Adding upstream version 86.0.1.upstream/86.0.1upstream

Signed-off-by: Daniel Baumann <daniel.baumann@progress-linux.org>

1 files changed, 289 insertions, 0 deletions

diff --git a/js/public/SourceText.h b/js/public/SourceText.h
new file mode 100644
index 0000000000..118c871095
--- /dev/null
+++ b/js/public/SourceText.h
@@ -0,0 +1,289 @@
+/* -*- Mode: C++; tab-width: 8; indent-tabs-mode: nil; c-basic-offset: 2 -*- */
+/* This Source Code Form is subject to the terms of the Mozilla Public
+ * License, v. 2.0. If a copy of the MPL was not distributed with this
+ * file, You can obtain one at http://mozilla.org/MPL/2.0/. */
+
+/*
+ * SourceText encapsulates a count of char16_t (UTF-16) or Utf8Unit (UTF-8)
+ * code units (note: code *units*, not bytes or code points) and those code
+ * units ("source units").  (Latin-1 is not supported: all places where Latin-1
+ * must be compiled first convert to a supported encoding.)
+ *
+ * A SourceText either observes without owning, or takes ownership of, source
+ * units passed to |SourceText::init|.  Thus SourceText can be used to
+ * efficiently avoid copying.
+ *
+ * Rules for use:
+ *
+ *  1) The passed-in source units must be allocated with js_malloc(),
+ *     js_calloc(), or js_realloc() if |SourceText::init| is instructed to take
+ *     ownership of the source units.
+ *  2) If |SourceText::init| merely borrows the source units, the user must
+ *     keep them alive until associated JS compilation is complete.
+ *  3) Code that calls |SourceText::take{Chars,Units}()| must keep the source
+ *     units alive until JS compilation completes.  Normally only the JS engine
+ *     should call |SourceText::take{Chars,Units}()|.
+ *  4) Use the appropriate SourceText parameterization depending on the source
+ *     units encoding.
+ *
+ * Example use:
+ *
+ *    size_t length = 512;
+ *    char16_t* chars = js_pod_malloc<char16_t>(length);
+ *    if (!chars) {
+ *        JS_ReportOutOfMemory(cx);
+ *        return false;
+ *    }
+ *    JS::SourceText<char16_t> srcBuf;
+ *    if (!srcBuf.init(cx, chars, length, JS::SourceOwnership::TakeOwnership)) {
+ *        return false;
+ *    }
+ *    JS::Rooted<JSScript*> script(cx);
+ *    if (!JS::Compile(cx, options, srcBuf, &script)) {
+ *        return false;
+ *    }
+ */
+
+#ifndef js_SourceText_h
+#define js_SourceText_h
+
+#include "mozilla/Assertions.h"  // MOZ_ASSERT
+#include "mozilla/Attributes.h"  // MOZ_COLD, MOZ_IS_CLASS_INIT, MOZ_MUST_USE
+#include "mozilla/Likely.h"      // MOZ_UNLIKELY
+#include "mozilla/Utf8.h"        // mozilla::Utf8Unit
+
+#include <stddef.h>     // size_t
+#include <stdint.h>     // UINT32_MAX
+#include <type_traits>  // std::conditional_t, std::is_same_v
+
+#include "js/UniquePtr.h"  // js::UniquePtr
+#include "js/Utility.h"    // JS::FreePolicy
+
+namespace JS {
+
+namespace detail {
+
+MOZ_COLD extern JS_PUBLIC_API void ReportSourceTooLong(JSContext* cx);
+
+}  // namespace detail
+
+enum class SourceOwnership {
+  Borrowed,
+  TakeOwnership,
+};
+
+template <typename Unit>
+class SourceText final {
+ private:
+  static_assert(std::is_same_v<Unit, mozilla::Utf8Unit> ||
+                    std::is_same_v<Unit, char16_t>,
+                "Unit must be either char16_t or Utf8Unit for "
+                "SourceText<Unit>");
+
+  /** |char16_t| or |Utf8Unit| source units of uncertain validity. */
+  const Unit* units_ = nullptr;
+
+  /** The length in code units of |units_|. */
+  uint32_t length_ = 0;
+
+  /**
+   * Whether this owns |units_| or merely observes source units owned by some
+   * other object.
