+static int countColorControlChars(const char* prompt)
+{
+ /* ANSI color control sequences have the form:
+ * "\x1b" "[" [0-9;]* "m"
+ * We parse them with a simple state machine.
+ */
+
+ enum {
+ search_esc,
+ expect_bracket,
+ expect_trail
+ } state = search_esc;
+ int len = 0, found = 0;
+ char ch;
+
+ /* XXX: Strictly we should be checking utf8 chars rather than
+ * bytes in case of the extremely unlikely scenario where
+ * an ANSI sequence is part of a utf8 sequence.
+ */
+ while ((ch = *prompt++) != 0) {
+ switch (state) {
+ case search_esc:
+ if (ch == '\x1b') {
+ state = expect_bracket;
+ }
+ break;
+ case expect_bracket:
+ if (ch == '[') {
+ state = expect_trail;
+ /* 3 for "\e[ ... m" */
+ len = 3;
+ break;
+ }
+ state = search_esc;
+ break;
+ case expect_trail:
+ if ((ch == ';') || ((ch >= '0' && ch <= '9'))) {
+ /* 0-9, or semicolon */
+ len++;
+ break;
+ }
+ if (ch == 'm') {
+ found += len;
+ }
+ state = search_esc;
+ break;
+ }
+ }
+
+ return found;
+}
+
+/**
+ * Stores the current cursor column in '*cols'.
+ * Returns 1 if OK, or 0 if failed to determine cursor pos.
+ */
+static int queryCursor(int fd, int* cols)
+{
+ /* control sequence - report cursor location */
+ fd_printf(fd, "\x1b[6n");
+
+ /* Parse the response: ESC [ rows ; cols R */
+ if (fd_read_char(fd, 100) == 0x1b &&
+ fd_read_char(fd, 100) == '[') {
+
+ int n = 0;
+ while (1) {
+ int ch = fd_read_char(fd, 100);
+ if (ch == ';') {
+ /* Ignore rows */
+ n = 0;
+ }
+ else if (ch == 'R') {
+ /* Got cols */
+ if (n != 0 && n < 1000) {
+ *cols = n;
+ }
+ break;
+ }
+ else if (ch >= 0 && ch <= '9') {
+ n = n * 10 + ch - '0';
+ }
+ else {
+ break;
+ }
+ }
+ return 1;
+ }
+
+ return 0;
+}
+
+/**
+ * Updates current->cols with the current window size (width)
+ */