fix for large decoded value

.gitignore

@@ -13,3 +13,5 @@ htmlcov/
 /*.txt
 /*.whl
 /xdelta3/lib/
+/tests/b1.bin
+/tests/b2.bin

.travis.yml

@@ -28,6 +28,7 @@ install:
 - gcc -v
 #- docker pull $DOCKER_IMAGE
 - pip freeze
+- make download-test-files
 
 script:
 - make test

Makefile

@@ -23,6 +23,15 @@ lint:
 	flake8 xdelta3/ tests/
 	pytest xdelta3 -p no:sugar -q
 
+.PHONY: download-test-files
+download-test-files:
+	curl -sL https://github.com/samuelcolvin/xdelta3-python/files/1579377/files.zip > test_html.zip
+	echo "52bf4ee680a86afdeed9aad30e7d68fa  test_html.zip" > test_html.zip.md5
+	md5sum -c test_html.zip.md5
+	unzip -o test_html.zip
+	mv b1.bin b2.bin tests
+	rm test_html.zip test_html.zip.md5
+
 .PHONY: test
 test: install
 	pytest --cov=xdelta3

tests/test_main.py

@@ -1,6 +1,7 @@
 import base64
 import os
 import string
+from pathlib import Path
 
 import pytest
 
@@ -64,3 +65,16 @@ def test_readme():
 
     value_two_rebuilt = xdelta3.decode(value_one, delta)
     assert value_two_rebuilt == value_two
+
+
+def test_large_decode():
+    this_dir = Path(__file__).parent
+    try:
+        b1 = (this_dir / 'b1.bin').read_bytes()
+        b2 = (this_dir / 'b2.bin').read_bytes()
+    except FileNotFoundError as e:
+        raise RuntimeError('file required for test not found, run `make download-test-files`') from e
+
+    d = xdelta3.encode(b1, b2)
+    b3 = xdelta3.decode(b1, d)
+    assert b2 == b3

xdelta3/_xdelta3.c

@@ -27,10 +27,16 @@ static PyObject * xdelta3_execute(PyObject *self, PyObject *args)
         output_buf, &output_size, output_alloc, flags);
   } else {
     // output shouldn't be bigger than the original plus the delta, but give a little leeway
-    output_alloc = input_size + source_size * 11 / 10;
-    output_buf = main_malloc(output_alloc);
-    result = xd3_decode_memory(input_bytes, input_size, source_bytes, source_size,
-        output_buf, &output_size, output_alloc, flags);
+    output_alloc = input_size + source_size;
+    while (1) {
+      output_buf = main_malloc(output_alloc);
+      result = xd3_decode_memory(input_bytes, input_size, source_bytes, source_size,
+          output_buf, &output_size, output_alloc, flags);
+      if (result != ENOSPC) {
+        break;
+      }
+      output_alloc = output_alloc * 2;
+    }
   }
 
   if (result == 0) {
@@ -40,12 +46,8 @@ static PyObject * xdelta3_execute(PyObject *self, PyObject *args)
   }
 
   if(result == ENOSPC) {
-    if (action == 0) {
-      // all is well, just not efficient delta could be found
-      PyErr_SetString(NoDeltaFound, "No delta found shorter than the input value");
-    } else {
-      PyErr_SetString(XDeltaError, "Output of decoding delta longer than expected");
-    }
+    // all is well, just no efficient delta could be found
+    PyErr_SetString(NoDeltaFound, "No delta found shorter than the input value");
   } else {
     char exc_str[80];
     sprintf(exc_str, "Error occur executing xdelta3: %s", xd3_strerror(result));