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Make multi-byte reads on unbuffered ports more efficient.

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Idea and original patch were by Ludovic Courts, this is Neil Jerram's
reworking of it.

	* libguile/srfi-4.c (scm_uniform_vector_read_x): Use scm_c_read,
	instead of equivalent code here.

	* libguile/ports.c (scm_fill_input): Add assertion that read
	buffer is empty when called.
	(port_and_swap_buffer, swap_buffer): New, for...
	(scm_c_read): Use caller's buffer for reading, to avoid making N
	1-byte low-level read calls, in the case where the port is
	unbuffered (or has a very small buffer).
This commit is contained in:
Neil Jerram 2008-09-15 00:25:25 +01:00
parent 4a281c91b4
commit bed2e15fc9
2 changed files with 71 additions and 51 deletions
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35
libguile/srfi-4.c
View file

@ -886,38 +886,11 @@ SCM_DEFINE (scm_uniform_vector_read_x, "uniform-vector-read!", 1, 3, 0,
if (SCM_NIMP (port_or_fd))
{
scm_t_port *pt = SCM_PTAB_ENTRY (port_or_fd);
if (pt->rw_active == SCM_PORT_WRITE)
scm_flush (port_or_fd);
ans = cend - cstart;
while (remaining > 0)
{
if (pt->read_pos < pt->read_end)
{
size_t to_copy = min (pt->read_end - pt->read_pos,
remaining);
memcpy (base + off, pt->read_pos, to_copy);
pt->read_pos += to_copy;
remaining -= to_copy;
off += to_copy;
}
else
{
if (scm_fill_input (port_or_fd) == EOF)
{
if (remaining % sz != 0)
SCM_MISC_ERROR ("unexpected EOF", SCM_EOL);
ans -= remaining / sz;
break;
}
}
}
if (pt->rw_random)
pt->rw_active = SCM_PORT_READ;
remaining -= scm_c_read (port_or_fd, base + off, remaining);
if (remaining % sz != 0)
SCM_MISC_ERROR ("unexpected EOF", SCM_EOL);
ans -= remaining / sz;
}
else /* file descriptor. */
{