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libsigrok
0.2.2
sigrok hardware access and backend library
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Helper functions to filter out unused probes from samples. More...
Functions | |
int | sr_filter_probes (unsigned int in_unitsize, unsigned int out_unitsize, const GArray *probe_array, const uint8_t *data_in, uint64_t length_in, uint8_t **data_out, uint64_t *length_out) |
Remove unused probes from samples. More... | |
Helper functions to filter out unused probes from samples.
int sr_filter_probes | ( | unsigned int | in_unitsize, |
unsigned int | out_unitsize, | ||
const GArray * | probe_array, | ||
const uint8_t * | data_in, | ||
uint64_t | length_in, | ||
uint8_t ** | data_out, | ||
uint64_t * | length_out | ||
) |
Remove unused probes from samples.
Convert sample from maximum probes – the way the hardware driver sent it – to a sample taking up only as much space as required, with unused probes removed.
The "unit size" is the number of bytes used to store probe values. For example, a unit size of 1 means one byte is used (which can store 8 probe values, each of them is 1 bit). A unit size of 2 means we can store 16 probe values, 3 means we can store 24 probe values, and so on.
If the data coming from the logic analyzer has a unit size of 4 for example (as the device has 32 probes), but only 2 of them are actually used in an acquisition, this function can convert the samples to only use up 1 byte per sample (unit size = 1) instead of 4 bytes per sample.
The output will contain the probe values in the order specified via the probelist. For example, if in_unitsize = 4, probelist = [5, 16, 30], and out_unitsize = 1, then the output samples (each of them one byte in size) will have the following format: bit 0 = value of probe 5, bit 1 = value of probe 16, bit 2 = value of probe 30. Unused bit(s) in the output byte(s) are zero.
The caller must make sure that length_in is not bigger than the memory actually allocated for the input data (data_in), as this function does not check that.
in_unitsize | The unit size (>= 1) of the input (data_in). |
out_unitsize | The unit size (>= 1) the output shall have (data_out). The requested unit size must be big enough to hold as much data as is specified by the number of enabled probes in 'probelist'. |
probe_array | Pointer to a list of probe numbers, numbered starting from 0. The list is terminated with -1. |
data_in | Pointer to the input data buffer. Must not be NULL. |
length_in | The input data length (>= 1), in number of bytes. |
data_out | Variable which will point to the newly allocated buffer of output data. The caller is responsible for g_free()'ing the buffer when it's no longer needed. Must not be NULL. |
length_out | Pointer to the variable which will contain the output data length (in number of bytes) when the function returns SR_OK. Must not be NULL. |
Definition at line 101 of file filter.c.
References sr_err, SR_ERR_ARG, SR_ERR_MALLOC, and SR_OK.