From 8c3f3303f20ab5f1031731af6df5c2ef1499cd36 Mon Sep 17 00:00:00 2001 From: =?UTF-8?q?John=20H=C3=B6gberg?= Date: Tue, 20 Feb 2018 11:30:09 +0100 Subject: Add a helper function for attaching tmp objects to NIF environments --- erts/emulator/beam/erl_nif.c | 96 ++++++++++++++++++++++++++------------------ 1 file changed, 58 insertions(+), 38 deletions(-) (limited to 'erts') diff --git a/erts/emulator/beam/erl_nif.c b/erts/emulator/beam/erl_nif.c index 7db4af8919..6ccf37e793 100644 --- a/erts/emulator/beam/erl_nif.c +++ b/erts/emulator/beam/erl_nif.c @@ -237,9 +237,11 @@ static void cache_env(ErlNifEnv* env); static void full_flush_env(ErlNifEnv *env); static void flush_env(ErlNifEnv* env); -/* Temporary object header, auto-deallocated when NIF returns - * or when independent environment is cleared. - */ +/* Temporary object header, auto-deallocated when NIF returns or when + * independent environment is cleared. + * + * The payload can be accessed with &tmp_obj_ptr[1] but keep in mind that its + * first element must not require greater alignment than `next`. */ struct enif_tmp_obj_t { struct enif_tmp_obj_t* next; void (*dtor)(struct enif_tmp_obj_t*); @@ -256,6 +258,46 @@ static ERTS_INLINE void free_tmp_objs(ErlNifEnv* env) } } +/* Whether the given environment is bound to a process and will be cleaned up + * when the NIF returns. It's safe to use temp_alloc for objects in + * env->tmp_obj_list when this is true. */ +static ERTS_INLINE int is_proc_bound(ErlNifEnv *env) +{ + return env->mod_nif != NULL; +} + +/* Allocates and attaches an object to the given environment, running its + * destructor when the environment is cleared. To avoid temporary variables the + * address of the allocated object is returned instead of the enif_tmp_obj_t. + * + * The destructor *must* call `erts_free(tmp_obj->allocator, tmp_obj)` to free + * the object. If the destructor needs to refer to the allocated object its + * address will be &tmp_obj[1]. */ +static ERTS_INLINE void *alloc_tmp_obj(ErlNifEnv *env, size_t size, + void (*dtor)(struct enif_tmp_obj_t*)) { + struct enif_tmp_obj_t *tmp_obj; + ErtsAlcType_t allocator; + + allocator = is_proc_bound(env) ? ERTS_ALC_T_TMP : ERTS_ALC_T_NIF; + + tmp_obj = erts_alloc(allocator, sizeof(struct enif_tmp_obj_t) + MAX(1, size)); + + tmp_obj->next = env->tmp_obj_list; + tmp_obj->allocator = allocator; + tmp_obj->dtor = dtor; + + env->tmp_obj_list = tmp_obj; + + return (void*)&tmp_obj[1]; +} + +/* Generic destructor for objects allocated through alloc_tmp_obj that don't + * care about their payload. */ +static void tmp_alloc_dtor(struct enif_tmp_obj_t *tmp_obj) +{ + erts_free(tmp_obj->allocator, tmp_obj); +} + void erts_post_nif(ErlNifEnv* env) { erts_unblock_fpe(env->fpe_was_unmasked); @@ -1019,11 +1061,6 @@ int enif_is_number(ErlNifEnv* env, ERL_NIF_TERM term) return is_number(term); } -static ERTS_INLINE int is_proc_bound(ErlNifEnv* env) -{ - return env->mod_nif != NULL; -} - static void aligned_binary_dtor(struct enif_tmp_obj_t* obj) { erts_free_aligned_binary_bytes_extra((byte*)obj, obj->allocator); @@ -1065,15 +1102,8 @@ int enif_inspect_binary(ErlNifEnv* env, Eterm bin_term, ErlNifBinary* bin) return 1; } -static void tmp_alloc_dtor(struct enif_tmp_obj_t* obj) -{ - erts_free(obj->allocator, obj); -} - int enif_inspect_iolist_as_binary(ErlNifEnv* env, Eterm term, ErlNifBinary* bin) { - struct enif_tmp_obj_t* tobj; - ErtsAlcType_t allocator; ErlDrvSizeT sz; if (is_binary(term)) { return enif_inspect_binary(env,term,bin); @@ -1089,14 +1119,7 @@ int enif_inspect_iolist_as_binary(ErlNifEnv* env, Eterm term, ErlNifBinary* bin) return 0; } - allocator = is_proc_bound(env) ? ERTS_ALC_T_TMP : ERTS_ALC_T_NIF; - tobj = erts_alloc(allocator, sz + sizeof(struct enif_tmp_obj_t)); - tobj->allocator = allocator; - tobj->next = env->tmp_obj_list; - tobj->dtor = &tmp_alloc_dtor; - env->tmp_obj_list = tobj; - - bin->data = (unsigned char*) &tobj[1]; + bin->data = alloc_tmp_obj(env, sz, &tmp_alloc_dtor); bin->size = sz; bin->bin_term = THE_NON_VALUE; bin->ref_bin = NULL; @@ -4236,34 +4259,31 @@ static unsigned calc_checksum(unsigned char* ptr, unsigned size); struct readonly_check_t { - struct enif_tmp_obj_t hdr; unsigned char* ptr; unsigned size; unsigned checksum; }; static void add_readonly_check(ErlNifEnv* env, unsigned char* ptr, unsigned sz) { - ErtsAlcType_t allocator = is_proc_bound(env) ? ERTS_ALC_T_TMP : ERTS_ALC_T_NIF; - struct readonly_check_t* obj = erts_alloc(allocator, - sizeof(struct readonly_check_t)); - obj->hdr.allocator = allocator; - obj->hdr.next = env->tmp_obj_list; - env->tmp_obj_list = &obj->hdr; - obj->hdr.dtor = &readonly_check_dtor; + struct readonly_check_t* obj; + + obj = alloc_tmp_obj(env, sizeof(struct readonly_check_t), + &readonly_check_dtor); + obj->ptr = ptr; obj->size = sz; - obj->checksum = calc_checksum(ptr, sz); + obj->checksum = calc_checksum(ptr, sz); } -static void readonly_check_dtor(struct enif_tmp_obj_t* o) +static void readonly_check_dtor(struct enif_tmp_obj_t* tmp_obj) { - struct readonly_check_t* obj = (struct readonly_check_t*) o; - unsigned chksum = calc_checksum(obj->ptr, obj->size); - if (chksum != obj->checksum) { + struct readonly_check_t* ro_check = (struct readonly_check_t*)&tmp_obj[1]; + unsigned chksum = calc_checksum(ro_check->ptr, ro_check->size); + if (chksum != ro_check->checksum) { fprintf(stderr, "\r\nReadonly data written by NIF, checksums differ" - " %x != %x\r\nABORTING\r\n", chksum, obj->checksum); + " %x != %x\r\nABORTING\r\n", chksum, ro_check->checksum); abort(); } - erts_free(obj->hdr.allocator, obj); + erts_free(tmp_obj->allocator, tmp_obj); } static unsigned calc_checksum(unsigned char* ptr, unsigned size) { -- cgit v1.2.3