Common (Percent): adds ffRssiToSignalQuality

src/common/percent.h

@@ -20,6 +20,14 @@ typedef struct FFPercentageModuleConfig {
     FFPercentageTypeFlags type;
 } FFPercentageModuleConfig;
 
+// Maps a received signal strength in dBm onto the 0-100 scale the percentage formatters want.
+// -50 dBm and above counts as a perfect link, -100 dBm and below as no link at all, and the range in
+// between is linear. Both ends are clamped rather than extrapolated, so the result is always a
+// percentage -- which also keeps it usable with `{?x}` guards, unlike a raw negative RSSI.
+[[gnu::const]] static inline double ffRssiToSignalQuality(int32_t rssi) {
+    return (double) (rssi >= -50 ? 100 : rssi <= -100 ? 0 : (rssi + 100) * 2);
+}
+
 // if (green <= yellow)
 // [0, green]: print green
 // (green, yellow]: print yellow

src/detection/wifi/wifi_apple.m

@@ -1,4 +1,5 @@
 #include "wifi.h"
+#include "common/percent.h"
 #include "common/processing.h"
 #include "common/strutil.h"
 #include "common/apple/cf_helpers.h"
@@ -7,11 +8,6 @@
 #import <IOKit/IOKitLib.h>
 #import <IOKit/kext/KextManager.h>
 
-static inline double rssiToSignalQuality(int rssi) {
-    return (double) (rssi >= -50 ? 100 : rssi <= -100 ? 0
-                                                      : (rssi + 100) * 2);
-}
-
 @interface CWNetworkProfile ()
 @property (readonly, retain, nullable) NSArray<NSDictionary*>* bssidList;
 @end
@@ -101,7 +97,7 @@ const char* ffDetectWifi(FFlist* result) {
                 }
                 break;
         }
-        item->conn.signalQuality = rssiToSignalQuality((int) inf.rssiValue);
+        item->conn.signalQuality = ffRssiToSignalQuality((int) inf.rssiValue);
         item->conn.txRate = inf.transmitRate;
 
         switch (inf.security) {

src/detection/wifi/wifi_linux.c

@@ -2,6 +2,7 @@
 #include "common/endian.h"
 #include "common/io.h"
 #include "common/debug.h"
+#include "common/percent.h"
 #include "common/strutil.h"
 
 #include <sys/time.h>
@@ -35,11 +36,6 @@ typedef struct FFWifiSecurityFlags {
     bool eap : 1;
 } FFWifiSecurityFlags;
 
-static inline double rssiToSignalQuality(int rssi) {
-    return (double) (rssi >= -50 ? 100 : rssi <= -100 ? 0
-                                                      : (rssi + 100) * 2);
-}
-
 static inline uint32_t ffWifiGetNetlinkPortId(int sockFd) {
     struct sockaddr_nl addr = {};
     socklen_t addrLen = sizeof(addr);
@@ -605,7 +601,7 @@ static void ffWifiParseBssAttr(const struct nlattr* bssAttr, FFWifiResult* item)
             item->conn.channel = ffWifiFreqToChannel(item->conn.frequency);
         } else if (type == NL80211_BSS_SIGNAL_MBM && payload >= sizeof(int32_t)) {
             int rssi = *(int32_t*) ffWifiNlAttrData(attr) / 100; // mBm (100 * dBm) => dBm
-            item->conn.signalQuality = rssiToSignalQuality(rssi);
+            item->conn.signalQuality = ffRssiToSignalQuality(rssi);
         } else if (type == NL80211_BSS_CAPABILITY && payload >= sizeof(uint16_t)) {
             uint16_t capability = *(uint16_t*) ffWifiNlAttrData(attr);
             sec.privacy = (capability & (1u << 4u)) != 0; // IEEE 802.11 capability bit 4: privacy
@@ -717,7 +713,7 @@ static void ffWifiParseStationInfo(const struct nlattr* staInfoAttr, FFWifiResul
 
         if (type == NL80211_STA_INFO_SIGNAL && payload >= sizeof(uint8_t) && item->conn.signalQuality == -DBL_MAX) {
             int rssi = (int8_t) *(const uint8_t*) ffWifiNlAttrData(attr);
-            item->conn.signalQuality = rssiToSignalQuality(rssi);
+            item->conn.signalQuality = ffRssiToSignalQuality(rssi);
         } else if (type == NL80211_STA_INFO_TX_BITRATE && (item->conn.txRate == -DBL_MAX || item->conn.channelWidth == 0)) {
             double tx = ffWifiParseBitrateFromRateInfo(attr, &item->conn.protocol, &item->conn.channelWidth);
             if (tx != -DBL_MAX) {