Refactor to use modulus for color channel switching

Added macros for colormax and step size. Updated load_current_state.
Added comments. Wrote channel_fade function which fades between two
color channels. Also wrote rgb_fade which is the loop function around
all the channels.

1 files changed, 78 insertions, 62 deletions

diff --git a/src/main.c b/src/main.c
index 0d035b4..788adf8 100644
--- a/src/main.c
+++ b/src/main.c
@@ -20,103 +20,119 @@
 #include <unistd.h>
 
 #define COLORFILE "/sys/class/leds/system76::kbd_backlight/color_left"
+#define COLORMAX  255
+#define COLORSTEP 5
 
 
-struct rgb {
-  int r;
-  int g;
-  int b;
-};
-
-
-void writecolor(struct rgb color, int usec_wait) {
+void writecolor(int r, int g, int b) {
   FILE* fd;
   fd = fopen(COLORFILE, "w");
-  fprintf(fd, "%02X%02X%02X\n", color.r, color.g, color.b);
+  fprintf(fd, "%02X%02X%02X\n", r, g, b);
   fclose(fd);
-  usleep(usec_wait);
 }
 
 
-void load_current_state(struct rgb* srgb) {
+/**
+ * load_current_state:
+ * Loads the current color state from the keyboard's sys file at
+ * /sys/class/leds/*kbd_backlight/..
+ *
+ * @r Pointer to red int buffer
+ * @g Pointer to green int buffer
+ * @b Pointer to blue int buffer
+ */
+int load_current_state(int* r, int* g, int* b) {
   char chan[3];
   FILE* fd;
 
   chan[3] = '\0';
   fd = fopen(COLORFILE, "r");
+  if(!fd) {
+    *r = 0;
+    *g = 0;
+    *b = 0;
+    return 2;
+  }
 
   chan[0] = fgetc(fd);
   chan[1] = fgetc(fd);
-  srgb->r = atoi(chan);
+  *r = atoi(chan);
 
   chan[0] = fgetc(fd);
   chan[1] = fgetc(fd);
-  srgb->g = atoi(chan);
+  *g = atoi(chan);
 
   chan[0] = fgetc(fd);
   chan[1] = fgetc(fd);
-  srgb->b = atoi(chan);
+  *b = atoi(chan);
 
   fclose(fd);
+  return 0;
 }
 
 
-int main(int argc, char* argv[]) {
-  int step = 4;
-  int wait = 10000;
+/**
+ * channel_fade:
+ * Fades one color channel into another in one step.
+ *
+ * @a Pointer to A color channel buffer
+ * @b Pointer to B color channel buffer
+ */
+void channel_fade(int* a, int* b) {
+  // Increase channel B with A maxed
+  if(*a <= COLORMAX) {
+    if(COLORMAX - *a >= COLORSTEP)
+      *a = *a + COLORSTEP;
+    else
+      *a = COLORMAX;
+  }
 
-  struct rgb color;
-  load_current_state(&color);
+  if(*b > 0) {
+    if(*b >= COLORSTEP)
+      *b = *b - COLORSTEP;
+    else
+      *b = 0;
+  }
+}
 
-  // Set wait time between steps
-  if(argc >= 2)
-    wait = atoi(argv[1]) * 1000;
 
-  // Step size
-  if(argc == 3)
-    step = atoi(argv[2]);
+/**
+ * rgb_fade:
+ * Infinite loop tha handles color fading
+ *
+ * @r    Initialization value for red channel
+ * @b    Initialization value for blue channel
+ * @g    Initialization value for green channel
+ * @wait Wait time in milliseconds between steps
+ */
+void rgb_fade(int r, int g, int b, int wait) {
+  int i = 0;
+  int highest = 0;
+  int colors[3] = {r, g, b};
+  int size = 3;
 
   while(1) {
-    // Increase green
-    while(color.g < 256) {
-      writecolor(color, wait);
-      color.g += step;
+    while(colors[i % size] < COLORMAX) {
+      channel_fade(&colors[i % size], &colors[(i + 1) % size]);
+      writecolor(colors[0], colors[1], colors[2]);
+      //printf("%02X %02X %02X\n", colors[0], colors[1], colors[2]);
+      usleep(wait * 1000);
     }
-    color.g = 255;
+    i++;
+  }
+}
 
-    // Decrease red
-    while(color.r > 0) {
-      writecolor(color, wait);
-      color.r -= step;
-    }
-    color.r = 0;
 
-    // Increase blue
-    while(color.b < 256) {
-      writecolor(color, wait);
-      color.b += step;
-    }
-    color.b = 255;
-
-    // Decrease green
-    while(color.g > 0) {
-      writecolor(color, wait);
-      color.g -= step;
-    }
-    color.g = 0;
+int main(int argc, char* argv[]) {
+  int wait = 500;
+  int r = 0;
+  int g = 0;
+  int b = 0;
 
-    // Increase red
-    while(color.r < 256) {
-      writecolor(color, wait);
-      color.r += step;
-    }
-    color.r = 255;
+  //Set wait time between steps if specified
+  if(argc == 2)
+    wait = atoi(argv[1]);
 
-    // Decrease blue
-    while(color.b > 0) {
-      writecolor(color, wait);
-      color.b -= step;
-    }
-    color.b = 0;
-  }
+  load_current_state(&r, &g, &b);
+  rgb_fade(r, g, b, wait);
 }