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// Provenance: own design — shared run scripts (spec §5.4)
using System.Buffers.Binary;
using System.Text;
using System.Text.Json;
using System.Text.Json.Serialization;
namespace Godosa.Core.Runs.Scripts;
public sealed record LabelState(string Name, long Start, string File, int Line);
public sealed record RunnerState(long Frame, ulong Digest, List<ScopeState> Scopes, List<LabelState> Labels);
public sealed record CachedCheckpoint(RunnerState State, byte[] Game);
public static class CheckpointKeys
{
public const string RunnerVersion = "run-scripts 1";
public static IReadOnlyDictionary<int, string> Compute(ScriptProgram p, string contentVersion, ulong seed)
{
var d = new StateDigest();
d.Add(RunnerVersion);
d.Add(contentVersion);
d.Add(seed);
d.Add((int)p.Mode);
foreach (var (k, v) in p.Vars.OrderBy(kv => kv.Key, StringComparer.Ordinal))
d.Add($"{k}={v}");
var keys = new Dictionary<int, string>();
for (var i = 0; i < p.Code.Count; i++)
{
var instr = p.Code[i];
d.Add((int)instr.Op);
d.Add(instr.Format);
d.Add(instr.At.File);
d.Add(instr.Text);
if (instr.Op == Op.Checkpoint)
keys[i] = d.Hex;
}
return keys;
}
}
public sealed class CheckpointCache(string dir, long capBytes)
{
private static readonly byte[] Magic = "GRS1"u8.ToArray();
private static readonly JsonSerializerOptions Json = new() { Converters = { new JsonStringEnumConverter() } };
public CachedCheckpoint? Load(string key)
{
var path = Path.Combine(dir, key + ".snap");
if (!File.Exists(path))
return null;
byte[] bytes;
try
{
bytes = File.ReadAllBytes(path);
}
catch (Exception e) when (e is IOException or UnauthorizedAccessException)
{
return null;
}
if (bytes.Length < 8 || !bytes.AsSpan(0, 4).SequenceEqual(Magic))
return null;
var length = BinaryPrimitives.ReadInt32LittleEndian(bytes.AsSpan(4));
if (length < 0 || 8 + length > bytes.Length)
return null;
RunnerState? state;
try
{
state = JsonSerializer.Deserialize<RunnerState>(Encoding.UTF8.GetString(bytes, 8, length), Json);
}
catch (JsonException)
{
return null; // a corrupt entry is a miss
}
return state == null ? null : new CachedCheckpoint(state, bytes[(8 + length)..]);
}
public void Save(string key, CachedCheckpoint cp)
{
Directory.CreateDirectory(dir);
var json = Encoding.UTF8.GetBytes(JsonSerializer.Serialize(cp.State, Json));
var path = Path.Combine(dir, key + ".snap");
var tmp = path + ".tmp";
using (var f = File.Create(tmp))
{
f.Write(Magic);
Span<byte> len = stackalloc byte[4];
BinaryPrimitives.WriteInt32LittleEndian(len, json.Length);
f.Write(len);
f.Write(json);
f.Write(cp.Game);
}
File.Move(tmp, path, overwrite: true);
Evict(path);
}
private void Evict(string keep)
{
var files = new DirectoryInfo(dir).GetFiles("*.snap").OrderBy(f => f.LastWriteTimeUtc).ToList();
var total = files.Sum(f => f.Length);
foreach (var f in files)
{
if (total <= capBytes)
break;
if (f.FullName == Path.GetFullPath(keep))
continue;
total -= f.Length;
f.Delete();
}
}
}
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