Godot 4 源码分析 - 文件读入编码处理

今天需要读入xml文件进行处理，结果读入一个带中文的文件时，出错了。当然程序还能运行，但编译器一直报错，而且XML解析也不正确

单步调试发现读入的内容出现乱码，具体逻辑：

String FileAccess::get_as_text(bool p_skip_cr) const {uint64_t original_pos = get_position();const_cast<FileAccess *>(this)->seek(0);String text = get_as_utf8_string(p_skip_cr);const_cast<FileAccess *>(this)->seek(original_pos);return text;
}String FileAccess::get_as_utf8_string(bool p_skip_cr, String encoding) const {encoding = encoding.to_lower();Vector<uint8_t> sourcef;uint64_t len = get_length();sourcef.resize(len + 1);uint8_t *w = sourcef.ptrw();uint64_t r = get_buffer(w, len);ERR_FAIL_COND_V(r != len, String());w[len] = 0;String s((const char *)w);s.parse_utf8((const char *)w, -1, p_skip_cr);return s;
}Error String::parse_utf8(const char *p_utf8, int p_len, bool p_skip_cr) {if (!p_utf8) {return ERR_INVALID_DATA;}String aux;int cstr_size = 0;int str_size = 0;/* HANDLE BOM (Byte Order Mark) */if (p_len < 0 || p_len >= 3) {bool has_bom = uint8_t(p_utf8[0]) == 0xef && uint8_t(p_utf8[1]) == 0xbb && uint8_t(p_utf8[2]) == 0xbf;if (has_bom) {//8-bit encoding, byte order has no meaning in UTF-8, just skip itif (p_len >= 0) {p_len -= 3;}p_utf8 += 3;}}bool decode_error = false;bool decode_failed = false;{const char *ptrtmp = p_utf8;const char *ptrtmp_limit = &p_utf8[p_len];int skip = 0;uint8_t c_start = 0;while (ptrtmp != ptrtmp_limit && *ptrtmp) {uint8_t c = *ptrtmp >= 0 ? *ptrtmp : uint8_t(256 + *ptrtmp);if (skip == 0) {if (p_skip_cr && c == '\r') {ptrtmp++;continue;}/* Determine the number of characters in sequence */if ((c & 0x80) == 0) {skip = 0;} else if ((c & 0xe0) == 0xc0) {skip = 1;} else if ((c & 0xf0) == 0xe0) {skip = 2;} else if ((c & 0xf8) == 0xf0) {skip = 3;} else if ((c & 0xfc) == 0xf8) {skip = 4;} else if ((c & 0xfe) == 0xfc) {skip = 5;} else {skip = 0;print_unicode_error(vformat("Invalid UTF-8 leading byte (%x)", c), true);decode_failed = true;}c_start = c;if (skip == 1 && (c & 0x1e) == 0) {print_unicode_error(vformat("Overlong encoding (%x ...)", c));decode_error = true;}str_size++;} else {if ((c_start == 0xe0 && skip == 2 && c < 0xa0) || (c_start == 0xf0 && skip == 3 && c < 0x90) || (c_start == 0xf8 && skip == 4 && c < 0x88) || (c_start == 0xfc && skip == 5 && c < 0x84)) {print_unicode_error(vformat("Overlong encoding (%x %x ...)", c_start, c));decode_error = true;}if (c < 0x80 || c > 0xbf) {print_unicode_error(vformat("Invalid UTF-8 continuation byte (%x ... %x ...)", c_start, c), true);decode_failed = true;skip = 0;} else {--skip;}}cstr_size++;ptrtmp++;}if (skip) {print_unicode_error(vformat("Missing %d UTF-8 continuation byte(s)", skip), true);decode_failed = true;}}if (str_size == 0) {clear();return OK; // empty string}resize(str_size + 1);char32_t *dst = ptrw();dst[str_size] = 0;int skip = 0;uint32_t unichar = 0;while (cstr_size) {uint8_t c = *p_utf8 >= 0 ? *p_utf8 : uint8_t(256 + *p_utf8);if (skip == 0) {if (p_skip_cr && c == '\r') {p_utf8++;continue;}/* Determine the number of characters in sequence */if ((c & 0x80) == 0) {*(dst++) = c;unichar = 0;skip = 0;} else if ((c & 0xe0) == 0xc0) {unichar = (0xff >> 3) & c;skip = 1;} else if ((c & 0xf0) == 0xe0) {unichar = (0xff >> 4) & c;skip = 2;} else if ((c & 0xf8) == 0xf0) {unichar = (0xff >> 5) & c;skip = 3;} else if ((c & 0xfc) == 0xf8) {unichar = (0xff >> 6) & c;skip = 4;} else if ((c & 0xfe) == 0xfc) {unichar = (0xff >> 7) & c;skip = 5;} else {*(dst++) = 0x20;unichar = 0;skip = 0;}} else {if (c < 0x80 || c > 0xbf) {*(dst++) = 0x20;skip = 0;} else {unichar = (unichar << 6) | (c & 0x3f);--skip;if (skip == 0) {if (unichar == 0) {print_unicode_error("NUL character", true);decode_failed = true;unichar = 0x20;}if ((unichar & 0xfffff800) == 0xd800) {print_unicode_error(vformat("Unpaired surrogate (%x)", unichar));decode_error = true;}if (unichar > 0x10ffff) {print_unicode_error(vformat("Invalid unicode codepoint (%x)", unichar));decode_error = true;}*(dst++) = unichar;}}}cstr_size--;p_utf8++;}if (skip) {*(dst++) = 0x20;}if (decode_failed) {return ERR_INVALID_DATA;} else if (decode_error) {return ERR_PARSE_ERROR;} else {return OK;}
}

