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// SPDX-License-Identifier: LGPL-2.1+
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#include "nm-default.h"
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#include "nm-ref-string.h"
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/*****************************************************************************/
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typedef struct {
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NMRefString r;
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volatile int ref_count;
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char str_data[];
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} RefString;
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G_LOCK_DEFINE_STATIC (gl_lock);
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static GHashTable *gl_hash;
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/* the first field of NMRefString is a pointer to the NUL terminated string.
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* This also allows to compare strings with nm_pstr_equal(), although, pointer
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* equality might be better. */
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G_STATIC_ASSERT (G_STRUCT_OFFSET (NMRefString, str) == 0);
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G_STATIC_ASSERT (G_STRUCT_OFFSET (RefString, r) == 0);
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G_STATIC_ASSERT (G_STRUCT_OFFSET (RefString, r.str) == 0);
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/*****************************************************************************/
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static guint
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_ref_string_hash (gconstpointer ptr)
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{
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const RefString *a = ptr;
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NMHashState h;
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nm_hash_init (&h, 1463435489u);
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nm_hash_update (&h, a->r.str, a->r.len);
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return nm_hash_complete (&h);
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}
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static gboolean
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_ref_string_equal (gconstpointer pa, gconstpointer pb)
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{
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const RefString *a = pa;
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const RefString *b = pb;
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return a->r.len == b->r.len
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&& memcmp (a->r.str, b->r.str, a->r.len) == 0;
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}
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/*****************************************************************************/
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static void
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_ASSERT (const RefString *rstr0)
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{
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#if NM_MORE_ASSERTS
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int r;
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nm_assert (rstr0);
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G_LOCK (gl_lock);
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r = g_atomic_int_get (&rstr0->ref_count);
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nm_assert (r > 0);
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nm_assert (r < G_MAXINT);
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nm_assert (rstr0 == g_hash_table_lookup (gl_hash, rstr0));
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G_UNLOCK (gl_lock);
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#endif
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}
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/**
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* nm_ref_string_new_len:
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* @cstr: the string to intern. Must contain @len bytes.
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* If @len is zero, @cstr may be %NULL. Note that it is
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* accetable that the string contains a NUL character
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* within the first @len bytes. That is, the string is
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* not treated as a NUL terminated string, but as binary.
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* Also, contrary to strncpy(), this will read all the
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* first @len bytes. It won't stop at the first NUL.
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* @len: the length of the string (usually there is no NUL character
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* within the first @len bytes, but that would be acceptable as well
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* to add binary data).
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*
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* Note that the resulting NMRefString instance will always be NUL terminated
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* (at position @len).
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*
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* Note that NMRefString are always interned/deduplicated. If such a string
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* already exists, the existing instance will be refered and returned.
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*
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*
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* Since all NMRefString are shared and interned, you may use
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* pointer equality to compare them. Note that if a NMRefString contains
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* a NUL character (meaning, if
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*
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* strlen (nm_ref_string_get_str (str)) != nm_ref_string_get_len (str)
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*
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* ), then pointer in-equality does not mean that the NUL terminated strings
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* are also unequal. In other words, for strings that contain NUL characters,
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*
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* if (str1 != str2)
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* assert (!nm_streq0 (nm_ref_string_get_str (str1), nm_ref_string_get_str (str2)));
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*
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* might not hold!
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*
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*
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* NMRefString is thread-safe.
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*
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* Returns: (transfer full): the interned string. This is
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* never %NULL, but note that %NULL is also a valid NMRefString.
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* The result must be unrefed with nm_ref_string_unref().
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*/
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NMRefString *
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nm_ref_string_new_len (const char *cstr, gsize len)
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{
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RefString *rstr0;
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G_LOCK (gl_lock);
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if (G_UNLIKELY (!gl_hash)) {
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gl_hash = g_hash_table_new_full (_ref_string_hash, _ref_string_equal, g_free, NULL);
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rstr0 = NULL;
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} else {
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NMRefString rr_lookup = {
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.len = len,
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.str = cstr,
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};
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rstr0 = g_hash_table_lookup (gl_hash, &rr_lookup);
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}
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if (rstr0) {
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nm_assert (({
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int r = g_atomic_int_get (&rstr0->ref_count);
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(r >= 0 && r < G_MAXINT);
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}));
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g_atomic_int_inc (&rstr0->ref_count);
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} else {
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rstr0 = g_malloc (sizeof (RefString) + 1 + len);
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rstr0->ref_count = 1;
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*((gsize *) &rstr0->r.len) = len;
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*((const char **) &rstr0->r.str) = rstr0->str_data;
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if (len > 0)
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memcpy (rstr0->str_data, cstr, len);
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rstr0->str_data[len] = '\0';
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if (!g_hash_table_add (gl_hash, rstr0))
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nm_assert_not_reached ();
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}
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G_UNLOCK (gl_lock);
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return &rstr0->r;
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}
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NMRefString *
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nm_ref_string_ref (NMRefString *rstr)
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{
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RefString *const rstr0 = (RefString *) rstr;
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if (!rstr)
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return NULL;
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_ASSERT (rstr0);
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g_atomic_int_inc (&rstr0->ref_count);
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return &rstr0->r;
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}
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void
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_nm_ref_string_unref_non_null (NMRefString *rstr)
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{
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RefString *const rstr0 = (RefString *) rstr;
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_ASSERT (rstr0);
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if (G_LIKELY (!g_atomic_int_dec_and_test (&rstr0->ref_count)))
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return;
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G_LOCK (gl_lock);
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/* in the fast-path above, we already decremented the ref-count to zero.
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* We need recheck that the ref-count is still zero. */
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if (g_atomic_int_get (&rstr0->ref_count) == 0) {
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if (!g_hash_table_remove (gl_hash, rstr0))
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nm_assert_not_reached ();
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} else {
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#if NM_MORE_ASSERTS > 5
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nm_assert (g_hash_table_lookup (gl_hash, rstr0) == rstr0);
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#endif
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}
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G_UNLOCK (gl_lock);
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}
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/*****************************************************************************/
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