Rewrote the calculation of prompt length, ignoring length of ANSI esc…

example.c

@@ -55,7 +55,8 @@ int main(int argc, char **argv) {
      *
      * The typed string is returned as a malloc() allocated string by
      * linenoise, so the user needs to free() it. */
-    while((line = linenoise("hello> ")) != NULL) {
+    const char *prompt = "\033[01;33mhello\033[0m>> ";
+    while((line = linenoise(prompt)) != NULL) {
         /* Do something with the string. */
         if (line[0] != '\0' && line[0] != '/') {
             printf("echo: '%s'\n", line);

linenoise.c

@@ -175,6 +175,7 @@ enum KEY_ACTION{
 static void linenoiseAtExit(void);
 int linenoiseHistoryAdd(const char *line);
 static void refreshLine(struct linenoiseState *l);
+size_t pstrlen(const char *s);
 
 /* Debugging macro. */
 #if 0
@@ -503,7 +504,7 @@ void refreshShowHints(struct abuf *ab, struct linenoiseState *l, int plen) {
  * cursor position, and number of columns of the terminal. */
 static void refreshSingleLine(struct linenoiseState *l) {
     char seq[64];
-    size_t plen = strlen(l->prompt);
+    size_t plen = pstrlen(l->prompt);
     int fd = l->ofd;
     char *buf = l->buf;
     size_t len = l->len;
@@ -778,7 +779,8 @@ static int linenoiseEdit(int stdin_fd, int stdout_fd, char *buf, size_t buflen,
     l.buf = buf;
     l.buflen = buflen;
     l.prompt = prompt;
-    l.plen = strlen(prompt);
+    // l.plen = strlen(prompt);
+    l.plen = pstrlen(prompt);
     l.oldpos = l.pos = 0;
     l.len = 0;
     l.cols = getColumns(stdin_fd, stdout_fd);
@@ -793,7 +795,7 @@ static int linenoiseEdit(int stdin_fd, int stdout_fd, char *buf, size_t buflen,
      * initially is just an empty string. */
     linenoiseHistoryAdd("");
 
-    if (write(l.ofd,prompt,l.plen) == -1) return -1;
+    if (write(l.ofd,prompt,strlen(prompt)) == -1) return -1;
     while(1) {
         char c;
         int nread;
@@ -1199,3 +1201,20 @@ int linenoiseHistoryLoad(const char *filename) {
     fclose(fp);
     return 0;
 }
+
+/* Calculatethe length of the prompt string as is seen from a terminal,
+ * that is to ignore the length of possible ANSI escape codes.
+ * Therefore possible mispositions of the cursor can be avoided.
+ */
+size_t pstrlen(const char *s) {
+    size_t len = 0, i = 0;
+    while (s[i] != '\0') {
+        if (s[i] == '\033') {
+            i = strpbrk(s + i, "m") - s + 1;
+            continue;
+        }
+        len++;
+        i++;
+    }
+    return len;
+}