X-Git-Url: https://git.distorted.org.uk/u/mdw/catacomb/blobdiff_plain/bc97f84ce8a8cb1d0476ec4128ca59c40d98e5d5..ae747c9bab929bc794ddad9f59c381657d347d1f:/gfx-sqr.c

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+/* -*-c-*-
+ *
+ * $Id: gfx-sqr.c,v 1.1 2000/10/08 15:49:37 mdw Exp $
+ *
+ * Sqaring binary polynomials
+ *
+ * (c) 2000 Straylight/Edgeware
+ */
+
+/*----- Licensing notice --------------------------------------------------* 
+ *
+ * This file is part of Catacomb.
+ *
+ * Catacomb is free software; you can redistribute it and/or modify
+ * it under the terms of the GNU Library General Public License as
+ * published by the Free Software Foundation; either version 2 of the
+ * License, or (at your option) any later version.
+ * 
+ * Catacomb is distributed in the hope that it will be useful,
+ * but WITHOUT ANY WARRANTY; without even the implied warranty of
+ * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+ * GNU Library General Public License for more details.
+ * 
+ * You should have received a copy of the GNU Library General Public
+ * License along with Catacomb; if not, write to the Free
+ * Software Foundation, Inc., 59 Temple Place - Suite 330, Boston,
+ * MA 02111-1307, USA.
+ */
+
+/*----- Revision history --------------------------------------------------* 
+ *
+ * $Log: gfx-sqr.c,v $
+ * Revision 1.1  2000/10/08 15:49:37  mdw
+ * First glimmerings of binary polynomial arithmetic.
+ *
+ */
+
+/*----- Header files ------------------------------------------------------*/
+
+#include "mpx.h"
+/* #include "gfx.h" */
+#include "gfx-sqr-tab.h"
+
+/*----- Static variables --------------------------------------------------*/
+
+static uint16 tab[256] = GFX_SQRTAB;
+
+/*----- Main code ---------------------------------------------------------*/
+
+/* --- @gfx_sqr@ --- *
+ *
+ * Arguments:	@mpw *dv, *dvl@ = destination vector base and limit
+ *		@const mpw *av, *avl@ = argument vector base and limit
+ *
+ * Returns:	---
+ *
+ * Use:		Performs squaring of binary polynomials.
+ */
+
+void gfx_sqr(mpw *dv, mpw *dvl, const mpw *av, const mpw *avl)
+{
+  mpd a = 0, aa = 0;
+  unsigned b = 0, bb = 0;
+
+  /* --- Simple stuff --- */
+
+  if (dv >= dvl)
+    return;
+  MPX_SHRINK(av, avl);
+
+  /* --- The main algorithm --- *
+   *
+   * Our method depends on the fact that, in a field of characteristic 2, we
+   * have that %$(a + b)^2 = a^2 + b^2$%.  Thus, to square a polynomial, it's
+   * sufficient just to put a zero bit between each of the bits of the
+   * original argument.  We use a precomputed table for this, and work on
+   * entire octets at a time.  Life is more complicated because we've got to
+   * be careful of bizarre architectures which don't have words with a
+   * multiple of 8 bits in them.
+   */
+
+  for (;;) {
+
+    /* --- Input buffering --- */
+
+    if (b < 8) {
+      if (av >= avl)
+	break;
+      a |= *av++ << b;
+      b += MPW_BITS;
+    }
+
+    /* --- Do the work in the middle --- */
+
+    aa |= (mpd)(tab[U8(a)]) << bb;
+    bb += 16;
+    a >>= 8;
+    b -= 8;
+
+    /* --- Output buffering --- */
+
+    if (bb > MPW_BITS) {
+      *dv++ = MPW(aa);
+      if (dv >= dvl)
+	return;
+      aa >>= MPW_BITS;
+      bb -= MPW_BITS;
+    }
+  }
+
+  /* --- Flush the input buffer --- */
+
+  if (b) for (;;) {
+    aa |= (mpd)(tab[U8(a)]) << bb;
+    bb += 16;
+    if (bb > MPW_BITS) {
+      *dv++ = MPW(aa);
+      if (dv >= dvl)
+	return;
+      aa >>= MPW_BITS;
+      bb -= MPW_BITS;
+    }      
+    a >>= 8;
+    if (b <= 8)
+      break;
+    else
+      b -= 8;
+  }
+
+  /* --- Flush the output buffer --- */
+
+  if (bb) for (;;) {
+    *dv++ = MPW(aa);
+    if (dv >= dvl)
+      return;
+    aa >>= MPW_BITS;
+    if (bb <= MPW_BITS)
+      break;
+    else
+      bb -= MPW_BITS;
+  }
+
+  /* --- Zero the rest of everything --- */
+
+  MPX_ZERO(dv, dvl);
+}
+
+/*----- Test rig ----------------------------------------------------------*/
+
+#ifdef TEST_RIG
+
+#include <mLib/alloc.h>
+#include <mLib/dstr.h>
+#include <mLib/quis.h>
+#include <mLib/testrig.h>
+
+#define ALLOC(v, vl, sz) do {						\
+  size_t _sz = (sz);							\
+  mpw *_vv = xmalloc(MPWS(_sz));					\
+  mpw *_vvl = _vv + _sz;						\
+  (v) = _vv;								\
+  (vl) = _vvl;								\
+} while (0)
+
+#define LOAD(v, vl, d) do {						\
+  const dstr *_d = (d);							\
+  mpw *_v, *_vl;							\
+  ALLOC(_v, _vl, MPW_RQ(_d->len));					\
+  mpx_loadb(_v, _vl, _d->buf, _d->len);					\
+  (v) = _v;								\
+  (vl) = _vl;								\
+} while (0)
+
+#define MAX(x, y) ((x) > (y) ? (x) : (y))
+  
+static void dumpmp(const char *msg, const mpw *v, const mpw *vl)
+{
+  fputs(msg, stderr);
+  MPX_SHRINK(v, vl);
+  while (v < vl)
+    fprintf(stderr, " %08lx", (unsigned long)*--vl);
+  fputc('\n', stderr);
+}
+
+static int vsqr(dstr *v)
+{
+  mpw *a, *al;
+  mpw *b, *bl;
+  mpw *d, *dl;
+  int ok = 1;
+
+  LOAD(a, al, &v[0]);
+  LOAD(b, bl, &v[1]);
+  ALLOC(d, dl, 2 * (al - a));
+
+  gfx_sqr(d, dl, a, al);
+  if (!mpx_ueq(d, dl, b, bl)) {
+    fprintf(stderr, "\n*** vsqr failed\n");
+    dumpmp("       a", a, al);
+    dumpmp("expected", b, bl);
+    dumpmp("  result", d, dl);
+    ok = 0;
+  }
+
+  free(a); free(b); free(d);
+  return (ok);
+}
+
+static test_chunk defs[] = {
+  { "sqr", vsqr, { &type_hex, &type_hex, 0 } },
+  { 0, 0, { 0 } }
+};
+
+int main(int argc, char *argv[])
+{
+  test_run(argc, argv, defs, SRCDIR"/tests/gfx");
+  return (0);
+}
+
+#endif
+
+/*----- That's all, folks -------------------------------------------------*/