fixup! dynamically allocate JQ_COLORS escapes for truecolor support

reorganize and reword code to make it easier to read

Author: SArpnt

src/jv_print.c

@@ -27,71 +27,78 @@
 // Color table. See https://en.wikipedia.org/wiki/ANSI_escape_code#Colors
 // for how to choose these. The order is same as jv_kind definition, and
 // the last color is used for object keys.
-#define DEF_COLORS \
+#define DEFAULT_COLORS \
   {COL("0;90"),    COL("0;39"),      COL("0;39"),     COL("0;39"),\
    COL("0;32"),    COL("1;39"),      COL("1;39"),     COL("1;34")};
-static const char *const def_colors[] = DEF_COLORS;
-static const char *colors[] = DEF_COLORS;
+static const char *const default_colors[] = DEFAULT_COLORS;
+static const char *colors[] = DEFAULT_COLORS;
 #define COLORS_LEN (sizeof(colors) / sizeof(colors[0]))
 #define FIELD_COLOR (colors[7])
 
 static char *colors_buf = NULL;
-int jq_set_colors(const char *c) {
-  if (c == NULL)
+int jq_set_colors(const char *code_str) {
+  if (code_str == NULL)
     return 1;
-  const char *offsets[COLORS_LEN + 1]; // extra item for the end of the last string
 
-  size_t cl = 0;
-  size_t cn = 0;
+  // the start of each color code in the env var, and the byte after the end of the last one
+  const char *codes[COLORS_LEN + 1];
+  size_t num_colors;
+  // must be initialized before `goto reset`, used later to loop over every color
+  size_t ci = 0;
 
-  while (cl < COLORS_LEN) {
-    offsets[cl++] = c;
-    // gcc won't optimize out strspn
+  for (num_colors = 0; num_colors < COLORS_LEN; num_colors++) {
+    codes[num_colors] = code_str;
     letter:
-    switch (c++[0]) {
+    switch (code_str[0]) {
     // technically posix doesn't specify ascii so a range wouldn't be portable
     case '0': case '1': case '2': case '3': case '4': case '5': case '6': case '7': case '8': case '9': case ';':
-      goto letter;
+      code_str++;
+      goto letter; // loops until end of color code
     case ':':
-      continue;
+      code_str++;
+      continue; // next color
     case '\0':
-      goto var_end;
+      goto set_codes_end; // done
     default:
-      return 0;
+      return 0; // invalid character
     }
   }
-  var_end:
-  // don't override last color on empty variable or trailing :
-  if (offsets[--cl] != c - 1) {
-    offsets[++cl] = c;
-  } else if (cl == 0) {
+  set_codes_end:
+  if (codes[num_colors] != code_str) {
+    // count the last color and store its end (plus one byte for consistency with starts)
+    // an empty last color would be ignored (for cases like "" and "0:")
+    num_colors++;
+    codes[num_colors] = code_str + 1;
+  } else if (num_colors == 0) {
     if (colors_buf != NULL) {
       jv_mem_free(colors_buf);
       colors_buf = NULL;
     }
-    goto reset;
+    goto default_colors;
   }
 
   colors_buf = jv_mem_realloc(
     colors_buf,
     // add ESC '[' 'm' to each string
-    // '\0' is already included in difference of offsets
-    offsets[cl] - offsets[0] + 3 * cl
+    // '\0' is already included in difference of codes
+    codes[num_colors] - codes[0] + 3 * num_colors
   );
   char *cb = colors_buf;
-  for (; cn < cl; cn++) {
-    colors[cn] = cb;
+  for (; ci < num_colors; ci++) {
+    colors[ci] = cb;
+    size_t len = codes[ci + 1] - 1 - codes[ci];
+
     cb[0] = ESC[0];
     cb[1] = '[';
-    size_t len = offsets[cn + 1] - 1 - offsets[cn];
-    memcpy(cb + 2, offsets[cn], len);
-    cb[len + 2] = 'm';
-    cb[len + 3] = '\0';
+    memcpy(cb + 2, codes[ci], len);
+    cb[2 + len] = 'm';
+    cb[3 + len] = '\0';
+
     cb += len + 4;
   }
-  reset:
-  for (; cn < COLORS_LEN; cn++)
-    colors[cn] = def_colors[cn];
+  default_colors:
+  for (; ci < COLORS_LEN; ci++)
+    colors[ci] = default_colors[ci];
   return 1;
 }