }
}