forked from Hay1tsme/segatools
153 lines
3.2 KiB
C
153 lines
3.2 KiB
C
#include <windows.h>
|
|
|
|
#include <assert.h>
|
|
#include <stdbool.h>
|
|
#include <stddef.h>
|
|
#include <stdint.h>
|
|
|
|
#include "hook/iobuf.h"
|
|
|
|
#include "jvs/jvs-frame.h"
|
|
|
|
#include "util/dprintf.h"
|
|
|
|
static HRESULT jvs_frame_check_sum(const struct iobuf *dest);
|
|
static HRESULT jvs_frame_encode_byte(struct iobuf *dest, uint8_t byte);
|
|
|
|
/* Deals in whole frames only for simplicity's sake, since that's all we need
|
|
to emulate the Nu's kernel driver interface. This could of course be
|
|
extended later for other arcade hardware platforms. */
|
|
|
|
HRESULT jvs_frame_decode(
|
|
struct iobuf *dest,
|
|
const void *ptr,
|
|
size_t nbytes)
|
|
{
|
|
const uint8_t *bytes;
|
|
bool escape;
|
|
size_t i;
|
|
|
|
assert(dest != NULL);
|
|
assert(ptr != NULL);
|
|
|
|
bytes = ptr;
|
|
|
|
if (nbytes == 0) {
|
|
dprintf("JVS Frame: Empty frame\n");
|
|
|
|
return E_FAIL;
|
|
}
|
|
|
|
if (bytes[0] != 0xE0) {
|
|
dprintf("JVS Frame: Sync byte was expected\n");
|
|
|
|
return E_FAIL;
|
|
}
|
|
|
|
escape = false;
|
|
|
|
for (i = 1 ; i < nbytes ; i++) {
|
|
if (bytes[i] == 0xE0) {
|
|
dprintf("JVS Frame: Unexpected sync byte\n");
|
|
|
|
return E_FAIL;
|
|
} else if (bytes[i] == 0xD0) {
|
|
if (escape) {
|
|
dprintf("JVS Frame: Escaping fault\n");
|
|
|
|
return E_FAIL;
|
|
}
|
|
|
|
escape = true;
|
|
} else {
|
|
if (dest->pos >= dest->nbytes) {
|
|
return HRESULT_FROM_WIN32(ERROR_INSUFFICIENT_BUFFER);
|
|
}
|
|
|
|
if (escape) {
|
|
escape = false;
|
|
dest->bytes[dest->pos++] = bytes[i] + 1;
|
|
} else {
|
|
dest->bytes[dest->pos++] = bytes[i];
|
|
}
|
|
}
|
|
}
|
|
|
|
return jvs_frame_check_sum(dest);
|
|
}
|
|
|
|
static HRESULT jvs_frame_check_sum(const struct iobuf *dest)
|
|
{
|
|
uint8_t checksum;
|
|
size_t i;
|
|
|
|
checksum = 0;
|
|
|
|
for (i = 0 ; i < dest->pos - 1 ; i++) {
|
|
checksum += dest->bytes[i];
|
|
}
|
|
|
|
if (checksum != dest->bytes[dest->pos - 1]) {
|
|
dprintf("JVS Frame: Checksum failure\n");
|
|
|
|
return HRESULT_FROM_WIN32(ERROR_CRC);
|
|
}
|
|
|
|
return S_OK;
|
|
}
|
|
|
|
HRESULT jvs_frame_encode(
|
|
struct iobuf *dest,
|
|
const void *ptr,
|
|
size_t nbytes)
|
|
{
|
|
const uint8_t *bytes;
|
|
uint8_t checksum;
|
|
size_t i;
|
|
HRESULT hr;
|
|
|
|
assert(dest != NULL);
|
|
assert(ptr != NULL);
|
|
|
|
bytes = ptr;
|
|
checksum = 0;
|
|
|
|
if (dest->pos + 1 > dest->nbytes) {
|
|
return HRESULT_FROM_WIN32(ERROR_INSUFFICIENT_BUFFER);
|
|
}
|
|
|
|
dest->bytes[dest->pos++] = 0xE0;
|
|
|
|
for (i = 0 ; i < nbytes ; i++) {
|
|
hr = jvs_frame_encode_byte(dest, bytes[i]);
|
|
|
|
if (FAILED(hr)) {
|
|
return hr;
|
|
}
|
|
|
|
checksum += bytes[i];
|
|
}
|
|
|
|
return jvs_frame_encode_byte(dest, checksum);
|
|
}
|
|
|
|
static HRESULT jvs_frame_encode_byte(struct iobuf *dest, uint8_t byte)
|
|
{
|
|
if (byte == 0xD0 || byte == 0xE0) {
|
|
if (dest->pos + 2 > dest->nbytes) {
|
|
return HRESULT_FROM_WIN32(ERROR_INSUFFICIENT_BUFFER);
|
|
}
|
|
|
|
dest->bytes[dest->pos++] = 0xD0;
|
|
dest->bytes[dest->pos++] = byte - 1;
|
|
} else {
|
|
if (dest->pos + 1 > dest->nbytes) {
|
|
return HRESULT_FROM_WIN32(ERROR_INSUFFICIENT_BUFFER);
|
|
}
|
|
|
|
dest->bytes[dest->pos++] = byte;
|
|
}
|
|
|
|
return S_OK;
|
|
}
|