Mechanical refactor to rearrange the source files into a more pleasing order.

2025-10-31 11:17:01 -07:00 · 2019-08-06 22:25:11 +02:00
parent 5748f017dd
commit 4b07c38782
35 changed files with 14 additions and 14 deletions
--- a/arch/ibm/decoder.cc
+++ b/arch/ibm/decoder.cc
@@ -0,0 +1,153 @@
+#include "globals.h"
+#include "decoders/decoders.h"
+#include "ibm.h"
+#include "crc.h"
+#include "fluxmap.h"
+#include "decoders/fluxmapreader.h"
+#include "sector.h"
+#include "record.h"
+#include <string.h>
+
+static_assert(std::is_trivially_copyable<IbmIdam>::value,
+		"IbmIdam is not trivially copyable");
+
+/*
+ * The markers at the beginning of records are special, and have
+ * missing clock pulses, allowing them to be found by the logic.
+ * 
+ * IAM record:
+ * flux:   XXXX-XXX-XXXX-X- = 0xf77a
+ * clock:  X X - X - X X X  = 0xd7
+ * data:    X X X X X X - - = 0xfc
+ * 
+ * (We just ignore this one --- it's useless and optional.)
+ */
+
+/* 
+ * IDAM record:
+ * flux:   XXXX-X-X-XXXXXX- = 0xf57e
+ * clock:  X X - - - X X X  = 0xc7
+ * data:    X X X X X X X - = 0xfe
+ */
+const FluxPattern FM_IDAM_PATTERN(16, 0xf57e);
+
+/* 
+ * DAM1 record:
+ * flux:   XXXX-X-X-XX-X-X- = 0xf56a
+ * clock:  X X - - - X X X  = 0xc7
+ * data:    X X X X X - - - = 0xf8
+ */
+const FluxPattern FM_DAM1_PATTERN(16, 0xf56a);
+
+/* 
+ * DAM2 record:
+ * flux:   XXXX-X-X-XX-XXXX = 0xf56f
+ * clock:  X X - - - X X X  = 0xc7
+ * data:    X X X X X - X X = 0xfb
+ */
+const FluxPattern FM_DAM2_PATTERN(16, 0xf56f);
+
+/* 
+ * TRS80DAM1 record:
+ * flux:   XXXX-X-X-XX-X-XX = 0xf56b
+ * clock:  X X - - - X X X  = 0xc7
+ * data:    X X X X X - - X = 0xf9
+ */
+const FluxPattern FM_TRS80DAM1_PATTERN(16, 0xf56b);
+
+/* 
+ * TRS80DAM2 record:
+ * flux:   XXXX-X-X-XX-XXX- = 0xf56c
+ * clock:  X X - - - X X X  = 0xc7
+ * data:    X X X X X - X - = 0xfa
+ */
+const FluxPattern FM_TRS80DAM2_PATTERN(16, 0xf56c);
+
+/* MFM record separator:
+ * 0xA1 is:
+ * data:    1  0  1  0  0  0  0  1  = 0xa1
+ * mfm:     01 00 01 00 10 10 10 01 = 0x44a9
+ * special: 01 00 01 00 10 00 10 01 = 0x4489
+ *                       ^^^^^
+ * When shifted out of phase, the special 0xa1 byte becomes an illegal
+ * encoding (you can't do 10 00). So this can't be spoofed by user data.
+ * 
+ * shifted: 10 00 10 01 00 01 00 1
+ */
+const FluxPattern MFM_PATTERN(16, 0x4489);
+
+const FluxMatchers ANY_RECORD_PATTERN(
+    {
+        &MFM_PATTERN,
+        &FM_IDAM_PATTERN,
+        &FM_DAM1_PATTERN,
+        &FM_DAM2_PATTERN,
+        &FM_TRS80DAM1_PATTERN,
+        &FM_TRS80DAM2_PATTERN,
+    }
+);
+
+AbstractDecoder::RecordType IbmDecoder::advanceToNextRecord()
+{
+	const FluxMatcher* matcher = nullptr;
+	_sector->clock = _fmr->seekToPattern(ANY_RECORD_PATTERN, matcher);
+
+    /* If this is the MFM prefix byte, the the decoder is going to expect three
+     * extra bytes on the front of the header. */
+    _currentHeaderLength = (matcher == &MFM_PATTERN) ? 3 : 0;
+
+    Fluxmap::Position here = tell();
+    if (_currentHeaderLength > 0)
+        readRawBits(_currentHeaderLength*16);
+    auto idbits = readRawBits(16);
+    uint8_t id = decodeFmMfm(idbits).slice(0, 1)[0];
+    seek(here);
+    
+    switch (id)
+    {
+        case IBM_IDAM:
+            return RecordType::SECTOR_RECORD;
+
+        case IBM_DAM1:
+        case IBM_DAM2:
+        case IBM_TRS80DAM1:
+        case IBM_TRS80DAM2:
+            return RecordType::DATA_RECORD;
+    }
+    return RecordType::UNKNOWN_RECORD;
+}
+
+void IbmDecoder::decodeSectorRecord()
+{
+    unsigned recordSize = _currentHeaderLength + IBM_IDAM_LEN;
+    auto bits = readRawBits(recordSize*16);
+    auto bytes = decodeFmMfm(bits).slice(0, recordSize);
+
+    ByteReader br(bytes);
+    br.seek(_currentHeaderLength);
+    br.read_8(); /* skip ID byte */
+    _sector->logicalTrack = br.read_8();
+    _sector->logicalSide = br.read_8();
+    _sector->logicalSector = br.read_8() - _sectorBase;
+    _currentSectorSize = 1 << (br.read_8() + 7);
+    uint16_t wantCrc = br.read_be16();
+    uint16_t gotCrc = crc16(CCITT_POLY, bytes.slice(0, _currentHeaderLength + 5));
+    if (wantCrc == gotCrc)
+        _sector->status = Sector::DATA_MISSING; /* correct but unintuitive */
+}
+
+void IbmDecoder::decodeDataRecord()
+{
+    unsigned recordLength = _currentHeaderLength + _currentSectorSize + 3;
+    auto bits = readRawBits(recordLength*16);
+    auto bytes = decodeFmMfm(bits).slice(0, recordLength);
+
+    ByteReader br(bytes);
+    br.seek(_currentHeaderLength);
+    br.read_8(); /* skip ID byte */
+
+    _sector->data = br.read(_currentSectorSize);
+    uint16_t wantCrc = br.read_be16();
+    uint16_t gotCrc = crc16(CCITT_POLY, bytes.slice(0, recordLength-2));
+    _sector->status = (wantCrc == gotCrc) ? Sector::OK : Sector::BAD_CHECKSUM;
+}