create new function puts_rgb8

move all color related code into color.*
in preparation for complete color optimization

tlc5947/color.c

@@ -47,6 +47,7 @@
  */
 static int islower(int c){return ((c>='a')&&(c<='z'));}
 static int toupper(int c){return islower(c)?(c-32):c;}
+static char get_hex(uint8_t i){return "0123456789ABCDEF"[i];}
 
 static uint8_t get_byte(const char* s){
     uint8_t i;
@@ -55,6 +56,10 @@ static uint8_t get_byte(const char* s){
     return i;
 }
 
+static void put_byte(char* s, uint8_t b){
+    s[0] = get_hex((b & 0xF0) >> 4);
+    s[1] = get_hex((b & 0x0F)     );
+}
 
 rgb12 get_rgb12(const char* s){
     return rgb8torgb12(get_rgb8(s));
@@ -69,6 +74,14 @@ rgb8 get_rgb8(const char* s){
     return c;
 }
 
+const char* put_rgb8(char* s, rgb8 c){
+    s[0] = '#';
+    put_byte(s + 1, c.r);
+    put_byte(s + 3, c.g);
+    put_byte(s + 5, c.b);
+    s[7] = 0;
+    return s + 7;
+}
 
 rgb8 rgb12torgb8(rgb12 c){
     rgb8 _c;

tlc5947/color.h

@@ -63,6 +63,14 @@ extern "C"{
 rgb12 get_rgb12(const char* s);
 rgb8 get_rgb8(const char* s);
 
+/**
+ * writes a string in the format to s:
+ *     "#RRGGBB\0"
+ * appends the terminating 0 character.
+ * returns s + 7
+ */
+const char* put_rgb8(char* s, rgb8 c);
+
 rgb8 rgb12torgb8(rgb12 c)__attribute__ ((const));
 
 rgb12 rgb8torgb12(rgb8 c)__attribute__ ((const));

tlc5947/tlc5947.c

@@ -602,9 +602,6 @@ static bool check_balanced_jumps(const char* s){
 
 static inline int isdigit(int c){return ((c>='0')&&(c<='9'));}
 static inline int isxdigit(int c){return (isdigit(c) || ((c>='A')&&(c<='F')) || ((c>='a')&&(c<='f')));}
-static inline __attribute__((pure)) char gethex(uint8_t i){
-    return "0123456789ABCDEF"[i];
-}
 
 /**
  * This function checks that all colors used
@@ -1174,14 +1171,9 @@ STATIC mp_obj_t tlc5947_tlc5947_get(mp_obj_t self_in, mp_obj_t led_in){
     rgb8 c = rgb12torgb8(get_buffer(self->buffer, led));
 
     char* str = m_malloc(8);
-    str[0] = '#';
-    str[1] = gethex((c.r&0xF0)>>4);
-    str[2] = gethex( c.r&0x0F);
-    str[3] = gethex((c.g&0xF0)>>4);
-    str[4] = gethex( c.g&0x0F);
-    str[5] = gethex((c.b&0xF0)>>4);
-    str[6] = gethex( c.b&0x0F);
-    str[7] = 0;
+
+    put_rgb8(str, c);
+
     return mp_obj_new_str(str, 7);
 }