53 lines
1.8 KiB
C
53 lines
1.8 KiB
C
/* Buffered input/output */
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#ifndef _io_
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#define _io_
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#include "misc.h"
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#include "mlvalues.h"
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#ifndef IO_BUFFER_SIZE
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#define IO_BUFFER_SIZE 4096
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#endif
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struct channel {
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int fd; /* Unix file descriptor */
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long offset; /* Absolute position of fd in the file */
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char * curr; /* Current position in the buffer */
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char * max; /* Logical end of the buffer */
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char * end; /* Physical end of the buffer */
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char buff[IO_BUFFER_SIZE]; /* The buffer itself */
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};
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/* For an output channel:
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[offset] is the absolute position of the beginning of the buffer [buff].
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For an input channel:
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[offset] is the absolute position of the logical end of the buffer [max].
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*/
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#define putch(channel, ch) \
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{ if ((channel)->curr >= (channel)->end) flush(channel); \
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*((channel)->curr)++ = (ch); \
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if ((channel)->curr > (channel)->max) (channel)->max = (channel)->curr; }
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#define getch(channel) \
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((channel)->curr >= (channel)->max \
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? refill(channel) \
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: (unsigned char) *((channel))->curr++)
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struct channel * open_descr P((int));
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value flush P((struct channel *));
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void putword P((struct channel *, uint32));
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void putblock P((struct channel *, char *, unsigned));
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unsigned char refill P((struct channel *));
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value pos_out P((struct channel *));
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value seek_out P((struct channel *, value));
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uint32 getword P((struct channel *));
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unsigned getblock P((struct channel *, char *, unsigned));
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int really_getblock P((struct channel *, char *, unsigned long));
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value close_in P((struct channel *));
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#endif /* _io_ */
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