检查 PDF 表单

PDF 表单在表单元数据方面与标准 PDF 文件有所不同。这种元数据决定了打开文件的编辑器类型：是表单编辑器还是标准 PDF 编辑器。

为了区分标准 PDF 文件和 PDF 表单，可以使用检查函数。这些函数会读取文件的前 300 个字节，并检查其中是否存在"ONLYOFFICEFORM"。如果为true，那么这就是一个 PDF 表单。否则，它就是一个标准的 PDF 文件。

备注

通过指定document.isForm参数，您可以加快文件的打开速度。

以下示例展示了不同编程语言的检查函数。

JavaScript

function isExtendedPDFFile(text) {
  if (!text) {
    return false;
  }
  const indexFirst = text.indexOf("%\u00CD\u00CA\u00D2\u00A9\u000D");
  if (indexFirst === -1) {
    return false;
  }
  let pFirst = text.slice(indexFirst + 6);
  if (!(pFirst.lastIndexOf("1 0 obj\u000A<<\u000A", 0) === 0)) {
    return false;
  }
  pFirst = pFirst.slice(11);
  const signature = "ONLYOFFICEFORM";
  const indexStream = pFirst.indexOf("stream\u000D\u000A");
  const indexMeta = pFirst.indexOf(signature);
  if (indexStream === -1 || indexMeta === -1 || indexStream < indexMeta) {
    return false;
  }
  let pMeta = pFirst.slice(indexMeta);
  pMeta = pMeta.slice(signature.length + 3);
  let indexMetaLast = pMeta.indexOf(" ");
  if (indexMetaLast === -1) {
    return false;
  }
  pMeta = pMeta.slice(indexMetaLast + 1);
  indexMetaLast = pMeta.indexOf(" ");
  if (indexMetaLast === -1) {
    return false;
  }
  return true;
}

Node.js

DocManager.prototype.isExtendedPDFFile = function isExtendedPDFFile(fileName) {
  let filePath = this.forcesavePath(fileName, null, false);
  if (filePath === "") {
    filePath = this.storagePath(fileName);
  }
  const bufferSize = 300;
  const buffer = Buffer.alloc(bufferSize);
  const fd = fileSystem.openSync(filePath, "r");
  fileSystem.readSync(fd, buffer, 0, bufferSize);
  fileSystem.closeSync(fd);
  const pBuffer = buffer.toString("latin1");
  const indexFirst = pBuffer.indexOf("%\u00CD\u00CA\u00D2\u00A9\u000D");
  if (indexFirst === -1) {
    return false;
  }
  let pFirst = pBuffer.slice(indexFirst + 6);
  if (!pFirst.startsWith("1 0 obj\u000A<<\u000A")) {
    return false;
  }
  pFirst = pFirst.slice(11);
  const indexStream = pFirst.indexOf("stream\u000D\u000A");
  const indexMeta = pFirst.indexOf(configServer.get("gFormatOformPdfMetaTag"));
  if (indexStream === -1 || indexMeta === -1 || indexStream < indexMeta) {
    return false;
  }
  let pMeta = pFirst.slice(indexMeta);
  pMeta = pMeta.slice(configServer.get("gFormatOformPdfMetaTag").length + 3);
  let indexMetaLast = pMeta.indexOf(" ");
  if (indexMetaLast === -1) {
    return false;
  }
  pMeta = pMeta.slice(indexMetaLast + 1);
  indexMetaLast = pMeta.indexOf(" ");
  if (indexMetaLast === -1) {
    return false;
  }
  return true;
};

