lib9p_srv: Rethink the dio interface

3 files changed, 91 insertions, 54 deletions

diff --git a/lib9p/srv.c b/lib9p/srv.c
index b5455e0..96954aa 100644
--- a/lib9p/srv.c
+++ b/lib9p/srv.c
@@ -108,6 +108,7 @@ struct srv_fidinfo {
 			lo_interface lib9p_srv_dio              io;
 			size_t                                  idx;
 			uint64_t                                off;
+			struct lib9p_srv_dirent                 buffered_dirent;
 		}                                       dir;
 		struct {
 			struct lib9p_s                          aname;
@@ -1163,32 +1164,77 @@ static void handle_Tread(struct srv_req *ctx,
 	ctx->user = srv_userid_incref(fidinfo->user);
 	switch (fidinfo->type) {
 	case SRV_FILETYPE_DIR:
-		/* Translate byte-offset to object-index. */
-		size_t idx;
-		if (req->offset == 0)
-			idx = 0;
-		else if (req->offset == fidinfo->dir.off)
-			idx = fidinfo->dir.idx;
-		else {
+		/* Seek.  */
+		if (req->offset == 0) {
+			fidinfo->dir.idx = 0;
+			fidinfo->dir.off = 0;
+			fidinfo->dir.buffered_dirent = (struct lib9p_srv_dirent){};
+		} else if (req->offset != fidinfo->dir.off) {
 			lib9p_errorf(&ctx->basectx,
 			             LIB9P_ERRNO_L_EINVAL, "invalid offset (must be 0 or %"PRIu64"): %"PRIu64,
 			             fidinfo->dir.off, req->offset);
 			goto tread_return;
 		}
-		/* Do it.  */
+		/* Read.  */
 		resp.data = heap = malloc(req->count); /* TODO: cap req->count */
-		size_t num = LO_CALL(fidinfo->dir.io, dread, ctx, (uint8_t *)resp.data, req->count, idx);
-		/* Translate object-count back to byte-count.  */
-		uint32_t len = 0;
-		for (size_t i = 0; i < num; i++) {
-			uint32_t i_len;
-			lib9p_stat_validate(&ctx->basectx, req->count, &((uint8_t *)resp.data)[len], &i_len, NULL);
-			len += i_len;
+		resp.count = 0;
+		struct srv_pathinfo *dir_pathinfo = NULL;
+		for (;;) {
+			lo_interface lib9p_srv_file member_file = {};
+			struct lib9p_srv_dirent member_dirent;
+			if (fidinfo->dir.buffered_dirent.name.len) {
+				member_dirent = fidinfo->dir.buffered_dirent;
+			} else {
+				member_dirent = LO_CALL(fidinfo->dir.io, dread, ctx, fidinfo->dir.idx);
+				if (lib9p_ctx_has_error(&ctx->basectx)) {
+					if (!resp.count)
+						goto tread_return;
+					lib9p_ctx_clear_error(&ctx->basectx);
+					break;
+				}
+			}
+			if (!member_dirent.name.len)
+				break;
+			struct lib9p_stat member_stat;
+			struct srv_pathinfo *member_pathinfo = map_load(&ctx->parent_sess->paths, member_dirent.qid.path);
+			if (member_pathinfo) {
+				member_stat = LO_CALL(member_pathinfo->file, stat, ctx);
+			} else {
+				if (!dir_pathinfo)
+					dir_pathinfo = map_load(&ctx->parent_sess->paths, fidinfo->path);
+				assert(dir_pathinfo);
+				member_file = LO_CALL(dir_pathinfo->file, dwalk, ctx, member_dirent.name);
+				assert(LO_IS_NULL(member_file) == lib9p_ctx_has_error(&ctx->basectx));
+				if (!lib9p_ctx_has_error(&ctx->basectx))
+					member_stat = LO_CALL(member_file, stat, ctx);
+			}
+			if (lib9p_ctx_has_error(&ctx->basectx)) {
+				if (!LO_IS_NULL(member_file))
+					LO_CALL(member_file, free);
+				if (!resp.count)
+					goto tread_return;
+				lib9p_ctx_clear_error(&ctx->basectx);
+				break;
+			}
+			lib9p_stat_assert(member_stat);
+			uint32_t nbytes = lib9p_stat_marshal(&ctx->basectx, req->count-resp.count, &member_stat,
+			                                     (uint8_t *)&resp.data[resp.count]);
+			if (!LO_IS_NULL(member_file))
+				LO_CALL(member_file, free);
+			if (!nbytes) {
+				if (!resp.count) {
+					lib9p_error(&ctx->basectx,
+					            LIB9P_ERRNO_L_ERANGE, "stat object does not fit into negotiated max message size");
+					goto tread_return;
+				}
+				fidinfo->dir.buffered_dirent = member_dirent;
+				break;
+			}
+			resp.count += nbytes;
+			fidinfo->dir.idx++;
+			fidinfo->dir.off += nbytes;
+			fidinfo->dir.buffered_dirent = (struct lib9p_srv_dirent){};
 		}
-		resp.count = len;
-		/* Remember.  */
-		fidinfo->dir.idx = idx+num;
-		fidinfo->dir.off = req->offset + len;
 		break;
 	case SRV_FILETYPE_FILE:
 		struct iovec iov;
diff --git a/lib9p/srv_include/lib9p/srv.h b/lib9p/srv_include/lib9p/srv.h
index 0ef674a..1c534e9 100644
--- a/lib9p/srv_include/lib9p/srv.h
+++ b/lib9p/srv_include/lib9p/srv.h
@@ -71,6 +71,11 @@ void lib9p_srv_acknowledge_flush(struct lib9p_srv_ctx *ctx);
 
