From: Fabrice Bellard <fabrice@bellard.org>
Date: Sat, 13 Jun 2026 16:03:49 +0000 (+0200)
Subject: optimized Array.prototype.slice and Array.prototype.splice
X-Git-Url: http://git.kaiwu.me/postgresql/log/contrib/postgres_fdw/stylesheets/print.css?a=commitdiff_plain;h=42d08be5f28abfdf881110bba3713f6a256d8d97;p=quickjs.git

optimized Array.prototype.slice and Array.prototype.splice
---

diff --git a/quickjs.c b/quickjs.c
index a8fb103..e3716a4 100644
--- a/quickjs.c
+++ b/quickjs.c
@@ -16795,18 +16795,6 @@ static JSValue js_array_iterator_next(JSContext *ctx, JSValueConst this_val,
 static JSValue js_create_array_iterator(JSContext *ctx, JSValueConst this_val,
                                         int argc, JSValueConst *argv, int magic);
 
-static BOOL js_is_fast_array(JSContext *ctx, JSValueConst obj)
-{
-    /* Try and handle fast arrays explicitly */
-    if (JS_VALUE_GET_TAG(obj) == JS_TAG_OBJECT) {
-        JSObject *p = JS_VALUE_GET_OBJ(obj);
-        if (p->class_id == JS_CLASS_ARRAY && p->fast_array) {
-            return TRUE;
-        }
-    }
-    return FALSE;
-}
-
 /* Access an Array's internal JSValue array if available */
 static BOOL js_get_fast_array(JSContext *ctx, JSValueConst obj,
                               JSValue **arrpp, uint32_t *countp)
@@ -41869,10 +41857,10 @@ static JSValue js_get_this(JSContext *ctx,
     return JS_DupValue(ctx, this_val);
 }
 
-static JSValue JS_ArraySpeciesCreate(JSContext *ctx, JSValueConst obj,
-                                     JSValueConst len_val)
+/* XXX: optimize */
+static JSValue JS_ArraySpeciesGetCtor(JSContext *ctx, JSValueConst obj)
 {
-    JSValue ctor, ret, species;
+    JSValue ctor, species;
     int res;
     JSContext *realm;
 
@@ -41880,7 +41868,7 @@ static JSValue JS_ArraySpeciesCreate(JSContext *ctx, JSValueConst obj,
     if (res < 0)
         return JS_EXCEPTION;
     if (!res)
-        return js_array_constructor(ctx, JS_UNDEFINED, 1, &len_val);
+        return JS_UNDEFINED;
     ctor = JS_GetProperty(ctx, obj, JS_ATOM_constructor);
     if (JS_IsException(ctor))
         return ctor;
@@ -41906,13 +41894,39 @@ static JSValue JS_ArraySpeciesCreate(JSContext *ctx, JSValueConst obj,
         if (JS_IsNull(ctor))
             ctor = JS_UNDEFINED;
     }
+    if (!JS_IsUndefined(ctor) &&
+        js_same_value(ctx, ctor, ctx->array_ctor)) {
+        JS_FreeValue(ctx, ctor);
+        ctor = JS_UNDEFINED;
+    }
+    return ctor;
+}
+
+static JSValue JS_ArrayCreateFromCtor(JSContext *ctx, JSValueConst ctor, int64_t len)
+{
+    JSValue len_val, ret;
+
+    len_val = JS_NewInt64(ctx, len);
     if (JS_IsUndefined(ctor)) {
-        return js_array_constructor(ctx, JS_UNDEFINED, 1, &len_val);
+        ret = js_array_constructor(ctx, JS_UNDEFINED, 1, (JSValueConst *)&len_val);
     } else {
-        ret = JS_CallConstructor(ctx, ctor, 1, &len_val);
-        JS_FreeValue(ctx, ctor);
-        return ret;
+        ret = JS_CallConstructor(ctx, ctor, 1, (JSValueConst *)&len_val);
     }
+    JS_FreeValue(ctx, len_val);
+    return ret;
+}
+
+/* len must be >= 0 */
+static JSValue JS_ArraySpeciesCreate(JSContext *ctx, JSValueConst obj, int64_t len)
+{
+    JSValue ctor, ret;
+
+    ctor = JS_ArraySpeciesGetCtor(ctx, obj);
+    if (JS_IsException(ctor))
+        return ctor;
+    ret = JS_ArrayCreateFromCtor(ctx, ctor, len);
+    JS_FreeValue(ctx, ctor);
+    return ret;
 }
 
 static const JSCFunctionListEntry js_array_funcs[] = {
@@ -42042,7 +42056,7 @@ static JSValue js_array_concat(JSContext *ctx, JSValueConst this_val,
     if (JS_IsException(obj))
         goto exception;
 
