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From 0000000000000000000000000000000000000000 Mon Sep 17 00:00:00 2001
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From: James M Snell <jsnell@cloudflare.com>
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Date: Thu, 6 Nov 2025 10:58:38 -0800
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Subject: Add v8::String::IsFlat API
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Tells us if a string is already flattened or not.
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Signed-off-by: James M Snell <jsnell@cloudflare.com>
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diff --git a/include/v8-primitive.h b/include/v8-primitive.h
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index 2b443d97d34fc6e69c47b9fd842898b9a2e43449..068adcc87d02e7c3333c3c6633b51be75f322e42 100644
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--- a/include/v8-primitive.h
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+++ b/include/v8-primitive.h
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@@ -157,6 +157,11 @@ class V8_EXPORT String : public Name {
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    */
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   bool ContainsOnlyOneByte() const;
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+  /**
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+   * Returns true if this string is flat
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+   */
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+  bool IsFlat() const;
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+
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   struct WriteFlags {
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     enum {
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       kNone = 0,
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diff --git a/src/api/api.cc b/src/api/api.cc
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index 8afb25744487519738fd58f49f197537ef070b4a..c1b6bb583314a90dfe77e2f2184db9f4cf722d77 100644
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--- a/src/api/api.cc
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+++ b/src/api/api.cc
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@@ -5819,6 +5819,10 @@ bool String::IsOneByte() const {
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   return Utils::OpenDirectHandle(this)->IsOneByteRepresentation();
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 }
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+bool String::IsFlat() const {
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+  return Utils::OpenDirectHandle(this)->IsFlat();
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+}
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+
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 class ContainsOnlyOneByteHelper {
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  public:
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   ContainsOnlyOneByteHelper() : is_one_byte_(true) {}