Ensuring string values are zero-terminated.

This helps when some code requires a string value to be zero-terminated
to avoid copying and adding \0 byte.

It adds small overhead (less than 3% in worst case of an empty string
value) to existing sizeof(njs_value_t) + sizeof(njs_string_t) = 32.

Author: xeioex

src/njs_scope.c

@@ -199,7 +199,7 @@ njs_scope_value_index(njs_vm_t *vm, const njs_value_t *src, njs_uint_t runtime,
                        + njs_string_map_size(length);
             }
 
-            value_size += sizeof(njs_string_t) + size;
+            value_size += sizeof(njs_string_t) + size + 1;
         }
 
         value_size += sizeof(njs_index_t);
@@ -221,6 +221,8 @@ njs_scope_value_index(njs_vm_t *vm, const njs_value_t *src, njs_uint_t runtime,
             string->length = src->string.data->length;
             string->size = src->string.data->size;
 
+            string->start[size] = '\0';
+
             memcpy(string->start, start, size);
         }
 

src/njs_string.c

@@ -147,6 +147,7 @@ njs_string_new(njs_vm_t *vm, njs_value_t *value, const u_char *start,
 }
 
 
+/* Underlying string data is zero-terminated. */
 u_char *
 njs_string_alloc(njs_vm_t *vm, njs_value_t *value, uint64_t size,
     uint64_t length)
@@ -172,7 +173,7 @@ njs_string_alloc(njs_vm_t *vm, njs_value_t *value, uint64_t size,
         total = size;
     }
 
-    string = njs_mp_alloc(vm->mem_pool, sizeof(njs_string_t) + total);
+    string = njs_mp_alloc(vm->mem_pool, sizeof(njs_string_t) + total + 1);
 
     if (njs_fast_path(string != NULL)) {
         value->string.data = string;
@@ -181,6 +182,8 @@ njs_string_alloc(njs_vm_t *vm, njs_value_t *value, uint64_t size,
         string->size = size;
         string->length = length;
 
+        string->start[size] = '\0';
+
         if (map_offset != 0) {
             map = (uint32_t *) (string->start + map_offset);
             map[0] = 0;

src/njs_value.h

@@ -517,6 +517,7 @@ typedef struct {
         njs_assert((value)->string.data != NULL);                             \
         (str)->length = (value)->string.data->size;                           \
         (str)->start = (u_char *) (value)->string.data->start;                \
+        njs_assert((str)->start[(str)->length] == '\0');                      \
     } while (0)