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// license:BSD-3-Clause
// copyright-holders:Wilbert Pol
/*********************************************************************
formats/dmk_dsk.cpp
DMK disk images
TODO:
- Add write/format support.
- Check support on other drivers besides msx.
*********************************************************************/
#include "dmk_dsk.h"
#include "coretmpl.h"
#include "ioprocs.h"
#include "multibyte.h"
namespace {
uint32_t wide_fm(uint16_t val)
{
uint32_t res = 0;
for (int i = 15; i >= 0; i--) {
res |= (util::BIT(val, i) << (i*2 + 1));
}
return res;
}
uint32_t data_to_wide_fm(uint8_t val)
{
uint16_t res = 0xaaaa; // clock
for (int i = 7; i >= 0; i--) {
res |= (util::BIT(val, i) << i*2); // data
}
return wide_fm(res);
}
} // anonymous namespace
dmk_format::dmk_format()
{
}
const char *dmk_format::name() const noexcept
{
return "dmk";
}
const char *dmk_format::description() const noexcept
{
return "DMK disk image";
}
const char *dmk_format::extensions() const noexcept
{
return "dmk";
}
int dmk_format::identify(util::random_read &io, uint32_t form_factor, const std::vector<uint32_t> &variants) const
{
uint64_t size;
if (io.length(size))
return 0;
const int header_size = 16;
uint8_t header[header_size];
size_t actual;
io.read_at(0, header, header_size, actual);
int tracks = header[1];
int track_size = get_u16le(&header[2]);
int heads = (header[4] & 0x10) ? 1 : 2;
// The first header byte must be 00 or FF
if (header[0] != 0x00 && header[0] != 0xff)
{
return 0;
}
// Bytes C-F must be zero
if (header[0x0c] != 0 || header[0xd] != 0 || header[0xe] != 0 || header[0xf] != 0)
{
return 0;
}
// Check track size within limits
if (track_size < 0x80 || track_size > 0x3FFF )
{
return 0;
}
if (size == header_size + heads * tracks * track_size)
{
return FIFID_STRUCT|FIFID_SIZE;
}
return 0;
}
bool dmk_format::load(util::random_read &io, uint32_t form_factor, const std::vector<uint32_t> &variants, floppy_image &image) const
{
size_t actual;
const int header_size = 16;
uint8_t header[header_size];
io.read_at(0, header, header_size, actual);
const int tracks = header[1];
const int track_size = get_u16le(&header[2]);
const int heads = (header[4] & 0x10) ? 1 : 2;
const bool is_sd = (header[4] & 0x40) ? true : false;
auto variant = floppy_image::SSDD;
if (is_sd)
{
if (heads == 2)
{
variant = floppy_image::DSSD;
}
else
{
variant = floppy_image::SSSD;
}
}
else
{
if (heads == 2)
{
variant = floppy_image::DSDD;
}
else
{
variant = floppy_image::SSDD;
}
}
image.set_variant(variant);
int fm_stride = is_sd ? 1 : 2;
for (int track = 0; track < tracks; track++)
{
for (int head = 0; head < heads; head++)
{
int fm_loss = 0;
std::vector<uint8_t> track_data(track_size);
std::vector<uint32_t> raw_track_data;
int mark_location[64*2+1];
uint8_t mark_value[64*2+1];
bool mark_is_mfm[64*2+1];
int iam_location = -1;
// Read track
io.read_at(header_size + (heads * track + head) * track_size, &track_data[0], track_size, actual);
for (int i = 0; i < 64*2+1; i++)
{
mark_location[i] = -1;
mark_value[i] = 0xfe;
mark_is_mfm[i] = !is_sd; // Use default encoding
}
int mark_count = 0;
// Find IDAM/DAM locations
uint16_t track_header_offset = 0;
uint16_t track_offset = get_u16le(&track_data[track_header_offset]) & 0x3fff;
