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Fix some theoretical problems with png reading #5515

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Merged
merged 2 commits into from
Nov 20, 2015
+9 −6
Merged

Fix some theoretical problems with png reading #5515

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17aad94
Fix some theoretical problems with png reading
mdboom Nov 19, 2015
d7d7038
Set exception if read past end of file
mdboom Nov 20, 2015
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1 change: 1 addition & 0 deletions lib/matplotlib/backends/backend_agg.py
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Original file line number Diff line number Diff line change
Expand Up @@ -526,6 +526,7 @@ def print_png(self, filename_or_obj, *args, **kwargs):
close = True
else:
close = False

try:
_png.write_png(renderer._renderer, filename_or_obj, self.figure.dpi)
finally:
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4 changes: 2 additions & 2 deletions lib/matplotlib/image.py
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Expand Up @@ -1279,8 +1279,8 @@ def pilread(fname):
from PIL import Image
except ImportError:
return None
image = Image.open(fname)
return pil_to_array(image)
with Image.open(fname) as image:
return pil_to_array(image)

handlers = {'png': _png.read_png, }
if format is None:
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10 changes: 6 additions & 4 deletions src/_png.cpp
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Expand Up @@ -328,10 +328,12 @@ static void _read_png_data(PyObject *py_file_obj, png_bytep data, png_size_t len
Py_ssize_t bufflen;
if (read_method) {
result = PyObject_CallFunction(read_method, (char *)"i", length);
}
if (PyBytes_AsStringAndSize(result, &buffer, &bufflen) == 0) {
if (bufflen == (Py_ssize_t)length) {
memcpy(data, buffer, length);
if (PyBytes_AsStringAndSize(result, &buffer, &bufflen) == 0) {
if (bufflen == (Py_ssize_t)length) {
memcpy(data, buffer, length);
} else {
PyErr_SetString(PyExc_IOError, "read past end of file");
}
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Ok, I see that now. Now, what if bufflen does not end up being the same as length? Are we assuming that an error has been set? Would it make sense for us to set an error if one hasn't been set?

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Good point. We should probably set an exception in that case. It basically means that it read past the end of the file (which could happen if the file were truncated or something).

}
}
Py_XDECREF(read_method);
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