Add a primitive (non-checksum-checking) parser. Looks like the decoding loses a

lot of sectors --- the read rate is terrible.

doc/index.md

@@ -422,6 +422,9 @@ Useful links:
     documentation](https://www.kryoflux.com/download/kryoflux_stream_protocol_rev1.1.pdf):
     the format of KryoFlux stream files (partially supported by FluxEngine)
 
+  - [The Amiga Floppy Boot Process and Physical
+    Layout](https://wiki.amigaos.net/wiki/Amiga_Floppy_Boot_Process_and_Physical_Layout)
+
 Who?
 ----
 

lib/amiga/parser.cc

@@ -7,6 +7,36 @@
 #include "record.h"
 #include <string.h>
 
+static std::vector<uint8_t> deinterleave(const uint8_t*& input, size_t len)
+{
+    assert(!(len & 1));
+    const uint8_t* odds = input;
+    const uint8_t* evens = input + len/2;
+    std::vector<uint8_t> output;
+    output.reserve(len);
+
+    for (int i=0; i<len/2; i++)
+    {
+        uint8_t y = *evens++;
+        uint8_t x = *odds++;
+
+        /* This is the 'Interleave bits with 64-bit multiply' technique from
+         * http://graphics.stanford.edu/~seander/bithacks.html#InterleaveBMN
+         */
+        uint16_t result =
+            ((x * 0x0101010101010101ULL & 0x8040201008040201ULL)
+                * 0x0102040810204081ULL >> 49) & 0x5555 |
+            ((y * 0x0101010101010101ULL & 0x8040201008040201ULL)
+                * 0x0102040810204081ULL >> 48) & 0xAAAA;
+        
+        output.push_back((uint8_t)(result >> 8));
+        output.push_back((uint8_t)result);
+    }
+
+    input += len;
+    return output;
+}
+
 std::vector<std::unique_ptr<Sector>> AmigaRecordParser::parseRecordsToSectors(
         const RecordVector& records) const
 {
@@ -18,6 +48,22 @@ std::vector<std::unique_ptr<Sector>> AmigaRecordParser::parseRecordsToSectors(
     for (auto& record : records)
     {
 		const std::vector<uint8_t>& data = record->data;
+        if (data.size() < 544)
+            continue;
+
+        const uint8_t* ptr = &data[4];
+
+        std::vector<uint8_t> header = deinterleave(ptr, 4);
+        std::vector<uint8_t> recoveryinfo = deinterleave(ptr, 16);
+        std::vector<uint8_t> headerchecksum = deinterleave(ptr, 4);
+        std::vector<uint8_t> datachecksum = deinterleave(ptr, 4);
+        std::vector<uint8_t> databytes = deinterleave(ptr, 512);
+
+        int track = header[1] >> 1;
+        int head = header[1] & 1;
+        auto sector = std::unique_ptr<Sector>(
+            new Sector(Sector::OK, track, head, header[2], databytes));
+        sectors.push_back(std::move(sector));
     }
 
     return sectors;

src/fe-readamiga.cc

@@ -18,7 +18,7 @@ static StringFlag outputFilename(
 
 int main(int argc, const char* argv[])
 {
-	setReaderDefaultSource(":t=0-81:s=0");
+	setReaderDefaultSource(":t=0-81:s=0-1");
     setReaderRevolutions(2);
     Flag::parseFlags(argc, argv);