-    arr = JS_ArraySpeciesCreate(ctx, obj, JS_NewInt32(ctx, 0));
+    arr = JS_ArraySpeciesCreate(ctx, obj, 0);
     if (JS_IsException(arr))
         goto exception;
     n = 0;
@@ -42145,13 +42159,12 @@ static JSValue js_array_every(JSContext *ctx, JSValueConst this_val,
         ret = JS_FALSE;
         break;
     case special_map:
-        /* XXX: JS_ArraySpeciesCreate should take int64_t */
-        ret = JS_ArraySpeciesCreate(ctx, obj, JS_NewInt64(ctx, len));
+        ret = JS_ArraySpeciesCreate(ctx, obj, len);
         if (JS_IsException(ret))
             goto exception;
         break;
     case special_filter:
-        ret = JS_ArraySpeciesCreate(ctx, obj, JS_NewInt32(ctx, 0));
+        ret = JS_ArraySpeciesCreate(ctx, obj, 0);
         if (JS_IsException(ret))
             goto exception;
         break;
@@ -42923,13 +42936,13 @@ exception:
 }
 
 static JSValue js_array_slice(JSContext *ctx, JSValueConst this_val,
-                              int argc, JSValueConst *argv, int splice)
+                              int argc, JSValueConst *argv)
 {
-    JSValue obj, arr, val, len_val;
-    int64_t len, start, k, final, n, count, del_count, new_len;
+    JSValue obj, arr, val, ctor;
+    int64_t len, start, k, final, n, count;
     int kPresent;
     JSValue *arrp;
-    uint32_t count32, i, item_count;
+    uint32_t count32;
 
     arr = JS_UNDEFINED;
     obj = JS_ToObject(ctx, this_val);
@@ -42939,69 +42952,150 @@ static JSValue js_array_slice(JSContext *ctx, JSValueConst this_val,
     if (JS_ToInt64Clamp(ctx, &start, argv[0], 0, len, len))
         goto exception;
 
-    if (splice) {
-        if (argc == 0) {
-            item_count = 0;
-            del_count = 0;
-        } else
-        if (argc == 1) {
-            item_count = 0;
-            del_count = len - start;
-        } else {
-            item_count = argc - 2;
-            if (JS_ToInt64Clamp(ctx, &del_count, argv[1], 0, len - start, 0))
-                goto exception;
-        }
-        if (len + item_count - del_count > MAX_SAFE_INTEGER) {
-            JS_ThrowTypeError(ctx, "Array loo long");
+    final = len;
+    if (!JS_IsUndefined(argv[1])) {
+        if (JS_ToInt64Clamp(ctx, &final, argv[1], 0, len, len))
             goto exception;
-        }
-        count = del_count;
-    } else {
-        item_count = 0; /* avoid warning */
-        final = len;
-        if (!JS_IsUndefined(argv[1])) {
-            if (JS_ToInt64Clamp(ctx, &final, argv[1], 0, len, len))
-                goto exception;
-        }
-        count = max_int64(final - start, 0);
     }
-    len_val = JS_NewInt64(ctx, count);
-    arr = JS_ArraySpeciesCreate(ctx, obj, len_val);
-    JS_FreeValue(ctx, len_val);
-    if (JS_IsException(arr))
+    count = max_int64(final - start, 0);
+
+    ctor = JS_ArraySpeciesGetCtor(ctx, obj);
+    if (JS_IsException(ctor))
         goto exception;
 
