autodata: stash pointers in a binary.

[ccan] / ccan / autodata / autodata.h

diff --git a/ccan/autodata/autodata.h b/ccan/autodata/autodata.h
new file mode 100644 (file)
index 0000000..d16c6a5
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+++ b/ccan/autodata/autodata.h
@@ -0,0 +1,106 @@
+// Licensed under BSD-MIT: See LICENSE.
+#ifndef CCAN_AUTODATA_H
+#define CCAN_AUTODATA_H
+#include "config.h"
+#include <ccan/compiler/compiler.h>
+#include <stdlib.h>
+
+#if HAVE_SECTION_START_STOP
+
+/**
+ * AUTODATA_TYPE - declare the type for a given autodata name.
+ * @name: the name for this set of autodata
+ * @type: the type this autodata points to
+ *
+ * This macro is usually placed in a header: it must preceed any
+ * autodata functions in the file.
+ *
+ * Example:
+ *     // My set of char pointers.
+ *     AUTODATA_TYPE(names, char);
+ */
+#define AUTODATA_TYPE(name, type)                                      \
+       typedef type autodata_##name##_;                                \
+       extern type *__start_autodata_##name[], *__stop_autodata_##name[]
+
+/**
+ * AUTODATA - add a pointer to this autodata set
+ * @name: the name of the set of autodata
+ * @ptr: the compile-time-known pointer
+ *
+ * This embeds @ptr into the binary, with the tag corresponding to
+ * @name (which must look like a valid identifier, no punctuation!).
+ * The type of @ptr must match that given by AUTODATA_TYPE.  It is
+ * usually a file-level declaration.
+ *
+ * Example:
+ *     // Put two char pointers into the names AUTODATA set.
+ *     AUTODATA(names, "Arabella");
+ *     AUTODATA(names, "Alex");
+ */
+#define AUTODATA(name, ptr) \
+       static const autodata_##name##_ *NEEDED         \
+       __attribute__((section("autodata_" #name)))     \
+       AUTODATA_VAR_(name, __LINE__) = (ptr);
+
+/**
+ * autodata_get - get an autodata set
+ * @name: the name of the set of autodata
+ * @nump: the number of items in the set.
+ *
+ * This extract the embedded pointers matching @name.  It may fail
+ * if malloc() fails, or if there is no AUTODATA at all.
+ *
+ * The return will be a pointer to an array of @type pointers (from
+ * AUTODATA_TYPE).
+ *
+ * Example:
+ *     static void print_embedded_names(void)
+ *     {
+ *             unsigned int i, num;
+ *             char **n = autodata_get(names, &num);
+ *
+ *             for (i = 0; i < num; i++)
+ *                     printf("%s\n", n[i]);
+ *     }
+ */
+#define autodata_get(name, nump)                                       \
+       ((autodata_##name##_ **)                                        \
+        autodata_get_section(__start_autodata_##name,                  \
+                             __stop_autodata_##name, (nump)))
+#endif /* HAVE_SECTION_START_STOP */
+
+/**
+ * autodata_free - free the table returned by autodata_get()
+ * @p: the table.
+ */
+void autodata_free(void *p);
+
+/* Internal functions. */
+#define AUTODATA_VAR__(name, line) autodata_##name##_##line
+#define AUTODATA_VAR_(name, line) AUTODATA_VAR__(name, line)
+
+#if HAVE_SECTION_START_STOP
+void *autodata_get_section(void *start, void *stop, size_t *nump);
+#else
+#define AUTODATA_TYPE(name, type)                                      \
+       typedef type autodata_##name##_;                                \
+       static const void *autodata_##name##_ex = &autodata_##name##_ex
+
+#define AUTODATA_MAGIC ((long)0xFEEDA10DA7AF00D5ULL)
+#define AUTODATA(name, ptr)                                            \
+       static const autodata_##name##_ *NEEDED                         \
+       AUTODATA_VAR_(name, __LINE__)[4] =                              \
+       { (void *)AUTODATA_MAGIC,                                       \
+         (void *)&AUTODATA_VAR_(name, __LINE__),                       \
+         (ptr),                                                        \
+         (void *)#name }
+
+#define autodata_get(name, nump)                                       \
+       ((autodata_##name##_ **)                                        \
+        autodata_make_table(&autodata_##name##_ex, #name, (nump)))
+
+void *autodata_make_table(const void *example, const char *name, size_t *nump);
+#endif
+
+#endif /* CCAN_AUTODATA_H */