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Simply grow string port buffers geometrically.

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* libguile/strports.c (SCM_WRITE_BLOCK): Remove.
  (st_flush): Multiply `pt->write_buf_size' by 2.
  (st_seek): Likewise when TARGET == PT->write_buf_size.
This commit is contained in:
Ludovic Courtès 2011-03-06 14:31:28 +01:00
parent 0b2c2ba353
commit d8f1c2162c
1 changed files with 7 additions and 21 deletions
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28
libguile/strports.c
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@ -129,27 +129,17 @@ st_resize_port (scm_t_port *pt, scm_t_off new_size)
} }
} }
/* amount by which write_buf is expanded. */ /* Ensure that `write_pos' < `write_end' by enlarging the buffer when
#define SCM_WRITE_BLOCK 80 necessary. Update `read_buf' to account for written chars. The
buffer is enlarged geometrically. */
/* ensure that write_pos < write_end by enlarging the buffer when
necessary. update read_buf to account for written chars.
The buffer is enlarged by 1.5 times, plus SCM_WRITE_BLOCK. Adding just a
fixed amount is no good, because there's a block copy for each increment,
and that copying would take quadratic time. In the past it was found to
be very slow just adding 80 bytes each time (eg. about 10 seconds for
writing a 100kbyte string). */
static void static void
st_flush (SCM port) st_flush (SCM port)
{ {
scm_t_port *pt = SCM_PTAB_ENTRY (port); scm_t_port *pt = SCM_PTAB_ENTRY (port);
if (pt->write_pos == pt->write_end) if (pt->write_pos == pt->write_end)
{ st_resize_port (pt, pt->write_buf_size * 2);
st_resize_port (pt, pt->write_buf_size * 3 / 2 + SCM_WRITE_BLOCK);
}
pt->read_pos = pt->write_pos; pt->read_pos = pt->write_pos;
if (pt->read_pos > pt->read_end) if (pt->read_pos > pt->read_end)
{ {
@ -246,12 +236,8 @@ st_seek (SCM port, scm_t_off offset, int whence)
SCM_EOL); SCM_EOL);
} }
} }
else else if (target == pt->write_buf_size)
{ st_resize_port (pt, target * 2);
st_resize_port (pt, target + (target == pt->write_buf_size
? SCM_WRITE_BLOCK
: 0));
}
} }
pt->read_pos = pt->write_pos = pt->read_buf + target; pt->read_pos = pt->write_pos = pt->read_buf + target;
if (pt->read_pos > pt->read_end) if (pt->read_pos > pt->read_end)