feat(lsm): add str copy_n functions

lsm/include/lsm/str.h

@@ -36,6 +36,17 @@ lsm_error lsm_str_init_zero(lsm_str **ptr);
  */
 lsm_error lsm_str_init_copy(lsm_str **ptr, char *s);
 
+/**
+ * Same as `lsm_str_init_copy`, except that it takes an additional argument
+ * specifying the length of the string to copy over. This can be used to more
+ * easily "cut" parts of a C-style string out into an LSM string.
+ *
+ * @param ptr pointer to store newly allocated pointer
+ * @param s string to copy into lsm string
+ * @param len length of string to copy
+ */
+lsm_error lsm_str_init_copy_n(lsm_str **ptr, char *s, uint64_t len);
+
 /**
  * Overwrite an existing lsm_str so it now represents the new provided string.
  * The string pointer of the original object is free'd if needed. Ownership of
@@ -52,10 +63,20 @@ void lsm_str_overwrite(lsm_str *str, char *s);
  * string is copied, leaving the original untouched.
  *
  * @param str lsm_str object to modify
- * @param s string to convert into lsm string; ownership is taken over
+ * @param s string to copy into lsm string
  */
 lsm_error lsm_str_overwrite_copy(lsm_str *str, char *s);
 
+/**
+ * Same as `lsm_str_overwrite_copy`, except the length is explicitely specified,
+ * allowing you to easily "cut" parts of a C string out into an LSM string.
+ *
+ * @param str lsm_str object to modify
+ * @param s string to copy into lsm string
+ * @param len length of the string to copy
+ */
+lsm_error lsm_str_overwrite_copy_n(lsm_str *str, char *s, uint64_t len);
+
 /**
  * Deallocate the existing internal string if needed and replace the lsm_str
  * with a string of length 0, wiping its contents. This function can be used as

lsm/src/str/lsm_str.c

@@ -47,6 +47,20 @@ lsm_error lsm_str_init_copy(lsm_str **ptr, char *s) {
   return lsm_error_ok;
 }
 
+lsm_error lsm_str_init_copy_n(lsm_str **ptr, char *s, uint64_t len) {
+  lsm_str *str = calloc(1, sizeof(lsm_str));
+
+  if (str == NULL) {
+    return lsm_error_failed_alloc;
+  }
+
+  lsm_str_overwrite_copy_n(str, s, len);
+
+  *ptr = str;
+
+  return lsm_error_ok;
+}
+
 void lsm_str_overwrite(lsm_str *str, char *s) {
   str->len = strlen(s);
 
@@ -59,8 +73,10 @@ void lsm_str_overwrite(lsm_str *str, char *s) {
 }
 
 lsm_error lsm_str_overwrite_copy(lsm_str *str, char *s) {
-  str->len = strlen(s);
+  return lsm_str_overwrite_copy_n(str, s, strlen(s));
+}
 
+lsm_error lsm_str_overwrite_copy_n(lsm_str *str, char *s, uint64_t len) {
   if (str->len <= 8) {
     memcpy(str->data.val, s, str->len);
   } else {
@@ -74,6 +90,8 @@ lsm_error lsm_str_overwrite_copy(lsm_str *str, char *s) {
     str->data.ptr = buf;
   }
 
+  str->len = len;
+
   return lsm_error_ok;
 }