feat: add sfsReadlink and sfsLink to sfs

src/sfs.c

@@ -1106,3 +1106,163 @@ int32 sfsCreateSymlink(const char* path, const char* target)
     if (newInode < 0)
         return -1;
 
+    if (sfsWriteAt(newInode, 0, target, targetLen) != (int64)targetLen) {
+        char parentBuf[256];
+        char leaf[sfsNameMax];
+        if (splitPath(path, parentBuf, sizeof(parentBuf), leaf, sizeof(leaf))) {
+            int32 parentInode = sfsLookup(parentBuf);
+            if (parentInode >= 0)
+                dirRemove(parentInode, leaf, strlen(leaf));
+        }
+        freeInodeNum(newInode);
+        return -1;
+    }
+    return newInode;
+}
+
+bool sfsReadlink(int32 inodeNum, char* buf, uint64 cap)
+{
+    if (!isMounted || inodeNum <= 0)
+        return false;
+    return readSymlinkTarget(inodeNum, buf, cap);
+}
+
+int32 sfsLink(const char* existingPath, const char* newPath)
+{
+    if (!isMounted)
+        return -1;
+
+    int32 target = sfsLookup(existingPath);
+    if (target < 0)
+        return -1;
+
+    SfsInode inode;
+    if (!readInode(target, &inode))
+        return -1;
+    if (inode.type == sfsTypeDir)
+        return -1;
+
+    char parentBuf[256];
+    char leaf[sfsNameMax];
+    if (!splitPath(newPath, parentBuf, sizeof(parentBuf), leaf, sizeof(leaf)))
+        return -1;
+
+    int32 parentInode = sfsLookup(parentBuf);
+    if (parentInode < 0 || sfsTypeOf(parentInode) != sfsTypeDir)
+        return -1;
+    /* Same parent-directory write check as createNode/sfsRemove above --
+       adding a new hardlink NAME needs write permission on the PARENT of
+       the new name, not on the existing target being linked to. */
+    if (!vfsPermitted(sfsModeOf(parentInode), sfsUidOf(parentInode), sfsGidOf(parentInode),
+                       currentThreadUid(), currentThreadGid(), fsModeOwnerWrite))
+        return -1;
+    if (dirFind(parentInode, leaf, strlen(leaf)) >= 0)
+        return -1;
+
+    inode.linkCount++;
+    inode.ctime = (uint32)rtcNow();
+    if (!writeInodeRaw(target, &inode))
+        return -1;
+
+    if (!dirAdd(parentInode, leaf, strlen(leaf), target, inode.type)) {
+        inode.linkCount--;
+        writeInodeRaw(target, &inode);
+        return -1;
+    }
+    return target;
+}
+
+uint32 sfsLinkCountOf(int32 inodeNum)
+{
+    if (!isMounted || inodeNum <= 0)
+        return 0;
+    SfsInode inode;
+    if (!readInode(inodeNum, &inode))
+        return 0;
+    return inode.linkCount;
+}
+
+bool sfsRemove(const char* path)
+{
+    if (!isMounted)
+        return false;
+
+    char parentBuf[256];
+    char leaf[sfsNameMax];
+    if (!splitPath(path, parentBuf, sizeof(parentBuf), leaf, sizeof(leaf)))
+        return false;
+
+    int32 parentInode = sfsLookup(parentBuf);
+    if (parentInode < 0)
+        return false;
+    /* Same parent-directory write check as createNode above -- removing an
+       entry needs write permission on the PARENT, not the entry itself,
+       mirroring vfs.c's vfsUnlink/vfsRmdir's own equivalent tmpfs check. */
+    if (!vfsPermitted(sfsModeOf(parentInode), sfsUidOf(parentInode), sfsGidOf(parentInode),
+                       currentThreadUid(), currentThreadGid(), fsModeOwnerWrite))
+        return false;
+    int32 target = dirFind(parentInode, leaf, strlen(leaf));
+    if (target < 0)
+        return false;
+
+    SfsInode inode;
+    if (!readInode(target, &inode))
+        return false;
+    if (inode.type == sfsTypeDir && inode.size > 0)
+        return false;
+
+    if (!dirRemove(parentInode, leaf, strlen(leaf)))
+        return false;
+
+    if (inode.linkCount > 1) {
+        inode.linkCount--;
+        inode.ctime = (uint32)rtcNow();
+        return writeInodeRaw(target, &inode);
+    }
+
+    if (!sfsTruncateInode(&inode, target, 0))
+        return false;
+    freeInodeNum(target);
+    return true;
+}
+
+uint64 sfsSizeOf(int32 inodeNum)
+{
+    if (!isMounted || inodeNum <= 0)
+        return 0;
+    SfsInode inode;
+    if (!readInode(inodeNum, &inode))
+        return 0;
+    return inode.size;
+}
+
+uint32 sfsTypeOf(int32 inodeNum)
+{
+    if (!isMounted || inodeNum <= 0)
+        return sfsTypeFree;
+    SfsInode inode;
+    if (!readInode(inodeNum, &inode))
+        return sfsTypeFree;
+    return inode.type;
+}
+
+uint64 sfsMtimeOf(int32 inodeNum)
+{
+    if (!isMounted || inodeNum <= 0)
+        return 0;
+    SfsInode inode;
+    if (!readInode(inodeNum, &inode))
+        return 0;
+    return inode.mtime;
+}
+
+uint64 sfsCtimeOf(int32 inodeNum)
+{
+    if (!isMounted || inodeNum <= 0)
+        return 0;
+    SfsInode inode;
+    if (!readInode(inodeNum, &inode))
+        return 0;
+    return inode.ctime;
+}
+