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-rw-r--r--libguile/strings.c37
1 files changed, 28 insertions, 9 deletions
diff --git a/libguile/strings.c b/libguile/strings.c
index 7399d8831..ffc1eb312 100644
--- a/libguile/strings.c
+++ b/libguile/strings.c
@@ -218,6 +218,12 @@ get_str_buf_start (SCM *str, SCM *buf, size_t *start)
}
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)
{
SCM buf;
@@ -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