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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/. */
/* JavaScript string operations. */
#ifndef js_String_h
#define js_String_h
#include "js/shadow/String.h" // JS::shadow::String
#include "mozilla/Assertions.h" // MOZ_ASSERT
#include "mozilla/Attributes.h" // MOZ_ALWAYS_INLINE, MOZ_MUST_USE
#include "mozilla/Likely.h" // MOZ_LIKELY
#include <algorithm> // std::copy_n
#include <stddef.h> // size_t
#include <stdint.h> // uint32_t, uint64_t, INT32_MAX
#include "jstypes.h" // JS_PUBLIC_API
#include "js/TypeDecls.h" // JS::Latin1Char
class JS_PUBLIC_API JSAtom;
class JSLinearString;
class JS_PUBLIC_API JSString;
namespace JS {
class JS_PUBLIC_API AutoRequireNoGC;
/**
* Maximum length of a JS string. This is chosen so that the number of bytes
* allocated for a null-terminated TwoByte string still fits in int32_t.
*/
static constexpr uint32_t MaxStringLength = (1 << 30) - 2;
static_assert((uint64_t(MaxStringLength) + 1) * sizeof(char16_t) <= INT32_MAX,
"size of null-terminated JSString char buffer must fit in "
"INT32_MAX");
/** Compute the length of a string. */
MOZ_ALWAYS_INLINE size_t GetStringLength(JSString* s) {
return shadow::AsShadowString(s)->length();
}
/** Compute the length of a linear string. */
MOZ_ALWAYS_INLINE size_t GetLinearStringLength(JSLinearString* s) {
return shadow::AsShadowString(s)->length();
}
/** Return true iff the given linear string uses Latin-1 storage. */
MOZ_ALWAYS_INLINE bool LinearStringHasLatin1Chars(JSLinearString* s) {
return shadow::AsShadowString(s)->hasLatin1Chars();
}
/** Return true iff the given string uses Latin-1 storage. */
MOZ_ALWAYS_INLINE bool StringHasLatin1Chars(JSString* s) {
return shadow::AsShadowString(s)->hasLatin1Chars();
}
/**
* Given a linear string known to use Latin-1 storage, return a pointer to that
* storage. This pointer remains valid only as long as no GC occurs.
*/
MOZ_ALWAYS_INLINE const Latin1Char* GetLatin1LinearStringChars(
const AutoRequireNoGC& nogc, JSLinearString* linear) {
return shadow::AsShadowString(linear)->latin1LinearChars();
}
/**
* Given a linear string known to use two-byte storage, return a pointer to that
* storage. This pointer remains valid only as long as no GC occurs.
*/
MOZ_ALWAYS_INLINE const char16_t* GetTwoByteLinearStringChars(
const AutoRequireNoGC& nogc, JSLinearString* linear) {
return shadow::AsShadowString(linear)->twoByteLinearChars();
}
/**
* Given an in-range index into the provided string, return the character at
* that index.
*/
MOZ_ALWAYS_INLINE char16_t GetLinearStringCharAt(JSLinearString* linear,
size_t index) {
shadow::String* s = shadow::AsShadowString(linear);
MOZ_ASSERT(index < s->length());
return s->hasLatin1Chars() ? s->latin1LinearChars()[index]
: s->twoByteLinearChars()[index];
}
/**
* Convert an atom to a linear string. All atoms are linear, so this
* operation is infallible.
*/
MOZ_ALWAYS_INLINE JSLinearString* AtomToLinearString(JSAtom* atom) {
return reinterpret_cast<JSLinearString*>(atom);
}
/**
* If the provided string uses externally-managed storage, return true and set
* |*callbacks| to the external-string callbacks used to create it and |*chars|
* to a pointer to its two-byte storage. (These pointers remain valid as long
* as the provided string is kept alive.)
