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https://github.com/davidgiven/fluxengine.git
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333 lines
9.8 KiB
C++
333 lines
9.8 KiB
C++
#include "globals.h"
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#include "record.h"
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#include "decoders/decoders.h"
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#include "encoders/encoders.h"
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#include "c64.h"
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#include "crc.h"
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#include "sectorset.h"
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#include "writer.h"
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#include "fmt/format.h"
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#include <ctype.h>
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#include "bytes.h"
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FlagGroup Commodore64EncoderFlags;
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static DoubleFlag postIndexGapUs(
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{ "--post-index-gap-us" },
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"Post-index gap before first sector header (microseconds).",
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0);
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static DoubleFlag clockCompensation(
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{ "--clock-compensation-factor" },
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"Scale the output clock by this much.",
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1.0);
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static bool lastBit;
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static double clockRateUsForTrack(unsigned track)
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{ //what are the clockrateUsfortrack for a c64 disk... ????
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/*
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Track # Sectors/Track Speed Zone bits/rotation
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1 – 17 21 3 61,538.4
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18 – 24 19 2 57,142.8
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25 – 30 18 1 53,333.4
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31 – 35 17 0 50,000.0
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*/
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if (track < 17)
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return 3.25; //200000.0/61538.4
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if (track < 24)
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return 3.50; //200000.0/57142.8
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if (track < 30)
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return 3.750; //200000.0/53,333.4
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return 4.00; //200000.0/50.000.0
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}
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static unsigned sectorsForTrack(unsigned track)
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/*
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Track Sectors/track # Sectors Storage in Bytes
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----- ------------- --------- ----------------
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1-17 21 357 7820
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18-24 19 133 7170
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25-30 18 108 6300
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31-40(*) 17 85 6020
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---
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683 (for a 35 track image)
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*/
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{
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if (track < 17)
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return 21;
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if (track < 24)
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return 19;
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if (track < 30)
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return 18;
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return 17;
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}
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static int encode_data_gcr(uint8_t data)
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{
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switch (data)
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{
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#define GCR_ENTRY(gcr, data) \
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case data: return gcr;
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#include "data_gcr.h"
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#undef GCR_ENTRY
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}
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return -1;
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};
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static void write_bits(std::vector<bool>& bits, unsigned& cursor, const std::vector<bool>& src)
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{
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for (bool bit : src) //Range-based for loop
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{
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if (cursor < bits.size())
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bits[cursor++] = bit;
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}
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}
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static void write_bits(std::vector<bool>& bits, unsigned& cursor, uint64_t data, int width)
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{
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cursor += width;
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for (int i=0; i<width; i++)
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{
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unsigned pos = cursor - i - 1;
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if (pos < bits.size())
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bits[pos] = data & 1;
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data >>= 1;
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}
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}
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void bindump(std::ostream& stream, std::vector<bool>& buffer)
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{
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size_t pos = 0;
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while ((pos < buffer.size()) and (pos <520))
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{
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stream << fmt::format("{:5d} : ", pos);
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for (int i=0; i<40; i++)
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{
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if ((pos+i) < buffer.size())
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stream << fmt::format("{:01b}", (buffer[pos+i]));
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else
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stream << "-- ";
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if ((((pos + i + 1) % 8) == 0) and i != 0)
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stream << " ";
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}
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stream << std::endl;
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pos += 40;
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}
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}
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static std::vector<bool> encode_data(uint8_t input)
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/*
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Four 8-bit data bytes are converted to four 10-bit GCR bytes at a time by the 1541 DOS.
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RAM is only an 8-bit storage device though. This hardware limitation prevents a 10-bit
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GCR byte from being stored in a single memory location. Four 10-bit GCR bytes total
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40 bits - a number evenly divisible by our overriding 8-bit constraint. Commodore sub-
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divides the 40 GCR bits into five 8-bit bytes to solve this dilemma. This explains why
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four 8-bit data bytes are converted to GCR form at a time. The following step by step
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example demonstrates how this bit manipulation is performed by the DOS.
