commit b088e7ba553d0fc9693f9829b8ff8ff25b96861e
Author: Janis <janis@nirgendwo.xyz>
Date: Fri Mar 17 17:41:30 2023 +0100
initial commit
diff --git a/.gitignore b/.gitignore
new file mode 100644
index 0000000..d864d9e
--- /dev/null
+++ b/.gitignore
@@ -0,0 +1,2 @@
+/zig-cache/
+/zig-out/
diff --git a/build.zig b/build.zig
new file mode 100644
index 0000000..d484d0e
--- /dev/null
+++ b/build.zig
@@ -0,0 +1,71 @@
+const std = @import("std");
+
+// Although this function looks imperative, note that its job is to
+// declaratively construct a build graph that will be executed by an external
+// runner.
+pub fn build(b: *std.Build) void {
+ // Standard target options allows the person running `zig build` to choose
+ // what target to build for. Here we do not override the defaults, which
+ // means any target is allowed, and the default is native. Other options
+ // for restricting supported target set are available.
+ const target = b.standardTargetOptions(.{});
+
+ // Standard optimization options allow the person running `zig build` to select
+ // between Debug, ReleaseSafe, ReleaseFast, and ReleaseSmall. Here we do not
+ // set a preferred release mode, allowing the user to decide how to optimize.
+ const optimize = b.standardOptimizeOption(.{});
+
+ const exe = b.addExecutable(.{
+ .name = "datastructures",
+ // In this case the main source file is merely a path, however, in more
+ // complicated build scripts, this could be a generated file.
+ .root_source_file = .{ .path = "src/main.zig" },
+ .target = target,
+ .optimize = optimize,
+ });
+
+ exe.linkLibC();
+
+ // This declares intent for the executable to be installed into the
+ // standard location when the user invokes the "install" step (the default
+ // step when running `zig build`).
+ exe.install();
+
+ // This *creates* a RunStep in the build graph, to be executed when another
+ // step is evaluated that depends on it. The next line below will establish
+ // such a dependency.
+ const run_cmd = exe.run();
+
+ // By making the run step depend on the install step, it will be run from the
+ // installation directory rather than directly from within the cache directory.
+ // This is not necessary, however, if the application depends on other installed
+ // files, this ensures they will be present and in the expected location.
+ run_cmd.step.dependOn(b.getInstallStep());
+
+ // This allows the user to pass arguments to the application in the build
+ // command itself, like this: `zig build run -- arg1 arg2 etc`
+ if (b.args) |args| {
+ run_cmd.addArgs(args);
+ }
+
+ // This creates a build step. It will be visible in the `zig build --help` menu,
+ // and can be selected like this: `zig build run`
+ // This will evaluate the `run` step rather than the default, which is "install".
+ const run_step = b.step("run", "Run the app");
+ run_step.dependOn(&run_cmd.step);
+
+ // Creates a step for unit testing.
+ const exe_tests = b.addTest(.{
+ .root_source_file = .{ .path = "src/main.zig" },
+ .target = target,
+ .optimize = optimize,
+ });
+
+ exe_tests.linkLibC();
+
+ // Similar to creating the run step earlier, this exposes a `test` step to
+ // the `zig build --help` menu, providing a way for the user to request
+ // running the unit tests.
