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/* -*- Mode: C++; tab-width: 8; indent-tabs-mode: nil; c-basic-offset: 2 -*-
* vim: set ts=8 sts=2 et sw=2 tw=80:
* 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/. */
#ifndef vm_StringType_h
#define vm_StringType_h
#include "mozilla/Maybe.h"
#include "mozilla/MemoryReporting.h"
#include "mozilla/Range.h"
#include "mozilla/TextUtils.h"
#include <type_traits> // std::is_same
#include "jsapi.h"
#include "jstypes.h" // js::Bit
#include "gc/Allocator.h"
#include "gc/Barrier.h"
#include "gc/Cell.h"
#include "gc/MaybeRooted.h"
#include "gc/Nursery.h"
#include "gc/RelocationOverlay.h"
#include "gc/Rooting.h"
#include "js/CharacterEncoding.h"
#include "js/RootingAPI.h"
#include "js/shadow/String.h" // JS::shadow::String
#include "js/String.h" // JS::MaxStringLength
#include "js/UniquePtr.h"
#include "util/Text.h"
#include "vm/Printer.h"
class JSDependentString;
class JSExtensibleString;
class JSExternalString;
class JSInlineString;
class JSRope;
namespace JS {
class JS_FRIEND_API AutoStableStringChars;
} // namespace JS
namespace js {
namespace frontend {
class ParserAtomsTable;
class TaggedParserAtomIndex;
class WellKnownParserAtoms;
struct CompilationAtomCache;
} // namespace frontend
class StaticStrings;
class PropertyName;
/* The buffer length required to contain any unsigned 32-bit integer. */
static const size_t UINT32_CHAR_BUFFER_LENGTH = sizeof("4294967295") - 1;
} /* namespace js */
// clang-format off
/*
* [SMDOC] JavaScript Strings
*
* Conceptually, a JS string is just an array of chars and a length. This array
* of chars may or may not be null-terminated and, if it is, the null character
* is not included in the length.
*
* To improve performance of common operations, the following optimizations are
* made which affect the engine's representation of strings:
*
* - The plain vanilla representation is a "linear" string which consists of a
* string header in the GC heap and a malloc'd char array.
*
* - To avoid copying a substring of an existing "base" string , a "dependent"
* string (JSDependentString) can be created which points into the base
* string's char array.
*
* - To avoid O(n^2) char buffer copying, a "rope" node (JSRope) can be created
* to represent a delayed string concatenation. Concatenation (called
* flattening) is performed if and when a linear char array is requested. In
* general, ropes form a binary dag whose internal nodes are JSRope string
* headers with no associated char array and whose leaf nodes are linear
* strings.
*
* - To avoid copying the leftmost string when flattening, we may produce an
* "extensible" string, which tracks not only its actual length but also its
* buffer's overall size. If such an "extensible" string appears as the
* leftmost string in a subsequent flatten, and its buffer has enough unused
* space, we can simply flatten the rest of the ropes into its buffer,
* leaving its text in place. We then transfer ownership of its buffer to the
* flattened rope, and mutate the donor extensible string into a dependent
* string referencing its original buffer.
*
* (The term "extensible" does not imply that we ever 'realloc' the buffer.
* Extensible strings may have dependent strings pointing into them, and the
* JSAPI hands out pointers to linear strings' buffers, so resizing with
* 'realloc' is generally not possible.)
*
* - To avoid allocating small char arrays, short strings can be stored inline
* in the string header (JSInlineString). These come in two flavours:
* JSThinInlineString, which is the same size as JSString; and
* JSFatInlineString, which has a larger header and so can fit more chars.
*
* - To avoid comparing O(n) string equality comparison, strings can be
* canonicalized to "atoms" (JSAtom) such that there is a single atom with a
* given (length,chars).
*
* - To avoid copying all strings created through the JSAPI, an "external"
* string (JSExternalString) can be created whose chars are managed by the
* JSAPI client.
*
* - To avoid using two bytes per character for every string, string
* characters are stored as Latin1 instead of TwoByte if all characters are
* representable in Latin1.
*
* - To avoid slow conversions from strings to integer indexes, we cache 16 bit
* unsigned indexes on strings representing such numbers.
*
* Although all strings share the same basic memory layout, we can conceptually
* arrange them into a hierarchy of operations/invariants and represent this
* hierarchy in C++ with classes:
*
* C++ type operations+fields / invariants+properties
* ========================== =========================================
* JSString (abstract) get(Latin1|TwoByte)CharsZ, get(Latin1|TwoByte)Chars, length / -
* | \
* | JSRope leftChild, rightChild / -
* |
* JSLinearString (abstract) latin1Chars, twoByteChars / -
* |
* +-- JSDependentString base / -
* |
* +-- JSExternalString - / char array memory managed by embedding
* |
* +-- JSExtensibleString tracks total buffer capacity (including current text)
* |
* +-- JSInlineString (abstract) - / chars stored in header
* | |
* | +-- JSThinInlineString - / header is normal
* | |
* | +-- JSFatInlineString - / header is fat
* |
* JSAtom (abstract) - / string equality === pointer equality
* | |
* | +-- js::NormalAtom - JSLinearString + atom hash code
* | |
* | +-- js::FatInlineAtom - JSFatInlineString + atom hash code
* |
* js::PropertyName - / chars don't contain an index (uint32_t)
*
* Classes marked with (abstract) above are not literally C++ Abstract Base
* Classes (since there are no virtual functions, pure or not, in this
* hierarchy), but have the same meaning: there are no strings with this type as
* its most-derived type.
*
* Atoms can additionally be permanent, i.e. unable to be collected, and can
* be combined with other string types to create additional most-derived types
* that satisfy the invariants of more than one of the abovementioned
* most-derived types. Furthermore, each atom stores a hash number (based on its
* chars). This hash number is used as key in the atoms table and when the atom
* is used as key in a JS Map/Set.
*
* Derived string types can be queried from ancestor types via isX() and
* retrieved with asX() debug-only-checked casts.
*
* The ensureX() operations mutate 'this' in place to effectively the type to be
* at least X (e.g., ensureLinear will change a JSRope to be a JSLinearString).
*/
// clang-format on
class JSString : public js::gc::CellWithLengthAndFlags {
protected:
static const size_t NUM_INLINE_CHARS_LATIN1 =
2 * sizeof(void*) / sizeof(JS::Latin1Char);
static const size_t NUM_INLINE_CHARS_TWO_BYTE =
2 * sizeof(void*) / sizeof(char16_t);
public:
// String length and flags are stored in the cell header.
MOZ_ALWAYS_INLINE
size_t length() const { return headerLengthField(); }
MOZ_ALWAYS_INLINE
uint32_t flags() const { return headerFlagsField(); }
protected:
/* Fields only apply to string types commented on the right. */
struct Data {
// Note: 32-bit length and flags fields are inherited from
// CellWithLengthAndFlags.
union {
union {
/* JS(Fat)InlineString */
JS::Latin1Char inlineStorageLatin1[NUM_INLINE_CHARS_LATIN1];
char16_t inlineStorageTwoByte[NUM_INLINE_CHARS_TWO_BYTE];
};
struct {
union {
const JS::Latin1Char* nonInlineCharsLatin1; /* JSLinearString, except
JS(Fat)InlineString */
const char16_t* nonInlineCharsTwoByte; /* JSLinearString, except
JS(Fat)InlineString */
JSString* left; /* JSRope */
} u2;
union {
JSLinearString* base; /* JSDependentString */
JSString* right; /* JSRope */
size_t capacity; /* JSLinearString (extensible) */
const JSExternalStringCallbacks*
externalCallbacks; /* JSExternalString */
} u3;
} s;
};
} d;
public:
/* Flags exposed only for jits */
/*
* Flag Encoding
*
* The first word of a JSString stores flags, index, and (on some
* platforms) the length. The flags store both the string's type and its
* character encoding.
