take: new module for parameter ownership.

[ccan] / ccan / take / _info

diff --git a/ccan/take/_info b/ccan/take/_info
new file mode 100644 (file)
index 0000000..34b0886
--- /dev/null
+++ b/ccan/take/_info
@@ -0,0 +1,59 @@
+#include <string.h>
+#include "config.h"
+
+/**
+ * take - routines to mark pointers to be consumed by called functions.
+ *
+ * This code helps to implement ownership transfer on a per-arg basis:
+ * the caller wraps the pointer argument in take() and the callee checks
+ * taken() to see if it should consume it.
+ *
+ * Author: Rusty Russell <rusty@rustcorp.com.au>
+ * License: CC0 (Public domain)
+ *
+ * Example:
+ *     // Given foo/bar.c outputs basename is bar.c
+ *     #include <ccan/take/take.h>
+ *     #include <string.h>
+ *
+ *     // Dumb basename program and driver.
+ *     static char *base(const char *file)
+ *     {
+ *             const char *p = strrchr(file, '/');
+ *             if (!p) 
+ *                     p = file;
+ *             else
+ *                     p++;
+ *
+ *             // Use arg in place if we're allowed.
+ *             if (taken(file))
+ *                     return memmove((char *)file, p, strlen(p)+1);
+ *             else
+ *                     return strdup(p);
+ *     }
+ *
+ *     int main(int argc, char *argv[])
+ *     {
+ *             char *b;
+ *
+ *             if (argv[1]) // Mangle in place.
+ *                     b = base(take(argv[1]));
+ *             else
+ *                     b = base("test/string");
+ *
+ *             printf("basename is %s\n", b);
+ *             return 0;
+ *     }
+ */
+int main(int argc, char *argv[])
+{
+       if (argc != 2)
+               return 1;
+
+       if (strcmp(argv[1], "depends") == 0) {
+               printf("ccan/likely\n");
+               return 0;
+       }
+
+       return 1;
+}