Java Spring

@SneakyThrows
public Boolean isExtendedPDFFile(final String fileName) {
  Resource resource = storageMutator.loadFileAsResource(fileName);
  byte[] bytes;
  try (InputStream inputStream = resource.getInputStream()) {
    bytes = inputStream.readNBytes(110);
  } catch (Exception e) {
    return false;
  }
  String pBuffer = new String(bytes, "Windows-1252");
  int indexFirst = pBuffer.indexOf("%\315\312\322\251\015");
  if (indexFirst == -1) {
    return false;
  }
  String pFirst = pBuffer.substring(indexFirst + 6);
  if (!pFirst.startsWith("1 0 obj\012<<\012")) {
    return false;
  }
  pFirst = pFirst.substring(11);
  int indexStream = pFirst.indexOf("stream\015\012");
  int indexMeta = pFirst.indexOf(Constants.G_FORMAT_OFORM_PDF_META_TAG);
  if (indexStream == -1 || indexMeta == -1 || indexStream < indexMeta) {
    return false;
  }
  String pMeta = pFirst.substring(indexMeta);
  pMeta = pMeta.substring(Constants.G_FORMAT_OFORM_PDF_META_TAG.length() + 3);
  int indexMetaLast = pMeta.indexOf(" ");
  if (indexMetaLast == -1) {
    return false;
  }
  pMeta = pMeta.substring(indexMetaLast + 1);
  indexMetaLast = pMeta.indexOf(" ");
  if (indexMetaLast == -1) {
    return false;
  }
  return true;
}

C++

bool COfficeFileFormatChecker::isPdfOformFormatFile(unsigned char *pBuffer, int dwBytes)
{
  pBuffer[dwBytes - 1] = 0;
  char* pFirst = strstr((char*)pBuffer, "%\315\312\322\251\015");
  if (!pFirst || pFirst - (char*)pBuffer + 6 >= dwBytes)
    return false;
  pFirst += 6;
  if (strncmp(pFirst, "1 0 obj\012<<\012", 11) != 0 || pFirst - (char*)pBuffer + 11 >= dwBytes)
    return false;
  pFirst += 11;
  char* pStream = strstr(pFirst, "stream\015\012");
  char* pMeta = strstr(pFirst, g_format_oform_pdf_meta_tag);
  if (!pStream || !pMeta || pStream < pMeta)
    return false;
  pMeta += strlen(g_format_oform_pdf_meta_tag) + 3;
  char* pMetaLast = strstr(pMeta, " ");
  if (!pMetaLast)
    return false;
  pMeta = pMetaLast + 1;
  pMetaLast = strstr(pMeta, " ");
  if (!pMetaLast)
    return false;
  return true;
}

Python

def is_pdf_form(text):
  if not text:
    return False

  index_first = text.find(b"%\xCD\xCA\xD2\xA9\x0D")
  if index_first == -1:
    return False

  p_first = text[index_first + 6:]
  if not p_first.startswith(b"1 0 obj\x0A<<\x0A"):
    return False

  p_first = p_first[11:]
  signature = b"ONLYOFFICEFORM"
  index_stream = p_first.find(b"stream\x0D\x0A")
  index_meta = p_first.find(signature)
  if index_stream == -1 or index_meta == -1 or index_stream < index_meta:
    return False

  p_meta = p_first[index_meta:]
  p_meta = p_meta[len(signature) + 3:]
  index_meta_last = p_meta.find(b" ")
  if index_meta_last == -1:
    return False

  p_meta = p_meta[index_meta_last + 1:]
  index_meta_last = p_meta.find(b" ")
  if index_meta_last == -1:
    return False

  return True

PHP

<?php

public function isOnlyofficeForm($file) {
  if ($file === null) return false;

  $limitDetect = 300;
  $onlyofficeFormMetaTag = "ONLYOFFICEFORM";
  $path = $file->getStoredFilePath() . "file";
  $content = file_get_contents($path, false, null, 0, $limitDetect);
  $indexFirst = strpos($content, "%\xCD\xCA\xD2\xA9\x0D");
  if ($indexFirst === false) {
    return false;
  }
  $pFirst = substr($content, $indexFirst + 6);
  if (!str_starts_with($pFirst, "1 0 obj\n<<\n")) {
    return false;
  }
  $pFirst = substr($pFirst, 11);
  $indexStream = strpos($pFirst, "stream\x0D\x0A");
  $indexMeta = strpos($pFirst, $onlyofficeFormMetaTag);
  if ($indexStream === false || $indexMeta === false || $indexStream < $indexMeta) {
    return false;
  }
  $pMeta = substr($pFirst, $indexMeta);
  $pMeta = substr($pMeta, strlen($onlyofficeFormMetaTag) + 3);
  $indexMetaLast = strpos($pMeta, " ");
  if ($indexMetaLast === false) {
    return false;
  }
  $pMeta = substr($pMeta, $indexMetaLast + 1);
  $indexMetaLast = strpos($pMeta, " ");
  if ($indexMetaLast === false) {
    return false;
  }
  return true;
}

?>