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authorSverker Eriksson <[email protected]>2019-02-14 19:08:49 +0100
committerSverker Eriksson <[email protected]>2019-02-15 15:15:19 +0100
commit2c8aafb446fd35d5f9c392ef2789905509f426ff (patch)
tree6842e0a95f0db1e4d4f0b665214b0222d4500efa
parent934f9974eb6bec43cd9445ec0f5019a4d1389428 (diff)
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erts: Reduce number of list traversals in term_to_binary
by patching list length when we reach end of list. And remove unnecessary traversals in is_string and is_external_string beyond the max length for STRING_EXT.
-rw-r--r--erts/emulator/beam/external.c62
1 files changed, 30 insertions, 32 deletions
diff --git a/erts/emulator/beam/external.c b/erts/emulator/beam/external.c
index 9a66e491f3..e87843bf2d 100644
--- a/erts/emulator/beam/external.c
+++ b/erts/emulator/beam/external.c
@@ -102,7 +102,7 @@ static byte* enc_term(ErtsAtomCacheMap *, Eterm, byte*, Uint32, struct erl_off_h
struct TTBEncodeContext_;
static int enc_term_int(struct TTBEncodeContext_*,ErtsAtomCacheMap *acmp, Eterm obj, byte* ep, Uint32 dflags,
struct erl_off_heap_header** off_heap, Sint *reds, byte **res);
-static Uint is_external_string(Eterm obj, int* p_is_string);
+static int is_external_string(Eterm obj, Uint* lenp);
static byte* enc_atom(ErtsAtomCacheMap *, Eterm, byte*, Uint32);
static byte* enc_pid(ErtsAtomCacheMap *, Eterm, byte*, Uint32);
struct B2TContext_t;
@@ -2481,11 +2481,21 @@ enc_term_int(TTBEncodeContext* ctx, ErtsAtomCacheMap *acmp, Eterm obj, byte* ep,
{
Eterm* cons = list_val(obj);
Eterm tl;
+ Uint len_cnt = WSTACK_POP(s);
obj = CAR(cons);
tl = CDR(cons);
- WSTACK_PUSH2(s, (is_list(tl) ? ENC_ONE_CONS : ENC_TERM),
- tl);
+ if (is_list(tl)) {
+ len_cnt++;
+ WSTACK_PUSH3(s, len_cnt, ENC_ONE_CONS, tl);
+ }
+ else {
+ byte* list_lenp = (byte*) WSTACK_POP(s);
+ ASSERT(list_lenp[-1] == LIST_EXT);
+ put_int32(len_cnt, list_lenp);
+
+ WSTACK_PUSH2(s, ENC_TERM, tl);
+ }
}
break;
case ENC_PATCH_FUN_SIZE:
@@ -2689,10 +2699,7 @@ enc_term_int(TTBEncodeContext* ctx, ErtsAtomCacheMap *acmp, Eterm obj, byte* ep,
}
case LIST_DEF:
{
- int is_str;
-
- i = is_external_string(obj, &is_str);
- if (is_str) {
+ if (is_external_string(obj, &i)) {
*ep++ = STRING_EXT;
put_int16(i, ep);
ep += 2;
@@ -2703,7 +2710,8 @@ enc_term_int(TTBEncodeContext* ctx, ErtsAtomCacheMap *acmp, Eterm obj, byte* ep,
}
} else {
*ep++ = LIST_EXT;
- put_int32(i, ep);
+ /* Patch list length when we find end of list */
+ WSTACK_PUSH2(s, (UWord)ep, 1);
ep += 4;
goto encode_one_cons;
}
@@ -2961,9 +2969,13 @@ enc_term_int(TTBEncodeContext* ctx, ErtsAtomCacheMap *acmp, Eterm obj, byte* ep,
return 0;
}
+/** @brief Is it a list of bytes not longer than MAX_STRING_LEN?
+ * @param lenp out: string length or number of list cells traversed
+ * @return true/false
+ */
static
-Uint
-is_external_string(Eterm list, int* p_is_string)
+int
+is_external_string(Eterm list, Uint* lenp)
{
Uint len = 0;
@@ -2975,29 +2987,15 @@ is_external_string(Eterm list, int* p_is_string)
Eterm* consp = list_val(list);
Eterm hd = CAR(consp);
- if (!is_byte(hd)) {
- break;
+ if (!is_byte(hd) || ++len > MAX_STRING_LEN) {
+ *lenp = len;
+ return 0;
}
- len++;
list = CDR(consp);
}
- /*
- * If we have reached the end of the list, and we have
- * not exceeded the maximum length of a string, this
- * is a string.
- */
- *p_is_string = is_nil(list) && len < MAX_STRING_LEN;
-
- /*
- * Continue to calculate the length.
- */
- while (is_list(list)) {
- Eterm* consp = list_val(list);
- len++;
- list = CDR(consp);
- }
- return len;
+ *lenp = len;
+ return is_nil(list);
}
@@ -4166,8 +4164,8 @@ encode_size_struct_int(TTBSizeContext* ctx, ErtsAtomCacheMap *acmp, Eterm obj,
result += (1 + encode_size_struct2(acmp, port_node_name(obj), dflags) +
4 + 1);
break;
- case LIST_DEF:
- if ((m = is_string(obj)) && (m < MAX_STRING_LEN)) {
+ case LIST_DEF:
+ if (is_external_string(obj, &m)) {
result += m + 2 + 1;
} else {
result += 5;
@@ -4317,7 +4315,7 @@ encode_size_struct_int(TTBSizeContext* ctx, ErtsAtomCacheMap *acmp, Eterm obj,
if (is_header(obj)) {
switch (obj) {
- case LIST_TAIL_OP:
+ case LIST_TAIL_OP:
obj = (Eterm) WSTACK_POP(s);
if (is_list(obj)) {
Eterm* cons = list_val(obj);