*
* If LATIN1_CHARS_BIT is set, the string's characters are stored as Latin1
* instead of TwoByte. This flag can also be set for ropes, if both the
* left and right nodes are Latin1. Flattening will result in a Latin1
* string in this case.
*
* The other flags store the string's type. Instead of using a dense index
* to represent the most-derived type, string types are encoded to allow
* single-op tests for hot queries (isRope, isDependent, isAtom) which, in
* view of subtyping, would require slower (isX() || isY() || isZ()).
*
* The string type encoding can be summarized as follows. The "instance
* encoding" entry for a type specifies the flag bits used to create a
* string instance of that type. Abstract types have no instances and thus
* have no such entry. The "subtype predicate" entry for a type specifies
* the predicate used to query whether a JSString instance is subtype
* (reflexively) of that type.
*
* String Instance Subtype
* type encoding predicate
* -----------------------------------------
* Rope 000000 000 xxxx0x xxx
* Linear - xxxx1x xxx
* Dependent 000110 000 xxx1xx xxx
* External 100010 000 100010 xxx
* Extensible 010010 000 010010 xxx
* Inline 001010 000 xx1xxx xxx
* FatInline 011010 000 x11xxx xxx
* NormalAtom 000011 000 xxxxx1 xxx
* PermanentAtom 100011 000 1xxxx1 xxx
* InlineAtom - xx1xx1 xxx
* FatInlineAtom - x11xx1 xxx
*
* Bits 0..2 are reserved for use by the GC (see
* gc::CellFlagBitsReservedForGC). In particular, bit 0 is currently used for
* FORWARD_BIT for forwarded nursery cells. The other 2 bits are currently
* unused.
*
* Note that the first 4 flag bits 3..6 (from right to left in the previous
* table) have the following meaning and can be used for some hot queries:
*
* Bit 3: IsAtom (Atom, PermanentAtom)
* Bit 4: IsLinear
* Bit 5: IsDependent
* Bit 6: IsInline (Inline, FatInline)
*
* If INDEX_VALUE_BIT is set, bits 16 and up will also hold an integer index.
*/
// The low bits of flag word are reserved by GC.
static_assert(js::gc::CellFlagBitsReservedForGC <= 3,
"JSString::flags must reserve enough bits for Cell");
static const uint32_t ATOM_BIT = js::Bit(3);
static const uint32_t LINEAR_BIT = js::Bit(4);
static const uint32_t DEPENDENT_BIT = js::Bit(5);
static const uint32_t INLINE_CHARS_BIT = js::Bit(6);
static const uint32_t EXTENSIBLE_FLAGS = LINEAR_BIT | js::Bit(7);
static const uint32_t EXTERNAL_FLAGS = LINEAR_BIT | js::Bit(8);
static const uint32_t FAT_INLINE_MASK = INLINE_CHARS_BIT | js::Bit(7);
static const uint32_t PERMANENT_ATOM_MASK = ATOM_BIT | js::Bit(8);
/* Initial flags for various types of strings. */
static const uint32_t INIT_THIN_INLINE_FLAGS = LINEAR_BIT | INLINE_CHARS_BIT;
static const uint32_t INIT_FAT_INLINE_FLAGS = LINEAR_BIT | FAT_INLINE_MASK;
static const uint32_t INIT_ROPE_FLAGS = 0;
static const uint32_t INIT_LINEAR_FLAGS = LINEAR_BIT;
static const uint32_t INIT_DEPENDENT_FLAGS = LINEAR_BIT | DEPENDENT_BIT;
static const uint32_t TYPE_FLAGS_MASK = js::BitMask(9) - js::BitMask(3);
static_assert((TYPE_FLAGS_MASK & RESERVED_MASK) == 0,
"GC reserved bits must not be used for Strings");
static const uint32_t LATIN1_CHARS_BIT = js::Bit(9);
static const uint32_t INDEX_VALUE_BIT = js::Bit(10);
static const uint32_t INDEX_VALUE_SHIFT = 16;
// NON_DEDUP_BIT is used in string deduplication during tenuring.
static const uint32_t NON_DEDUP_BIT = js::Bit(11);
// If IN_STRING_TO_ATOM_CACHE is set, this string had an entry in the
// StringToAtomCache at some point. Note that GC can purge the cache without
// clearing this bit.
static const uint32_t IN_STRING_TO_ATOM_CACHE = js::Bit(12);
static const uint32_t MAX_LENGTH = JS::MaxStringLength;
static const JS::Latin1Char MAX_LATIN1_CHAR = 0xff;
/*
* Helper function to validate that a string of a given length is
* representable by a JSString. An allocation overflow is reported if false
* is returned.
*/
static inline bool validateLength(JSContext* maybecx, size_t length);
static constexpr size_t offsetOfFlags() { return offsetOfHeaderFlags(); }
static constexpr size_t offsetOfLength() { return offsetOfHeaderLength(); }
bool sameLengthAndFlags(const JSString& other) const {
return length() == other.length() && flags() == other.flags();
}
static void staticAsserts() {
static_assert(JSString::MAX_LENGTH < UINT32_MAX,
"Length must fit in 32 bits");
static_assert(
sizeof(JSString) == (offsetof(JSString, d.inlineStorageLatin1) +
NUM_INLINE_CHARS_LATIN1 * sizeof(char)),
"Inline Latin1 chars must fit in a JSString");
static_assert(
sizeof(JSString) == (offsetof(JSString, d.inlineStorageTwoByte) +
NUM_INLINE_CHARS_TWO_BYTE * sizeof(char16_t)),
"Inline char16_t chars must fit in a JSString");
/* Ensure js::shadow::String has the same layout. */
using JS::shadow::String;
static_assert(
JSString::offsetOfRawHeaderFlagsField() == offsetof(String, flags_),
"shadow::String flags offset must match JSString");
#if JS_BITS_PER_WORD == 32
static_assert(JSString::offsetOfLength() == offsetof(String, length_),
"shadow::String length offset must match JSString");
#endif
static_assert(offsetof(JSString, d.s.u2.nonInlineCharsLatin1) ==
offsetof(String, nonInlineCharsLatin1),
"shadow::String nonInlineChars offset must match JSString");
static_assert(offsetof(JSString, d.s.u2.nonInlineCharsTwoByte) ==
offsetof(String, nonInlineCharsTwoByte),
"shadow::String nonInlineChars offset must match JSString");
static_assert(
offsetof(JSString, d.s.u3.externalCallbacks) ==
offsetof(String, externalCallbacks),
"shadow::String externalCallbacks offset must match JSString");
static_assert(offsetof(JSString, d.inlineStorageLatin1) ==
offsetof(String, inlineStorageLatin1),
"shadow::String inlineStorage offset must match JSString");
static_assert(offsetof(JSString, d.inlineStorageTwoByte) ==
offsetof(String, inlineStorageTwoByte),
"shadow::String inlineStorage offset must match JSString");
static_assert(ATOM_BIT == String::ATOM_BIT,
"shadow::String::ATOM_BIT must match JSString::ATOM_BIT");
