string_bytes.cc

// Copyright Joyent, Inc. and other Node contributors.
//
// Permission is hereby granted, free of charge, to any person obtaining a
// copy of this software and associated documentation files (the
// "Software"), to deal in the Software without restriction, including
// without limitation the rights to use, copy, modify, merge, publish,
// distribute, sublicense, and/or sell copies of the Software, and to permit
// persons to whom the Software is furnished to do so, subject to the
// following conditions:
//
// The above copyright notice and this permission notice shall be included
// in all copies or substantial portions of the Software.
//
// THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS
// OR IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF
// MERCHANTABILITY, FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN
// NO EVENT SHALL THE AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM,
// DAMAGES OR OTHER LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR
// OTHERWISE, ARISING FROM, OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE
// USE OR OTHER DEALINGS IN THE SOFTWARE.

#include "string_bytes.h"

#include "env-inl.h"
#include "nbytes.h"
#include "node_buffer.h"
#include "node_errors.h"
#include "simdutf.h"
#include "util.h"
#include "v8-external-memory-accounter.h"

#include <climits>
#include <cstring> // memcpy

#include <algorithm>

// When creating strings >= this length v8's gc spins up and consumes
// most of the execution time. For these cases it's more performant to
// use external string resources.
#define EXTERN_APEX 0xFBEE9

namespace node {

using v8::ExternalMemoryAccounter;
using v8::HandleScope;
using v8::Isolate;
using v8::Just;
using v8::Local;
using v8::Maybe;
using v8::MaybeLocal;
using v8::Nothing;
using v8::String;
using v8::Value;

namespace {

template <typename ResourceType, typename TypeName>
class ExternString: public ResourceType {
 public:
 ~ExternString() override {
 free(const_cast<TypeName*>(data_));
 external_memory_accounter_->Decrease(isolate(), byte_length());
 delete external_memory_accounter_;
 }

 const TypeName* data() const override {
 return data_;
 }

 size_t length() const override {
 return length_;
 }

 size_t byte_length() const { return length() * sizeof(*data()); }

 static MaybeLocal<Value> NewFromCopy(Isolate* isolate,
 const TypeName* data,
 size_t length) {
 if (length == 0) {
 return String::Empty(isolate);
 }

 if (length < EXTERN_APEX) {
 return NewSimpleFromCopy(isolate, data, length);
 }

 TypeName* new_data = node::UncheckedMalloc<TypeName>(length);
 if (new_data == nullptr) {
 isolate->ThrowException(node::ERR_MEMORY_ALLOCATION_FAILED(isolate));
 return MaybeLocal<Value>();
 }
 memcpy(new_data, data, length * sizeof(*new_data));

 return ExternString<ResourceType, TypeName>::New(isolate, new_data, length);
 }

 // uses "data" for external resource, and will be free'd on gc
 static MaybeLocal<Value> New(Isolate* isolate,
 TypeName* data,
 size_t length) {
 if (length == 0)
 return String::Empty(isolate);

 if (length < EXTERN_APEX) {
 MaybeLocal<Value> str = NewSimpleFromCopy(isolate, data, length);
 free(data);
 return str;
 }

 ExternString* h_str = new ExternString<ResourceType, TypeName>(isolate,
 data,
 length);
 Local<Value> str;

 if (!NewExternal(isolate, h_str).ToLocal(&str)) {
 delete h_str;
 isolate->ThrowException(node::ERR_STRING_TOO_LONG(isolate));
 return MaybeLocal<Value>();
 }

 return str;
 }

 inline Isolate* isolate() const { return isolate_; }

 private:
 ExternString(Isolate* isolate, const TypeName* data, size_t length)
 : isolate_(isolate),
 external_memory_accounter_(new ExternalMemoryAccounter()),
 data_(data),
 length_(length) {
 external_memory_accounter_->Increase(isolate, byte_length());
 }
 static MaybeLocal<Value> NewExternal(Isolate* isolate,
 ExternString* h_str);

