💩 Prepare to implement readXrefStreamAt

vbuch · Nov 29, 2023 · 661e8ff · 661e8ff
1 parent 3f67d7b
commit 661e8ff
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Showing 3 changed files with 58 additions and 24 deletions.
diff --git a/packages/eslint-config/eslint.js b/packages/eslint-config/eslint.js
@@ -34,7 +34,15 @@ module.exports = {
         "jest/no-conditional-expect": "off",
         "import/prefer-default-export": "off",
         "no-bitwise": "off",
-        "jest/valid-title": ["error", {"ignoreTypeOfDescribeName": true}]
+        "jest/valid-title": ["error", {"ignoreTypeOfDescribeName": true}],
+        "no-unused-vars": [
+            "error",
+            { 
+                "argsIgnorePattern": "^_",
+                "varsIgnorePattern": "^_",
+                "caughtErrorsIgnorePattern": "^_"
+            }
+        ]
     },
     settings: {
         "import/resolver": {

diff --git a/packages/placeholder-plain/src/__snapshots__/readRefTable.test.js.snap b/packages/placeholder-plain/src/__snapshots__/readRefTable.test.js.snap
@@ -4,9 +4,9 @@ exports[`getXref Throws an error when size has unexpected value 1`] = `"Failed t
 
 exports[`getXref Throws an error when size is not found 1`] = `"Size not found in xref table."`;
 
-exports[`getXref Throws an error when xref is not at its expected position 1`] = `"Expected xref at 2 but found other content."`;
+exports[`getXref Throws an error when xref is not at its expected position 1`] = `"Cross-Reference Streams not yet implemented."`;
 
-exports[`getXref Throws an error when xref is not found at position 1`] = `"Could not find xref anywhere at or after 0."`;
+exports[`getXref Throws an error when xref is not found at position 1`] = `"Cross-Reference Streams not yet implemented."`;
 
 exports[`readRefTable Expects to merge correctly the refTable of resources 1`] = `
 Object {

diff --git a/packages/placeholder-plain/src/readRefTable.js b/packages/placeholder-plain/src/readRefTable.js
@@ -12,35 +12,26 @@ export const getLastTrailerPosition = (pdf) => {
     return parseInt(xRefPosition);
 };
 
-export const getXref = (pdf, position) => {
-    let refTable = pdf.slice(position); // slice starting from where xref starts
+/**
+ * @param {Buffer} pdfSlice
+ * @param {number} position
+ * @returns {GetXRefReturnType | null}
+ */
+const readXrefTableAt = (pdfSlice, position) => {
+    let refTable = pdfSlice.subarray(position); // slice starting from where xref starts
     const realPosition = refTable.indexOf(Buffer.from('xref', 'utf8'));
     if (realPosition === -1) {
-        throw new SignPdfError(
-            `Could not find xref anywhere at or after ${position}.`,
-            SignPdfError.TYPE_PARSE,
-        );
+        return null;
     }
     if (realPosition > 0) {
-        const prefix = refTable.slice(0, realPosition);
+        const prefix = refTable.subarray(0, realPosition);
         if (prefix.toString().replace(/\s*/g, '') !== '') {
-            throw new SignPdfError(
-                `Expected xref at ${position} but found other content.`,
-                SignPdfError.TYPE_PARSE,
-            );
+            return null;
         }
     }
 
-    const nextEofPosition = refTable.indexOf(Buffer.from('%%EOF', 'utf8'));
-    if (nextEofPosition === -1) {
-        throw new SignPdfError(
-            'Expected EOF after xref and trailer but could not find one.',
-            SignPdfError.TYPE_PARSE,
-        );
-    }
-    refTable = refTable.slice(0, nextEofPosition);
-    refTable = refTable.slice(realPosition + 4); // move ahead with the "xref"
-    refTable = refTable.slice(refTable.indexOf('\n') + 1); // move after the next new line
+    // move ahead with the "xref\n"
+    refTable = refTable.subarray(realPosition + 5);
 
     // extract the size
     let size = refTable.toString().split('/Size')[1];
@@ -81,6 +72,41 @@ export const getXref = (pdf, position) => {
     };
 };
 
+/**
+ * @param {Buffer} _pdfSlice
+ * @param {number} _position
+ * @returns {GetXRefReturnType | null}
+ */
+const readXrefStreamAt = (_pdfSlice, _position) => {
+    throw new SignPdfError(
+        'Cross-Reference Streams not yet implemented.',
+        SignPdfError.TYPE_PARSE,
+    );
+};
+
+/**
+ * @typedef {object} GetXRefReturnType
+ * // TODO
+ */
+
+/**
+ * @param {Buffer} pdf
+ * @param {number} position
+ * @returns {GetXRefReturnType}
+ * @throws {SignPdfError}
+ */
+export const getXref = (pdf, position) => {
+    const table = readXrefTableAt(pdf, position)
+        || readXrefStreamAt(pdf, position);
+    if (!table) {
+        throw new SignPdfError(
+            `Could not find xref anywhere at or after startxref position ${position}.`,
+            SignPdfError.TYPE_PARSE,
+        );
+    }
+    return table;
+};
+
 /**
  * @typedef {Map<*, *>} GetFullXrefTableReturnType
  */