user/fs: create a shared library for handling directory reads

4 files changed, 69 insertions, 48 deletions

diff --git a/src/user/app/init/driver/tmpfs.c b/src/user/app/init/driver/tmpfs.c
index 7bda37f..5db78f1 100644
--- a/src/user/app/init/driver/tmpfs.c
+++ b/src/user/app/init/driver/tmpfs.c
@@ -4,6 +4,7 @@
 #include <stddef.h>
 #include <stdlib.h>
 #include <unistd.h>
+#include <user/lib/fs/dir.h>
 
 struct node {
 	const char *name;
@@ -40,8 +41,9 @@ static struct node *tmpfs_open(const char *path, struct fs_wait_response *res) {
 		node = malloc(sizeof *node);
 		memset(node, 0, sizeof *node);
 
-		char *namebuf = malloc(res->len);
+		char *namebuf = malloc(res->len + 1);
 		memcpy(namebuf, path, res->len);
+		namebuf[res->len] = '\0';
 		node->name = namebuf;
 		node->namelen = res->len;
 		node->next = root;
@@ -65,27 +67,11 @@ void tmpfs_drv(void) {
 			case VFSOP_READ:
 				ptr = (void*)res.id;
 				if (ptr == &special_root) {
-					// TODO directory offset handling
-					size_t buf_pos = 0;
-					size_t to_skip = res.offset;
-
-					for (struct node *iter = root; iter; iter = iter->next) {
-						if (iter->namelen <= to_skip) {
-							to_skip -= iter->namelen;
-							continue;
-						}
-
-						if (iter->namelen + buf_pos - to_skip >= sizeof(buf)) {
-							memcpy(buf + buf_pos, iter->name + to_skip, sizeof(buf) - buf_pos - to_skip);
-							buf_pos = sizeof(buf);
-							break;
-						}
-						memcpy(buf + buf_pos, iter->name + to_skip, iter->namelen - to_skip);
-						buf_pos += iter->namelen - to_skip;
-						buf[buf_pos++] = '\0';
-						to_skip = 0;
-					}
-					_syscall_fs_respond(buf, buf_pos, 0);
+					struct dirbuild db;
+					dir_start(&db, res.offset, buf, sizeof buf);
+					for (struct node *iter = root; iter; iter = iter->next)
+						dir_append(&db, iter->name);
+					_syscall_fs_respond(buf, dir_finish(&db), 0);
 				} else {
 					fs_normslice(&res.offset, &res.len, ptr->size, false);
 					_syscall_fs_respond(ptr->buf + res.offset, res.len, 0);
diff --git a/src/user/bootstrap/tar.c b/src/user/bootstrap/tar.c
index c690f2c..2025ed1 100644
--- a/src/user/bootstrap/tar.c
+++ b/src/user/bootstrap/tar.c
@@ -5,6 +5,7 @@
 #include <shared/mem.h>
 #include <stdint.h>
 #include <unistd.h>
+#include <user/lib/fs/dir.h>
 
 #define BUF_SIZE 64
 
@@ -61,7 +62,6 @@ static void tar_read(struct fs_wait_response *res, void *base, size_t base_len)
 	int size;
 
 	static char buf[BUF_SIZE]; // TODO reuse a single buffer
-	size_t buf_pos = 0;
 
 	if (meta == root_fakemeta) type = '5'; /* see comment in tar_open() */
 
@@ -74,43 +74,27 @@ static void tar_read(struct fs_wait_response *res, void *base, size_t base_len)
 			break;
 
 		case '5': /* directory */
-			if (res->offset < 0) {
-				_syscall_fs_respond(NULL, -1, 0);
-				break;
-			}
-			size_t to_skip = res->offset;
-			meta_len = strlen(meta);
+			struct dirbuild db;
+			dir_start(&db, res->offset, buf, sizeof buf);
 
-			/* find files in dir */
+			meta_len = strlen(meta);
 			for (size_t off = 0; off < base_len;) {
 				if (0 != memcmp(base + off + 257, "ustar", 5))
 					break; // not a metadata sector
-				// TODO more meaningful variable names and clean code up
 
 				/* check if prefix matches */
-				if (0 == memcmp(base + off, meta, meta_len) &&
-						*(char*)(base + off + meta_len) != '\0') {
+				if (0 == memcmp(base + off, meta, meta_len)
+					&& *(char*)(base + off + meta_len) != '\0') {
 					char *suffix = base + off + meta_len;
-					size_t suffix_len = strlen(suffix);
 
 					/* check if the path contains any non-trailing slashes */
 					char *next = suffix;
+					// TODO strchr
 					while (*next && *next != '/') next++;
 					if (*next == '/') next++;
+
 					if (*next == '\0') {
-						if (to_skip > suffix_len) {
-							to_skip -= suffix_len;
-						} else {
-							suffix += to_skip;
-							suffix_len -= to_skip;
-							to_skip = 0;
-
-							/* it doesn't - so let's add it to the result */
-							memcpy(buf + buf_pos, suffix, suffix_len);
-							buf[buf_pos + suffix_len] = '\0';
-							buf_pos += suffix_len + 1;
-							// TODO no buffer overrun check
-						}
+						if (dir_append(&db, suffix)) break;
 					}
 				}
 
@@ -119,7 +103,7 @@ static void tar_read(struct fs_wait_response *res, void *base, size_t base_len)
 				off += (size + 511) & ~511; // skip the data sectors
 			}
 
-			_syscall_fs_respond(buf, buf_pos, 0);
+			_syscall_fs_respond(buf, dir_finish(&db), 0);
 			break;
 
 		default:
diff --git a/src/user/lib/fs/dir.c b/src/user/lib/fs/dir.c
new file mode 100644
index 0000000..25ae606
--- /dev/null
+++ b/src/user/lib/fs/dir.c
@@ -0,0 +1,37 @@
+#include <errno.h>
+#include <string.h>
+#include <user/lib/fs/dir.h>
+
+void dir_start(struct dirbuild *db, long offset, char *buf, size_t buflen) {
+	db->offset = offset;
+	db->buf = buf;
+	db->bpos = 0;
+	db->blen = buflen;
+	db->error = 0;
+
+	if (offset < 0)
+		db->error = -ENOSYS; // TODO
+}
+
+bool dir_append(struct dirbuild *db, const char *name) {
+	if (db->error) return true;
+
+	long len = strlen(name) + 1;
+
+	if (db->offset < len) {
+		name += db->offset;
+		len  -= db->offset;
+		db->offset = 0;
+
+		// TODO no buffer overrun check
+		memcpy(db->buf + db->bpos, name, len);
+		db->bpos += len;
+	} else {
+		db->offset -= len;
+	}
+	return false;
+}
+
+long dir_finish(struct dirbuild *db) {
+	return db->error ? db->error : db->bpos;
+}
diff --git a/src/user/lib/fs/dir.h b/src/user/lib/fs/dir.h
new file mode 100644
index 0000000..1a8c7f5
--- /dev/null
+++ b/src/user/lib/fs/dir.h
@@ -0,0 +1,14 @@
+#pragma once
+#include <stdbool.h>
+#include <stddef.h>
+
+struct dirbuild {
+	long offset;
+	char *buf;
+	long bpos, blen;
+	long error;
+};
+
+void dir_start(struct dirbuild *db, long offset, char *buf, size_t buflen);
+bool dir_append(struct dirbuild *db, const char *name);
+long dir_finish(struct dirbuild *db);