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Make literal strings (i.e., returned by `read') read-only.

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* libguile/read.c (scm_read_string): Use `scm_i_make_read_only_string ()' to
  return a read-only string, as mandated by R5RS.  Reported by Bill
  Schottstaedt <bil@ccrma.Stanford.EDU>.

* libguile/strings.c (scm_i_make_read_only_string): New function.
  (scm_i_shared_substring_read_only): Special-case the empty string
  so that the read-only and read-write empty strings are `eq?'.  This
  optimization is relied on by the `substring/shared' `empty string'
  test case in `srfi-13.test'.

* libguile/strings.h (scm_i_make_read_only_string): New declaration.

* test-suite/tests/strings.test ("string-set!")["literal string"]: New test.

* NEWS: Update.
This commit is contained in:
Ludovic Courtès 2008-09-22 23:03:20 +02:00
parent 40de0323e7
commit be5c4a82ab
5 changed files with 38 additions and 13 deletions
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37
libguile/strings.c
View file

@ -217,6 +217,12 @@ get_str_buf_start (SCM *str, SCM *buf, size_t *start)
*buf = STRING_STRINGBUF (*str);
}
SCM
scm_i_make_read_only_string (SCM str)
{
return scm_i_substring_read_only (str, 0, STRING_LENGTH (str));
}
SCM
scm_i_substring (SCM str, size_t start, size_t end)
{
@ -234,15 +240,28 @@ scm_i_substring (SCM str, size_t start, size_t end)
SCM
scm_i_substring_read_only (SCM str, size_t start, size_t end)
{
SCM buf;
size_t str_start;
get_str_buf_start (&str, &buf, &str_start);
scm_i_pthread_mutex_lock (&stringbuf_write_mutex);
SET_STRINGBUF_SHARED (buf);
scm_i_pthread_mutex_unlock (&stringbuf_write_mutex);
return scm_double_cell (RO_STRING_TAG, SCM_UNPACK(buf),
(scm_t_bits)str_start + start,
(scm_t_bits) end - start);
SCM result;
if (SCM_UNLIKELY (STRING_LENGTH (str) == 0))
/* We want the empty string to be `eq?' with the read-only empty
string. */
result = str;
else
{
SCM buf;
size_t str_start;
get_str_buf_start (&str, &buf, &str_start);
scm_i_pthread_mutex_lock (&stringbuf_write_mutex);
SET_STRINGBUF_SHARED (buf);
scm_i_pthread_mutex_unlock (&stringbuf_write_mutex);
result = scm_double_cell (RO_STRING_TAG, SCM_UNPACK (buf),
(scm_t_bits) str_start + start,
(scm_t_bits) end - start);
}
return result;
}
SCM