+ const test_step = b.step("test", "Run unit tests");
+ test_step.dependOn(&exe_tests.step);
+}
diff --git a/src/main.zig b/src/main.zig
new file mode 100644
index 0000000..3065525
--- /dev/null
+++ b/src/main.zig
@@ -0,0 +1,306 @@
+const std = @import("std");
+
+const BTree = struct {
+ const Self = @This();
+
+ const B: usize = 3;
+ const CAPACITY: usize = 2 * B - 1;
+ const NUM_EDGES: usize = 2 * B;
+
+ ally: std.mem.Allocator = std.heap.c_allocator,
+ root: ?NodeOrLeaf,
+
+ fn create(ally: std.mem.Allocator) Self {
+ return Self{
+ .ally = ally,
+ .root = null,
+ };
+ }
+
+ fn insert(self: *Self, value: u32) !void {
+ if (self.root) |*root| {
+ switch (root.*) {
+ .internal => |node| {
+ std.debug.print("can't insert values into {?} yet :|\n", .{node});
+ },
+ .leaf => |leaf| {
+ try leaf.insert_value(value);
+ },
+ }
+ } else {
+ var leaf: *Leaf = try self.ally.create(Leaf);
+ errdefer self.ally.destroy(leaf);
+ leaf.init(self.ally);
+ try leaf.insert_value(value);
+ self.root = NodeOrLeaf{ .leaf = leaf };
+ }
+ }
+
+ fn destroy(self: *Self) void {
+ if (self.root) |*root| {
+ root.destroy();
+ }
+ }
+
+ const NodeOrLeafTag = enum {
+ internal,
+ leaf,
+ };
+
+ const NodeOrLeaf = union(NodeOrLeafTag) {
+ internal: *Node,
+ leaf: *Leaf,
+
+ fn destroy(self: *NodeOrLeaf) void {
+ self.as_leaf().destroy();
+ }
+
+ fn as_leaf(self: *NodeOrLeaf) *Leaf {
+ switch (self.*) {
+ .internal => |node| {
+ return node.as_leaf();
+ },
+ .leaf => |leaf| {
+ return leaf;
+ },
+ }
+ }
+
+ fn from_leaf(leaf: *Leaf) NodeOrLeaf {
+ if (leaf.level == 0) {
+ return .{ .leaf = leaf };
+ } else {
+ return .{ .node = @ptrCast(Node, leaf) };
+ }
+ }
+ };
+
+ const Node = struct {
+ leaf: Leaf,
+
+ edges: [NUM_EDGES]?NodeOrLeaf = undefined,
+
+ fn create(ally: std.mem.Allocator) !Leaf {
+ var node = try ally.create(Node);
+ node.init(ally);
+
+ return node;
+ }
+
+ fn init(self: *Leaf, ally: std.mem.Allocator) void {
+ self.* = Node{ .leaf = Leaf{ .ally = ally } };
+ }
+
+ fn as_leaf(self: *Node) *Leaf {
+ return &self.leaf;
+ }
+
+ fn insert_node(self: *Node, child: NodeOrLeaf) void {
+ const self_leaf = self.as_leaf();
+ const ls = child.as_leaf().get_values()[0];
+
+ var idx: u16 = 0;
+ for (self_leaf.get_values(), 0..) |v, i| {
+ idx = @intCast(u16, i);
+ if (v > ls) {
+ break;
+ }
+ }
+
+ if (self.get_edges()[idx]) |edge| {
+ std.debug.print("edge already present?: {?}", .{edge});
+ } else {
+ child.as_leaf().parent = .{ .parent = self, .idx = idx };
+ self.get_edges()[idx] = child;
+ }
+ }
+
+ fn get_edges(self: *Node) []?NodeOrLeaf {
+ const len = self.leaf.len;
+ return self.edges[0..len];
+ }
+ };
+
+ const ParentPtr = struct {
+ parent: *Node,
+ idx: u16,
+ };
+
+ const Leaf = struct {
+ ally: std.mem.Allocator,
+ level: usize = 0,
+ parent: ?ParentPtr = null,
+
+ len: u16 = 0,
+ values: [CAPACITY]u32 = undefined,
+
+ fn create(ally: std.mem.Allocator) !*Leaf {
+ var leaf = try ally.create(Leaf);
+ leaf.init(ally);
+
+ return leaf;
+ }
+
+ fn init(self: *Leaf, ally: std.mem.Allocator) void {
+ self.* = Leaf{ .ally = ally };
+ }
+
+ fn destroy(self: *Leaf) void {
+ self.ally.destroy(self);
+ }
+
+ fn push_value(self: *Leaf, value: u32) void {
+ std.debug.assert(self.len < CAPACITY);
+ var tmp = value;
+ for (self.get_values()) |*val| {
+ if (val.* < value) {
+ continue;
+ }
+ const t = val.*;
+ val.* = tmp;
+ tmp = t;
+ }
+ self.values[self.len] = tmp;
+ self.len = self.len + 1;
+ }
+
+ const SplitResult = struct {
+ // attached
+ left: *Leaf,
+ // lose value, previously attacked, must be inserted
+ middle: u32,
