tal: add TAL_TAKE.

[ccan] / ccan / tal / tal.h

diff --git a/ccan/tal/tal.h b/ccan/tal/tal.h
index d511e88aa7b637c7dc8d98b1cccf3ad923025c92..24db0864332a721f5aabc4750d19a2af15aea993 100644 (file)
--- a/ccan/tal/tal.h
+++ b/ccan/tal/tal.h
@@ -17,6 +17,18 @@
  */
 typedef void tal_t;
 
+/**
+ * TAL_TAKE - fake tal_t to indicate function will own arguments.
+ *
+ * Various functions take a context on which to allocate: if you use
+ * TAL_TAKE there instead, it means that the argument(s) are actually
+ * tal objects.  The returned value will share the same parent; it may
+ * even be the same pointer as the arguments.  The arguments themselves
+ * will be reused, freed, or made a child of the return value: they are
+ * no longer valid for external use.
+ */
+#define TAL_TAKE ((tal_t *)-2L)
+
 /**
  * tal - basic allocator function
  * @ctx: NULL, or tal allocated object to be parent.
@@ -146,22 +158,23 @@ tal_t *tal_parent(const tal_t *ctx);
 
 /**
  * tal_memdup - duplicate memory.
- * @ctx: NULL, or tal allocated object to be parent.
+ * @ctx: NULL, or tal allocated object to be parent (or TAL_TAKE).
  * @p: the memory to copy
  * @n: the number of bytes.
+ *
  */
 void *tal_memdup(const tal_t *ctx, const void *p, size_t n);
 
 /**
- * tal_strdup - duplicate a string.
- * @ctx: NULL, or tal allocated object to be parent.
+ * tal_strdup - duplicate a string
+ * @ctx: NULL, or tal allocated object to be parent (or TAL_TAKE).
  * @p: the string to copy
  */
 char *tal_strdup(const tal_t *ctx, const char *p);
 
 /**
  * tal_strndup - duplicate a limited amount of a string.
- * @ctx: NULL, or tal allocated object to be parent.
+ * @ctx: NULL, or tal allocated object to be parent (or TAL_TAKE).
  * @p: the string to copy
  * @n: the maximum length to copy.
  *
@@ -171,16 +184,22 @@ char *tal_strndup(const tal_t *ctx, const char *p, size_t n);
 
 /**
  * tal_asprintf - allocate a formatted string
- * @ctx: NULL, or tal allocated object to be parent.
+ * @ctx: NULL, or tal allocated object to be parent (or TAL_TAKE).
  * @fmt: the printf-style format.
+ *
+ * If @ctx is TAL_TAKE, @fmt is freed and its parent will be the parent
+ * of the return value.
  */
 char *tal_asprintf(const tal_t *ctx, const char *fmt, ...) PRINTF_FMT(2,3);
 
 /**
  * tal_vasprintf - allocate a formatted string (va_list version)
- * @ctx: NULL, or tal allocated object to be parent.
+ * @ctx: NULL, or tal allocated object to be parent (or TAL_TAKE).
  * @fmt: the printf-style format.
  * @va: the va_list containing the format args.
+ *
+ * If @ctx is TAL_TAKE, @fmt is freed and its parent will be the parent
+ * of the return value.
  */
 char *tal_vasprintf(const tal_t *ctx, const char *fmt, va_list ap)
        PRINTF_FMT(2,0);