 // This method does not actually create ExternString instances.
 static MaybeLocal<Value> NewSimpleFromCopy(Isolate* isolate,
 const TypeName* data,
 size_t length);

 Isolate* isolate_;
 ExternalMemoryAccounter* external_memory_accounter_;
 const TypeName* data_;
 size_t length_;
};

typedef ExternString<String::ExternalOneByteStringResource, char>
 ExternOneByteString;
typedef ExternString<String::ExternalStringResource, uint16_t>
 ExternTwoByteString;

template <typename EncodeFn>
static MaybeLocal<Value> EncodeOneByteString(Isolate* isolate,
 size_t length,
 EncodeFn encode) {
 // 512B stack threshold: covers common small outputs (hex SHA-256/512, UUIDs).
 // Larger thresholds were benchmarked
 MaybeStackBuffer<char, 512> buf(length);
 encode(buf.out());
 // Copy stack-backed data, but release heap-backed storage to V8.
 if (buf.IsAllocated()) {
 char* data = buf.out();
 buf.Release();
 return ExternOneByteString::New(isolate, data, length);
 }
 return String::NewFromOneByte(isolate,
 reinterpret_cast<const uint8_t*>(buf.out()),
 v8::NewStringType::kNormal,
 static_cast<int>(length));
}

template <typename EncodeFn>
static MaybeLocal<Value> EncodeTwoByteString(Isolate* isolate,
 size_t char_length,
 EncodeFn encode) {
 // 256 uint16_t = 512 bytes on the stack, matching the one-byte
 MaybeStackBuffer<uint16_t, 256> buf(char_length);
 encode(buf.out());
 // Copy stack-backed data, but release heap-backed storage to V8.
 if (buf.IsAllocated()) {
 uint16_t* data = buf.out();
 buf.Release();
 return ExternTwoByteString::New(isolate, data, char_length);
 }
 return String::NewFromTwoByte(isolate,
 buf.out(),
 v8::NewStringType::kNormal,
 static_cast<int>(char_length));
}

template <>
MaybeLocal<Value> ExternOneByteString::NewExternal(
 Isolate* isolate, ExternOneByteString* h_str) {
 return String::NewExternalOneByte(isolate, h_str).FromMaybe(Local<Value>());
}


template <>
MaybeLocal<Value> ExternTwoByteString::NewExternal(
 Isolate* isolate, ExternTwoByteString* h_str) {
 return String::NewExternalTwoByte(isolate, h_str).FromMaybe(Local<Value>());
}

template <>
MaybeLocal<Value> ExternOneByteString::NewSimpleFromCopy(Isolate* isolate,
 const char* data,
 size_t length) {
 Local<String> str;
 if (!String::NewFromOneByte(isolate,
 reinterpret_cast<const uint8_t*>(data),
 v8::NewStringType::kNormal,
 length)
 .ToLocal(&str)) {
 isolate->ThrowException(node::ERR_STRING_TOO_LONG(isolate));
 return MaybeLocal<Value>();
 }
 return str;
}

template <>
MaybeLocal<Value> ExternTwoByteString::NewSimpleFromCopy(Isolate* isolate,
 const uint16_t* data,
 size_t length) {
 Local<String> str;
 if (!String::NewFromTwoByte(isolate, data, v8::NewStringType::kNormal, length)
 .ToLocal(&str)) {
 isolate->ThrowException(node::ERR_STRING_TOO_LONG(isolate));
 return MaybeLocal<Value>();
 }
 return str;
}

} // anonymous namespace

static size_t keep_buflen_in_range(size_t len) {
 if (len > static_cast<size_t>(std::numeric_limits<int>::max())) {
 return static_cast<size_t>(std::numeric_limits<int>::max());
 }
 return len;
}

size_t StringBytes::WriteUCS2(Isolate* isolate,
 char* buf,
 size_t buflen,
 Local<String> str) {
 uint16_t* const dst = reinterpret_cast<uint16_t*>(buf);

 const size_t max_chars = buflen / sizeof(*dst);
 const size_t nchars = std::min(max_chars, static_cast<size_t>(str->Length()));
 if (nchars == 0) {
 return 0;
 }

 uint16_t* const aligned_dst = nbytes::AlignUp(dst, sizeof(*dst));
 CHECK_EQ(reinterpret_cast<uintptr_t>(aligned_dst) % sizeof(*dst), 0);
 if (aligned_dst == dst) {
 str->WriteV2(isolate, 0, nchars, dst);
 } else {
 // Write all but the last char.
 str->WriteV2(isolate, 0, nchars - 1, aligned_dst);