bool idam_is_mfm = (track_data[track_header_offset + 1] & 0x80) ? true : false;
track_header_offset += 2;
while ( track_offset != 0 && track_offset >= 0x83 && track_offset < track_size && track_header_offset < 0x80 )
{
// Assume 3 bytes before IDAM pointers are the start of IDAM indicators
int mark_offset = idam_is_mfm ? 3 : 0;
mark_location[mark_count] = track_offset - mark_offset;
mark_value[mark_count] = 0xfe;
mark_is_mfm[mark_count] = idam_is_mfm;
mark_count++;
int stride = idam_is_mfm ? 1 : fm_stride;
// Scan for DAM location
for (int i = track_offset + 10*stride; i < track_offset + 53*stride; i++)
{
if ((track_data[i] >= 0xf8 && track_data[i] <= 0xfb))
{
if (!idam_is_mfm || (track_data[i-1] == 0xa1 && track_data[i-2] == 0xa1))
{
mark_location[mark_count] = i - mark_offset;
mark_value[mark_count] = track_data[i];
mark_is_mfm[mark_count] = idam_is_mfm;
mark_count++;
break;
}
}
}
idam_is_mfm = (track_data[track_header_offset + 1] & 0x80) ? true : false;
track_offset = get_u16le(&track_data[track_header_offset]) & 0x3fff;
track_header_offset += 2;
}
// Prevent encoding from switching after last sector
if (mark_count > 0)
{
mark_is_mfm[mark_count] = mark_is_mfm[mark_count - 1];
}
// Find IAM location
for(int i = mark_location[0] - 1; i >= 3; i--)
{
// It's usually 3 bytes but several dumped tracks seem to contain only 2 bytes
if (track_data[i] == 0xfc && (is_sd || (track_data[i-1] == 0xc2 && track_data[i-2] == 0xc2)))
{
iam_location = i - (is_sd ? 0 : 3);
break;
}
}
int curr_mark = 0;
bool enc_mfm = mark_is_mfm[curr_mark];
for (int offset = 0x80; offset < track_size; offset++)
{
if (offset == iam_location)
{
if (!is_sd)
{
// Write IAM
raw_w(raw_track_data, 16, 0x5224);
raw_w(raw_track_data, 16, 0x5224);
raw_w(raw_track_data, 16, 0x5224);
offset += 3;
}
else
{
raw_w(raw_track_data, 32, wide_fm(0xf77a)); // FC clocked with D7
offset += fm_stride;
}
}
// If close to mark, switch encoding
if (offset + 8 >= mark_location[curr_mark])
{
bool new_enc = mark_is_mfm[curr_mark];
if (new_enc != enc_mfm)
{
enc_mfm = new_enc;
}
}
if (offset == mark_location[curr_mark]
|| (!enc_mfm && offset - fm_stride + 1 == mark_location[curr_mark])
)
{
if (enc_mfm)
{
raw_w(raw_track_data, 16, 0x4489);
raw_w(raw_track_data, 16, 0x4489);
raw_w(raw_track_data, 16, 0x4489);
offset += 3;
if (fm_stride == 1)
{
fm_loss += 3;
}
}
else
{
uint16_t mark;
switch (mark_value[curr_mark])
{
default:
case 0xfb: mark = 0xf56f; break;
case 0xfa: mark = 0xf56e; break;
case 0xf9: mark = 0xf56b; break;
case 0xf8: mark = 0xf56a; break;
case 0xfe: mark = 0xf57e; break;
}
raw_w(raw_track_data, 32, wide_fm(mark));
offset += fm_stride;
}
curr_mark++;
}
if (enc_mfm)
{
if (fm_stride == 1)
{
fm_loss++;
}
mfm_w(raw_track_data, 8, track_data[offset]);
}
else
raw_w(raw_track_data, 32, data_to_wide_fm(track_data[offset]));
if (!enc_mfm)
offset += fm_stride - 1;
}
if (fm_loss != 0)
{
if (enc_mfm)
{
for (int jj = 0; jj < fm_loss; jj++)
{
mfm_w(raw_track_data, 8, 0x4e);
}
}
else
{
for (int jj = 0; jj < fm_loss/2; jj++)
{
raw_w(raw_track_data, 32, data_to_wide_fm(0xff));
}
}
}
generate_track_from_levels(track, head, raw_track_data, 0, image);
}
}
return true;
}
bool dmk_format::supports_save() const noexcept
{
return false;
}
const dmk_format FLOPPY_DMK_FORMAT;
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