Add SectorLambda

tool/lambda/lib/parserom.c

@@ -0,0 +1,72 @@
+/*-*- mode:c;indent-tabs-mode:nil;c-basic-offset:2;tab-width:8;coding:utf-8 -*-│
+│vi: set net ft=c ts=2 sts=2 sw=2 fenc=utf-8                                :vi│
+╞══════════════════════════════════════════════════════════════════════════════╡
+│ Copyright 2022 Justine Alexandra Roberts Tunney                              │
+│                                                                              │
+│ Permission to use, copy, modify, and/or distribute this software for         │
+│ any purpose with or without fee is hereby granted, provided that the         │
+│ above copyright notice and this permission notice appear in all copies.      │
+│                                                                              │
+│ THE SOFTWARE IS PROVIDED "AS IS" AND THE AUTHOR DISCLAIMS ALL                │
+│ WARRANTIES WITH REGARD TO THIS SOFTWARE INCLUDING ALL IMPLIED                │
+│ WARRANTIES OF MERCHANTABILITY AND FITNESS. IN NO EVENT SHALL THE             │
+│ AUTHOR BE LIABLE FOR ANY SPECIAL, DIRECT, INDIRECT, OR CONSEQUENTIAL         │
+│ DAMAGES OR ANY DAMAGES WHATSOEVER RESULTING FROM LOSS OF USE, DATA OR        │
+│ PROFITS, WHETHER IN AN ACTION OF CONTRACT, NEGLIGENCE OR OTHER               │
+│ TORTIOUS ACTION, ARISING OUT OF OR IN CONNECTION WITH THE USE OR             │
+│ PERFORMANCE OF THIS SOFTWARE.                                                │
+╚─────────────────────────────────────────────────────────────────────────────*/
+#include "tool/lambda/lib/blc.h"
+
+static struct Parse ParseImpl(int tail, int need, FILE *f) {
+  struct Parse p, q;
+  int b, i, j, t, start;
+  for (start = end;;) {
+    if (end + 2 > TERMS) Error(5, "OUT OF TERMS");
+    if ((b = GetBit(f)) == -1) {
+      if (need) Error(9, "UNFINISHED EXPRESSION");
+      break;
+    } else if (b) {
+      for (t = 0; NeedBit(f);) ++t;
+      mem[end++] = VAR;
+      mem[end++] = t;
+      break;
+    } else if (NeedBit(f)) {
+      t = end;
+      end += 2;
+      p = ParseImpl(0, 1, f);
+      q = ParseImpl(t + 2, 1, f);
+      mem[t + 0] = APP;
+      mem[t + 1] = q.i - (t + 2);
+      break;
+    } else {
+      mem[end++] = ABS;
+    }
+  }
+  p.i = start;
+  p.n = end - start;
+  if (p.n && tail) {
+    /* find backwards overlaps within 8-bit displacement */
+    i = tail - 32768;
+    j = start - p.n;
+    for (i = i < 0 ? 0 : i; i <= j; ++i) {
+      if (!memcmp(mem + i, mem + p.i, p.n * sizeof(*mem))) {
+        memset(mem + start, -1, p.n * sizeof(*mem));
+        end = start;
+        p.i = i;
+        break;
+      }
+    }
+  }
+  return p;
+}
+
+/**
+ * Parses binary lambda calculus closed expression from stream.
+ *
+ * If `tail` is non-zero then this subroutine will perform expensive
+ * deduplication so that optimal ROMs may be computed ahead of time.
+ */
+struct Parse Parse(int tail, FILE *f) {
+  return ParseImpl(tail, 0, f);
+}