diff options
| -rw-r--r-- | Makefile.am | 2 | ||||
| -rw-r--r-- | shared/meson.build | 1 | ||||
| -rw-r--r-- | shared/nm-glib-aux/nm-ref-string.c | 187 | ||||
| -rw-r--r-- | shared/nm-glib-aux/nm-ref-string.h | 52 |
4 files changed, 242 insertions, 0 deletions
diff --git a/Makefile.am b/Makefile.am index f863b29f34..48e0cd55df 100644 --- a/Makefile.am +++ b/Makefile.am @@ -373,6 +373,8 @@ shared_nm_glib_aux_libnm_glib_aux_la_SOURCES = \ shared/nm-glib-aux/nm-obj.h \ shared/nm-glib-aux/nm-random-utils.c \ shared/nm-glib-aux/nm-random-utils.h \ + shared/nm-glib-aux/nm-ref-string.c \ + shared/nm-glib-aux/nm-ref-string.h \ shared/nm-glib-aux/nm-secret-utils.c \ shared/nm-glib-aux/nm-secret-utils.h \ shared/nm-glib-aux/nm-shared-utils.c \ diff --git a/shared/meson.build b/shared/meson.build index d542804eb4..aa10f792f8 100644 --- a/shared/meson.build +++ b/shared/meson.build @@ -185,6 +185,7 @@ shared_nm_glib_aux = static_library( 'nm-glib-aux/nm-json-aux.c', 'nm-glib-aux/nm-keyfile-aux.c', 'nm-glib-aux/nm-random-utils.c', + 'nm-glib-aux/nm-ref-string.c', 'nm-glib-aux/nm-secret-utils.c', 'nm-glib-aux/nm-shared-utils.c', 'nm-glib-aux/nm-time-utils.c'), diff --git a/shared/nm-glib-aux/nm-ref-string.c b/shared/nm-glib-aux/nm-ref-string.c new file mode 100644 index 0000000000..6259758c9e --- /dev/null +++ b/shared/nm-glib-aux/nm-ref-string.c @@ -0,0 +1,187 @@ +// SPDX-License-Identifier: LGPL-2.1+ + +#include "nm-default.h" + +#include "nm-ref-string.h" + +/*****************************************************************************/ + +typedef struct { + NMRefString r; + volatile int ref_count; + char str_data[]; +} RefString; + +G_LOCK_DEFINE_STATIC (gl_lock); +static GHashTable *gl_hash; + +/* the first field of NMRefString is a pointer to the NUL terminated string. + * This also allows to compare strings with nm_pstr_equal(), although, pointer + * equality might be better. */ +G_STATIC_ASSERT (G_STRUCT_OFFSET (NMRefString, str) == 0); +G_STATIC_ASSERT (G_STRUCT_OFFSET (RefString, r) == 0); +G_STATIC_ASSERT (G_STRUCT_OFFSET (RefString, r.str) == 0); + +/*****************************************************************************/ + +static guint +_ref_string_hash (gconstpointer ptr) +{ + const RefString *a = ptr; + NMHashState h; + + nm_hash_init (&h, 1463435489u); + nm_hash_update (&h, a->r.str, a->r.len); + return nm_hash_complete (&h); +} + +static gboolean +_ref_string_equal (gconstpointer pa, gconstpointer pb) +{ + const RefString *a = pa; + const RefString *b = pb; + + return a->r.len == b->r.len + && memcmp (a->r.str, b->r.str, a->r.len) == 0; +} + +/*****************************************************************************/ + +static void +_ASSERT (const RefString *rstr0) +{ + int r; + + nm_assert (rstr0); + + G_LOCK (gl_lock); + r = g_atomic_int_get (&rstr0->ref_count); + + nm_assert (r > 0); + nm_assert (r < G_MAXINT); + + nm_assert (rstr0 == g_hash_table_lookup (gl_hash, rstr0)); + G_UNLOCK (gl_lock); +} + +/** + * nm_ref_string_new_len: + * @cstr: the string to intern. Must contain @len bytes. + * If @len is zero, @cstr may be %NULL. Note that it is + * accetable that the string contains a NUL character + * within the first @len bytes. That is, the string is + * not treated as a NUL terminated string, but as binary. + * Also, contrary to strncpy(), this will read all the + * first @len bytes. It won't stop at the first NUL. + * @len: the length of the string (usually there is no NUL character + * within the first @len bytes, but that would be acceptable as well + * to add binary data). + * + * Note that the resulting NMRefString instance will always be NUL terminated + * (at position @len). + * + * Note that NMRefString are always interned/deduplicated. If such a string + * already exists, the existing instance will be refered and returned. + * + * + * Since all NMRefString are shared and interned, you may use + * pointer