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138 lines
4.3 KiB
Plaintext
138 lines
4.3 KiB
Plaintext
<!doctype linuxdoc system>
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<article>
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<title>Diskette Sector I/O Routines
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<author>Christian Groessler, <htmlurl url="mailto:cpg@aladdin.de" name="cpg@aladdin.de">
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<date>20-Feb-2005
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<abstract>
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The cc65 library provides functions to read and write raw disk sectors.
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Include the dio.h header file to get the necessary definitions.
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</abstract>
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<!-- Table of contents -->
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<toc>
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<!-- Begin the document -->
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<sect>Opening the disk for low level I/O<p>
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Prior to using these functions a handle to the drive has to be obtained. This
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is done with the <tt>dio_open</tt> function. After use, the handle should be
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released with the <tt>dio_close</tt> function.
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<tscreen><verb>
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dhandle_t __fastcall__ dio_open (driveid_t drive_id);
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</verb></tscreen>
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The <tt>drive_id</tt> specifies the drive to access, with 0 being the first
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disk drive, 1 the second, and so on.
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<tscreen><verb>
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unsigned char __fastcall__ dio_close (dhandle_t handle);
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</verb></tscreen>
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Closes a handle obtained by <tt>dio_open</tt>. Returns status code.
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<p>
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<sect>Reading and writing sectors<p>
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The read and write functions are:
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<tscreen><verb>
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unsigned char __fastcall__ dio_read (dhandle_t handle,
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sectnum_t sect_num,
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void *buffer);
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</verb></tscreen>
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This function will read the sector specified by <tt>sect_num</tt> into the memory
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location at buffer.
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<tscreen><verb>
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unsigned char __fastcall__ dio_write (dhandle_t handle,
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sectnum_t sect_num,
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const void *buffer);
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</verb></tscreen>
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This function will write the memory contents at buffer to the sector specified
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by <tt>sect_num</tt>. No verify is performed.
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<tscreen><verb>
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unsigned char __fastcall__ dio_write_verify (dhandle_t handle,
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sectnum_t sect_num,
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const void *buffer);
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</verb></tscreen>
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This function will write the memory contents at buffer to the sector specified
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by <tt>sect_num</tt>. A verification is performed.
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<p>
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Use the <tt><ref name="dio_query_sectsize" id="sectsizecount"></tt> function to query
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the size of a sector and the <tt><ref name="dio_query_sectcount" id="sectsizecount"></tt>
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function to query the number of available sectors.
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<p>
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All these functions will return 0 for success and an OS specific error code in
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case of failure.
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<p>
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<sect>Querying sector size and count<label id="sectsizecount"><p>
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Some systems support multiple diskette formats which have different sector sizes
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and/or different sector counts.
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<p>
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The following function returns the sector size of the currently inserted disk:
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<tscreen><verb>
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sectsize_t __fastcall__ dio_query_sectsize(dhandle_t handle);
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</verb></tscreen>
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On the Atari platform, the sector size is handled specially. Please refer
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to the DIO section in the <htmlurl url="atari.html" name="Atari">
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specific platform documentation.
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<p>
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The following function returns the sector count of the currently inserted disk:
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<tscreen><verb>
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sectnum_t __fastcall__ dio_query_sectcount(dhandle_t handle);
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</verb></tscreen>
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<sect>Converting sector numbers<p>
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Since the read and write functions expect a sector number, for systems where
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the sectors aren't addressed by a logical sector number (e.g. CBM drives),
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there are 2 conversion functions. One of them converts a logical sector number
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to a head/track/sector triple. The other conversion function works the other
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way round.
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<tscreen><verb>
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unsigned char __fastcall__ dio_phys_to_log (dhandle_t handle,
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const dio_phys_pos *physpos,
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sectnum_t *sectnum);
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</verb></tscreen>
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This function converts track/head/sector to logical sector number.
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<tscreen><verb>
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unsigned char __fastcall__ dio_log_to_phys (dhandle_t handle,
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const _sectnum_t *sectnum,
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dio_phys_pos *physpos);
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</verb></tscreen>
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This function converts a logical sector number to track/head/sector notation.
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<p>
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Note, that on systems which natively use logical sector numbers (e.g. Atari),
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the conversion functions are dummies. They ignore head/track
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(<tt>dio_phys_to_log</tt>) or return them as zero (<tt>dio_log_to_phys</tt>).
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The logical sector number is returned as physical sector and vice versa.
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<p>
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</article>
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