libsigrok/filter.c

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/*
* This file is part of the sigrok project.
*
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* Copyright (C) 2010-2012 Bert Vermeulen <bert@biot.com>
*
* This program is free software: you can redistribute it and/or modify
* it under the terms of the GNU General Public License as published by
* the Free Software Foundation, either version 3 of the License, or
* (at your option) any later version.
*
* This program is distributed in the hope that it will be useful,
* but WITHOUT ANY WARRANTY; without even the implied warranty of
* MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
* GNU General Public License for more details.
*
* You should have received a copy of the GNU General Public License
* along with this program. If not, see <http://www.gnu.org/licenses/>.
*/
#include <stdlib.h>
#include <stdint.h>
#include <string.h>
#include "libsigrok.h"
#include "libsigrok-internal.h"
/**
* Remove unused probes from samples.
*
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* 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.
*
* @param in_unitsize The unit size (>= 1) of the input (data_in).
* @param 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'.
* @param probelist Pointer to a list of probe numbers, numbered starting
* from 0. The list is terminated with -1.
* @param data_in Pointer to the input data buffer. Must not be NULL.
* @param length_in The input data length (>= 1), in number of bytes.
* @param 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.
* @param 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.
*
* @return SR_OK upon success, SR_ERR_MALLOC upon memory allocation errors,
* or SR_ERR_ARG upon invalid arguments.
* If something other than SR_OK is returned, the values of
* out_unitsize, data_out, and length_out are undefined.
*/
SR_API int sr_filter_probes(int in_unitsize, int out_unitsize,
const int *probelist, const uint8_t *data_in,
uint64_t length_in, uint8_t **data_out,
uint64_t *length_out)
{
unsigned int in_offset, out_offset;
int num_enabled_probes, out_bit, i;
uint64_t sample_in, sample_out;
if (!probelist) {
sr_err("filter: %s: probelist was NULL", __func__);
return SR_ERR_ARG;
}
if (!data_in) {
sr_err("filter: %s: data_in was NULL", __func__);
return SR_ERR_ARG;
}
if (!data_out) {
sr_err("filter: %s: data_out was NULL", __func__);
return SR_ERR_ARG;
}
if (!length_out) {
sr_err("filter: %s: length_out was NULL", __func__);
return SR_ERR_ARG;
}
num_enabled_probes = 0;
for (i = 0; probelist[i] != -1; i++)
num_enabled_probes++;
/* Are there more probes than the target unit size supports? */
if (num_enabled_probes > out_unitsize * 8) {
sr_err("filter: %s: too many probes (%d) for the target unit "
"size (%d)", __func__, num_enabled_probes, out_unitsize);
return SR_ERR_ARG;
}
if (!(*data_out = g_try_malloc(length_in))) {
sr_err("filter: %s: data_out malloc failed", __func__);
return SR_ERR_MALLOC;
}
if (num_enabled_probes == in_unitsize * 8) {
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/* All probes are used -- no need to compress anything. */
memcpy(*data_out, data_in, length_in);
*length_out = length_in;
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return SR_OK;
}
/* If we reached this point, not all probes are used, so "compress". */
in_offset = out_offset = 0;
while (in_offset <= length_in - in_unitsize) {
memcpy(&sample_in, data_in + in_offset, in_unitsize);
sample_out = out_bit = 0;
for (i = 0; probelist[i] != -1; i++) {
if (sample_in & (1 << (probelist[i])))
sample_out |= (1 << out_bit);
out_bit++;
}
memcpy((*data_out) + out_offset, &sample_out, out_unitsize);
in_offset += in_unitsize;
out_offset += out_unitsize;
}
*length_out = out_offset;
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return SR_OK;
}