hackrf_transfer: add fixed point support for frequency and sample rate

Author: antoinevg

host/hackrf-tools/src/hackrf_transfer.c

@@ -255,6 +255,49 @@ int parse_u32(char* s, uint32_t* const value)
 	}
 }
 
+int parse_fp64(char* s, uint8_t Qn, uint64_t* const value)
+{
+    uint64_t m = 0;
+    uint64_t n = 0;
+    uint64_t div = 1;
+	uint64_t div_max = log10(1 << Qn) * 10;
+
+	// parse integer component
+	for (; (*s >= '0') && (*s <= '9'); s++) {
+		m = (m * 10) + (*s - '0');
+	}
+	*value = (m << Qn);
+
+	if (*s != '.') {
+		return HACKRF_SUCCESS;
+	}
+	s++;
+
+	// parse fractional component
+	for (; (*s >= '0') && (*s <= '9') && (div < div_max); s++) {
+		n = (n * 10) + (*s - '0');
+		div *= 10;
+	}
+
+	if (div == 1) {
+		return HACKRF_SUCCESS;
+	}
+
+	*value += ((n << Qn) + (div / 2)) / div;
+
+	return HACKRF_SUCCESS;
+}
+
+int parse_frequency_fp(char* optarg, fp_40_24_t* value)
+{
+	return parse_fp64(optarg, 24, value);
+}
+
+int parse_sample_rate_fp(char* optarg, fp_28_36_t* value)
+{
+	return parse_fp64(optarg, 36, value);
+}
+
 /* Parse frequencies as doubles to take advantage of notation parsing */
 int parse_frequency_i64(char* optarg, char* endptr, int64_t* value)
 {