tiny.trace.checkpoint

1const std = @import("std");23const Allocator = std.mem.Allocator;45pub const CaptureFn = *const fn (context: *anyopaque, allocator: Allocator) anyerror![]u8;6pub const PrepareRestoreFn = *const fn (context: *anyopaque, bytes: []const u8) anyerror!void;7pub const CommitRestoreFn = *const fn (context: *anyopaque) void;8pub const CancelRestoreFn = *const fn (context: *anyopaque) void;910pub const Provider = struct {11    context: *anyopaque,12    capture: CaptureFn,13    prepare_restore: PrepareRestoreFn,14    commit_restore: CommitRestoreFn,15    cancel_restore: CancelRestoreFn,1617    pub fn captureAlloc(self: Provider, allocator: Allocator) ![]u8 {18        return try self.capture(self.context, allocator);19    }2021    pub fn prepareRestoreBytes(self: Provider, bytes: []const u8) !void {22        try self.prepare_restore(self.context, bytes);23    }2425    pub fn commitRestore(self: Provider) void {26        self.commit_restore(self.context);27    }2829    pub fn cancelRestore(self: Provider) void {30        self.cancel_restore(self.context);31    }32};3334const ProviderTestState = struct {35    value: [32]u8 = undefined,36    value_len: usize = 0,37    staged: [32]u8 = undefined,38    staged_len: usize = 0,39    prepared: bool = false,4041    fn init(bytes: []const u8) ProviderTestState {42        var self: ProviderTestState = .{};43        self.setValue(bytes);44        return self;45    }4647    fn setValue(self: *ProviderTestState, bytes: []const u8) void {48        std.debug.assert(bytes.len <= self.value.len);49        @memcpy(self.value[0..bytes.len], bytes);50        self.value_len = bytes.len;51    }5253    fn current(self: *const ProviderTestState) []const u8 {54        return self.value[0..self.value_len];55    }5657    fn capture(context: *anyopaque, allocator: Allocator) ![]u8 {58        const self: *@This() = @ptrCast(@alignCast(context));59        return try allocator.dupe(u8, self.current());60    }6162    fn prepareRestore(context: *anyopaque, bytes: []const u8) !void {63        const self: *@This() = @ptrCast(@alignCast(context));64        if (bytes.len > self.staged.len) return error.TestProviderCapacityExceeded;65        @memcpy(self.staged[0..bytes.len], bytes);66        self.staged_len = bytes.len;67        self.prepared = true;68    }6970    fn commitRestore(context: *anyopaque) void {71        const self: *@This() = @ptrCast(@alignCast(context));72        std.debug.assert(self.prepared);73        @memcpy(self.value[0..self.staged_len], self.staged[0..self.staged_len]);74        self.value_len = self.staged_len;75        self.prepared = false;76    }7778    fn cancelRestore(context: *anyopaque) void {79        const self: *@This() = @ptrCast(@alignCast(context));80        self.prepared = false;81    }82};8384test "provider stages restore before an infallible commit" {85    var state = ProviderTestState.init("before");86    const provider = Provider{87        .context = &state,88        .capture = ProviderTestState.capture,89        .prepare_restore = ProviderTestState.prepareRestore,90        .commit_restore = ProviderTestState.commitRestore,91        .cancel_restore = ProviderTestState.cancelRestore,92    };9394    {95        const bytes = try provider.captureAlloc(std.testing.allocator);96        defer std.testing.allocator.free(bytes);97        state.setValue("after");98        try provider.prepareRestoreBytes(bytes);99        try std.testing.expectEqualStrings("after", state.current());100        provider.commitRestore();101    }102103    try std.testing.expectEqualStrings("before", state.current());104}105106test "provider cancel discards a staged restore" {107    var state = ProviderTestState.init("before");108    const provider = Provider{109        .context = &state,110        .capture = ProviderTestState.capture,111        .prepare_restore = ProviderTestState.prepareRestore,112        .commit_restore = ProviderTestState.commitRestore,113        .cancel_restore = ProviderTestState.cancelRestore,114    };115116    try provider.prepareRestoreBytes("after");117    provider.cancelRestore();118119    try std.testing.expectEqualStrings("before", state.current());120    try std.testing.expect(!state.prepared);121}

1pub const checkpoint = @import("checkpoint.zig");