1 files changed, 150 insertions, 0 deletions
diff --git a/source/snap.c b/source/snap.c
new file mode 100644
index 0000000..1ddb6b9
--- /dev/null
+++ b/source/snap.c
@@ -0,0 +1,150 @@
+/*
+
+   3dsspec - Nintendo 3DS Sinclair Spectrum 48K emulator.
+
+   Copyright (C) 2021  Ian Cowburn
+   
+   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  02111-1307, USA.
+  
+   $Id: snap.c 4 2006-09-15 00:30:18Z ianc $
+
+*/
+#include "snap.h"
+
+/* ---------------------------------------- MACROS
+*/
+#ifndef TRUE
+#define TRUE 1
+#endif
+
+#ifndef FALSE
+#define FALSE 0
+#endif
+
+#define ROMLEN 0x4000
+
+
+/* ---------------------------------------- PRIVATE DATA
+*/
+static Z80Byte	*tap_file;
+static int	tap_len;
+static int	tap_ptr;
+
+
+/* ---------------------------------------- PRIVATE FUNCTIONS
+*/
+static Z80Byte GetByte(void)
+{
+    Z80Byte ret=0;
+
+    if (tap_len)
+    {
+	ret=tap_file[tap_ptr];
+	tap_ptr=(tap_ptr+1)%tap_len;
+    }
+
+    return ret;
+}
+
+
+static Z80Word GetLSBWord(void)
+{
+    int c1,c2;
+
+    c1=GetByte();
+    c2=GetByte();
+
+    return c1+(c2<<8);
+}
+
+
+/* ---------------------------------------- INTERFACES
+*/
+void TAPSetTape(Z80Byte *tape, int len)
+{
+    tap_file = tape;
+    tap_len = len;
+    tap_ptr = 0;
+}
+
+
+int TAPLoad(Z80Byte id, Z80Word *addr, Z80Word *len, SNAP_Poke poke)
+{
+    Z80Word blen;
+    Z80Byte type,b,csum,tape_csum;
+
+    if (!tap_file)
+    {
+    	return FALSE;
+    }
+
+    b=0;
+
+    blen=GetLSBWord();
+    type=GetByte();
+    csum=id;
+
+    /* Have we found the requested block?
+    */
+    if (id==type)
+    {
+    	/* Knock of block type
+	*/
+	blen--;
+
+	while(blen && *len)
+	{
+	    b=GetByte();
+	    csum^=b;
+
+	    poke(*addr,b);
+
+	    (*addr)++;
+	    (*len)--;
+	    blen--;
+	}
+
+	/* Get the checksum
+	*/
+	if (blen)
+	{
+	    tape_csum=GetByte();
+	    blen--;
+	}
+	else
+	    tape_csum=b;
+
+	/* In case we've been request less bytes than the block size
+	*/
+	while(blen--)
+	    GetByte();
+
+	/* Check the checksum
+	*/
+	return csum==tape_csum;
+    }
+    else
+    {
+    	/* If it's the wrong type, skip it
+	*/
+	while(blen--)
+	    GetByte();
+
+	return FALSE;
+    }
+}
+
+
+/* END OF FILE */