+   */
+  bool ownsUnits_ = false;
+
+ public:
+  // A C++ character type that can represent the source units -- suitable for
+  // passing to C++ string functions.
+  using CharT =
+      std::conditional_t<std::is_same_v<Unit, char16_t>, char16_t, char>;
+
+ public:
+  /**
+   * Construct a SourceText.  It must be initialized using |init()| before it
+   * can be used as compilation source text.
+   */
+  SourceText() = default;
+
+  /**
+   * Construct a SourceText from contents extracted from |other|.  This
+   * SourceText will then act exactly as |other| would have acted, had it
+   * not been passed to this function.  |other| will return to its default-
+   * constructed state and must have |init()| called on it to use it.
+   */
+  SourceText(SourceText&& other)
+      : units_(other.units_),
+        length_(other.length_),
+        ownsUnits_(other.ownsUnits_) {
+    other.units_ = nullptr;
+    other.length_ = 0;
+    other.ownsUnits_ = false;
+  }
+
+  ~SourceText() {
+    if (ownsUnits_) {
+      js_free(const_cast<Unit*>(units_));
+    }
+  }
+
+  /**
+   * Initialize this with source unit data: |char16_t| for UTF-16 source
+   * units, or |Utf8Unit| for UTF-8 source units.
+   *
+   * If |ownership == TakeOwnership|, *this function* takes ownership of
+   * |units|, *even if* this function fails, and you MUST NOT free |units|
+   * yourself.  This single-owner-friendly approach reduces risk of leaks on
+   * failure.
+   *
+   * |units| may be null if |unitsLength == 0|; if so, this will silently be
+   * initialized using non-null, unowned units.
+   */
+  MOZ_IS_CLASS_INIT MOZ_MUST_USE bool init(JSContext* cx, const Unit* units,
+                                           size_t unitsLength,
+                                           SourceOwnership ownership) {
+    MOZ_ASSERT_IF(units == nullptr, unitsLength == 0);
+
+    // Ideally we'd use |Unit| and not cast below, but the risk of a static
+    // initializer is too great.
+    static const CharT emptyString[] = {'\0'};
+
+    // Initialize all fields *before* checking length.  This ensures that
+    // if |ownership == SourceOwnership::TakeOwnership|, |units| will be
+    // freed when |this|'s destructor is called.
+    if (units) {
+      units_ = units;
+      length_ = static_cast<uint32_t>(unitsLength);
+      ownsUnits_ = ownership == SourceOwnership::TakeOwnership;
+    } else {
+      units_ = reinterpret_cast<const Unit*>(emptyString);
+      length_ = 0;
+      ownsUnits_ = false;
+    }
+
+    // IMPLEMENTATION DETAIL, DO NOT RELY ON: This limit is used so we can
+    // store offsets in |JSScript|s as |uint32_t|.  It could be lifted
+    // fairly easily if desired, as the compiler uses |size_t| internally.
+    if (MOZ_UNLIKELY(unitsLength > UINT32_MAX)) {
+      detail::ReportSourceTooLong(cx);
+      return false;
+    }
+
+    return true;
+  }
+
+  /**
+   * Exactly identical to the |init()| overload above that accepts
+   * |const Unit*|, but instead takes character data: |const CharT*|.
+   *
+   * (We can't just write this to accept |const CharT*|, because then in the
+   * UTF-16 case this overload and the one above would be identical.  So we
+   * use SFINAE to expose the |CharT| overload only if it's different.)
+   */
+  template <typename Char,
+            typename = std::enable_if_t<std::is_same_v<Char, CharT> &&
+                                        !std::is_same_v<Char, Unit>>>
+  MOZ_IS_CLASS_INIT MOZ_MUST_USE bool init(JSContext* cx, const Char* chars,
+                                           size_t charsLength,
+                                           SourceOwnership ownership) {
+    return init(cx, reinterpret_cast<const Unit*>(chars), charsLength,
+                ownership);
+  }
+
+  /**
+   * Initialize this using source units transferred out of |data|.
