Add a utility for string substitution, rename apname to service_name

common.c

@@ -537,3 +537,33 @@ ssize_t non_blocking_write(int fd, const void *buf, size_t count) {
   //  return write(fd,buf,count);
 }
 
+/* from http://coding.debuntu.org/c-implementing-str_replace-replace-all-occurrences-substring#comment-722 */
+
+char *str_replace ( const char *string, const char *substr, const char *replacement ){
+  char *tok = NULL;
+  char *newstr = NULL;
+  char *oldstr = NULL;
+  char *head = NULL;
+ 
+  /* if either substr or replacement is NULL, duplicate string a let caller handle it */
+  if ( substr == NULL || replacement == NULL ) return strdup (string);
+  newstr = strdup (string);
+  head = newstr;
+  while ( (tok = strstr ( head, substr ))){
+    oldstr = newstr;
+    newstr = malloc ( strlen ( oldstr ) - strlen ( substr ) + strlen ( replacement ) + 1 );
+    /*failed to alloc mem, free old string and return NULL */
+    if ( newstr == NULL ){
+      free (oldstr);
+      return NULL;
+    }
+    memcpy ( newstr, oldstr, tok - oldstr );
+    memcpy ( newstr + (tok - oldstr), replacement, strlen ( replacement ) );
+    memcpy ( newstr + (tok - oldstr) + strlen( replacement ), tok + strlen ( substr ), strlen ( oldstr ) - strlen ( substr ) - ( tok - oldstr ) );
+    memset ( newstr + strlen ( oldstr ) - strlen ( substr ) + strlen ( replacement ) , 0, 1 );
+    /* move back head right after the last replacement */
+    head = newstr + (tok - oldstr) + strlen( replacement );
+    free (oldstr);
+  }
+  return newstr;
+}

common.h

@@ -51,7 +51,7 @@ enum playback_mode_type {
 typedef struct {
   config_t *cfg;
   char *password;
-  char *apname;
+  char *service_name; // the name for the shairport service, e.g. "Shairport Sync Version %v running on host %h"
 #ifdef CONFIG_METADATA
   int metadata_enabled;
   char *metadata_pipename;
@@ -110,6 +110,9 @@ void set_requested_connection_state_to_output(int v);
 
 ssize_t non_blocking_write(int fd, const void *buf, size_t count); // used in a few places
 
+/* from http://coding.debuntu.org/c-implementing-str_replace-replace-all-occurrences-substring#comment-722 */
+char *str_replace ( const char *string, const char *substr, const char *replacement );
+
 int debuglev;
 void die(char *format, ...);
 void warn(char *format, ...);