+ // free floating leaf, must be attached
+ right: *Leaf,
+ };
+
+ fn split_at(self: *Leaf, value: u32) !SplitResult {
+ var idx: u16 = 0;
+ for (self.get_values(), 0..) |v, i| {
+ idx = @intCast(u16, i);
+ if (v > value) {
+ break;
+ }
+ }
+
+ std.debug.assert(idx > 0 and idx < CAPACITY - 1);
+
+ var new = try Leaf.create(self.ally);
+ new.level = self.level;
+ var middle: u32 = undefined;
+
+ // take from right half
+ if (idx > B) {
+ new.len = self.len - (idx + 1);
+ std.mem.copy(u32, &new.values, self.values[(idx + 1)..self.len]);
+
+ middle = self.values[idx];
+
+ self.len = idx;
+ self.push_value(value);
+ } else {
+ // take from left half
+ new.len = self.len - (idx);
+ std.mem.copy(u32, &new.values, self.values[idx..self.len]);
+
+ new.push_value(value);
+
+ middle = self.values[idx - 1];
+
+ self.len = idx - 1;
+ }
+
+ return .{ .left = self, .middle = middle, .right = new };
+ }
+
+ fn insert_value(self: *Leaf, value: u32) !void {
+ if (self.len < CAPACITY) {
+ self.push_value(value);
+ } else {
+ return error.LeafAtCapacity;
+ }
+ }
+
+ fn get_values(self: *Leaf) []u32 {
+ const len = self.len;
+ return self.values[0..len];
+ }
+ };
+};
+
+pub fn main() !void {
+ // Prints to stderr (it's a shortcut based on `std.io.getStdErr()`)
+ std.debug.print("All your {s} are belong to us.\n", .{"codebase"});
+
+ // stdout is for the actual output of your application, for example if you
+ // are implementing gzip, then only the compressed bytes should be sent to
+ // stdout, not any debugging messages.
+ const stdout_file = std.io.getStdOut().writer();
+ var bw = std.io.bufferedWriter(stdout_file);
+ const stdout = bw.writer();
+
+ try stdout.print("Run `zig build test` to run the tests.\n", .{});
+
+ try bw.flush(); // don't forget to flush!
+}
+
+test "btree leaf" {
+ std.testing.refAllDeclsRecursive(BTree);
+ std.testing.refAllDeclsRecursive(BTree.Leaf);
+
+ var leaf = BTree.Leaf{ .ally = std.testing.allocator, .parent = null, .len = 2, .values = [_]u32{ 5, 6, undefined, undefined, undefined } };
+ const values = leaf.get_values();
+
+ std.debug.print("{?}\n", .{leaf});
+ std.debug.print("{any}\n", .{values});
+}
+
+fn printValues(leaf: *BTree.Leaf) void {
+ const values = leaf.get_values();
+ std.debug.print("{any}\n", .{values});
+}
+
+test "leaf split" {
+ std.debug.print("testing splitting\n", .{});
+
+ var tree = BTree.create(std.testing.allocator);
+ defer tree.destroy();
+ try tree.insert(2);
+ try tree.insert(4);
+ try tree.insert(6);
+ try tree.insert(3);
+ try tree.insert(7);
+ std.debug.print("before split:", .{});
+ printValues(tree.root.?.as_leaf());
+
+ const split = try tree.root.?.as_leaf().split_at(5);
+
+ std.debug.print("after split:", .{});
+ printValues(tree.root.?.as_leaf());
+
+ std.debug.print("split: {?}\n", .{split});
+ tree.ally.destroy(split.right);
+}
+
+test "btree new" {
+ std.debug.print("testing insertion\n", .{});
+ var tree = BTree.create(std.testing.allocator);
+ defer tree.destroy();
+ try tree.insert(5);
+ printValues(tree.root.?.as_leaf());
+ try tree.insert(4);
+ printValues(tree.root.?.as_leaf());
+ try tree.insert(6);
+ printValues(tree.root.?.as_leaf());
+ try tree.insert(3);
+ printValues(tree.root.?.as_leaf());
+ try tree.insert(7);
+ printValues(tree.root.?.as_leaf());
+ //try tree.insert(8);
+}
+
+test "simple test" {
+ var list = std.ArrayList(i32).init(std.testing.allocator);
+ defer list.deinit(); // try commenting this out and see if zig detects the memory leak!
+ try list.append(42);
+ try std.testing.expectEqual(@as(i32, 42), list.pop());
+}