+   */
+  MOZ_MUST_USE bool init(JSContext* cx,
+                         js::UniquePtr<Unit[], JS::FreePolicy> data,
+                         size_t dataLength) {
+    return init(cx, data.release(), dataLength, SourceOwnership::TakeOwnership);
+  }
+
+  /**
+   * Exactly identical to the |init()| overload above that accepts
+   * |UniquePtr<Unit[], JS::FreePolicy>|, but instead takes character data:
+   * |UniquePtr<CharT[], JS::FreePolicy>|.
+   *
+   * (We can't just duplicate the signature above with s/Unit/CharT/, because
+   * then in the UTF-16 case this overload and the one above would be identical.
+   * So we use SFINAE to expose the |CharT| overload only if it's different.)
+   */
+  template <typename Char,
+            typename = std::enable_if_t<std::is_same_v<Char, CharT> &&
+                                        !std::is_same_v<Char, Unit>>>
+  MOZ_MUST_USE bool init(JSContext* cx,
+                         js::UniquePtr<Char[], JS::FreePolicy> data,
+                         size_t dataLength) {
+    return init(cx, data.release(), dataLength, SourceOwnership::TakeOwnership);
+  }
+
+  /**
+   * Access the encapsulated data using a code unit type.
+   *
+   * This function is useful for code that wants to interact with source text
+   * as *code units*, not as string data.  This doesn't matter for UTF-16,
+   * but it's a crucial distinction for UTF-8.  When UTF-8 source text is
+   * encapsulated, |Unit| being |mozilla::Utf8Unit| unambiguously indicates
+   * that the code units are UTF-8.  In contrast |const char*| returned by
+   * |get()| below could hold UTF-8 (or its ASCII subset) or Latin-1 or (in
+   * particularly cursed embeddings) EBCDIC or some other legacy character
+   * set.  Prefer this function to |get()| wherever possible.
+   */
+  const Unit* units() const { return units_; }
+
+  /**
+   * Access the encapsulated data using a character type.
+   *
+   * This function is useful for interactions with character-centric actions
+   * like interacting with UniqueChars/UniqueTwoByteChars or printing out
+   * text in a debugger, that only work with |CharT|.  But as |CharT| loses
+   * encoding specificity when UTF-8 source text is encapsulated, prefer
+   * |units()| to this function.
+   */
+  const CharT* get() const { return reinterpret_cast<const CharT*>(units_); }
+
+  /**
+   * Returns true if this owns the source units and will free them on
+   * destruction.  If true, it is legal to call |take{Chars,Units}()|.
+   */
+  bool ownsUnits() const { return ownsUnits_; }
+
+  /**
+   * Count of the underlying source units -- code units, not bytes or code
+   * points -- in this.
+   */
+  uint32_t length() const { return length_; }
+
+  /**
+   * Retrieve and take ownership of the underlying source units.  The caller
+   * is now responsible for calling js_free() on the returned value, *but
+   * only after JS script compilation has completed*.
+   *
+   * After underlying source units have been taken, this will continue to
+   * refer to the same data -- it just won't own the data.  get() and
+   * length() will return the same values, but ownsUnits() will be false.
+   * The taken source units must be kept alive until after JS script
+   * compilation completes, as noted above, for this to be safe.
+   *
+   * The caller must check ownsUnits() before calling takeUnits().  Taking
+   * and then free'ing an unowned buffer will have dire consequences.
+   */
+  Unit* takeUnits() {
+    MOZ_ASSERT(ownsUnits_);
+    ownsUnits_ = false;
+    return const_cast<Unit*>(units_);
+  }
+
+  /**
+   * Akin to |takeUnits()| in all respects, but returns characters rather
+   * than units.
+   */
+  CharT* takeChars() { return reinterpret_cast<CharT*>(takeUnits()); }
+
+ private:
+  SourceText(const SourceText&) = delete;
+  void operator=(const SourceText&) = delete;
+};
+
+}  // namespace JS
+
+#endif /* js_SourceText_h */