-    k = start;
     final = start + count;
-    n = 0;
-    /* The fast array test on arr ensures that
-       JS_CreateDataPropertyUint32() won't modify obj in case arr is
-       an exotic object */
-    /* Special case fast arrays */
-    if (js_get_fast_array(ctx, obj, &arrp, &count32) &&
-        js_is_fast_array(ctx, arr)) {
-        /* XXX: should share code with fast array constructor */
-        for (; k < final && k < count32; k++, n++) {
-            if (JS_CreateDataPropertyUint32(ctx, arr, n, JS_DupValue(ctx, arrp[k]), JS_PROP_THROW) < 0)
+    if (JS_IsUndefined(ctor) &&
+        js_get_fast_array(ctx, obj, &arrp, &count32) &&
+        final <= count32) {
+        /* fast case */
+        arr = js_create_array(ctx, count, (JSValueConst *)arrp + start);
+    } else {
+        arr = JS_ArrayCreateFromCtor(ctx, ctor, count);
+        JS_FreeValue(ctx, ctor);
+        if (JS_IsException(arr))
+            goto exception;
+
+        n = 0;
+        for (k = start; k < final; k++, n++) {
+            kPresent = JS_TryGetPropertyInt64(ctx, obj, k, &val);
+            if (kPresent < 0)
                 goto exception;
+            if (kPresent) {
+                if (JS_CreateDataPropertyUint32(ctx, arr, n, val, JS_PROP_THROW) < 0)
+                    goto exception;
+            }
         }
+        if (JS_SetProperty(ctx, arr, JS_ATOM_length, JS_NewInt64(ctx, n)) < 0)
+            goto exception;
     }
-    /* Copy the remaining elements if any (handle case of inherited properties) */
-    for (; k < final; k++, n++) {
-        kPresent = JS_TryGetPropertyInt64(ctx, obj, k, &val);
-        if (kPresent < 0)
+    JS_FreeValue(ctx, obj);
+    return arr;
+
+ exception:
+    JS_FreeValue(ctx, obj);
+    JS_FreeValue(ctx, arr);
+    return JS_EXCEPTION;
+}
+
+static JSValue js_array_splice(JSContext *ctx, JSValueConst this_val,
+                              int argc, JSValueConst *argv)
+{
+    JSValue obj, arr, val, ctor;
+    int64_t len, start, k, final, n, del_count, new_len;
+    int kPresent;
+    uint32_t i, item_count;
+    JSObject *p;
+    
+    arr = JS_UNDEFINED;
+    obj = JS_ToObject(ctx, this_val);
+    if (js_get_length64(ctx, &len, obj))
+        goto exception;
+
+    if (JS_ToInt64Clamp(ctx, &start, argv[0], 0, len, len))
+        goto exception;
+
+    if (argc == 0) {
+        item_count = 0;
+        del_count = 0;
+    } else if (argc == 1) {
+        item_count = 0;
+        del_count = len - start;
+    } else {
+        item_count = argc - 2;
+        if (JS_ToInt64Clamp(ctx, &del_count, argv[1], 0, len - start, 0))
             goto exception;
-        if (kPresent) {
-            if (JS_CreateDataPropertyUint32(ctx, arr, n, val, JS_PROP_THROW) < 0)
-                goto exception;
-        }
     }
-    if (JS_SetProperty(ctx, arr, JS_ATOM_length, JS_NewInt64(ctx, n)) < 0)
+    if (len + item_count - del_count > MAX_SAFE_INTEGER) {
+        JS_ThrowTypeError(ctx, "Array loo long");
+        goto exception;
+    }
+    final = start + del_count;
+    /* warning: 'len' may be different from the actual array length
+       because it may have been modified */
+    new_len = len + item_count - del_count;
+    
+    ctor = JS_ArraySpeciesGetCtor(ctx, obj);
+    if (JS_IsException(ctor))
         goto exception;
 