static_assert(LINEAR_BIT == String::LINEAR_BIT,
"shadow::String::LINEAR_BIT must match JSString::LINEAR_BIT");
static_assert(INLINE_CHARS_BIT == String::INLINE_CHARS_BIT,
"shadow::String::INLINE_CHARS_BIT must match "
"JSString::INLINE_CHARS_BIT");
static_assert(LATIN1_CHARS_BIT == String::LATIN1_CHARS_BIT,
"shadow::String::LATIN1_CHARS_BIT must match "
"JSString::LATIN1_CHARS_BIT");
static_assert(
TYPE_FLAGS_MASK == String::TYPE_FLAGS_MASK,
"shadow::String::TYPE_FLAGS_MASK must match JSString::TYPE_FLAGS_MASK");
static_assert(
EXTERNAL_FLAGS == String::EXTERNAL_FLAGS,
"shadow::String::EXTERNAL_FLAGS must match JSString::EXTERNAL_FLAGS");
}
/* Avoid silly compile errors in JSRope::flatten */
friend class JSRope;
friend class js::gc::RelocationOverlay;
protected:
template <typename CharT>
MOZ_ALWAYS_INLINE void setNonInlineChars(const CharT* chars);
template <typename CharT>
static MOZ_ALWAYS_INLINE void checkStringCharsArena(const CharT* chars) {
#ifdef MOZ_DEBUG
js::AssertJSStringBufferInCorrectArena(chars);
#endif
}
protected:
void setFlattenData(uintptr_t data) { setTemporaryGCUnsafeData(data); }
uintptr_t unsetFlattenData(uint32_t len, uint32_t flags) {
return unsetTemporaryGCUnsafeData(len, flags);
}
// Get correct non-inline chars enum arm for given type
template <typename CharT>
MOZ_ALWAYS_INLINE const CharT* nonInlineCharsRaw() const;
public:
MOZ_ALWAYS_INLINE
bool empty() const { return length() == 0; }
inline bool getChar(JSContext* cx, size_t index, char16_t* code);
/* Strings have either Latin1 or TwoByte chars. */
bool hasLatin1Chars() const { return flags() & LATIN1_CHARS_BIT; }
bool hasTwoByteChars() const { return !(flags() & LATIN1_CHARS_BIT); }
/* Strings might contain cached indexes. */
bool hasIndexValue() const { return flags() & INDEX_VALUE_BIT; }
uint32_t getIndexValue() const {
MOZ_ASSERT(hasIndexValue());
MOZ_ASSERT(isLinear());
return flags() >> INDEX_VALUE_SHIFT;
}
inline size_t allocSize() const;
/* Fallible conversions to more-derived string types. */
inline JSLinearString* ensureLinear(JSContext* cx);
static bool ensureLinear(JSContext* cx, JSString* str) {
return str->ensureLinear(cx) != nullptr;
}
/* Type query and debug-checked casts */
MOZ_ALWAYS_INLINE
bool isRope() const { return !(flags() & LINEAR_BIT); }
MOZ_ALWAYS_INLINE
JSRope& asRope() const {
MOZ_ASSERT(isRope());
return *(JSRope*)this;
}
MOZ_ALWAYS_INLINE
bool isLinear() const { return flags() & LINEAR_BIT; }
MOZ_ALWAYS_INLINE
JSLinearString& asLinear() const {
MOZ_ASSERT(JSString::isLinear());
return *(JSLinearString*)this;
}
MOZ_ALWAYS_INLINE
bool isDependent() const { return flags() & DEPENDENT_BIT; }
MOZ_ALWAYS_INLINE
JSDependentString& asDependent() const {
MOZ_ASSERT(isDependent());
return *(JSDependentString*)this;
}
MOZ_ALWAYS_INLINE
bool isExtensible() const {
return (flags() & TYPE_FLAGS_MASK) == EXTENSIBLE_FLAGS;
}
MOZ_ALWAYS_INLINE
JSExtensibleString& asExtensible() const {
MOZ_ASSERT(isExtensible());
return *(JSExtensibleString*)this;
}
MOZ_ALWAYS_INLINE
bool isInline() const { return flags() & INLINE_CHARS_BIT; }
MOZ_ALWAYS_INLINE
JSInlineString& asInline() const {
MOZ_ASSERT(isInline());
return *(JSInlineString*)this;
}
MOZ_ALWAYS_INLINE
bool isFatInline() const {
return (flags() & FAT_INLINE_MASK) == FAT_INLINE_MASK;
}
/* For hot code, prefer other type queries. */
bool isExternal() const {
return (flags() & TYPE_FLAGS_MASK) == EXTERNAL_FLAGS;
}
MOZ_ALWAYS_INLINE
JSExternalString& asExternal() const {
MOZ_ASSERT(isExternal());
return *(JSExternalString*)this;
}
MOZ_ALWAYS_INLINE
bool isAtom() const { return flags() & ATOM_BIT; }
MOZ_ALWAYS_INLINE
bool isPermanentAtom() const {
return (flags() & PERMANENT_ATOM_MASK) == PERMANENT_ATOM_MASK;
}
MOZ_ALWAYS_INLINE
JSAtom& asAtom() const {
MOZ_ASSERT(isAtom());
return *(JSAtom*)this;
}
MOZ_ALWAYS_INLINE
void setNonDeduplicatable() { setFlagBit(NON_DEDUP_BIT); }
MOZ_ALWAYS_INLINE
void clearNonDeduplicatable() { clearFlagBit(NON_DEDUP_BIT); }
MOZ_ALWAYS_INLINE
bool isDeduplicatable() { return !(flags() & NON_DEDUP_BIT); }
void setInStringToAtomCache() {
MOZ_ASSERT(!isAtom());
setFlagBit(IN_STRING_TO_ATOM_CACHE);
}
bool inStringToAtomCache() const { return flags() & IN_STRING_TO_ATOM_CACHE; }
// Fills |array| with various strings that represent the different string
// kinds and character encodings.
static bool fillWithRepresentatives(JSContext* cx,
js::HandleArrayObject array);
/* Only called by the GC for dependent strings. */
inline bool hasBase() const { return isDependent(); }
inline JSLinearString* base() const;
// The base may be forwarded and becomes a relocation overlay.
// The return value can be a relocation overlay when the base is forwarded,
// or the return value can be the actual base when it is not forwarded.
inline JSLinearString* nurseryBaseOrRelocOverlay() const;
inline bool canOwnDependentChars() const;
inline void setBase(JSLinearString* newBase);
void traceBase(JSTracer* trc);
/* Only called by the GC for strings with the AllocKind::STRING kind. */
inline void finalize(JSFreeOp* fop);
/* Gets the number of bytes that the chars take on the heap. */
size_t sizeOfExcludingThis(mozilla::MallocSizeOf mallocSizeOf);
bool ownsMallocedChars() const {
return isLinear() && !isInline() && !isDependent() && !isExternal();
}
/* Encode as many scalar values of the string as UTF-8 as can fit
* into the caller-provided buffer replacing unpaired surrogates
* with the REPLACEMENT CHARACTER.
*
* Returns the number of code units read and the number of code units
* written.
*
* The semantics of this method match the semantics of
* TextEncoder.encodeInto().
*
* This function doesn't modify the representation -- rope, linear,
* flat, atom, etc. -- of this string. If this string is a rope,
* it also doesn't modify the representation of left or right halves
* of this string, or of those halves, and so on.
*
* Returns mozilla::Nothing on OOM.
