diff --git a/thunk.c b/thunk.c
new file mode 100644
index 0000000..62520a2
--- /dev/null
+++ b/thunk.c
@@ -0,0 +1,315 @@
+/*
+ *  Generic thunking code to convert data between host and target CPU
+ * 
+ *  Copyright (c) 2003 Fabrice Bellard
+ *
+ *  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., 675 Mass Ave, Cambridge, MA 02139, USA.
+ */
+#include <stdlib.h>
+#include <stdio.h>
+#include <stdarg.h>
+
+#include "gemu.h"
+#include "thunk.h"
+
+//#define DEBUG
+
+#define MAX_STRUCTS 128
+
+/* XXX: make it dynamic */
+static StructEntry struct_entries[MAX_STRUCTS];
+
+static inline int thunk_type_size(const argtype *type_ptr, int is_host)
+{
+    int type, size;
+    const StructEntry *se;
+
+    type = *type_ptr;
+    switch(type) {
+    case TYPE_CHAR:
+        return 1;
+    case TYPE_SHORT:
+        return 2;
+    case TYPE_INT:
+        return 4;
+    case TYPE_LONGLONG:
+    case TYPE_ULONGLONG:
+        return 8;
+    case TYPE_LONG:
+    case TYPE_ULONG:
+    case TYPE_PTRVOID:
+    case TYPE_PTR:
+        if (is_host) {
+            return HOST_LONG_SIZE;
+        } else {
+            return TARGET_LONG_SIZE;
+        }
+        break;
+    case TYPE_ARRAY:
+        size = type_ptr[1];
+        return size * thunk_type_size(type_ptr + 2, is_host);
+    case TYPE_STRUCT:
+        se = struct_entries + type_ptr[1];
+        return se->size[is_host];
+    default:
+        return -1;
+    }
+}
+
+static inline int thunk_type_align(const argtype *type_ptr, int is_host)
+{
+    int type;
+    const StructEntry *se;
+
+    type = *type_ptr;
+    switch(type) {
+    case TYPE_CHAR:
+        return 1;
+    case TYPE_SHORT:
+        return 2;
+    case TYPE_INT:
+        return 4;
+    case TYPE_LONGLONG:
+    case TYPE_ULONGLONG:
+        return 8;
+    case TYPE_LONG:
+    case TYPE_ULONG:
+    case TYPE_PTRVOID:
+    case TYPE_PTR:
+        if (is_host) {
+            return HOST_LONG_SIZE;
+        } else {
+            return TARGET_LONG_SIZE;
+        }
+        break;
+    case TYPE_ARRAY:
+        return thunk_type_align(type_ptr + 2, is_host);
+    case TYPE_STRUCT:
+        se = struct_entries + type_ptr[1];
+        return se->align[is_host];
+    default:
+        return -1;
+    }
+}
+
+static inline const argtype *thunk_type_next(const argtype *type_ptr)
+{
+    int type;
+
+    type = *type_ptr++;
+    switch(type) {
+    case TYPE_CHAR:
+    case TYPE_SHORT:
+    case TYPE_INT:
+    case TYPE_LONGLONG:
+    case TYPE_ULONGLONG:
+    case TYPE_LONG:
+    case TYPE_ULONG:
+    case TYPE_PTRVOID:
+        return type_ptr;
+    case TYPE_PTR:
+        return thunk_type_next(type_ptr);
+    case TYPE_ARRAY:
+        return thunk_type_next(type_ptr + 1);
+    case TYPE_STRUCT:
+        return type_ptr + 1;
+    default:
+        return NULL;
+    }
+}
+
+void thunk_register_struct(int id, const char *name, const argtype *types)
+{
+    const argtype *type_ptr;
+    StructEntry *se;
+    int nb_fields, offset, max_align, align, size, i, j;
+
+    se = struct_entries + id;
+    
+    /* first we count the number of fields */
+    type_ptr = types;
+    nb_fields = 0;
+    while (*type_ptr != TYPE_NULL) {
+        type_ptr = thunk_type_next(type_ptr);
+        nb_fields++;
+    }
+    se->field_types = types;
+    se->nb_fields = nb_fields;
+    se->name = name;
+#ifdef DEBUG
+    printf("struct %s: id=%d nb_fields=%d\n", 
+           se->name, id, se->nb_fields);
+#endif
+    /* now we can alloc the data */
+
+    for(i = 0;i < 2; i++) {
+        offset = 0;
+        max_align = 1;
+        se->field_offsets[i] = malloc(nb_fields * sizeof(int));
+        type_ptr = se->field_types;
+        for(j = 0;j < nb_fields; j++) {
+            size = thunk_type_size(type_ptr, i);
+            align = thunk_type_align(type_ptr, i);
+            offset = (offset + align - 1) & ~(align - 1);
+            se->field_offsets[i][j] = offset;
+            offset += size;
+            if (align > max_align)
+                max_align = align;
+        }
+        offset = (offset + max_align - 1) & ~(max_align - 1);
+        se->size[i] = offset;
+        se->align[i] = max_align;
+#ifdef DEBUG
+        printf("%s: size=%d align=%d\n", 
