109 lines
1.9 KiB
C
109 lines
1.9 KiB
C
/*
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* fifo.c
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*
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* A general implementation of a fifo buffer
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*
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*/
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#include <fifo.h>
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//This initializes the FIFO structure with the given buffer and size
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void fifo_init(fifo_t * f, char * buf, int16_t size)
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{
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f->head = 0;
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f->tail = 0;
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f->size = size;
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f->buf = buf;
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f->low = 0;
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f->high = 0;
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}
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// Get one byte from the fifo buffer
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uint8_t fifo_get(fifo_t *f)
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{
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uint8_t ch = 0;
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if( !fifo_empty(f) )
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{
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fifo_advance(f,&f->tail);
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ch = f->buf[f->tail];
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}
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return ch;
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}
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// Put one byte into the buffer
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void fifo_put(fifo_t *f, uint8_t byte)
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{
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if( fifo_unused(f) <= 0 )
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return;
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fifo_advance(f,&f->head);
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f->buf[f->head] = byte;
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}
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void fifo_clear(fifo_t *f)
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{
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f->head = f->tail = 0;
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}
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int fifo_used(fifo_t *f)
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{
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if( f->head > f->tail )
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return (f->head - f->tail);
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return (f->size - f->tail + f->head);
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}
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int fifo_unused(fifo_t *f)
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{
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if( f->head > f->tail )
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return (f->size-f->head+f->tail);
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return (f->tail-f->head);
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}
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int fifo_full(fifo_t *f)
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{
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if( f->head+1 >= f->size )
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return (f->tail == 0);
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return (f->head+1 == f->tail);
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}
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int fifo_empty(fifo_t *f)
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{
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return (f->head == f->tail);
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}
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void fifo_advance(fifo_t *f, int16_t *ix)
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{
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if( ++*ix > f->size )
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*ix=0;
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}
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//This reads at most nbytes bytes from the FIFO
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//The number of bytes read is returned
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int fifo_read(fifo_t *f, unsigned char *buf, int16_t nbytes){
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int n = 0;
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while( n < nbytes && !fifo_empty(f) )
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{
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n++;
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*buf++ = fifo_get(f);
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}
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return n;
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}
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//This writes up to nbytes bytes to the FIFO
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//If the head runs in to the tail, not all bytes are written
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//The number of bytes written is returned
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int fifo_write(fifo_t *f, const unsigned char *buf, int16_t nbytes){
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int n = 0;
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while( n < nbytes && !fifo_full(f) )
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{
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fifo_put(f,*buf++);
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n++;
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}
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return n;
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}
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