feat(focas): coalesce adjacent PMC reads into one pmc_rdpmcrng (#266)

Claude-Session: https://claude.ai/code/session_01Ef2ozxS7QPanGT8uoATbTe
2026-10-08 16:59:07 -04:00
parent 5b36c717de
commit 8d916f2af7
11 changed files with 790 additions and 11 deletions
@@ -56,6 +56,51 @@ internal class FakeFocasClient : IFocasClient
        return Task.FromResult((value, status));
    }

+    /// <summary>PMC byte memory the range read serves, keyed by (upper-case letter, byte address); absent = 0.</summary>
+    public Dictionary<(string Letter, int Address), byte> PmcMemory { get; } = new();
+    /// <summary>Gets the log of range reads issued (letter, slot type, start, end).</summary>
+    public List<(string Letter, FocasDataType SlotType, int Start, int End)> PmcRangeReads { get; } = new();
+    /// <summary>Ranges (letter, start, end) the fake CNC rejects with <see cref="PmcRangeRejectStatus"/>.</summary>
+    public List<Func<string, int, int, bool>> PmcRangeRejectors { get; } = new();
+    /// <summary>The status a rejected range returns.</summary>
+    public uint PmcRangeRejectStatus { get; set; } = FocasStatusMapper.BadOutOfRange;
+    /// <summary>When true every range read throws (transport failure).</summary>
+    public bool ThrowOnPmcRange { get; set; }
+
+    /// <summary>Reads a PMC range as raw big-endian slots from <see cref="PmcMemory"/>.</summary>
+    /// <param name="letter">PMC letter.</param>
+    /// <param name="slotType">Slot type.</param>
+    /// <param name="start">First byte.</param>
+    /// <param name="end">Last byte, inclusive.</param>
+    /// <param name="ct">The cancellation token.</param>
+    public virtual Task<(IReadOnlyList<long>? slots, uint status)> ReadPmcSlotsAsync(
+        string letter, FocasDataType slotType, int start, int end, CancellationToken ct)
+    {
+        PmcRangeReads.Add((letter, slotType, start, end));
+        if (ThrowOnPmcRange) throw new InvalidOperationException("transport down");
+        if (PmcRangeRejectors.Any(r => r(letter, start, end)))
+            return Task.FromResult<(IReadOnlyList<long>?, uint)>((null, PmcRangeRejectStatus));
+
+        var width = slotType switch
+        {
+            FocasDataType.Int16 => 2,
+            FocasDataType.Int32 or FocasDataType.Float32 => 4,
+            FocasDataType.Float64 => 8,
+            _ => 1,
+        };
+        var slots = new List<long>();
+        for (var o = start; o + width - 1 <= end; o += width)
+        {
+            long v = 0;
+            for (var k = 0; k < width; k++)
+                v = (v << 8) | (PmcMemory.TryGetValue((letter, o + k), out var b) ? b : (byte)0);
+            // Sign-extend like the wire parser (Int16/Int32/Int64 big-endian); width 1 stays 0..255.
+            v = width switch { 2 => (short)v, 4 => (int)v, _ => v };
+            slots.Add(v);
+        }
+        return Task.FromResult<(IReadOnlyList<long>?, uint)>((slots, FocasStatusMapper.Good));
+    }
+
    /// <summary>Writes a value to a FOCAS address asynchronously.</summary>
    /// <param name="address">The FOCAS address to write to.</param>
    /// <param name="type">The data type of the value.</param>