 // Shift everything to unaligned-left.
 memmove(dst, aligned_dst, (nchars - 1) * sizeof(*dst));

 // One more char to be written.
 uint16_t last;
 str->WriteV2(isolate, nchars - 1, 1, &last);
 memcpy(dst + nchars - 1, &last, sizeof(last));
 }

 return nchars * sizeof(*dst);
}

size_t StringBytes::Write(Isolate* isolate,
 char* buf,
 size_t buflen,
 Local<Value> val,
 enum encoding encoding) {
 HandleScope scope(isolate);
 size_t nbytes;
 buflen = keep_buflen_in_range(buflen);
 CHECK(val->IsString() == true);
 Local<String> str = val.As<String>();
 String::ValueView input_view(isolate, str);

 switch (encoding) {
 case ASCII:
 case LATIN1:
 if (input_view.is_one_byte()) {
 nbytes = std::min(buflen, static_cast<size_t>(input_view.length()));
 memcpy(buf, input_view.data8(), nbytes);
 } else {
 nbytes = std::min(buflen, static_cast<size_t>(input_view.length()));
 // Do not use v8::String::WriteOneByteV2 as it asserts the string to be
 // a one byte string. For compatibility, convert the uint16_t to uint8_t
 // even though this may loose accuracy.
 for (size_t i = 0; i < nbytes; i++) {
 buf[i] = static_cast<uint8_t>(input_view.data16()[i]);
 }
 }
 break;

 case BUFFER:
 case UTF8:
 if (input_view.is_one_byte()) {
 // Use simdutf for one-byte strings instead of V8's WriteUtf8V2.
 nbytes = simdutf::convert_latin1_to_utf8_safe(
 reinterpret_cast<const char*>(input_view.data8()),
 input_view.length(),
 buf,
 buflen);
 } else {
 nbytes = str->WriteUtf8V2(
 isolate, buf, buflen, String::WriteFlags::kReplaceInvalidUtf8);
 }
 break;

 case UCS2: {
 nbytes = WriteUCS2(isolate, buf, buflen, str);

 // Node's "ucs2" encoding wants LE character data stored in
 // the Buffer, so we need to reorder on BE platforms. See
 // https://nodejs.org/api/buffer.html regarding Node's "ucs2"
 // encoding specification
 if constexpr (IsBigEndian()) CHECK(nbytes::SwapBytes16(buf, nbytes));

 break;
 }

 case BASE64URL:
 if (input_view.is_one_byte()) { // 8-bit case
 size_t written_len = buflen;
 auto result = simdutf::base64_to_binary_safe(
 reinterpret_cast<const char*>(input_view.data8()),
 input_view.length(),
 buf,
 written_len,
 simdutf::base64_url);
 if (result.error == simdutf::error_code::SUCCESS) {
 nbytes = written_len;
 } else {
 // The input does not follow the WHATWG forgiving-base64 specification
 // (adapted for base64url with + and / replaced by - and _).
 // https://infra.spec.whatwg.org/#forgiving-base64-decode
 nbytes = nbytes::Base64Decode(
 buf,
 buflen,
 reinterpret_cast<const char*>(input_view.data8()),
 input_view.length());
 }
 } else {
 TwoByteValue value(isolate, str);
 size_t written_len = buflen;
 auto result = simdutf::base64_to_binary_safe(
 reinterpret_cast<const char16_t*>(value.out()),
 value.length(),
 buf,
 written_len,
 simdutf::base64_url);
 if (result.error == simdutf::error_code::SUCCESS) {
 nbytes = written_len;
 } else {
 // The input does not follow the WHATWG forgiving-base64 specification
 // (adapted for base64url with + and / replaced by - and _).
 // https://infra.spec.whatwg.org/#forgiving-base64-decode
 nbytes = nbytes::Base64Decode(buf, buflen, *value, value.length());
 }
 }
 break;

