https://github.com/python/cpython/commit/71defb69438ce13708d8f9a73756d2073e0b2081
commit: 71defb69438ce13708d8f9a73756d2073e0b2081
branch: main
author: Cody Maloney <[email protected]>
committer: vstinner <[email protected]>
date: 2025-09-15T22:38:01+02:00
summary:
gh-129813, PEP 782: Use PyBytesWriter in _io.FileIO.readall (#138901)
Performance about the same, using the benchmark from gh-120754:
```
pyperf compare_to main.json pep782.json
read_file_small: Mean +- std dev: [main] 5.71 us +- 0.05 us -> [pep782] 5.68 us
+- 0.05 us: 1.01x faster
read_file_large: Mean +- std dev: [main] 89.7 us +- 0.9 us -> [pep782] 86.9 us
+- 0.8 us: 1.03x faster
read_all_rst_bytes: Mean +- std dev: [main] 926 us +- 8 us -> [pep782] 920 us
+- 12 us: 1.01x faster
read_all_rst_text: Mean +- std dev: [main] 2.24 ms +- 0.02 ms -> [pep782] 2.17
ms +- 0.04 ms: 1.03x faster
Benchmark hidden because not significant (1): read_all_py_bytes
Geometric mean: 1.01x faster
```
files:
M Modules/_io/fileio.c
diff --git a/Modules/_io/fileio.c b/Modules/_io/fileio.c
index c0b6c6425184af..ed731da32beb43 100644
--- a/Modules/_io/fileio.c
+++ b/Modules/_io/fileio.c
@@ -739,7 +739,7 @@ _io_FileIO_readall_impl(fileio *self)
/*[clinic end generated code: output=faa0292b213b4022 input=10d8b2ec403302dc]*/
{
Py_off_t pos, end;
- PyObject *result;
+ PyBytesWriter *writer;
Py_ssize_t bytes_read = 0;
Py_ssize_t n;
size_t bufsize;
@@ -794,10 +794,10 @@ _io_FileIO_readall_impl(fileio *self)
}
}
-
- result = PyBytes_FromStringAndSize(NULL, bufsize);
- if (result == NULL)
+ writer = PyBytesWriter_Create(bufsize);
+ if (writer == NULL) {
return NULL;
+ }
while (1) {
if (bytes_read >= (Py_ssize_t)bufsize) {
@@ -806,18 +806,18 @@ _io_FileIO_readall_impl(fileio *self)
PyErr_SetString(PyExc_OverflowError,
"unbounded read returned more bytes "
"than a Python bytes object can hold");
- Py_DECREF(result);
+ PyBytesWriter_Discard(writer);
return NULL;
}
- if (PyBytes_GET_SIZE(result) < (Py_ssize_t)bufsize) {
- if (_PyBytes_Resize(&result, bufsize) < 0)
+ if (PyBytesWriter_GetSize(writer) < (Py_ssize_t)bufsize) {
+ if (PyBytesWriter_Resize(writer, bufsize) < 0)
return NULL;
}
}
n = _Py_read(self->fd,
- PyBytes_AS_STRING(result) + bytes_read,
+ (char*)PyBytesWriter_GetData(writer) + bytes_read,
bufsize - bytes_read);
if (n == 0)
@@ -827,20 +827,16 @@ _io_FileIO_readall_impl(fileio *self)
PyErr_Clear();
if (bytes_read > 0)
break;
- Py_DECREF(result);
+ PyBytesWriter_Discard(writer);
Py_RETURN_NONE;
}
- Py_DECREF(result);
+ PyBytesWriter_Discard(writer);
return NULL;
}
bytes_read += n;
}
- if (PyBytes_GET_SIZE(result) > bytes_read) {
- if (_PyBytes_Resize(&result, bytes_read) < 0)
- return NULL;
- }
- return result;
+ return PyBytesWriter_FinishWithSize(writer, bytes_read);
}
/*[clinic input]
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