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Optimize 'get-bytevector-some'; it may now read less than possible.

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* libguile/r6rs-ports.c (scm_get_bytevector_some): Rewrite to
  efficiently take the contents of the read/putback buffers.  In the
  docstring, clarify that it might not return all available bytes.

* doc/ref/api-io.texi (R6RS Binary Input): Clarify that
  'get-bytevector-some' might not return all available bytes.

* test-suite/tests/r6rs-ports.test ("get-bytevector-some [only-some]"):
  Remove bogus test, which requires more than the R6RS requires.
This commit is contained in:
Mark H Weaver 2013-03-31 21:21:14 -04:00
parent 337edc591f
commit 21bbe22a14
3 changed files with 30 additions and 83 deletions
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82
libguile/r6rs-ports.c
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@ -550,71 +550,41 @@ SCM_DEFINE (scm_get_bytevector_n_x, "get-bytevector-n!", 4, 0, 0,
SCM_DEFINE (scm_get_bytevector_some, "get-bytevector-some", 1, 0, 0,
(SCM port),
"Read from @var{port}, blocking as necessary, until data "
"are available or and end-of-file is reached. Return either "
"a new bytevector containing the data read or the "
"end-of-file object.")
"Read from @var{port}, blocking as necessary, until bytes "
"are available or an end-of-file is reached. Return either "
"the end-of-file object or a new bytevector containing some "
"of the available bytes (at least one), and update the port "
"position to point just past these bytes.")
#define FUNC_NAME s_scm_get_bytevector_some
{
/* Read at least one byte, unless the end-of-file is already reached, and
read while characters are available (buffered). */
SCM result;
char *c_bv;
unsigned c_len;
size_t c_total;
scm_t_port *pt;
size_t size;
SCM bv;
SCM_VALIDATE_BINARY_INPUT_PORT (1, port);
pt = SCM_PTAB_ENTRY (port);
c_len = 4096;
c_bv = (char *) scm_gc_malloc_pointerless (c_len, SCM_GC_BYTEVECTOR);
c_total = 0;
if (pt->rw_active == SCM_PORT_WRITE)
scm_ptobs[SCM_PTOBNUM (port)].flush (port);
do
if (pt->rw_random)
pt->rw_active = SCM_PORT_READ;
if (pt->read_pos >= pt->read_end)
{
int c_chr;
if (c_total + 1 > c_len)
{
/* Grow the bytevector. */
c_bv = (char *) scm_gc_realloc (c_bv, c_len, c_len * 2,
SCM_GC_BYTEVECTOR);
c_len *= 2;
}
/* We can't use `scm_c_read ()' since it blocks. */
c_chr = scm_get_byte_or_eof (port);
if (c_chr != EOF)
{
c_bv[c_total] = (char) c_chr;
c_total++;
}
else
break;
}
/* XXX: We want to check for the availability of a byte, but that's
what `scm_char_ready_p' actually does. */
while (scm_is_true (scm_char_ready_p (port)));
if (c_total == 0)
{
result = SCM_EOF_VAL;
scm_gc_free (c_bv, c_len, SCM_GC_BYTEVECTOR);
}
else
{
if (c_len > c_total)
{
/* Shrink the bytevector. */
c_bv = (char *) scm_gc_realloc (c_bv, c_len, c_total,
SCM_GC_BYTEVECTOR);
c_len = (unsigned) c_total;
}
result = scm_c_take_gc_bytevector ((signed char *) c_bv, c_len);
if (scm_fill_input (port) == EOF)
return SCM_EOF_VAL;
}
return result;
size = pt->read_end - pt->read_pos;
if (pt->read_buf == pt->putback_buf)
size += pt->saved_read_end - pt->saved_read_pos;
bv = scm_c_make_bytevector (size);
scm_take_from_input_buffers
(port, (char *) SCM_BYTEVECTOR_CONTENTS (bv), size);
return bv;
}
#undef FUNC_NAME