Add init method to dstr for initializing directyl from a string

Change the api so _put_ functions that copy in data are named "_append_"
instead.

include/ucore/dstr.h

@@ -35,6 +35,18 @@ struct DStr {
  */
 void uc_dstr_init(struct DStr *str);
 
+/** Initialize a DStr from an existing string
+ *
+ *  @return 0 on success (!= 0 if an allocation fail)
+ */
+int uc_dstr_init_str(struct DStr *str, const char *init);
+
+/** Initialize a DStr from an existing string with a given length
+ *
+ *  @return 0 on success (!= 0 if an allocation fail)
+ */
+int uc_dstr_init_str_sz(struct DStr *str, const char *init, size_t len);
+
 /** Destroy/free the string. 
  * (Frees str->str, not str itself)
  */
@@ -95,7 +107,7 @@ char *uc_dstr_put(struct DStr *str, size_t len);
  * @param is_x ctype.h compatible function to use as a filter.
  * @return number of chars appended
  */
-size_t uc_dstr_put_str_filter(struct DStr *str, const char *restrict s, int (*is_x)(int c));
+size_t uc_dstr_append_str_filter(struct DStr *str, const char *restrict s, int (*is_x)(int c));
 
 /* Append a string of the give size.
  * (The nul terminator is not appended) 
@@ -104,20 +116,20 @@ size_t uc_dstr_put_str_filter(struct DStr *str, const char *restrict s, int (*is
  * @param len bytes to append (not including the nul terminator) 
  * @return 0 on success (!= 0 if an allocation fail)
  */
-int uc_dstr_put_str_sz(struct DStr *str, const char *restrict s, size_t len);
+int uc_dstr_append_str_sz(struct DStr *str, const char *restrict s, size_t len);
 
 /* Append a string.
  * (The nul terminator is not appended) 
  *
  *  @return 0 on success (!= 0 if an allocation fail)
  */
-int uc_dstr_put_str(struct DStr *str, const char *restrict s);
+int uc_dstr_append_str(struct DStr *str, const char *restrict s);
 
 /* Append a single char.
  *
  *  @return 0 on success (!= 0 if an allocation fail)
  */
-int uc_dstr_put_char(struct DStr *str, char c);
+int uc_dstr_append_char(struct DStr *str, char c);
 
 /* Make the DStr take ownership of the given dynamically allocated string.
  * Any existing string in the DStr is freed.