tiny.sql.FileSnapshot

1pub const Snapshot = struct {2    source: SnapshotSource,3    view: pager.View,45    /// Returns the digest of a stored tree identity read through this6    /// snapshot. A leased durable snapshot asks its database's memo, and any7    /// other snapshot hashes the state directly.8    pub fn digestIdentity(9        self: Snapshot,10        identity_page: u32,11        state: *const lattice.State,12        entries: u64,13    ) [lattice.digest_size]u8 {14        std.debug.assert(identity_page != 0);15        return switch (self.source) {16            .durable => |durable| if (durable.guard) |guard|17                guard.database.digest_memo.digest(identity_page, state, entries)18            else19                state.digest(entries),20            .sparse => state.digest(entries),21        };22    }2324    pub fn retain(self: Snapshot) Error!?ReadLease {25        return switch (self.source) {26            .durable => |durable| if (durable.guard) |guard|27                try guard.retain()28            else29                null,30            .sparse => null,31        };32    }3334    pub fn copyPage(self: Snapshot, page_id: u32, image: *[page.size]u8) Error!bool {35        return try self.copyMarkedPage(page_id, image) != null;36    }3738    /// Copies page `page_id` into `image` and returns the check mark of the39    /// stored image it copied, or null when the snapshot holds no such page.40    pub fn copyMarkedPage(self: Snapshot, page_id: u32, image: *[page.size]u8) Error!?PageMark {41        const phase = trace.scope("file.snapshot.copy_page");42        defer phase.end();43        switch (self.source) {44            .durable => |durable| return try copyDurablePage(durable, self.view, page_id, image),45            .sparse => |sparse| {46                const found = try sparse.database.impl().copyPage(47                    sparse.generation,48                    page_id,49                    image,50                );51                return if (found) .none else null;52            },53        }54    }5556    fn copyDurablePage(57        durable: DurableSnapshot,58        view: pager.View,59        page_id: u32,60        image: *[page.size]u8,61    ) Error!?PageMark {62        if (durable.guard) |guard| {63            if (!guard.valid()) return error.InvalidReadLease;64        }65        if (durable.recovery_required) |required| {66            if (required.*) return error.RecoveryRequired;67        }68        if (page_id == 0) return error.InvalidPageId;69        if (try durable.pager.markedPageAt(page_id, view)) |stored| {70            image.* = stored.bytes.*;71            return .{ .flag = stored.checked };72        }73        if (view.base_generation == 0 or page_id > durable.pager.basePageCount()) return null;74        const key = ReadCacheKey{ .generation = view.base_generation, .page_id = page_id };75        if (durable.read_cache.get(key, image)) {76            return .{ .flag = durable.read_cache.checkMark(key) };77        }78        const base_file = (durable.base_file orelse return error.InvalidDatabaseFile).*;79        const n = try base_file.readPositionalAll(durable.io, image[0..], pageOffset(page_id));80        if (n != page.size) return error.InvalidDatabaseFile;81        durable.read_cache.put(key, image) catch |err| switch (err) {82            error.CacheDisabled => return .none,83        };84        return .{ .flag = durable.read_cache.checkMark(key) };85    }86};

1pub const FileSnapshot = file.Snapshot;