+               i == THUNK_HOST ? "host" : "target", offset, max_align);
+#endif
+    }
+}
+
+void thunk_register_struct_direct(int id, const char *name, StructEntry *se1)
+{
+    StructEntry *se;
+    se = struct_entries + id;
+    *se = *se1;
+    se->name = name;
+}
+
+
+/* now we can define the main conversion functions */
+const argtype *thunk_convert(void *dst, const void *src, 
+                             const argtype *type_ptr, int to_host)
+{
+    int type;
+
+    type = *type_ptr++;
+    switch(type) {
+    case TYPE_CHAR:
+        *(uint8_t *)dst = *(uint8_t *)src;
+        break;
+    case TYPE_SHORT:
+        *(uint16_t *)dst = tswap16(*(uint16_t *)src);
+        break;
+    case TYPE_INT:
+        *(uint32_t *)dst = tswap32(*(uint32_t *)src);
+        break;
+    case TYPE_LONGLONG:
+    case TYPE_ULONGLONG:
+        *(uint64_t *)dst = tswap64(*(uint64_t *)src);
+        break;
+#if HOST_LONG_BITS == 32 && TARGET_LONG_BITS == 32
+    case TYPE_LONG:
+    case TYPE_ULONG:
+    case TYPE_PTRVOID:
+        *(uint32_t *)dst = tswap32(*(uint32_t *)src);
+        break;
+#elif HOST_LONG_BITS == 64 && TARGET_LONG_BITS == 32
+    case TYPE_LONG:
+    case TYPE_ULONG:
+    case TYPE_PTRVOID:
+        if (target_to_host) {
+            *(uint64_t *)dst = tswap32(*(uint32_t *)src);
+        } else {
+            *(uint32_t *)dst = tswap32(*(uint64_t *)src & 0xffffffff);
+        }
+        break;
+#else
+#error unsupported conversion
+#endif
+    case TYPE_ARRAY:
+        {
+            int array_length, i, dst_size, src_size;
+            const uint8_t *s;
+            uint8_t  *d;
+
+            array_length = *type_ptr++;
+            dst_size = thunk_type_size(type_ptr, to_host);
+            src_size = thunk_type_size(type_ptr, 1 - to_host);
+            d = dst;
+            s = src;
+            for(i = 0;i < array_length; i++) {
+                thunk_convert(d, s, type_ptr, to_host);
+                d += dst_size;
+                s += src_size;
+            }
+            type_ptr = thunk_type_next(type_ptr);
+        }
+        break;
+    case TYPE_STRUCT:
+        {
+            int i;
+            const StructEntry *se;
+            const uint8_t *s;
+            uint8_t  *d;
+            const argtype *field_types;
+            const int *dst_offsets, *src_offsets;
+            
+            se = struct_entries + *type_ptr++;
+            if (se->convert[0] != NULL) {
+                /* specific conversion is needed */
+                (*se->convert[to_host])(dst, src);
+            } else {
+                /* standard struct conversion */
+                field_types = se->field_types;
+                dst_offsets = se->field_offsets[to_host];
+                src_offsets = se->field_offsets[1 - to_host];
+                d = dst;
+                s = src;
+                for(i = 0;i < se->nb_fields; i++) {
+                    field_types = thunk_convert(d + dst_offsets[i], 
+                                                s + src_offsets[i], 
+                                                field_types, to_host);
+                }
+            }
+        }
+        break;
+    default:
+        fprintf(stderr, "Invalid type 0x%x\n", type);
+        break;
+    }
+    return type_ptr;
+}
+
+/* from em86 */
+
+/* Utility function: Table-driven functions to translate bitmasks
+ * between X86 and Alpha formats...
+ */
+unsigned int target_to_host_bitmask(unsigned int x86_mask, 
+                                    bitmask_transtbl * trans_tbl)
+{
+    bitmask_transtbl *	btp;
+    unsigned int	alpha_mask = 0;
+
+    for(btp = trans_tbl; btp->x86_mask && btp->alpha_mask; btp++) {
+	if((x86_mask & btp->x86_mask) == btp->x86_bits) {
+	    alpha_mask |= btp->alpha_bits;
+	}
+    }
+    return(alpha_mask);
+}
+
+unsigned int host_to_target_bitmask(unsigned int alpha_mask, 
+                                    bitmask_transtbl * trans_tbl)
+{
+    bitmask_transtbl *	btp;
+    unsigned int	x86_mask = 0;
+
+    for(btp = trans_tbl; btp->x86_mask && btp->alpha_mask; btp++) {
+	if((alpha_mask & btp->alpha_mask) == btp->alpha_bits) {
+	    x86_mask |= btp->x86_mask;
+	}
+    }
+    return(x86_mask);
+}