*/
MOZ_ALWAYS_INLINE bool IsExternalString(
JSString* str, const JSExternalStringCallbacks** callbacks,
const char16_t** chars) {
shadow::String* s = shadow::AsShadowString(str);
if (!s->isExternal()) {
return false;
}
*callbacks = s->externalCallbacks;
*chars = s->nonInlineCharsTwoByte;
return true;
}
namespace detail {
extern JS_FRIEND_API JSLinearString* StringToLinearStringSlow(JSContext* cx,
JSString* str);
} // namespace detail
/** Convert a string to a linear string. */
MOZ_ALWAYS_INLINE JSLinearString* StringToLinearString(JSContext* cx,
JSString* str) {
if (MOZ_LIKELY(shadow::AsShadowString(str)->isLinear())) {
return reinterpret_cast<JSLinearString*>(str);
}
return detail::StringToLinearStringSlow(cx, str);
}
/** Copy characters in |s[start..start + len]| to |dest[0..len]|. */
MOZ_ALWAYS_INLINE void CopyLinearStringChars(char16_t* dest, JSLinearString* s,
size_t len, size_t start = 0) {
#ifdef DEBUG
size_t stringLen = GetLinearStringLength(s);
MOZ_ASSERT(start <= stringLen);
MOZ_ASSERT(len <= stringLen - start);
#endif
shadow::String* str = shadow::AsShadowString(s);
if (str->hasLatin1Chars()) {
const Latin1Char* src = str->latin1LinearChars();
for (size_t i = 0; i < len; i++) {
dest[i] = src[start + i];
}
} else {
const char16_t* src = str->twoByteLinearChars();
std::copy_n(src + start, len, dest);
}
}
/**
* Copy characters in |s[start..start + len]| to |dest[0..len]|, lossily
* truncating 16-bit values to |char| if necessary.
*/
MOZ_ALWAYS_INLINE void LossyCopyLinearStringChars(char* dest, JSLinearString* s,
size_t len,
size_t start = 0) {
#ifdef DEBUG
size_t stringLen = GetLinearStringLength(s);
MOZ_ASSERT(start <= stringLen);
MOZ_ASSERT(len <= stringLen - start);
#endif
shadow::String* str = shadow::AsShadowString(s);
if (LinearStringHasLatin1Chars(s)) {
const Latin1Char* src = str->latin1LinearChars();
for (size_t i = 0; i < len; i++) {
dest[i] = char(src[start + i]);
}
} else {
const char16_t* src = str->twoByteLinearChars();
for (size_t i = 0; i < len; i++) {
dest[i] = char(src[start + i]);
}
}
}
/**
* Copy characters in |s[start..start + len]| to |dest[0..len]|.
*
* This function is fallible. If you already have a linear string, use the
* infallible |JS::CopyLinearStringChars| above instead.
*/
inline MOZ_MUST_USE bool CopyStringChars(JSContext* cx, char16_t* dest,
JSString* s, size_t len,
size_t start = 0) {
JSLinearString* linear = StringToLinearString(cx, s);
if (!linear) {
return false;
}
CopyLinearStringChars(dest, linear, len, start);
return true;
}
/**
* Copy characters in |s[start..start + len]| to |dest[0..len]|, lossily
* truncating 16-bit values to |char| if necessary.
*
* This function is fallible. If you already have a linear string, use the
* infallible |JS::LossyCopyLinearStringChars| above instead.
*/
inline MOZ_MUST_USE bool LossyCopyStringChars(JSContext* cx, char* dest,
JSString* s, size_t len,
size_t start = 0) {
JSLinearString* linear = StringToLinearString(cx, s);
if (!linear) {
return false;
}
LossyCopyLinearStringChars(dest, linear, len, start);
return true;
}
} // namespace JS
/** DO NOT USE, only present for Rust bindings as a temporary hack */
[[deprecated]] extern JS_PUBLIC_API bool JS_DeprecatedStringHasLatin1Chars(
JSString* str);
#endif // js_String_h
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