其实已经读入到w里，但String::parse_utf8出错。

回头看了一下，原目标文件为GB2312编码。而Godot的FileAccess不支持别的编码。

那就加上，在不影响原有逻辑的基础上，小动一下：

ClassDB::bind_method(D_METHOD("get_as_text", "skip_cr", "encoding"), &FileAccess::get_as_text, DEFVAL(false), DEFVAL("utf-8"));String FileAccess::get_as_text(bool p_skip_cr, String encoding) const {uint64_t original_pos = get_position();const_cast<FileAccess *>(this)->seek(0);String text = get_as_utf8_string(p_skip_cr, encoding);const_cast<FileAccess *>(this)->seek(original_pos);return text;
}String FileAccess::get_as_utf8_string(bool p_skip_cr, String encoding) const {encoding = encoding.to_lower();Vector<uint8_t> sourcef;uint64_t len = get_length();sourcef.resize(len + 1);uint8_t *w = sourcef.ptrw();uint64_t r = get_buffer(w, len);ERR_FAIL_COND_V(r != len, String());w[len] = 0;if (encoding == "gb2312") {std::string str((const char *)w);String s(str);return s;}String s((const char *)w);s.parse_utf8((const char *)w, -1, p_skip_cr);return s;
}

GDScript中调用：

	var xml : Xml = Xml.new("D:\\ExenObj\\Exe\\DrGraph\\Files\\Demo.sch")xml.Read("gb2312");class Xml:var RootNode: XmlNode = nullvar FileName: String = ""func _init(fileName: String) -> void:FileName = fileNamefunc Read(encoding: String = "utf-8") -> void:if FileAccess.file_exists(FileName):			var fs = FileAccess.open(FileName, FileAccess.READ)var text = fs.get_as_text(false, encoding)var textStart = Helper.RegMatchAt(text, "<[^!?]")var pos = 0;if textStart.length() > 0:pos = text.find(textStart)if pos > 0:var header = text.substr(0, pos - 1)			text = text.substr(pos)var from = 0while pos > 0:pos = header.find("<!", from)if pos == -1:breakfrom = pos + 1pos = header.find("\n", from)var str = header.substr(from, pos - from)var entityName = Helper.RegMatchAt(str, "Cbw.*?(?= )")var value = Helper.RegMatchAt(str, "(?<=').*?(?=')")if entityName.length() > 0 and value.length() > 0:print(entityName, " = ", value)RootNode = XmlNode.new("root");RootNode.xml = self;RootNode.from_string(text)fs.close()

如此，恢复正常。XML文本内容解析为图形效果

<CbwObjects><TLine name="Line967"><Points><Point x="258" y="868"/><Point x="606" y="1043"/></Points></TLine><TLine name="Line968"><Points><Point x="329" y="698"/><Point x="142" y="864"/></Points></TLine><TRectangle name="Rect147"><Points><Point x="433" y="804"/><Point x="712" y="917"/></Points></TRectangle><TRectangle name="Rect148"><Points><Point x="378" y="638"/><Point x="461" y="764"/></Points></TRectangle><TRectangle name="Rect149"><Points><Point x="105" y="651"/><Point x="201" y="826"/></Points></TRectangle><TRectangle name="Rect150"><Points><Point x="139" y="1011"/><Point x="341" y="866"/></Points></TRectangle><TRectangle name="Rect151"><Points><Point x="847" y="832"/><Point x="939" y="1043"/></Points></TRectangle><TRectangle name="Rect152"><Points><Point x="850" y="635"/><Point x="985" y="710"/></Points></TRectangle><TEllipse name="Ellipse74"><Points><Point x="551.451219512195" y="644.367464840815"/><Point x="788" y="762"/></Points></TEllipse><TLine name="Line799" pen="&CbwPen0;"><Points><Point x="230" y="46"/><Point x="417" y="284"/></Points></TLine>
</CbwObjects>