Added Nitfol and Frotz source code.

[projects/chimara/chimara.git] / interpreters / nitfol / op_jmp.c

diff --git a/interpreters/nitfol/op_jmp.c b/interpreters/nitfol/op_jmp.c
new file mode 100644 (file)
index 0000000..9da59de
--- /dev/null
+++ b/interpreters/nitfol/op_jmp.c
@@ -0,0 +1,162 @@
+/*  Nitfol - z-machine interpreter using Glk for output.
+    Copyright (C) 1999  Evin Robertson
+
+    This program is free software; you can redistribute it and/or modify
+    it under the terms of the GNU General Public License as published by
+    the Free Software Foundation; either version 2 of the License, or
+    (at your option) any later version.
+
+    This program 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 General Public License for more details.
+
+    You should have received a copy of the GNU General Public License
+    along with this program; if not, write to the Free Software
+    Foundation, Inc., 59 Temple Place, Suite 330, Boston, MA 02111, USA.
+
+    The author can be reached at nitfol@deja.com
+*/
+#include "nitfol.h"
+
+
+N_INLINE static void skip_branch(zbyte branch)
+{
+  if(!(branch & b01000000)) /* Bit 6 clear means 'branch occupies two bytes' */
+    PC++;
+}
+
+N_INLINE static void take_branch(zbyte branch)
+{
+  int o = branch & b00111111;
+
+  if(!(branch & b01000000)) {/* Bit 6 clear means 'branch occupies two bytes'*/
+    o = (o << 8) + HIBYTE(PC);
+    PC++;
+    if(branch & b00100000)
+      o = -((1 << 14) - o);
+  }
+
+  if(o == 0)
+    mop_func_return(0);
+  else if(o == 1)
+    mop_func_return(1);
+  else
+    PC += o - 2;
+
+#ifndef FAST
+  if(PC > game_size) {
+    n_show_error(E_INSTR, "attempt to conditionally jump outside of story", o - 2);
+    PC -= o - 2;
+    return;
+  }
+#endif
+  
+  /*  printf("cjmp %x -> %x\n", oldPC, PC); */
+}
+
+
+void mop_skip_branch(void)
+{
+  zbyte branch = HIBYTE(PC);
+  PC++;
+
+  if(branch & b10000000)  /* Bit 7 set means 'branch when true' */
+    skip_branch(branch);
+  else
+    take_branch(branch);
+
+}
+
+void mop_take_branch(void)
+{
+  zbyte branch = HIBYTE(PC);
+  PC++;
+
+  if(branch & b10000000)  /* Bit 7 set means 'branch when true' */
+    take_branch(branch);
+  else
+    skip_branch(branch);
+}
+
+void mop_cond_branch(BOOL cond)
+{
+  zbyte branch = HIBYTE(PC);
+  PC++;
+  if((branch >> 7) ^ cond)
+    skip_branch(branch);
+  else
+    take_branch(branch);
+}
+
+
+void op_je(void)
+{
+  int i;
+  for(i = 1; i < numoperands; i++)
+    if(operand[0] == operand[i]) {
+      mop_take_branch();
+      return;
+    }
+
+  mop_skip_branch();
+}
+
+void op_jg(void)
+{
+  if(is_greaterthan(operand[0], operand[1]))
+    mop_take_branch();
+  else
+    mop_skip_branch();
+}
+
+void op_jl(void)
+{
+  if(is_lessthan(operand[0], operand[1]))
+    mop_take_branch();
+  else
+    mop_skip_branch();
+}
+
+void op_jump(void)
+{
+  operand[0] -= 2;  /* not documented in zspec */
+  if(is_neg(operand[0])) {
+#ifndef FAST
+    if(neg(operand[0]) > PC) {
+      n_show_error(E_INSTR, "attempt to jump before beginning of story", -neg(operand[0]));
+      return;
+    }
+#endif
+    PC -= neg(operand[0]);
+  }
+  else {
+    PC += operand[0];
+    if(PC > game_size) {
+      n_show_error(E_INSTR, "attempt to jump past end of story", operand[0]);
+      PC -= operand[0];
+      return;
+    }
+  }
+  /*  printf("jump %x -> %x\n", oldPC, PC); */
+}
+
+void op_jz(void)
+{
+  mop_cond_branch(operand[0] == 0);
+}
+
+void op_test(void)
+{
+  mop_cond_branch((operand[0] & operand[1]) == operand[1]);
+}
+
+void op_verify(void)
+{
+  mop_cond_branch(LOWORD(HD_CHECKSUM) == z_checksum);
+}
+
+void op_piracy(void)
+{
+  mop_cond_branch(aye_matey);
+}