*/
mozilla::Maybe<mozilla::Tuple<size_t, size_t>> encodeUTF8Partial(
const JS::AutoRequireNoGC& nogc, mozilla::Span<char> buffer) const;
private:
// To help avoid writing Spectre-unsafe code, we only allow MacroAssembler
// to call the method below.
friend class js::jit::MacroAssembler;
static size_t offsetOfNonInlineChars() {
static_assert(
offsetof(JSString, d.s.u2.nonInlineCharsTwoByte) ==
offsetof(JSString, d.s.u2.nonInlineCharsLatin1),
"nonInlineCharsTwoByte and nonInlineCharsLatin1 must have same offset");
return offsetof(JSString, d.s.u2.nonInlineCharsTwoByte);
}
public:
static const JS::TraceKind TraceKind = JS::TraceKind::String;
JS::Zone* zone() const {
if (isTenured()) {
// Allow permanent atoms to be accessed across zones and runtimes.
if (isPermanentAtom()) {
return zoneFromAnyThread();
}
return asTenured().zone();
}
return nurseryZone();
}
void setLengthAndFlags(uint32_t len, uint32_t flags) {
setHeaderLengthAndFlags(len, flags);
}
void setFlagBit(uint32_t flag) { setHeaderFlagBit(flag); }
void clearFlagBit(uint32_t flag) { clearHeaderFlagBit(flag); }
void fixupAfterMovingGC() {}
js::gc::AllocKind getAllocKind() const {
using js::gc::AllocKind;
AllocKind kind;
if (isAtom()) {
if (isFatInline()) {
kind = AllocKind::FAT_INLINE_ATOM;
} else {
kind = AllocKind::ATOM;
}
} else if (isFatInline()) {
kind = AllocKind::FAT_INLINE_STRING;
} else if (isExternal()) {
kind = AllocKind::EXTERNAL_STRING;
} else {
kind = AllocKind::STRING;
}
MOZ_ASSERT_IF(isTenured(), kind == asTenured().getAllocKind());
return kind;
}
#if defined(DEBUG) || defined(JS_JITSPEW)
void dump(); // Debugger-friendly stderr dump.
void dump(js::GenericPrinter& out);
void dumpNoNewline(js::GenericPrinter& out);
void dumpCharsNoNewline(js::GenericPrinter& out);
void dumpRepresentation(js::GenericPrinter& out, int indent) const;
void dumpRepresentationHeader(js::GenericPrinter& out,
const char* subclass) const;
void dumpCharsNoQuote(js::GenericPrinter& out);
template <typename CharT>
static void dumpChars(const CharT* s, size_t len, js::GenericPrinter& out);
template <typename CharT>
static void dumpCharsNoQuote(const CharT* s, size_t len,
js::GenericPrinter& out);
bool equals(const char* s);
#endif
void traceChildren(JSTracer* trc);
// Override base class implementation to tell GC about permanent atoms.
bool isPermanentAndMayBeShared() const { return isPermanentAtom(); }
static void addCellAddressToStoreBuffer(js::gc::StoreBuffer* buffer,
js::gc::Cell** cellp) {
buffer->putCell(reinterpret_cast<JSString**>(cellp));
}
static void removeCellAddressFromStoreBuffer(js::gc::StoreBuffer* buffer,
js::gc::Cell** cellp) {
buffer->unputCell(reinterpret_cast<JSString**>(cellp));
}
private:
JSString() = delete;
JSString(const JSString& other) = delete;
void operator=(const JSString& other) = delete;
};
class JSRope : public JSString {
template <typename CharT>
js::UniquePtr<CharT[], JS::FreePolicy> copyCharsInternal(
JSContext* cx, arena_id_t destArenaId) const;
enum UsingBarrier { WithIncrementalBarrier, NoBarrier };
template <UsingBarrier b, typename CharT>
JSLinearString* flattenInternal(JSContext* cx);
template <UsingBarrier b>
JSLinearString* flattenInternal(JSContext* cx);
friend class JSString;
JSLinearString* flatten(JSContext* cx);
void init(JSContext* cx, JSString* left, JSString* right, size_t length);
public:
template <js::AllowGC allowGC>
static inline JSRope* new_(
JSContext* cx,
typename js::MaybeRooted<JSString*, allowGC>::HandleType left,
typename js::MaybeRooted<JSString*, allowGC>::HandleType right,
size_t length, js::gc::InitialHeap = js::gc::DefaultHeap);
js::UniquePtr<JS::Latin1Char[], JS::FreePolicy> copyLatin1Chars(
JSContext* maybecx, arena_id_t destArenaId) const;
JS::UniqueTwoByteChars copyTwoByteChars(JSContext* maybecx,
arena_id_t destArenaId) const;
template <typename CharT>
js::UniquePtr<CharT[], JS::FreePolicy> copyChars(
JSContext* maybecx, arena_id_t destArenaId) const;
// Hash function specific for ropes that avoids allocating a temporary
// string. There are still allocations internally so it's technically
// fallible.
//
// Returns the same value as if this were a linear string being hashed.
[[nodiscard]] bool hash(uint32_t* outhHash) const;
JSString* leftChild() const {
MOZ_ASSERT(isRope());
return d.s.u2.left;
}
JSString* rightChild() const {
MOZ_ASSERT(isRope());
return d.s.u3.right;
}
void traceChildren(JSTracer* trc);
#if defined(DEBUG) || defined(JS_JITSPEW)
void dumpRepresentation(js::GenericPrinter& out, int indent) const;
#endif
private:
// To help avoid writing Spectre-unsafe code, we only allow MacroAssembler
// to call the methods below.
friend class js::jit::MacroAssembler;
static size_t offsetOfLeft() { return offsetof(JSRope, d.s.u2.left); }
static size_t offsetOfRight() { return offsetof(JSRope, d.s.u3.right); }
};
static_assert(sizeof(JSRope) == sizeof(JSString),
"string subclasses must be binary-compatible with JSString");
class JSLinearString : public JSString {
friend class JSString;
friend class JS::AutoStableStringChars;
friend class js::TenuringTracer;
/* Vacuous and therefore unimplemented. */
JSLinearString* ensureLinear(JSContext* cx) = delete;
bool isLinear() const = delete;
JSLinearString& asLinear() const = delete;
template <typename CharT>
static bool isIndexSlow(const CharT* s, size_t length, uint32_t* indexp);
protected:
/* Returns void pointer to latin1/twoByte chars, for finalizers. */
MOZ_ALWAYS_INLINE
void* nonInlineCharsRaw() const {
MOZ_ASSERT(!isInline());
static_assert(
offsetof(JSLinearString, d.s.u2.nonInlineCharsTwoByte) ==
offsetof(JSLinearString, d.s.u2.nonInlineCharsLatin1),
"nonInlineCharsTwoByte and nonInlineCharsLatin1 must have same offset");
return (void*)d.s.u2.nonInlineCharsTwoByte;
}
MOZ_ALWAYS_INLINE const JS::Latin1Char* rawLatin1Chars() const;
MOZ_ALWAYS_INLINE const char16_t* rawTwoByteChars() const;
public:
void init(const char16_t* chars, size_t length);
void init(const JS::Latin1Char* chars, size_t length);
template <js::AllowGC allowGC, typename CharT>
static inline JSLinearString* new_(
JSContext* cx, js::UniquePtr<CharT[], JS::FreePolicy> chars,
size_t length, js::gc::InitialHeap heap);
template <typename CharT>
MOZ_ALWAYS_INLINE const CharT* nonInlineChars(
const JS::AutoRequireNoGC& nogc) const;
MOZ_ALWAYS_INLINE
const JS::Latin1Char* nonInlineLatin1Chars(
const JS::AutoRequireNoGC& nogc) const {
MOZ_ASSERT(!isInline());
MOZ_ASSERT(hasLatin1Chars());
return d.s.u2.nonInlineCharsLatin1;
}
MOZ_ALWAYS_INLINE
const char16_t* nonInlineTwoByteChars(const JS::AutoRequireNoGC& nogc) const {
MOZ_ASSERT(!isInline());
MOZ_ASSERT(hasTwoByteChars());
return d.s.u2.nonInlineCharsTwoByte;
}
template <typename CharT>
MOZ_ALWAYS_INLINE const CharT* chars(const JS::AutoRequireNoGC& nogc) const;
MOZ_ALWAYS_INLINE
const JS::Latin1Char* latin1Chars(const JS::AutoRequireNoGC& nogc) const {
return rawLatin1Chars();
}
MOZ_ALWAYS_INLINE
const char16_t* twoByteChars(const JS::AutoRequireNoGC& nogc) const {
return rawTwoByteChars();
}
mozilla::Range<const JS::Latin1Char> latin1Range(
const JS::AutoRequireNoGC& nogc) const {
MOZ_ASSERT(JSString::isLinear());
return mozilla::Range<const JS::Latin1Char>(latin1Chars(nogc), length());
}
mozilla::Range<const char16_t> twoByteRange(
const JS::AutoRequireNoGC& nogc) const {
MOZ_ASSERT(JSString::isLinear());
return mozilla::Range<const char16_t>(twoByteChars(nogc), length());
}
MOZ_ALWAYS_INLINE
char16_t latin1OrTwoByteChar(size_t index) const {
MOZ_ASSERT(JSString::isLinear());
MOZ_ASSERT(index < length());
JS::AutoCheckCannotGC nogc;
return hasLatin1Chars() ? latin1Chars(nogc)[index]
: twoByteChars(nogc)[index];
}
bool isIndexSlow(uint32_t* indexp) const {
MOZ_ASSERT(JSString::isLinear());
size_t len = length();
if (len == 0 || len > js::UINT32_CHAR_BUFFER_LENGTH) {
return false;
}
JS::AutoCheckCannotGC nogc;
if (hasLatin1Chars()) {
const JS::Latin1Char* s = latin1Chars(nogc);
return mozilla::IsAsciiDigit(*s) && isIndexSlow(s, len, indexp);
}
const char16_t* s = twoByteChars(nogc);
return mozilla::IsAsciiDigit(*s) && isIndexSlow(s, len, indexp);
}
/*
* Returns true if this string's characters store an unsigned 32-bit
* integer value, initializing *indexp to that value if so.
