226 lines
7.1 KiB
Zig
Executable File
226 lines
7.1 KiB
Zig
Executable File
const debug = @import("./debug.zig");
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const io = @import("./io.zig");
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const math = @import("./math.zig");
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///
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/// Returns a dynamically sized stack capable of holding `Element`.
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///
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pub fn Stack(comptime Element: type) type {
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return struct {
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capacity: usize,
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values: []Element,
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const Self = @This();
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///
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/// Clears all elements from `self` while preserving the current internal buffer.
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///
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/// To clean up memory allocations made by the stack and deinitialize it, see [deinit] instead.
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///
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pub fn clear(self: *Self) void {
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self.values = self.values[0 .. 0];
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}
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///
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/// Deinitializes `self` and sets it to an invalid state, freeing all memory allocated by `allocator`.
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///
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/// To clear all items from the stack while preserving the current internal buffer, see [clear] instead.
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///
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/// *Note* `allocator` must reference the same allocation strategy as the one originally used to initialize
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/// `self`.
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///
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pub fn deinit(self: *Self, allocator: io.Allocator) void {
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io.deallocate(allocator, self.values);
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self.capacity = 0;
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}
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///
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/// Attempts to remove `amount` number of `Element`s from the stack, returning `bool` if it was successful,
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/// otherwise `false` if the stack contains fewer elements than `amount`.
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///
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pub fn drop(self: *Self, amount: usize) bool {
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if (amount > self.values.len) return false;
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self.values = self.values[0 .. self.values.len - amount];
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return true;
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}
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///
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/// Attempts to grow the internal buffer of `self` by `growth_amount` using `allocator`.
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///
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/// The function returns [AllocatorError] instead if `allocator` cannot commit the memory required to grow the
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/// internal buffer by `growth_amount`, leaving `self` in the same state that it was in prior to starting the
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/// grow.
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///
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/// Growing ahead of pushing operations is useful when the upper bound of pushes is well-understood, as it can
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/// reduce the number of allocations required per push.
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///
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/// *Note* `allocator` must reference the same allocation strategy as the one originally used to initialize
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/// `self`.
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///
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pub fn grow(self: *Self, allocator: io.Allocator, growth_amount: usize) io.AllocationError!void {
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const grown_capacity = self.capacity + growth_amount;
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const values = (try io.allocate_many(Element, grown_capacity, allocator))[0 .. self.values.len];
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errdefer io.deallocate(allocator, values);
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{
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var index: usize = 0;
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while (index < self.values.len) {
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values[index] = self.values[index];
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}
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}
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io.deallocate(allocator, self.values);
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self.values = values;
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self.capacity = grown_capacity;
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}
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///
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/// Attempts to allocate and return an empty stack with an internal buffer of `initial_capacity` size using
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/// `allocator` as the memory allocation strategy.
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///
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/// The function returns [AllocationError] instead if `allocator` cannot commit the memory required for an
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/// internal buffer of `initial_capacity` size.
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///
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pub fn init(allocator: io.Allocator, initial_capacity: usize) !Self {
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const values = try io.allocate_many(Element, initial_capacity, allocator);
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errdefer io.deallocate(values);
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return Self{
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.capacity = initial_capacity,
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.values = values[0 .. 0],
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};
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}
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///
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/// Attempts to push every `Element` in `values` to `self` using `allocator` to grow the internal buffer as
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/// necessary.
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///
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/// The function returns [AllocationError] instead if `allocator` cannot commit the memory required to grow the
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/// internal buffer of `self` when necessary.
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///
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/// *Note* `allocator` must reference the same allocation strategy as the one originally used to initialize
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/// `self`.
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///
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pub fn push_all(self: *Self, allocator: io.Allocator, values: []const Element) io.AllocationError!void {
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const new_length = self.values.len + values.len;
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if (new_length >= self.capacity) {
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try self.grow(allocator, math.min(new_length, self.capacity));
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}
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const offset_index = self.values.len;
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self.values = self.values.ptr[0 .. new_length];
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{
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var index: usize = 0;
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while (index < values.len) : (index += 1) self.values[offset_index + index] = values[index];
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}
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}
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///
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/// Attempts to push the `Element` in `value` to `self` by `amount` number of times using `allocator` to grow
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/// the internal buffer as necessary.
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///
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/// The function returns [AllocationError] instead if `allocator` cannot commit the memory required to grow the
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/// internal buffer of `self` when necessary.
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///
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/// *Note* `allocator` must reference the same allocation strategy as the one originally used to initialize
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/// `self`.
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///
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pub fn push_many(self: *Self, allocator: io.Allocator, value: Element, amount: usize) io.AllocationError!void {
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const new_length = self.values.len + amount;
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if (new_length >= self.capacity) {
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try self.grow(allocator, math.max(usize, new_length, self.capacity));
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}
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const offset_index = self.values.len;
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self.values = self.values.ptr[0 .. new_length];
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{
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var index: usize = 0;
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while (index < amount) : (index += 1) self.values[offset_index + index] = value;
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}
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}
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///
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/// Attempts to push the `Element` in `value` to `self` using `allocator` to grow the internal buffer as
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/// necessary.
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///
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/// The function returns [AllocationError] instead if `allocator` cannot commit the memory required to grow the
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/// internal buffer of `self` when necessary.
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///
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/// *Note* `allocator` must reference the same allocation strategy as the one originally used to initialize
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/// `self`.
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///
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pub fn push_one(self: *Self, allocator: io.Allocator, value: Element) io.AllocationError!void {
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if (self.values.len == self.capacity) {
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try self.grow(allocator, math.max(1, self.capacity));
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}
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const offset_index = self.values.len;
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self.values = self.values.ptr[0 .. self.values.len + 1];
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self.values[offset_index] = value;
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}
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};
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}
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///
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/// Binds `stack` to a [io.Allocator], returning it.
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///
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pub fn stack_as_allocator(stack: *Stack(u8)) io.Allocator {
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return io.Allocator.bind(stack, struct {
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pub fn reallocate(writable_stack: *Stack(u8), existing_allocation: ?[*]u8, allocation_size: usize) ?[*]u8 {
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if (allocation_size == 0) return null;
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writable_stack.push_all(io.bytes_of(&allocation_size)) catch return null;
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const usize_size = @sizeOf(usize);
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errdefer debug.assert(writable_stack.drop(usize_size));
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const allocation_index = writable_stack.values.len;
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if (existing_allocation) |allocation| {
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const existing_allocation_size = @intToPtr(*const usize, @ptrToInt(allocation) - usize_size).*;
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writable_stack.push_all(allocation[0 .. existing_allocation_size]) catch return null;
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} else {
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writable_stack.push_many(0, allocation_size) catch return null;
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}
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return @ptrCast([*]u8, &writable_stack.values[allocation_index]);
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}
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});
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}
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///
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/// Binds `stack` to a [io.Writer], returning it.
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///
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pub fn stack_as_writer(stack: *Stack(u8)) io.Writer {
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return io.Writer.bind(stack, struct {
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pub fn write(writable_stack: *Stack(u8), buffer: []const u8) io.WriteError!usize {
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writable_stack.push_all(buffer) catch |grow_error| switch (grow_error) {
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error.OutOfMemory => return error.IoUnavailable,
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};
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return buffer.len;
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}
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});
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}
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