initial commit

apps/OpenSignServer/cloud/parsefunction/pdf/customSignPdf/readPdf.js

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+import readRefTable from './readRefTable.js';
+import findObject from './findObject.js';
+
+const getValue = (trailer, key) => {
+    let index = trailer.indexOf(key);
+
+    if (index === -1) {
+        return undefined;
+    }
+
+    const slice = trailer.slice(index);
+    index = slice.indexOf('/', 1);
+    if (index === -1) {
+        index = slice.indexOf('>', 1);
+    }
+    return slice.slice(key.length + 1, index).toString().trim(); // key + at least one space
+};
+
+/**
+ * Simplified parsing of a PDF Buffer.
+ * Extracts reference table, root info and trailer start.
+ *
+ * See section 7.5.5 (File Trailer) of the PDF specs.
+ *
+ * @param {Buffer} pdfBuffer
+ */
+const readPdf = (pdfBuffer) => {
+    // Extract the trailer dictionary.
+    const trailerStart = pdfBuffer.lastIndexOf('trailer');
+    // The trailer is followed by xref. Then an EOF. EOF's length is 6 characters.
+    const trailer = pdfBuffer.slice(trailerStart, pdfBuffer.length - 6);
+
+    let xRefPosition = trailer.slice(trailer.lastIndexOf('startxref') + 10).toString();
+
+    xRefPosition = parseInt(xRefPosition);
+    const refTable = readRefTable(pdfBuffer);
+
+    const rootRef = getValue(trailer, '/Root');
+    const root = findObject(pdfBuffer, refTable, rootRef).toString();
+
+    const infoRef = getValue(trailer, '/Info');
+
+    return {
+        xref: refTable,
+        rootRef,
+        root,
+        infoRef,
+        trailerStart,
+        previousXrefs: [],
+        xRefPosition,
+    };
+};
+
+export default readPdf;