* Leading '0' isn't allowed except 0 itself.
* (Thus if calling isIndex returns true, js::IndexToString(cx, *indexp) will
* be a string equal to this string.)
*/
bool isIndex(uint32_t* indexp) const {
MOZ_ASSERT(JSString::isLinear());
if (JSString::hasIndexValue()) {
*indexp = getIndexValue();
return true;
}
return isIndexSlow(indexp);
}
void maybeInitializeIndex(uint32_t index, bool allowAtom = false) {
MOZ_ASSERT(JSString::isLinear());
MOZ_ASSERT_IF(hasIndexValue(), getIndexValue() == index);
MOZ_ASSERT_IF(!allowAtom, !isAtom());
if (hasIndexValue() || index > UINT16_MAX) {
return;
}
mozilla::DebugOnly<uint32_t> containedIndex;
MOZ_ASSERT(isIndexSlow(&containedIndex));
MOZ_ASSERT(index == containedIndex);
setFlagBit((index << INDEX_VALUE_SHIFT) | INDEX_VALUE_BIT);
MOZ_ASSERT(getIndexValue() == index);
}
/*
* Returns a property name represented by this string, or null on failure.
* You must verify that this is not an index per isIndex before calling
* this method.
*/
inline js::PropertyName* toPropertyName(JSContext* cx);
inline void finalize(JSFreeOp* fop);
inline size_t allocSize() const;
#if defined(DEBUG) || defined(JS_JITSPEW)
void dumpRepresentationChars(js::GenericPrinter& out, int indent) const;
void dumpRepresentation(js::GenericPrinter& out, int indent) const;
#endif
/*
* Once a JSLinearString sub-class has been added to the atom state, this
* operation changes the string to the JSAtom type, in place.
*/
MOZ_ALWAYS_INLINE JSAtom* morphAtomizedStringIntoAtom(js::HashNumber hash);
MOZ_ALWAYS_INLINE JSAtom* morphAtomizedStringIntoPermanentAtom(
js::HashNumber hash);
};
static_assert(sizeof(JSLinearString) == sizeof(JSString),
"string subclasses must be binary-compatible with JSString");
class JSDependentString : public JSLinearString {
friend class JSString;
void init(JSContext* cx, JSLinearString* base, size_t start, size_t length);
/* Vacuous and therefore unimplemented. */
bool isDependent() const = delete;
JSDependentString& asDependent() const = delete;
/* The offset of this string's chars in base->chars(). */
MOZ_ALWAYS_INLINE size_t baseOffset() const {
MOZ_ASSERT(JSString::isDependent());
JS::AutoCheckCannotGC nogc;
size_t offset;
if (hasTwoByteChars()) {
offset = twoByteChars(nogc) - base()->twoByteChars(nogc);
} else {
offset = latin1Chars(nogc) - base()->latin1Chars(nogc);
}
MOZ_ASSERT(offset < base()->length());
return offset;
}
public:
static inline JSLinearString* new_(JSContext* cx, JSLinearString* base,
size_t start, size_t length,
js::gc::InitialHeap heap);
template <typename T>
void relocateNonInlineChars(T chars, size_t offset) {
setNonInlineChars(chars + offset);
}
#if defined(DEBUG) || defined(JS_JITSPEW)
void dumpRepresentation(js::GenericPrinter& out, int indent) const;
#endif
private:
// To help avoid writing Spectre-unsafe code, we only allow MacroAssembler
// to call the method below.
friend class js::jit::MacroAssembler;
inline static size_t offsetOfBase() {
return offsetof(JSDependentString, d.s.u3.base);
}
};
static_assert(sizeof(JSDependentString) == sizeof(JSString),
"string subclasses must be binary-compatible with JSString");
class JSExtensibleString : public JSLinearString {
/* Vacuous and therefore unimplemented. */
bool isExtensible() const = delete;
JSExtensibleString& asExtensible() const = delete;
public:
MOZ_ALWAYS_INLINE
size_t capacity() const {
MOZ_ASSERT(JSString::isExtensible());
return d.s.u3.capacity;
}
#if defined(DEBUG) || defined(JS_JITSPEW)
void dumpRepresentation(js::GenericPrinter& out, int indent) const;
#endif
};
static_assert(sizeof(JSExtensibleString) == sizeof(JSString),
"string subclasses must be binary-compatible with JSString");
class JSInlineString : public JSLinearString {
public:
MOZ_ALWAYS_INLINE
const JS::Latin1Char* latin1Chars(const JS::AutoRequireNoGC& nogc) const {
MOZ_ASSERT(JSString::isInline());
MOZ_ASSERT(hasLatin1Chars());
return d.inlineStorageLatin1;
}
MOZ_ALWAYS_INLINE
const char16_t* twoByteChars(const JS::AutoRequireNoGC& nogc) const {
MOZ_ASSERT(JSString::isInline());
MOZ_ASSERT(hasTwoByteChars());
return d.inlineStorageTwoByte;
}
template <typename CharT>
static bool lengthFits(size_t length);
#if defined(DEBUG) || defined(JS_JITSPEW)
void dumpRepresentation(js::GenericPrinter& out, int indent) const;
#endif
private:
// To help avoid writing Spectre-unsafe code, we only allow MacroAssembler
// to call the method below.
friend class js::jit::MacroAssembler;
static size_t offsetOfInlineStorage() {
return offsetof(JSInlineString, d.inlineStorageTwoByte);
}
};
static_assert(sizeof(JSInlineString) == sizeof(JSString),
"string subclasses must be binary-compatible with JSString");
/*
* On 32-bit platforms, JSThinInlineString can store 8 Latin1 characters or 4
* TwoByte characters inline. On 64-bit platforms, these numbers are 16 and 8,
* respectively.
