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49 lines
1.1 KiB
C
49 lines
1.1 KiB
C
#ifndef CRUNCH_H
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#define CRUNCH_H
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#ifdef __cplusplus
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extern "C" {
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#endif
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#include <stdint.h>
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/* To save bandwidth, we compress the byte stream from the sampler when
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* sending it over USB. The encoding used is:
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*
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* 0nnn.nnnn: value 0x00..0x7f
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* 11nn.nnnn: value 0x80 then 0x00..0x3f
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* 10n : value 0x80|n
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*
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* The end of the buffer is terminated with zeroes, which are ignored
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* (not written to the output).
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*
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* This saves ~40%, which gets us in under the bandwidth cap.
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*/
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typedef struct crunch_state_t
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{
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const uint8_t* inputptr;
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uint32_t inputlen;
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uint8_t* outputptr;
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uint32_t outputlen;
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uint32_t fifo;
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uint8_t fifolen;
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bool haspending;
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uint8_t pendingbyte;
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}
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crunch_state_t;
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/* Crunches as much as possible and then stops. */
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extern void crunch(crunch_state_t* state);
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extern void donecrunch(crunch_state_t* state);
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/* Uncrunches as much as possible and then stops. */
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extern void uncrunch(crunch_state_t* state);
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extern void doneuncrunch(crunch_state_t* state);
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#ifdef __cplusplus
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}
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#endif
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#endif
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