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STEP 1. Four 8-bit Data Bytes
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$08 $10 $00 $12
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STEP 2. Hexadecimal to Binary Conversion
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1. Binary Equivalents
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$08 $10 $00 $12
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00001000 00010000 00000000 00010010
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STEP 3. Binary to GCR Conversion
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1. Four 8-bit Data Bytes
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00001000 00010000 00000000 00010010
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2. High and Low Nybbles
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0000 1000 0001 0000 0000 0000 0001 0010
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3. High and Low Nybble GCR Equivalents
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01010 01001 01011 01010 01010 01010 01011 10010
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4. Four 10-bit GCR Bytes
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0101001001 0101101010 0101001010 0101110010
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STEP 4. 10-bit GCR to 8-bit GCR Conversion
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1. Concatenate Four 10-bit GCR Bytes
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0101001001010110101001010010100101110010
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2. Five 8-bit Subdivisions
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01010010 01010110 10100101 00101001 01110010
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STEP 5. Binary to Hexadecimal Conversion
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1. Hexadecimal Equivalents
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01010010 01010110 10100101 00101001 01110010
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$52 $56 $A5 $29 $72
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STEP 6. Four 8-bit Data Bytes are Recorded as Five 8-bit GCR Bytes
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$08 $10 $00 $12
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are recorded as
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$52 $56 $A5 $29 $72
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*/
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{
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std::vector<bool> output(10, false);
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uint8_t hi =0;
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uint8_t lo =0;
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uint8_t lo_GCR =0;
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uint8_t hi_GCR =0;
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//Convert the byte in high and low nibble
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lo = input >> 4; //get the lo nibble shift the bits 4 to the right
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hi = input & 15; //get the hi nibble bij masking the lo bits (00001111)
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lo_GCR = encode_data_gcr(lo); //example value: 0000 GCR = 01010
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hi_GCR = encode_data_gcr(hi); //example value: 1000 GCR = 01001
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//output = [0,1,2,3,4,5,6,7,8,9]
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//value = [0,1,0,1,0,0,1,0,0,1]
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// 01010 01001
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int b = 4;
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for (int i = 0; i < 10; i++)
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{
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if (i < 5) //01234
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{ //i = 0 op
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output[4-i] = (lo_GCR & 1); //01010
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//01010 -> & 00001 -> 00000 output[4] = 0
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//00101 -> & 00001 -> 00001 output[3] = 1
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//00010 -> & 00001 -> 00000 output[2] = 0
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//00001 -> & 00001 -> 00001 output[1] = 1
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//00000 -> & 00001 -> 00000 output[0] = 0
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lo_GCR >>= 1;
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} else
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{
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output[i+b] = (hi_GCR & 1); //01001
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//01001 -> & 00001 -> 00001 output[9] = 1
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//00100 -> & 00001 -> 00000 output[8] = 0
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//00010 -> & 00001 -> 00000 output[7] = 0
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//00001 -> & 00001 -> 00001 output[6] = 1
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//00000 -> & 00001 -> 00000 output[5] = 0
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hi_GCR >>= 1;
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b = b-2;
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}
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}
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return output;
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}
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static void write_sector(std::vector<bool>& bits, unsigned& cursor, const Sector* sector)
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{
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try
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{
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/* Source: http://www.unusedino.de/ec64/technical/formats/g64.html
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1. Header sync FF FF FF FF FF (40 'on' bits, not GCR)
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2. Header info 52 54 B5 29 4B 7A 5E 95 55 55 (10 GCR bytes)
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3. Header gap 55 55 55 55 55 55 55 55 55 (9 bytes, never read)
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4. Data sync FF FF FF FF FF (40 'on' bits, not GCR)
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5. Data block 55...4A (325 GCR bytes)
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6. Inter-sector gap 55 55 55 55...55 55 (4 to 12 bytes, never read)
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1. Header sync (SYNC for the next sector)
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*/
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if ((sector->data.size() != C64_SECTOR_LENGTH))
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Error() << fmt::format("unsupported sector size {} --- you must pick 256", sector->data.size());
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//1. Write header Sync (not GCR)
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for (int i=0; i<6; i++)
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write_bits(bits, cursor, C64_HEADER_DATA_SYNC, 1*8); /* sync */
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//2. Write Header info 10 GCR bytes
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/*
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The 10 byte header info (#2) is GCR encoded and must be decoded to it's
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normal 8 bytes to be understood. Once decoded, its breakdown is as follows:
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Byte $00 - header block ID ($08)
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01 - header block checksum 16 (EOR of $02-$05)
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02 - Sector
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03 - Track
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04 - Format ID byte #2
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05 - Format ID byte #1
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06-07 - $0F ("off" bytes)
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*/
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uint8_t encodedTrack = ((sector->logicalTrack) + 1); // C64 track numbering starts with 1. Fluxengine with 0.