*/
class JSThinInlineString : public JSInlineString {
public:
static const size_t MAX_LENGTH_LATIN1 = NUM_INLINE_CHARS_LATIN1;
static const size_t MAX_LENGTH_TWO_BYTE = NUM_INLINE_CHARS_TWO_BYTE;
template <js::AllowGC allowGC>
static inline JSThinInlineString* new_(JSContext* cx,
js::gc::InitialHeap heap);
template <typename CharT>
inline CharT* init(size_t length);
template <typename CharT>
static bool lengthFits(size_t length);
};
static_assert(sizeof(JSThinInlineString) == sizeof(JSString),
"string subclasses must be binary-compatible with JSString");
/*
* On both 32-bit and 64-bit platforms, MAX_LENGTH_TWO_BYTE is 12 and
* MAX_LENGTH_LATIN1 is 24. This is deliberate, in order to minimize potential
* performance differences between 32-bit and 64-bit platforms.
*
* There are still some differences due to NUM_INLINE_CHARS_* being different.
* E.g. TwoByte strings of length 5--8 will be JSFatInlineStrings on 32-bit
* platforms and JSThinInlineStrings on 64-bit platforms. But the more
* significant transition from inline strings to non-inline strings occurs at
* length 12 (for TwoByte strings) and 24 (Latin1 strings) on both 32-bit and
* 64-bit platforms.
*/
class JSFatInlineString : public JSInlineString {
static const size_t INLINE_EXTENSION_CHARS_LATIN1 =
24 - NUM_INLINE_CHARS_LATIN1;
static const size_t INLINE_EXTENSION_CHARS_TWO_BYTE =
12 - NUM_INLINE_CHARS_TWO_BYTE;
protected: /* to fool clang into not warning this is unused */
union {
char inlineStorageExtensionLatin1[INLINE_EXTENSION_CHARS_LATIN1];
char16_t inlineStorageExtensionTwoByte[INLINE_EXTENSION_CHARS_TWO_BYTE];
};
public:
template <js::AllowGC allowGC>
static inline JSFatInlineString* new_(JSContext* cx,
js::gc::InitialHeap heap);
static const size_t MAX_LENGTH_LATIN1 =
JSString::NUM_INLINE_CHARS_LATIN1 + INLINE_EXTENSION_CHARS_LATIN1;
static const size_t MAX_LENGTH_TWO_BYTE =
JSString::NUM_INLINE_CHARS_TWO_BYTE + INLINE_EXTENSION_CHARS_TWO_BYTE;
template <typename CharT>
inline CharT* init(size_t length);
template <typename CharT>
static bool lengthFits(size_t length);
// Only called by the GC for strings with the AllocKind::FAT_INLINE_STRING
// kind.
MOZ_ALWAYS_INLINE void finalize(JSFreeOp* fop);
};
static_assert(sizeof(JSFatInlineString) % js::gc::CellAlignBytes == 0,
"fat inline strings shouldn't waste space up to the next cell "
"boundary");
class JSExternalString : public JSLinearString {
void init(const char16_t* chars, size_t length,
const JSExternalStringCallbacks* callbacks);
/* Vacuous and therefore unimplemented. */
bool isExternal() const = delete;
JSExternalString& asExternal() const = delete;
public:
static inline JSExternalString* new_(
JSContext* cx, const char16_t* chars, size_t length,
const JSExternalStringCallbacks* callbacks);
const JSExternalStringCallbacks* callbacks() const {
MOZ_ASSERT(JSString::isExternal());
return d.s.u3.externalCallbacks;
}
// External chars are never allocated inline or in the nursery, so we can
// safely expose this without requiring an AutoCheckCannotGC argument.
const char16_t* twoByteChars() const { return rawTwoByteChars(); }
// Only called by the GC for strings with the AllocKind::EXTERNAL_STRING
// kind.
inline void finalize(JSFreeOp* fop);
#if defined(DEBUG) || defined(JS_JITSPEW)
void dumpRepresentation(js::GenericPrinter& out, int indent) const;
#endif
};
static_assert(sizeof(JSExternalString) == sizeof(JSString),
"string subclasses must be binary-compatible with JSString");
class JSAtom : public JSLinearString {
/* Vacuous and therefore unimplemented. */
bool isAtom() const = delete;
JSAtom& asAtom() const = delete;
public:
/* Returns the PropertyName for this. isIndex() must be false. */
inline js::PropertyName* asPropertyName();
MOZ_ALWAYS_INLINE
bool isPermanent() const { return JSString::isPermanentAtom(); }
// Transform this atom into a permanent atom. This is only done during
// initialization of the runtime. Permanent atoms are always pinned.
MOZ_ALWAYS_INLINE void morphIntoPermanentAtom() {
MOZ_ASSERT(static_cast<JSString*>(this)->isAtom());
setFlagBit(PERMANENT_ATOM_MASK);
}
inline js::HashNumber hash() const;
inline void initHash(js::HashNumber hash);
#if defined(DEBUG) || defined(JS_JITSPEW)
void dump(js::GenericPrinter& out);
void dump();
#endif
};
static_assert(sizeof(JSAtom) == sizeof(JSString),
"string subclasses must be binary-compatible with JSString");
namespace js {
class NormalAtom : public JSAtom {
protected:
HashNumber hash_;
public:
HashNumber hash() const { return hash_; }
void initHash(HashNumber hash) { hash_ = hash; }
};
static_assert(sizeof(NormalAtom) == sizeof(JSString) + sizeof(uint64_t),
"NormalAtom must have size of a string + HashNumber, "
"aligned to gc::CellAlignBytes");
class FatInlineAtom : public JSAtom {
protected: // Silence Clang unused-field warning.
char inlineStorage_[sizeof(JSFatInlineString) - sizeof(JSString)];
HashNumber hash_;
public:
HashNumber hash() const { return hash_; }
void initHash(HashNumber hash) { hash_ = hash; }
inline void finalize(JSFreeOp* fop);
};
static_assert(
sizeof(FatInlineAtom) == sizeof(JSFatInlineString) + sizeof(uint64_t),
"FatInlineAtom must have size of a fat inline string + HashNumber, "
"aligned to gc::CellAlignBytes");
} // namespace js
inline js::HashNumber JSAtom::hash() const {
if (isFatInline()) {
return static_cast<const js::FatInlineAtom*>(this)->hash();
}
return static_cast<const js::NormalAtom*>(this)->hash();
}
inline void JSAtom::initHash(js::HashNumber hash) {
if (isFatInline()) {
return static_cast<js::FatInlineAtom*>(this)->initHash(hash);
}
return static_cast<js::NormalAtom*>(this)->initHash(hash);
}
MOZ_ALWAYS_INLINE JSAtom* JSLinearString::morphAtomizedStringIntoAtom(
js::HashNumber hash) {
MOZ_ASSERT(!isAtom());
setFlagBit(ATOM_BIT);
JSAtom* atom = &asAtom();
atom->initHash(hash);
return atom;
}
MOZ_ALWAYS_INLINE JSAtom* JSLinearString::morphAtomizedStringIntoPermanentAtom(
js::HashNumber hash) {
MOZ_ASSERT(!isAtom());
setFlagBit(PERMANENT_ATOM_MASK);
JSAtom* atom = &asAtom();
atom->initHash(hash);
return atom;
}
namespace js {
// Returns true if the characters of `s` store an unsigned 32-bit integer value,
// initializing `*indexp` to that value if so.
// Leading '0' isn't allowed except 0 itself.
template <typename CharT>
bool CheckStringIsIndex(const CharT* s, size_t length, uint32_t* indexp);
/**
* An indexable characters class exposing unaligned, little-endian encoded
* char16_t data.
