libhw_generic: Re-think duplex_iovec

1 files changed, 26 insertions, 2 deletions

diff --git a/libhw_generic/include/libhw/generic/io.h b/libhw_generic/include/libhw/generic/io.h
index a7f7378..7825c9f 100644
--- a/libhw_generic/include/libhw/generic/io.h
+++ b/libhw_generic/include/libhw/generic/io.h
@@ -8,6 +8,7 @@
 #define _LIBHW_GENERIC_IO_H_
 
 #include <stddef.h>    /* for size_t */
+#include <stdint.h>    /* for uintptr_t */
 #include <sys/types.h> /* for ssize_t */
 
 #include <libobj/obj.h>
@@ -23,12 +24,35 @@ struct iovec {
 };
 #endif
 
+#define IOVEC_DISCARD ((void*)(~((uintptr_t)0)))
+
 struct duplex_iovec {
-	void    *iov_read_dst;
-	void    *iov_write_src;
+	/**
+	 * NULL is a valid pointer value in iov_read_to and
+	 * iov_write_from.  To skip a read or write, use the special
+	 * value IOVEC_DISCARD.
+	 */
+	void    *iov_read_to;
+	void    *iov_write_from;
 	size_t   iov_len;
 };
 
+/* utilities ******************************************************************/
+
+/* slice iovec lists */
+int  io_slice_cnt       (                          const struct        iovec *src, int src_cnt, size_t byte_start, size_t byte_max_cnt);
+void io_slice           (struct        iovec *dst, const struct        iovec *src, int src_cnt, size_t byte_start, size_t byte_max_cnt);
+int  io_duplex_slice_cnt(                          const struct duplex_iovec *src, int src_cnt, size_t byte_start, size_t byte_max_cnt);
+void io_duplex_slice    (struct duplex_iovec *dst, const struct duplex_iovec *src, int src_cnt, size_t byte_start, size_t byte_max_cnt);
+
+/* convert iovec lists */
+void io_rd_to_duplex(struct duplex_iovec *dst, const struct iovec *src, int iovcnt);
+void io_wr_to_duplex(struct duplex_iovec *dst, const struct iovec *src, int iovcnt);
+
+/* slice and convert in one go */
+void io_slice_rd_to_duplex(struct duplex_iovec *dst, const struct iovec *src, int src_cnt, size_t byte_start, size_t byte_max_cnt);
+void io_slice_wr_to_duplex(struct duplex_iovec *dst, const struct iovec *src, int src_cnt, size_t byte_start, size_t byte_max_cnt);
+
 /* basic interfaces ***********************************************************/
 
 /**