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apd_dsk: added notes (nw)

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This commit is contained in:
Nigel Barnes 2017-03-23 18:02:32 +00:00
parent 9dfaaa3fcb
commit d0d342d76c
1 changed files with 55 additions and 3 deletions
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58
src/lib/formats/apd_dsk.cpp
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@ -6,6 +6,58 @@
Archimedes Protected Disk Image format Archimedes Protected Disk Image format
APD file structure
------------------
The APD file is a GZip compressed version of the original APD file.
Compressed file always starts:
1F 8B 08 00 00 00 00 00 00 0B EC BD
^^ ^^ ^^ ^^ ^^ ^^ ^^ ^^ ^^ ^^
| | | | | | | | | |
| | | | | | | | | +- OS
| | | | | | | | +---- xfl
| | | | +--+--+--+------- time
| | | +------------------- gzip flags
| | +---------------------- gzip compression*
| |
+--+------------------------- gzip header
* Compression method: 8 is the only supported format
Original APD file structure:
0 - 7 "APDX0001" identifier
8 - B t0sd - Track 0 SD length in bits
C - F t0dd - Track 0 DD length in bits
10 - 13 t0qd - Track 0 QD length in bits
14 - 1F t1sd - Track 1 SD length in bits
20 - 23 t1dd - Track 1 DD length in bits
24 - 27 t1qd - Track 1 QD length in bits
... ... repeated to Track 159
77C - 787 Track 160 (blank)
7C4 - 7CF Track 166 (blank)
7D0 Track 0 SD data
+ (t0sd + 7) >> 3 Track 0 DD data
+ (t0dd + 7) >> 3 Track 0 QD data
+ (t0qd + 7) >> 3 Track 1 SD data
+ (t1sd + 7) >> 3 Track 1 DD data
+ (t1dd + 7) >> 3 Track 1 QD data
SD data is big-endian raw FM words
DD/QD data is big-endian raw MFM words
As far as I can tell, the tracks are always sequential, so
physical tracks translate as:
Physical APD
-------------- -------
Side 0 Track 0 > Track 0
Side 1 Track 0 > Track 1
Side 0 Track 1 > Track 2
etc.
*********************************************************************/ *********************************************************************/
#include <zlib.h> #include <zlib.h>
@ -96,17 +148,17 @@ bool apd_format::load(io_generic *io, uint32_t form_factor, floppy_image *image)
err = inflateInit2(&d_stream, MAX_WBITS | 16); err = inflateInit2(&d_stream, MAX_WBITS | 16);
if (err != Z_OK) { if (err != Z_OK) {
LOG_FORMATS("inflateInit2 error: %d\n", err); osd_printf_error("inflateInit2 error: %d\n", err);
return false; return false;
} }
err = inflate(&d_stream, Z_FINISH); err = inflate(&d_stream, Z_FINISH);
if (err != Z_STREAM_END && err != Z_OK) { if (err != Z_STREAM_END && err != Z_OK) {
LOG_FORMATS("inflate error: %d\n", err); osd_printf_error("inflate error: %d\n", err);
return false; return false;
} }
err = inflateEnd(&d_stream); err = inflateEnd(&d_stream);
if (err != Z_OK) { if (err != Z_OK) {
LOG_FORMATS("inflateEnd error: %d\n", err); osd_printf_error("inflateEnd error: %d\n", err);
return false; return false;
} }
size = inflate_size; size = inflate_size;