*/
class LittleEndianChars {
public:
explicit constexpr LittleEndianChars(const uint8_t* leTwoByte)
: current(leTwoByte) {}
constexpr char16_t operator[](size_t index) const {
size_t offset = index * sizeof(char16_t);
return (current[offset + 1] << 8) | current[offset];
}
constexpr const uint8_t* get() { return current; }
private:
const uint8_t* current;
};
class StaticStrings {
// NOTE: The WellKnownParserAtoms rely on these tables and may need to be
// update if these tables are changed.
friend class js::frontend::ParserAtomsTable;
friend class js::frontend::TaggedParserAtomIndex;
friend class js::frontend::WellKnownParserAtoms;
friend struct js::frontend::CompilationAtomCache;
private:
// Strings matches `[A-Za-z0-9$_]{2}` pattern.
// Store each character in 6 bits.
// See fromSmallChar/toSmallChar for the mapping.
static constexpr size_t SMALL_CHAR_BITS = 6;
static constexpr size_t SMALL_CHAR_MASK = js::BitMask(SMALL_CHAR_BITS);
// To optimize ASCII -> small char, allocate a table.
static constexpr size_t SMALL_CHAR_TABLE_SIZE = 128U;
static constexpr size_t NUM_SMALL_CHARS = js::Bit(SMALL_CHAR_BITS);
static constexpr size_t NUM_LENGTH2_ENTRIES =
NUM_SMALL_CHARS * NUM_SMALL_CHARS;
JSAtom* length2StaticTable[NUM_LENGTH2_ENTRIES] = {}; // zeroes
public:
/* We keep these public for the JITs. */
static const size_t UNIT_STATIC_LIMIT = 256U;
JSAtom* unitStaticTable[UNIT_STATIC_LIMIT] = {}; // zeroes
static const size_t INT_STATIC_LIMIT = 256U;
JSAtom* intStaticTable[INT_STATIC_LIMIT] = {}; // zeroes
StaticStrings() = default;
bool init(JSContext* cx);
void trace(JSTracer* trc);
static bool hasUint(uint32_t u) { return u < INT_STATIC_LIMIT; }
JSAtom* getUint(uint32_t u) {
MOZ_ASSERT(hasUint(u));
return intStaticTable[u];
}
static bool hasInt(int32_t i) { return uint32_t(i) < INT_STATIC_LIMIT; }
JSAtom* getInt(int32_t i) {
MOZ_ASSERT(hasInt(i));
return getUint(uint32_t(i));
}
static bool hasUnit(char16_t c) { return c < UNIT_STATIC_LIMIT; }
JSAtom* getUnit(char16_t c) {
MOZ_ASSERT(hasUnit(c));
return unitStaticTable[c];
}
/* May not return atom, returns null on (reported) failure. */
inline JSLinearString* getUnitStringForElement(JSContext* cx, JSString* str,
size_t index);
template <typename CharT>
static bool isStatic(const CharT* chars, size_t len);
/* Return null if no static atom exists for the given (chars, length). */
template <typename Chars>
MOZ_ALWAYS_INLINE JSAtom* lookup(Chars chars, size_t length) {
static_assert(std::is_same_v<Chars, const Latin1Char*> ||
std::is_same_v<Chars, const char16_t*> ||
std::is_same_v<Chars, LittleEndianChars>,
"for understandability, |chars| must be one of a few "
"identified types");
switch (length) {
case 1: {
char16_t c = chars[0];
if (c < UNIT_STATIC_LIMIT) {
return getUnit(c);
}
return nullptr;
}
case 2:
if (fitsInSmallChar(chars[0]) && fitsInSmallChar(chars[1])) {
return getLength2(chars[0], chars[1]);
}
return nullptr;
case 3:
/*
* Here we know that JSString::intStringTable covers only 256 (or at
* least not 1000 or more) chars. We rely on order here to resolve the
* unit vs. int string/length-2 string atom identity issue by giving
* priority to unit strings for "0" through "9" and length-2 strings for
* "10" through "99".
*/
static_assert(INT_STATIC_LIMIT <= 999,
"static int strings assumed below to be at most "
"three digits");
if ('1' <= chars[0] && chars[0] <= '9' && '0' <= chars[1] &&
chars[1] <= '9' && '0' <= chars[2] && chars[2] <= '9') {
int i =
(chars[0] - '0') * 100 + (chars[1] - '0') * 10 + (chars[2] - '0');
if (unsigned(i) < INT_STATIC_LIMIT) {
return getInt(i);
}
}
return nullptr;
}
return nullptr;
}
MOZ_ALWAYS_INLINE JSAtom* lookup(const char* chars, size_t length) {
// Collapse calls for |const char*| into |const Latin1Char char*| to avoid
// excess instantiations.
return lookup(reinterpret_cast<const Latin1Char*>(chars), length);
}
template <typename CharT,
typename = std::enable_if_t<!std::is_const_v<CharT>>>
MOZ_ALWAYS_INLINE JSAtom* lookup(CharT* chars, size_t length) {
// Collapse the remaining |CharT*| to |const CharT*| to avoid excess
// instantiations.
return lookup(const_cast<const CharT*>(chars), length);
}
private:
using SmallChar = uint8_t;
struct SmallCharTable {
SmallChar storage[SMALL_CHAR_TABLE_SIZE];
constexpr SmallChar& operator[](size_t idx) { return storage[idx]; }
constexpr const SmallChar& operator[](size_t idx) const {
return storage[idx];
}
};
static const SmallChar INVALID_SMALL_CHAR = -1;
static bool fitsInSmallChar(char16_t c) {
return c < SMALL_CHAR_TABLE_SIZE &&
toSmallCharTable[c] != INVALID_SMALL_CHAR;
}
static constexpr Latin1Char fromSmallChar(SmallChar c);
static constexpr SmallChar toSmallChar(uint32_t c);
static constexpr SmallCharTable createSmallCharTable();
static const SmallCharTable toSmallCharTable;
static constexpr Latin1Char firstCharOfLength2(size_t s) {
return fromSmallChar(s >> SMALL_CHAR_BITS);
}
static constexpr Latin1Char secondCharOfLength2(size_t s) {
return fromSmallChar(s & SMALL_CHAR_MASK);
}
static MOZ_ALWAYS_INLINE size_t getLength2Index(char16_t c1, char16_t c2) {
MOZ_ASSERT(fitsInSmallChar(c1));
MOZ_ASSERT(fitsInSmallChar(c2));
return (size_t(toSmallCharTable[c1]) << SMALL_CHAR_BITS) +
toSmallCharTable[c2];
}
// Same as getLength2Index, but withtout runtime assertion,
// this should be used only for known static string.
static constexpr size_t getLength2IndexStatic(char c1, char c2) {
return (size_t(toSmallChar(c1)) << SMALL_CHAR_BITS) + toSmallChar(c2);
}
MOZ_ALWAYS_INLINE JSAtom* getLength2FromIndex(size_t index) {
return length2StaticTable[index];
}
MOZ_ALWAYS_INLINE JSAtom* getLength2(char16_t c1, char16_t c2) {
return getLength2FromIndex(getLength2Index(c1, c2));
}
};
/*
* Declare length-2 strings. We only store strings where both characters are
* alphanumeric. The lower 10 short chars are the numerals, the next 26 are
* the lowercase letters, and the next 26 are the uppercase letters.
