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Speed up reading of small files. This avoids multiple C read() calls on pyc files.

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This commit is contained in:
Antoine Pitrou 2012-04-17 13:50:58 +02:00
parent 006917ec7f
commit a3f4457b17
1 changed files with 11 additions and 3 deletions
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14
Modules/_io/fileio.c
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@ -572,6 +572,7 @@ new_buffersize(fileio *self, size_t currentsize
#endif #endif
) )
{ {
size_t addend;
#ifdef HAVE_FSTAT #ifdef HAVE_FSTAT
if (end != (Py_off_t)-1) { if (end != (Py_off_t)-1) {
/* Files claiming a size smaller than SMALLCHUNK may /* Files claiming a size smaller than SMALLCHUNK may
@ -589,9 +590,16 @@ new_buffersize(fileio *self, size_t currentsize
} }
#endif #endif
/* Expand the buffer by an amount proportional to the current size, /* Expand the buffer by an amount proportional to the current size,
giving us amortized linear-time behavior. Use a less-than-double giving us amortized linear-time behavior. For bigger sizes, use a
growth factor to avoid excessive allocation. */ less-than-double growth factor to avoid excessive allocation. */
return currentsize + (currentsize >> 3) + 6; if (currentsize > 65536)
addend = currentsize >> 3;
else
addend = 256 + currentsize;
if (addend < SMALLCHUNK)
/* Avoid tiny read() calls. */
addend = SMALLCHUNK;
return addend + currentsize;
} }
static PyObject * static PyObject *