X-Git-Url: https://sigrok.org/gitweb/?a=blobdiff_plain;f=filter.c;h=5698d333f0eea57de70aa97c5ca5277a1c2f4312;hb=488a13b110d3563194dd63e087e295a4aa114002;hp=69cb45ca725a888686f570fb49adf961aa24b8ce;hpb=8225e92175c64909eddaecf8bd512049acf653a2;p=libsigrok.git

diff --git a/filter.c b/filter.c
index 69cb45ca..5698d333 100644
--- a/filter.c
+++ b/filter.c
@@ -21,22 +21,87 @@
 #include <stdint.h>
 #include <string.h>
 #include <sigrok.h>
+#include "sigrok-internal.h"
 
-/*
+/**
+ * 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.
+ *
+ * @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).
+ * @param probelist Pointer to a list of integers (probe numbers). The probe
+ *                  numbers in this list are 1-based, i.e. the first probe
+ *                  is expected to be numbered 1 (not 0!). Must not be NULL.
+ * @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.
  */
-int filter_probes(int in_unitsize, int out_unitsize, int *probelist,
-		  const char *data_in, uint64_t length_in, char **data_out,
-		  uint64_t *length_out)
+int sr_filter_probes(int in_unitsize, int out_unitsize, const int *probelist,
+		     const unsigned char *data_in, uint64_t length_in,
+		     char **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 (!(*data_out = malloc(length_in)))
+	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;
+	}
+
+	if (!(*data_out = g_try_malloc(length_in))) {
+		sr_err("filter: %s: data_out malloc failed", __func__);
 		return SR_ERR_MALLOC;
+	}
 
 	num_enabled_probes = 0;
 	for (i = 0; probelist[i]; i++)