*/
constexpr Latin1Char StaticStrings::fromSmallChar(SmallChar c) {
if (c < 10) {
return c + '0';
}
if (c < 36) {
return c + 'a' - 10;
}
if (c < 62) {
return c + 'A' - 36;
}
if (c == 62) {
return '$';
}
return '_';
}
constexpr StaticStrings::SmallChar StaticStrings::toSmallChar(uint32_t c) {
if (mozilla::IsAsciiDigit(c)) {
return c - '0';
}
if (mozilla::IsAsciiLowercaseAlpha(c)) {
return c - 'a' + 10;
}
if (mozilla::IsAsciiUppercaseAlpha(c)) {
return c - 'A' + 36;
}
if (c == '$') {
return 62;
}
if (c == '_') {
return 63;
}
return StaticStrings::INVALID_SMALL_CHAR;
}
/*
* Represents an atomized string which does not contain an index (that is, an
* unsigned 32-bit value). Thus for any PropertyName propname,
* ToString(ToUint32(propname)) never equals propname.
*
* To more concretely illustrate the utility of PropertyName, consider that it
* is used to partition, in a type-safe manner, the ways to refer to a
* property, as follows:
*
* - uint32_t indexes,
* - PropertyName strings which don't encode uint32_t indexes, and
* - jsspecial special properties (non-ES5 properties like object-valued
* jsids, JSID_EMPTY, JSID_VOID, and maybe in the future Harmony-proposed
* private names).
*/
class PropertyName : public JSAtom {
private:
/* Vacuous and therefore unimplemented. */
PropertyName* asPropertyName() = delete;
};
static_assert(sizeof(PropertyName) == sizeof(JSString),
"string subclasses must be binary-compatible with JSString");
static MOZ_ALWAYS_INLINE jsid NameToId(PropertyName* name) {
return JS::PropertyKey::fromNonIntAtom(name);
}
using PropertyNameVector = JS::GCVector<PropertyName*>;
template <typename CharT>
void CopyChars(CharT* dest, const JSLinearString& str);
static inline UniqueChars StringToNewUTF8CharsZ(JSContext* maybecx,
JSString& str) {
JS::AutoCheckCannotGC nogc;
JSLinearString* linear = str.ensureLinear(maybecx);
if (!linear) {
return nullptr;
}
return UniqueChars(
linear->hasLatin1Chars()
? JS::CharsToNewUTF8CharsZ(maybecx, linear->latin1Range(nogc)).c_str()
: JS::CharsToNewUTF8CharsZ(maybecx, linear->twoByteRange(nogc))
.c_str());
}
/**
* Allocate a string with the given contents. If |allowGC == CanGC|, this may
* trigger a GC.
*/
template <js::AllowGC allowGC, typename CharT>
extern JSLinearString* NewString(
JSContext* cx, UniquePtr<CharT[], JS::FreePolicy> chars, size_t length,
js::gc::InitialHeap heap = js::gc::DefaultHeap);
/* Like NewString, but doesn't try to deflate to Latin1. */
template <js::AllowGC allowGC, typename CharT>
extern JSLinearString* NewStringDontDeflate(
JSContext* cx, UniquePtr<CharT[], JS::FreePolicy> chars, size_t length,
js::gc::InitialHeap heap = js::gc::DefaultHeap);
extern JSLinearString* NewDependentString(
JSContext* cx, JSString* base, size_t start, size_t length,
js::gc::InitialHeap heap = js::gc::DefaultHeap);
/* Take ownership of an array of Latin1Chars. */
extern JSLinearString* NewLatin1StringZ(
JSContext* cx, UniqueChars chars,
js::gc::InitialHeap heap = js::gc::DefaultHeap);
/* Copy a counted string and GC-allocate a descriptor for it. */
template <js::AllowGC allowGC, typename CharT>
extern JSLinearString* NewStringCopyN(
JSContext* cx, const CharT* s, size_t n,
js::gc::InitialHeap heap = js::gc::DefaultHeap);
template <js::AllowGC allowGC>
inline JSLinearString* NewStringCopyN(
JSContext* cx, const char* s, size_t n,
js::gc::InitialHeap heap = js::gc::DefaultHeap) {
return NewStringCopyN<allowGC>(cx, reinterpret_cast<const Latin1Char*>(s), n,
heap);
}
/* Like NewStringCopyN, but doesn't try to deflate to Latin1. */
template <js::AllowGC allowGC, typename CharT>
extern JSLinearString* NewStringCopyNDontDeflate(
JSContext* cx, const CharT* s, size_t n,
js::gc::InitialHeap heap = js::gc::DefaultHeap);
/* Copy a C string and GC-allocate a descriptor for it. */
template <js::AllowGC allowGC>
inline JSLinearString* NewStringCopyZ(
JSContext* cx, const char16_t* s,
js::gc::InitialHeap heap = js::gc::DefaultHeap) {
return NewStringCopyN<allowGC>(cx, s, js_strlen(s), heap);
}
template <js::AllowGC allowGC>
inline JSLinearString* NewStringCopyZ(
JSContext* cx, const char* s,
js::gc::InitialHeap heap = js::gc::DefaultHeap) {
return NewStringCopyN<allowGC>(cx, s, strlen(s), heap);
}
template <js::AllowGC allowGC>
extern JSLinearString* NewStringCopyUTF8N(
JSContext* cx, const JS::UTF8Chars utf8,
js::gc::InitialHeap heap = js::gc::DefaultHeap);
template <js::AllowGC allowGC>
inline JSLinearString* NewStringCopyUTF8Z(
JSContext* cx, const JS::ConstUTF8CharsZ utf8,
js::gc::InitialHeap heap = js::gc::DefaultHeap) {
return NewStringCopyUTF8N<allowGC>(
cx, JS::UTF8Chars(utf8.c_str(), strlen(utf8.c_str())), heap);
}
JSString* NewMaybeExternalString(
JSContext* cx, const char16_t* s, size_t n,
const JSExternalStringCallbacks* callbacks, bool* allocatedExternal,
js::gc::InitialHeap heap = js::gc::DefaultHeap);
/**
* Allocate a new string consisting of |chars[0..length]| characters.
*/
extern JSLinearString* NewStringFromLittleEndianNoGC(
JSContext* cx, LittleEndianChars chars, size_t length,
js::gc::InitialHeap heap = js::gc::DefaultHeap);
static_assert(sizeof(HashNumber) == 4);
template <AllowGC allowGC>
extern JSString* ConcatStrings(
JSContext* cx, typename MaybeRooted<JSString*, allowGC>::HandleType left,
typename MaybeRooted<JSString*, allowGC>::HandleType right,
js::gc::InitialHeap heap = js::gc::DefaultHeap);
/*
* Test if strings are equal. The caller can call the function even if str1
* or str2 are not GC-allocated things.
*/
extern bool EqualStrings(JSContext* cx, JSString* str1, JSString* str2,
bool* result);
/* Use the infallible method instead! */
extern bool EqualStrings(JSContext* cx, JSLinearString* str1,
JSLinearString* str2, bool* result) = delete;
/* EqualStrings is infallible on linear strings. */
extern bool EqualStrings(JSLinearString* str1, JSLinearString* str2);
/**
* Compare two strings that are known to be the same length.
* Exposed for the JITs; for ordinary uses, EqualStrings() is more sensible.
*
* Precondition: str1->length() == str2->length().
*/
extern bool EqualChars(JSLinearString* str1, JSLinearString* str2);
/*
* Return less than, equal to, or greater than zero depending on whether
* `s1[0..len1]` is less than, equal to, or greater than `s2`.
*/
extern int32_t CompareChars(const char16_t* s1, size_t len1,
JSLinearString* s2);
/*
* Compare two strings, like CompareChars, but store the result in `*result`.
* This flattens the strings and therefore can fail.
*/
extern bool CompareStrings(JSContext* cx, JSString* str1, JSString* str2,
int32_t* result);
/*
* Same as CompareStrings but for atoms. Don't use this to just test
* for equality; use this when you need an ordering on atoms.
*/
extern int32_t CompareAtoms(JSAtom* atom1, JSAtom* atom2);
/**
* Return true if the string contains only ASCII characters.
*/