add io_stream:seek

res/modules/internal/stream_providers/file.lua

@@ -3,6 +3,7 @@ local io_stream = require "core:io_stream"
 local lib = {
     read = file.__read_descriptor,
     write = file.__write_descriptor,
+    seek = file.__seek_descriptor,
     flush = file.__flush_descriptor,
     is_alive = file.__has_descriptor,
     close = file.__close_descriptor

res/modules/internal/stream_providers/named_pipe_unix.lua

@@ -58,6 +58,10 @@ function lib.write(fd, bytearray)
     end
 end
 
+function lib.seek(fd, mode, offset)
+    error("cannot seek the named pipe")
+end
+
 function lib.flush(fd)
     -- no flush on unix
 end

res/modules/internal/stream_providers/named_pipe_windows.lua

@@ -62,7 +62,7 @@ function lib.read(handle, len)
 
     if not has_data then
         return out
-    elseif hasData == -1 then
+    elseif has_data == -1 then
         error("failed to read from named pipe: "..tostring(C.GetLastError()))
     end
 
@@ -84,8 +84,8 @@ end
 
 function lib.write(handle, bytearray)
     local len = #bytearray
-    
     local buffer = FFI.new("uint8_t[?]", len)
+
     for i = 1, len do
         buffer[i-1] = bytearray[i]
     end
@@ -97,6 +97,10 @@ function lib.write(handle, bytearray)
     end
 end
 
+function lib.seek(handle, mode, offset)
+    error("cannot seek the named pipe")
+end
+
 function lib.flush(handle)
     C.FlushFileBuffers(handle)
 end

res/modules/io_stream.lua

@@ -369,6 +369,10 @@ function io_stream:write(arg, ...)
     end
 end
 
+function io_stream:seek(mode, offset)
+    self.ioLib.seek(self.descriptor, mode, offset)
+end
+
 function io_stream:is_alive()
     return self.ioLib.is_alive(self.descriptor)
 end

src/logic/scripting/lua/libs/libfile.cpp

@@ -347,6 +347,41 @@ static int l_write_descriptor(lua::State* L) {
     return 0;
 }
 
+static int l_seek_descriptor(lua::State* L) {
+    int descriptor = lua::tointeger(L, 1);
+
+    if (!scripting::descriptors_manager::has_descriptor(descriptor)) {
+        throw std::runtime_error("unknown descriptor");
+    }
+
+    std::string mode = lua::require_string(L, 2);
+    std::ios_base::seekdir dir;
+
+    switch (mode[0]) {
+        case 'b':
+            dir = std::ios_base::beg;
+            break;
+        case 'c':
+            dir = std::ios_base::cur;
+            break;
+        case 'e':
+            dir = std::ios_base::end;
+            break;
+        default:
+            throw std::runtime_error("invalid seek mode");
+    }
+
+    auto* stream = scripting::descriptors_manager::get_output(descriptor);
+
+    stream->seekp(lua::tointeger(L, 3), dir);
+
+    if (!stream->good()) {
+        throw std::runtime_error("failed to seek stream");
+    }
+
+    return 0;
+}
+
 static int l_flush_descriptor(lua::State* L) {
     int descriptor = lua::tointeger(L, 1);
 
@@ -406,9 +441,9 @@ const luaL_Reg filelib[] = {
     {"__has_descriptor", lua::wrap<l_has_descriptor>},
     {"__read_descriptor", lua::wrap<l_read_descriptor>},
     {"__write_descriptor", lua::wrap<l_write_descriptor>},
+    {"__seek_descriptor", lua::wrap<l_seek_descriptor>},
     {"__flush_descriptor", lua::wrap<l_flush_descriptor>},
     {"__close_descriptor", lua::wrap<l_close_descriptor>},
     {"__close_all_descriptors", lua::wrap<l_close_all_descriptors>},
     {nullptr, nullptr}
 };
-