-    if (splice) {
-        new_len = len + item_count - del_count;
+    p = JS_VALUE_GET_PTR(obj);
+    if (JS_IsUndefined(ctor) &&
+        p->class_id == JS_CLASS_ARRAY &&
+        p->fast_array &&
+        final <= p->u.array.count && 
+        (get_shape_prop(p->shape)->flags & JS_PROP_WRITABLE) && /* writable array length */
+        can_extend_fast_array(p)) {
+        uint32_t count32 = p->u.array.count;
+        JSValue *arrp = p->u.array.u.values;
+
+        /* fast case */
+        arr = js_create_array(ctx, del_count, (JSValueConst *)arrp + start);
+        if (JS_IsException(arr))
+            goto exception;
+        
+        if (item_count != del_count) {
+            /* resize */
+            uint32_t new_count32;
+            new_count32 = count32 + item_count - del_count;
+            if (del_count > item_count) {
+                for(i = 0; i < del_count - item_count; i++)
+                    JS_FreeValue(ctx, arrp[start + item_count + i]);
+                memmove(arrp + start + item_count, arrp + final,
+                        (count32 - final) * sizeof(arrp[0]));
+            } else {
+                if (unlikely(new_count32 > p->u.array.u1.size)) {
+                    if (expand_fast_array(ctx, p, new_count32))
+                        goto exception;
+                    arrp = p->u.array.u.values;
+                }
+                memmove(arrp + start + item_count, arrp + final,
+                        (count32 - final) * sizeof(arrp[0]));
+                for(i = 0; i < item_count - del_count; i++)
+                    arrp[start + del_count + i] = JS_UNDEFINED;
+            }
+            p->u.array.count = new_count32;
+        }
+        for(i = 0; i < item_count; i++)
+            set_value(ctx, &arrp[start + i], JS_DupValue(ctx, argv[i + 2]));
+    } else {
+        arr = JS_ArrayCreateFromCtor(ctx, ctor, del_count);
+        JS_FreeValue(ctx, ctor);
+        if (JS_IsException(arr))
+            goto exception;
+        
+        n = 0;
+        for (k = start; k < final; k++, n++) {
+            kPresent = JS_TryGetPropertyInt64(ctx, obj, k, &val);
+            if (kPresent < 0)
+                goto exception;
+            if (kPresent) {
+                if (JS_CreateDataPropertyUint32(ctx, arr, n, val, JS_PROP_THROW) < 0)
+                    goto exception;
+            }
+        }
+        if (JS_SetProperty(ctx, arr, JS_ATOM_length, JS_NewInt64(ctx, n)) < 0)
+            goto exception;
+        
         if (item_count != del_count) {
             if (JS_CopySubArray(ctx, obj, start + item_count,
                                 start + del_count, len - (start + del_count),
@@ -43017,9 +43111,9 @@ static JSValue js_array_slice(JSContext *ctx, JSValueConst this_val,
             if (JS_SetPropertyInt64(ctx, obj, start + i, JS_DupValue(ctx, argv[i + 2])) < 0)
                 goto exception;
         }
-        if (JS_SetProperty(ctx, obj, JS_ATOM_length, JS_NewInt64(ctx, new_len)) < 0)
-            goto exception;
     }
+    if (JS_SetProperty(ctx, obj, JS_ATOM_length, JS_NewInt64(ctx, new_len)) < 0)
+        goto exception;
     JS_FreeValue(ctx, obj);
     return arr;
 
@@ -43235,7 +43329,7 @@ static JSValue js_array_flatten(JSContext *ctx, JSValueConst this_val,
                 goto exception;
         }
     }
-    arr = JS_ArraySpeciesCreate(ctx, obj, JS_NewInt32(ctx, 0));
+    arr = JS_ArraySpeciesCreate(ctx, obj, 0);
     if (JS_IsException(arr))
         goto exception;
     if (JS_FlattenIntoArray(ctx, arr, obj, sourceLen, 0, depthNum,
@@ -44698,8 +44792,8 @@ static const JSCFunctionListEntry js_array_proto_funcs[] = {
     JS_CFUNC_DEF("toReversed", 0, js_array_toReversed ),
     JS_CFUNC_DEF("sort", 1, js_array_sort ),
     JS_CFUNC_DEF("toSorted", 1, js_array_toSorted ),
-    JS_CFUNC_MAGIC_DEF("slice", 2, js_array_slice, 0 ),
-    JS_CFUNC_MAGIC_DEF("splice", 2, js_array_slice, 1 ),
+    JS_CFUNC_DEF("slice", 2, js_array_slice ),
+    JS_CFUNC_DEF("splice", 2, js_array_splice ),
     JS_CFUNC_DEF("toSpliced", 2, js_array_toSpliced ),
     JS_CFUNC_DEF("copyWithin", 2, js_array_copyWithin ),
     JS_CFUNC_MAGIC_DEF("flatMap", 1, js_array_flatten, 1 ),