diff options
| author | Nadeem Vawda <nadeem.vawda@gmail.com> | 2011-10-13 11:34:16 (GMT) |
|---|---|---|
| committer | Nadeem Vawda <nadeem.vawda@gmail.com> | 2011-10-13 11:34:16 (GMT) |
| commit | d41a98bdd9076eeadf4d3ba6d8db287e26b89777 (patch) | |
| tree | 41e6908d7d713d1981060eded58e10c00098850c /Modules/_io | |
| parent | f1ab47ebc4d6f6cdb0ea7f9ec73d874aae03a1f2 (diff) | |
| download | cpython-d41a98bdd9076eeadf4d3ba6d8db287e26b89777.zip cpython-d41a98bdd9076eeadf4d3ba6d8db287e26b89777.tar.gz cpython-d41a98bdd9076eeadf4d3ba6d8db287e26b89777.tar.bz2 | |
Issue #13159: Replace FileIO's quadratic-time buffer growth algorithm with a linear-time one.
Also fix the bz2 module, whose classes used the same algorithm.
Diffstat (limited to 'Modules/_io')
| -rw-r--r-- | Modules/_io/fileio.c | 19 |
1 files changed, 4 insertions, 15 deletions
diff --git a/Modules/_io/fileio.c b/Modules/_io/fileio.c index b1d492b..be5c9f8 100644 --- a/Modules/_io/fileio.c +++ b/Modules/_io/fileio.c @@ -43,12 +43,6 @@ #define SMALLCHUNK BUFSIZ #endif -#if SIZEOF_INT < 4 -#define BIGCHUNK (512 * 32) -#else -#define BIGCHUNK (512 * 1024) -#endif - typedef struct { PyObject_HEAD int fd; @@ -565,15 +559,10 @@ new_buffersize(fileio *self, size_t currentsize) } } #endif - if (currentsize > SMALLCHUNK) { - /* Keep doubling until we reach BIGCHUNK; - then keep adding BIGCHUNK. */ - if (currentsize <= BIGCHUNK) - return currentsize + currentsize; - else - return currentsize + BIGCHUNK; - } - return currentsize + SMALLCHUNK; + /* Expand the buffer by an amount proportional to the current size, + giving us amortized linear-time behavior. Use a less-than-double + growth factor to avoid excessive allocation. */ + return currentsize + (currentsize >> 3) + 6; } static PyObject * |