111 lines
1.9 KiB
C
111 lines
1.9 KiB
C
/* $Source$
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* $State$
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* $Revision$
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*/
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#include <stdio.h>
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#include <stdlib.h>
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#include <errno.h>
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#include <unistd.h>
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#include <string.h>
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#include <cpm.h>
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#include "cpmsys.h"
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ssize_t read(int fd, void* buffer, size_t count)
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{
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uint8_t* bbuffer = buffer;
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struct FCBE* fcbe = &__fd[fd];
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uint8_t olduser;
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ssize_t result;
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uint8_t* src;
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__init_file_descriptors();
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if (fcbe->fcb.dr == 0)
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{
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/* Read from the console. */
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if (count == 0)
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return 0;
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*(uint8_t*)buffer = cpm_conin();
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return 1;
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}
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olduser = cpm_get_user();
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cpm_set_user(fcbe->user);
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if (U16(fcbe->fcb.r) >= fcbe->length)
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goto done;
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if (fcbe->offset || !SECTOR_ALIGNED(count))
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{
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/* We need to read bytes until we're at a sector boundary. */
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cpm_set_dma(__transfer_buffer);
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if (cpm_read_random_safe(&fcbe->fcb) != 0)
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goto eio;
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/* Copy enough bytes to reach the end of the sector. */
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src = __transfer_buffer + fcbe->offset;
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while ((count != 0) && (fcbe->offset != 128))
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{
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*bbuffer++ = *src++;
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fcbe->offset++;
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count--;
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}
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/* If we've read enough bytes, advance to the next sector. */
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if (fcbe->offset == 128)
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{
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U16(fcbe->fcb.r)++;
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fcbe->offset = 0;
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}
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}
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while (count >= 128)
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{
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if (U16(fcbe->fcb.r) >= fcbe->length)
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goto done;
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/* Read entire sectors directly into the destination buffer. */
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cpm_set_dma(bbuffer);
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if (cpm_read_random_safe(&fcbe->fcb) != 0)
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goto eio;
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count -= 128;
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bbuffer += 128;
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U16(fcbe->fcb.r)++;
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}
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if (count != 0)
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{
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if (U16(fcbe->fcb.r) >= fcbe->length)
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goto done;
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/* There's some trailing data to read. */
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cpm_set_dma(__transfer_buffer);
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if (cpm_read_random_safe(&fcbe->fcb) != 0)
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goto eio;
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src = __transfer_buffer;
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while (count != 0)
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{
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*bbuffer++ = *src++;
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count--;
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}
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fcbe->offset = count;
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}
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done:
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result = bbuffer - (uint8_t*)buffer;
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exit:
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cpm_set_user(olduser);
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return result;
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eio:
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errno = EIO;
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result = -1;
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goto exit;
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}
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