equality to compare them. Note that if a NMRefString contains + * a NUL character (meaning, if + * + * strlen (nm_ref_string_get_str (str)) != nm_ref_string_get_len (str) + * + * ), then pointer in-equality does not mean that the NUL terminated strings + * are also unequal. In other words, for strings that contain NUL characters, + * + * if (str1 != str2) + * assert (!nm_streq0 (nm_ref_string_get_str (str1), nm_ref_string_get_str (str2))); + * + * might not hold! + * + * + * NMRefString is thread-safe. + * + * Returns: (transfer full): the interned string. This is + * never %NULL, but note that %NULL is also a valid NMRefString. + * The result must be unrefed with nm_ref_string_unref(). + */ +NMRefString * +nm_ref_string_new_len (const char *cstr, gsize len) +{ + RefString *rstr0; + + G_LOCK (gl_lock); + + if (G_UNLIKELY (!gl_hash)) { + gl_hash = g_hash_table_new_full (_ref_string_hash, _ref_string_equal, g_free, NULL); + rstr0 = NULL; + } else { + NMRefString rr_lookup = { + .len = len, + .str = cstr, + }; + + rstr0 = g_hash_table_lookup (gl_hash, &rr_lookup); + } + + if (rstr0) { + nm_assert (({ + int r = g_atomic_int_get (&rstr0->ref_count); + + (r >= 0 && r < G_MAXINT); + })); + g_atomic_int_inc (&rstr0->ref_count); + } else { + rstr0 = g_malloc (sizeof (RefString) + 1 + len); + rstr0->ref_count = 1; + *((gsize *) rstr0->r.len) = len; + *((const char **) rstr0->r.str) = rstr0->str_data; + if (len > 0) + memcpy (rstr0->str_data, cstr, len); + rstr0->str_data[len] = '\0'; + + if (!g_hash_table_add (gl_hash, rstr0)) + nm_assert_not_reached (); + } + + G_UNLOCK (gl_lock); + + return &rstr0->r; +} + +NMRefString * +nm_ref_string_ref (NMRefString *rstr) +{ + RefString *const rstr0 = (RefString *) rstr; + + if (!rstr) + return NULL; + + _ASSERT (rstr0); + + g_atomic_int_inc (&rstr0->ref_count); + return &rstr0->r; +} + +void +_nm_ref_string_unref_non_null (NMRefString *rstr) +{ + RefString *const rstr0 = (RefString *) rstr; + + _ASSERT (rstr0); + + if (G_LIKELY (!g_atomic_int_dec_and_test (&rstr0->ref_count))) + return; + + G_LOCK (gl_lock); + + /* in the fast-path above, we already decremented the ref-count to zero. + * We need recheck that the ref-count is still zero. */ + + if (g_atomic_int_get (&rstr0->ref_count) == 0) + g_hash_table_remove (gl_hash, rstr0); + + G_UNLOCK (gl_lock); +} + +/*****************************************************************************/ diff --git a/shared/nm-glib-aux/nm-ref-string.h b/shared/nm-glib-aux/nm-ref-string.h new file mode 100644 index 0000000000..2a0b072df8 --- /dev/null +++ b/shared/nm-glib-aux/nm-ref-string.h @@ -0,0 +1,52 @@ +// SPDX-License-Identifier: LGPL-2.1+ + +#ifndef __NM_REF_STRING_H__ +#define __NM_REF_STRING_H__ + +/*****************************************************************************/ + +typedef struct { + const char *const str; + const gsize len; +} NMRefString; + +/*****************************************************************************/ + +NMRefString *nm_ref_string_new_len (const char *cstr, gsize len); + +static inline NMRefString * +nm_ref_string_new (const char *cstr) +{ + return cstr + ? nm_ref_string_new_len (cstr, strlen (cstr)) + : NULL; +} + +NMRefString *nm_ref_string_ref (NMRefString *rstr); +void _nm_ref_string_unref_non_null (NMRefString *rstr); + +static inline void +nm_ref_string_unref (NMRefString *rstr) +{ + if (rstr) + _nm_ref_string_unref_non_null (rstr); +} + +NM_AUTO_DEFINE_FCN_VOID0 (NMRefString *, _nm_auto_ref_string, _nm_ref_string_unref_non_null) +#define nm_auto_ref_string nm_auto(_nm_auto_ref_string) + +/*****************************************************************************/ + +static inline const char * +nm_ref_string_get_str (NMRefString *rstr) +{ + return rstr ? rstr->str : NULL; +} + +static inline gsize +nm_ref_string_get_len (NMRefString *rstr) +{ + return rstr ? rstr->len : 0u; +} + +#endif /* __NM_REF_STRING_H__ */ |