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Issue #13159: Replace FileIO's quadratic-time buffer growth algorithm with a linear-time one. 

Also fix the builtin file class and the bz2 module, which used the same algorithm.
This commit is contained in:
Nadeem Vawda 2011-10-13 13:52:46 +02:00
parent 40ab00233e
commit 36248154a9
4 changed files with 15 additions and 45 deletions
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3
Misc/NEWS
View File

@ -229,6 +229,9 @@ Library
Extension Modules
-----------------
- Issue #13159: FileIO, BZ2File, and the built-in file class now use a
linear-time buffer growth strategy instead of a quadratic one.
- Issue #13070: Fix a crash when a TextIOWrapper caught in a reference cycle
would be finalized after the reference to its underlying BufferedRWPair's
writer got cleared by the GC.

19
Modules/_io/fileio.c
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@ -42,12 +42,6 @@
#define SMALLCHUNK BUFSIZ
#endif
#if SIZEOF_INT < 4
#define BIGCHUNK (512 * 32)
#else
#define BIGCHUNK (512 * 1024)
#endif
typedef struct {
PyObject_HEAD
int fd;
@ -528,15 +522,10 @@ 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 *

19
Modules/bz2module.c
View File

@ -224,25 +224,14 @@ Util_CatchBZ2Error(int bzerror)
#define SMALLCHUNK BUFSIZ
#endif
#if SIZEOF_INT < 4
#define BIGCHUNK (512 * 32)
#else
#define BIGCHUNK (512 * 1024)
#endif
/* This is a hacked version of Python's fileobject.c:new_buffersize(). */
static size_t
Util_NewBufferSize(size_t currentsize)
{
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;
}
/* This is a hacked version of Python's fileobject.c:get_line(). */

19
Objects/fileobject.c
View File

@ -992,12 +992,6 @@ file_isatty(PyFileObject *f)
#define SMALLCHUNK BUFSIZ
#endif
#if SIZEOF_INT < 4
#define BIGCHUNK (512 * 32)
#else
#define BIGCHUNK (512 * 1024)
#endif
static size_t
new_buffersize(PyFileObject *f, size_t currentsize)
{
@ -1026,15 +1020,10 @@ new_buffersize(PyFileObject *f, size_t currentsize)
/* Add 1 so if the file were to grow we'd notice. */
}
#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;
}
#if defined(EWOULDBLOCK) && defined(EAGAIN) && EWOULDBLOCK != EAGAIN