Introduce METER_BUFFER_CHECK and METER_BUFFER_APPEND_CHR to cleanup writing to bar buffers

Closes: #294

MemoryMeter.c

@@ -24,12 +24,11 @@ static void MemoryMeter_updateValues(Meter* this, char* buffer, size_t size) {
    Platform_setMemoryValues(this);
 
    written = Meter_humanUnit(buffer, this->values[0], size);
-   buffer += written;
+   METER_BUFFER_CHECK(buffer, size, written);
-   if ((size -= written) > 0) {
+
-      *buffer++ = '/';
+   METER_BUFFER_APPEND_CHR(buffer, size, '/');
-      size--;
+
    Meter_humanUnit(buffer, this->total, size);
-   }
 }
 
 static void MemoryMeter_display(const Object* cast, RichString* out) {

Meter.c

@@ -155,7 +155,7 @@ ListItem* Meter_toListItem(Meter* this, bool moving) {
 
 static void TextMeterMode_draw(Meter* this, int x, int y, int w) {
    char buffer[METER_BUFFER_LEN];
-   Meter_updateValues(this, buffer, METER_BUFFER_LEN - 1);
+   Meter_updateValues(this, buffer, sizeof(buffer));
    (void) w;
 
    attrset(CRT_colors[METER_TEXT]);
@@ -175,7 +175,7 @@ static const char BarMeterMode_characters[] = "|#*@$%&.";
 
 static void BarMeterMode_draw(Meter* this, int x, int y, int w) {
    char buffer[METER_BUFFER_LEN];
-   Meter_updateValues(this, buffer, METER_BUFFER_LEN - 1);
+   Meter_updateValues(this, buffer, sizeof(buffer));
 
    w -= 2;
    attrset(CRT_colors[METER_TEXT]);
@@ -309,8 +309,8 @@ static void GraphMeterMode_draw(Meter* this, int x, int y, int w) {
       for (int i = 0; i < nValues - 1; i++)
          data->values[i] = data->values[i + 1];
 
-      char buffer[nValues];
+      char buffer[METER_BUFFER_LEN];
-      Meter_updateValues(this, buffer, nValues - 1);
+      Meter_updateValues(this, buffer, sizeof(buffer));
 
       double value = 0.0;
       for (uint8_t i = 0; i < this->curItems; i++)
@@ -378,7 +378,7 @@ static void LEDMeterMode_draw(Meter* this, int x, int y, int w) {
       LEDMeterMode_digits = LEDMeterMode_digitsAscii;
 
    char buffer[METER_BUFFER_LEN];
-   Meter_updateValues(this, buffer, METER_BUFFER_LEN - 1);
+   Meter_updateValues(this, buffer, sizeof(buffer));
 
    RichString_begin(out);
    Meter_displayBuffer(this, buffer, &out);

Meter.h

@@ -20,6 +20,29 @@ in the source distribution for its full text.
 
 #define METER_BUFFER_LEN 256
 
+#define METER_BUFFER_CHECK(buffer, size, written)          \
+   do {                                                    \
+      if ((written) < 0 || (size_t)(written) >= (size)) {  \
+         return;                                           \
+      }                                                    \
+      (buffer) += (written);                               \
+      (size) -= (size_t)(written);                         \
+   } while (0)
+
+#define METER_BUFFER_APPEND_CHR(buffer, size, c)           \
+   do {                                                    \
+      if ((size) < 2) {                                    \
+         return;                                           \
+      }                                                    \
+      *(buffer)++ = c;                                     \
+      *(buffer) = '\0';                                    \
+      (size)--;                                            \
+      if ((size) == 0) {                                   \
+         return;                                           \
+      }                                                    \
+   } while (0)
+
+
 struct Meter_;
 typedef struct Meter_ Meter;
 

SwapMeter.c

@@ -22,12 +22,11 @@ static void SwapMeter_updateValues(Meter* this, char* buffer, size_t size) {
    Platform_setSwapValues(this);
 
    written = Meter_humanUnit(buffer, this->values[0], size);
-   buffer += written;
+   METER_BUFFER_CHECK(buffer, size, written);
-   if ((size -= written) > 0) {
+
-      *buffer++ = '/';
+   METER_BUFFER_APPEND_CHR(buffer, size, '/');
-      size--;
+
    Meter_humanUnit(buffer, this->total, size);
-   }
 }
 
 static void SwapMeter_display(const Object* cast, RichString* out) {

linux/ZramMeter.c

@@ -20,32 +20,17 @@ static void ZramMeter_updateValues(Meter* this, char* buffer, size_t size) {
    this->curItems = 1;
 
    written = Meter_humanUnit(buffer, this->values[0], size);
-   buffer += written;
+   METER_BUFFER_CHECK(buffer, size, written);
-   size -= written;
+
-   if (size <= 0) {
+   METER_BUFFER_APPEND_CHR(buffer, size, '(');
-      return;
+
-   }
-   *buffer++ = '(';
-   size--;
-   if (size <= 0) {
-      return;
-   }
    written = Meter_humanUnit(buffer, this->values[1], size);
-   buffer += written;
+   METER_BUFFER_CHECK(buffer, size, written);
-   size -= written;
+
-   if (size <= 0) {
+   METER_BUFFER_APPEND_CHR(buffer, size, ')');
-      return;
+
-   }
+   METER_BUFFER_APPEND_CHR(buffer, size, '/');
-   *buffer++ = ')';
+
-   size--;
-   if (size <= 0) {
-      return;
-   }
-   *buffer++ = '/';
-   size--;
-   if (size <= 0) {
-      return;
-   }
    Meter_humanUnit(buffer, this->total, size);
 }
 

zfs/ZfsArcMeter.c

@@ -38,12 +38,11 @@ static void ZfsArcMeter_updateValues(Meter* this, char* buffer, size_t size) {
    Platform_setZfsArcValues(this);
 
    written = Meter_humanUnit(buffer, this->values[5], size);
-   buffer += written;
+   METER_BUFFER_CHECK(buffer, size, written);
-   if ((size -= written) > 0) {
+
-      *buffer++ = '/';
+   METER_BUFFER_APPEND_CHR(buffer, size, '/');
-      size--;
+
    Meter_humanUnit(buffer, this->total, size);
-   }
 }
 
 static void ZfsArcMeter_display(const Object* cast, RichString* out) {