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uint8_t encodedSector = sector->logicalSector;
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uint8_t formatByte1 = C64_FORMAT_ID_BYTE1;
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uint8_t formatByte2 = C64_FORMAT_ID_BYTE2;
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uint8_t headerChecksum = (encodedTrack ^ encodedSector ^ formatByte1 ^ formatByte2);
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write_bits(bits, cursor, encode_data(C64_HEADER_BLOCK_ID));
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write_bits(bits, cursor, encode_data(headerChecksum));
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write_bits(bits, cursor, encode_data(encodedSector));
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write_bits(bits, cursor, encode_data(encodedTrack));
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write_bits(bits, cursor, encode_data(formatByte1));
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write_bits(bits, cursor, encode_data(formatByte2));
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write_bits(bits, cursor, encode_data(C64_PADDING));
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write_bits(bits, cursor, encode_data(C64_PADDING));
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//3. Write header GAP not GCR
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for (int i=0; i<9; i++)
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write_bits(bits, cursor, C64_HEADER_GAP, 1*8); /* header gap */
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//4. Write Data sync not GCR
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for (int i=0; i<6; i++)
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write_bits(bits, cursor, C64_HEADER_DATA_SYNC, 1*8); /* sync */
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//5. Write data block 325 GCR bytes
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/*
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The 325 byte data block (#5) is GCR encoded and must be decoded to its
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normal 260 bytes to be understood. The data block is made up of the following:
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Byte $00 - data block ID ($07)
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01-100 - 256 bytes data
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101 - data block checksum (EOR of $01-100)
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102-103 - $00 ("off" bytes, to make the sector size a multiple of 5)
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*/
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write_bits(bits, cursor, encode_data(C64_DATA_BLOCK_ID));
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uint8_t dataChecksum = xorBytes(sector->data);
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ByteReader br(sector->data);
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int i = 0;
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for (i = 0; i < C64_SECTOR_LENGTH; i++)
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{
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uint8_t val = br.read_8();
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write_bits(bits, cursor, encode_data(val));
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}
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write_bits(bits, cursor, encode_data(dataChecksum));
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write_bits(bits, cursor, encode_data(C64_PADDING));
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write_bits(bits, cursor, encode_data(C64_PADDING));
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//6. Write inter-sector gap 9 - 12 bytes nor gcr
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for (int i=0; i<9; i++)
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write_bits(bits, cursor, C64_INTER_SECTOR_GAP, 1*8); /* sync */
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}
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catch(const std::exception& e)
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{
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std::cerr << e.what() << '\n';
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}
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}
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std::unique_ptr<Fluxmap> Commodore64Encoder::encode(
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int physicalTrack, int physicalSide, const SectorSet& allSectors)
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{
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try
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{
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if ((physicalTrack < 0) || (physicalTrack >= C64_TRACKS_PER_DISK))
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return std::unique_ptr<Fluxmap>();
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double clockRateUs = clockRateUsForTrack(physicalTrack) * clockCompensation;
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int bitsPerRevolution = 200000.0 / clockRateUs;
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std::vector<bool> bits(bitsPerRevolution);
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unsigned cursor = 0;
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fillBitmapTo(bits, cursor, postIndexGapUs / clockRateUs, { true, false });
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lastBit = false;
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unsigned numSectors = sectorsForTrack(physicalTrack);
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for (int sectorId=0; sectorId<numSectors; sectorId++)
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{
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const auto& sectorData = allSectors.get(physicalTrack, physicalSide, sectorId);
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write_sector(bits, cursor, sectorData);
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}
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if (cursor >= bits.size())
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Error() << fmt::format("track data overrun by {} bits", cursor - bits.size());
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fillBitmapTo(bits, cursor, bits.size(), { true, false });
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std::unique_ptr<Fluxmap> fluxmap(new Fluxmap);
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fluxmap->appendBits(bits, clockRateUs*1e3);
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return fluxmap;
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}
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catch(const std::exception& e)
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{
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std::cerr << e.what() << '\n';
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}
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}
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