libhw_generic: Re-think duplex_iovec

1 files changed, 98 insertions, 0 deletions

diff --git a/libhw_generic/io.c b/libhw_generic/io.c
new file mode 100644
index 0000000..4ebff10
--- /dev/null
+++ b/libhw_generic/io.c
@@ -0,0 +1,98 @@
+/* libhw_generic/io.c - Utilities for device-independent I/O definitions
+ *
+ * Copyright (C) 2025  Luke T. Shumaker <lukeshu@lukeshu.com>
+ * SPDX-License-Identifier: AGPL-3.0-or-later
+ */
+
+#include <libmisc/assert.h>
+
+#include <libhw/generic/io.h>
+
+#define IOV_ITER(ACTION)                                                \
+	assert(src_cnt >= 0);                                           \
+	assert(src_cnt == 0 || src);                                    \
+                                                                        \
+	const size_t byte_end = byte_beg + byte_max_cnt;                \
+	int j = 0;                                                      \
+	size_t byte_pos = 0;                                            \
+	for (int i = 0;                                                 \
+	     i < src_cnt && (byte_max_cnt == 0 || byte_pos < byte_end); \
+	     i++) {                                                     \
+		size_t off = 0, len;                                    \
+		if (byte_pos < byte_beg) {                              \
+			if (byte_beg - byte_pos >= src[i].iov_len) {    \
+				byte_pos += src[i].iov_len;             \
+				continue;                               \
+			}                                               \
+			off = byte_beg-byte_pos;                        \
+			len = src[i].iov_len-off;                       \
+			byte_pos = byte_beg;                            \
+		} else {                                                \
+			len = src[i].iov_len;                           \
+		}                                                       \
+		if (byte_max_cnt && byte_end - byte_pos < len)          \
+			len = byte_end - byte_pos;                      \
+		do { ACTION } while (0);                                \
+		byte_pos += len;                                        \
+		j++;                                                    \
+	}
+
+int io_slice_cnt(const struct iovec *src, int src_cnt, size_t byte_beg, size_t byte_max_cnt) {
+	IOV_ITER();
+	return j;
+}
+
+int io_duplex_slice_cnt(const struct duplex_iovec *src, int src_cnt, size_t byte_beg, size_t byte_max_cnt) {
+	IOV_ITER();
+	return j;
+}
+
+void io_slice(struct iovec *dst, const struct iovec *src, int src_cnt, size_t byte_beg, size_t byte_max_cnt) {
+	assert(src_cnt == 0 || dst);
+	IOV_ITER(
+		dst[j] = ((struct iovec){
+			.iov_base = src[i].iov_base+off,
+			.iov_len  = len,
+		});
+	);
+}
+void io_slice_duplex(struct duplex_iovec *dst, const struct duplex_iovec *src, int src_cnt, size_t byte_beg, size_t byte_max_cnt) {
+	assert(src_cnt == 0 || dst);
+	IOV_ITER(
+		dst[j] = ((struct duplex_iovec){
+			.iov_read_to    = src[i].iov_read_to+off,
+			.iov_write_from = src[i].iov_write_from+off,
+			.iov_len        = len,
+		});
+	);
+}
+
+void io_slice_rd_to_duplex(struct duplex_iovec *dst, const struct iovec *src, int src_cnt, size_t byte_beg, size_t byte_max_cnt) {
+	assert(src_cnt == 0 || dst);
+	IOV_ITER(
+		dst[j] = ((struct duplex_iovec){
+			.iov_read_to    = src[i].iov_base+off,
+			.iov_write_from = IOVEC_DISCARD,
+			.iov_len        = len,
+		});
+	);
+}
+
+void io_slice_wr_to_duplex(struct duplex_iovec *dst, const struct iovec *src, int src_cnt, size_t byte_beg, size_t byte_max_cnt) {
+	assert(src_cnt == 0 || dst);
+	IOV_ITER(
+		dst[j] = ((struct duplex_iovec){
+			.iov_read_to    = IOVEC_DISCARD,
+			.iov_write_from = src[i].iov_base+off,
+			.iov_len        = len,
+		});
+	);
+}
+
+void io_rd_to_duplex(struct duplex_iovec *dst, const struct iovec *src, int iovcnt) {
+	io_slice_rd_to_duplex(dst, src, iovcnt, 0, 0);
+}
+
+void io_wr_to_duplex(struct duplex_iovec *dst, const struct iovec *src, int iovcnt) {
+	io_slice_wr_to_duplex(dst, src, iovcnt, 0, 0);
+}