 /* interface definitions ******************************************************/
 
+struct lib9p_srv_dirent {
+	struct lib9p_qid        qid;
+	struct lib9p_s          name;
+};
+
 lo_interface lib9p_srv_fio;
 lo_interface lib9p_srv_dio;
 
@@ -146,20 +151,16 @@ LO_INTERFACE(lib9p_srv_file);
 	                                              uint64_t byte_offset)
 LO_INTERFACE(lib9p_srv_fio);
 
-/* FIXME: The dio interface just feels clunky.  I'm not in a rush to
- * change it because util9p_static_dir is already implemented and I
- * don't anticipate the sbc-harness needing another dio
- * implementation.  But if I wanted lib9p to be used outside of
- * sbc-harness, this is one of the first things that I'd want to
- * change.
- */
 #define lib9p_srv_dio_LO_IFACE                                                 \
 	LO_FUNC(struct lib9p_qid           , qid    )                          \
 	LO_FUNC(void                       , iofree )                          \
-	LO_FUNC(size_t /* <- obj cnt */    , dread  , struct lib9p_srv_ctx *,  \
-	                                              uint8_t *buf,            \
-	                           /* num bytes -> */ uint32_t byte_count,     \
-	             /* starting at this object -> */ size_t obj_offset)
+	/**                                                                    \
+	 * Return the idx-th dirent.  idx will always be either 0 or           \
+	 * prev_idx+1.  A dirrent with an empty name signals EOF.  The string
+	 * must remain valid until the next dread() call or iofree().          \
+	 */                                                                    \
+	LO_FUNC(struct lib9p_srv_dirent    , dread  , struct lib9p_srv_ctx *,  \
+	                                              size_t idx)
 LO_INTERFACE(lib9p_srv_dio);
 
 #define LIB9P_SRV_NOTDIR(TYP, NAM)                                                                                                                                   \
diff --git a/lib9p_util/static.c b/lib9p_util/static.c
index e1df3ca..d2413c6 100644
--- a/lib9p_util/static.c
+++ b/lib9p_util/static.c
@@ -110,33 +110,23 @@ static lo_interface lib9p_srv_dio util9p_static_dir_dopen(struct util9p_static_d
 static void util9p_static_dir_iofree(struct util9p_static_dir *self) {
 	assert(self);
 }
-static size_t util9p_static_dir_dread(struct util9p_static_dir *self, struct lib9p_srv_ctx *ctx,
-                                      uint8_t *buf,
-                                      uint32_t byte_count,
-                                      size_t _obj_offset) {
+static struct lib9p_srv_dirent util9p_static_dir_dread(struct util9p_static_dir *self, struct lib9p_srv_ctx *ctx, size_t idx) {
 	assert(self);
 	assert(ctx);
 
-	uint32_t byte_offset = 0;
-	size_t obj_offset = _obj_offset;
-	while (!LO_IS_NULL(self->members[obj_offset])) {
-		lo_interface lib9p_srv_file file = self->members[obj_offset];
-		struct lib9p_stat stat = LO_CALL(file, stat, ctx);
-		if (lib9p_ctx_has_error(&ctx->basectx))
-			break;
-		lib9p_stat_assert(stat);
-		uint32_t nbytes = lib9p_stat_marshal(&ctx->basectx, byte_count-byte_offset, &stat,
-		                                     &buf[byte_offset]);
-		if (!nbytes) {
-			if (obj_offset == _obj_offset)
-				lib9p_error(&ctx->basectx,
-				            LIB9P_ERRNO_L_ERANGE, "stat object does not fit into negotiated max message size");
-			break;
-		}
-		byte_offset += nbytes;
-		obj_offset++;
-	}
-	return obj_offset - _obj_offset;
+	lo_interface lib9p_srv_file file = self->members[idx];
+	if (LO_IS_NULL(file))
+		return (struct lib9p_srv_dirent){};
+
+	struct lib9p_stat stat = LO_CALL(file, stat, ctx);
+	if (lib9p_ctx_has_error(&ctx->basectx))
+		return (struct lib9p_srv_dirent){};
+	lib9p_stat_assert(stat);
+
+	return (struct lib9p_srv_dirent){
+		.qid  = stat.qid,
+		.name = stat.name,
+	};
 }
 
 /* file ***********************************************************************/