Better error messages

zlib_into.c

@@ -7,7 +7,7 @@
 
 #define DEF_MEM_LEVEL 8
 
-// malloc & free copied from CPython
+// malloc & free functions copied from CPython
 static void*
 PyZlib_Malloc(voidpf ctx, uInt items, uInt size)
 {
@@ -28,6 +28,36 @@ PyZlib_Free(voidpf ctx, void *ptr)
     free(ptr);
 }
 
+// zlib_error copied from CPython
+static void
+zlib_error(z_stream zst, int err, const char *msg)
+{
+    const char *zmsg = Z_NULL;
+    /* In case of a version mismatch, zst.msg won't be initialized.
+       Check for this case first, before looking at zst.msg. */
+    if (err == Z_VERSION_ERROR)
+        zmsg = "library version mismatch";
+    if (zmsg == Z_NULL)
+        zmsg = zst.msg;
+    if (zmsg == Z_NULL) {
+        switch (err) {
+        case Z_BUF_ERROR:
+            zmsg = "incomplete or truncated stream";
+            break;
+        case Z_STREAM_ERROR:
+            zmsg = "inconsistent stream state";
+            break;
+        case Z_DATA_ERROR:
+            zmsg = "invalid input data";
+            break;
+        }
+    }
+    if (zmsg == Z_NULL)
+        PyErr_Format(PyExc_RuntimeError, "Error %d %s", err, msg);
+    else
+        PyErr_Format(PyExc_RuntimeError, "Error %d %s: %.200s", err, msg, zmsg);
+}
+
 static PyObject *
 compress_into(PyObject *module, PyObject *args) {
     PyObject *return_value = NULL;
@@ -67,8 +97,7 @@ compress_into(PyObject *module, PyObject *args) {
         goto done;
     default:
         deflateEnd(&zst);
-        PyErr_SetString(PyExc_RuntimeError, "Other error");
-        //zlib_error(state, zst, err, "while compressing data");
+        zlib_error(zst, err, "while compressing data");
         goto done;
     }
 
@@ -86,7 +115,7 @@ compress_into(PyObject *module, PyObject *args) {
             goto done;
         default:
             deflateEnd(&zst);
-            PyErr_SetString(PyExc_RuntimeError, "Other error");
+            zlib_error(zst, err, "while compressing data");
             goto done;
     }
     bytes_written = output.len - zst.avail_out;