 case BASE64: {
 if (input_view.is_one_byte()) { // 8-bit case
 size_t written_len = buflen;
 auto result = simdutf::base64_to_binary_safe(
 reinterpret_cast<const char*>(input_view.data8()),
 input_view.length(),
 buf,
 written_len);
 if (result.error == simdutf::error_code::SUCCESS) {
 nbytes = written_len;
 } else {
 // The input does not follow the WHATWG forgiving-base64 specification
 // https://infra.spec.whatwg.org/#forgiving-base64-decode
 nbytes = nbytes::Base64Decode(
 buf,
 buflen,
 reinterpret_cast<const char*>(input_view.data8()),
 input_view.length());
 }
 } else {
 TwoByteValue value(isolate, str);
 size_t written_len = buflen;
 auto result = simdutf::base64_to_binary_safe(
 reinterpret_cast<const char16_t*>(value.out()),
 value.length(),
 buf,
 written_len);
 if (result.error == simdutf::error_code::SUCCESS) {
 nbytes = written_len;
 } else {
 // The input does not follow the WHATWG base64 specification
 // https://infra.spec.whatwg.org/#forgiving-base64-decode
 nbytes = nbytes::Base64Decode(buf, buflen, *value, value.length());
 }
 }
 break;
 }
 case HEX:
 if (input_view.is_one_byte()) {
 nbytes =
 nbytes::HexDecode(buf,
 buflen,
 reinterpret_cast<const char*>(input_view.data8()),
 input_view.length());
 } else {
 TwoByteValue value(isolate, str);
 nbytes = nbytes::HexDecode(buf, buflen, value.out(), value.length());
 }
 break;

 default:
 UNREACHABLE("unknown encoding");
 }

 return nbytes;
}

// Quick and dirty size calculation
// Will always be at least big enough, but may have some extra
// UTF8 can be as much as 3x the size, Base64 can have 1-2 extra bytes
Maybe<size_t> StringBytes::StorageSize(Isolate* isolate,
 Local<Value> val,
 enum encoding encoding) {
 HandleScope scope(isolate);

 if (Buffer::HasInstance(val) && (encoding == BUFFER || encoding == LATIN1)) {
 return Just(Buffer::Length(val));
 }

 Local<String> str;
 if (!val->ToString(isolate->GetCurrentContext()).ToLocal(&str))
 return Nothing<size_t>();
 String::ValueView view(isolate, str);
 size_t data_size = 0;

 switch (encoding) {
 case ASCII:
 case LATIN1:
 data_size = view.length();
 break;

 case BUFFER:
 case UTF8:
 // A single UCS2 codepoint never takes up more than 3 utf8 bytes.
 // It is an exercise for the caller to decide when a string is
 // long enough to justify calling Size() instead of StorageSize()
 data_size = 3 * view.length();
 break;

 case UCS2:
 data_size = view.length() * sizeof(uint16_t);
 break;

 case BASE64URL:
 data_size = simdutf::base64_length_from_binary(view.length(),
 simdutf::base64_url);
 break;

 case BASE64:
 data_size = simdutf::base64_length_from_binary(view.length());
 break;

 case HEX:
 data_size = view.length() / 2;
 break;

 default:
 UNREACHABLE("unknown encoding");
 }

 return Just(data_size);
}

Maybe<size_t> StringBytes::Size(Isolate* isolate,
 Local<Value> val,
 enum encoding encoding) {
 HandleScope scope(isolate);

 if (Buffer::HasInstance(val) && (encoding == BUFFER || encoding == LATIN1))
 return Just(Buffer::Length(val));

 Local<String> str;
 if (!val->ToString(isolate->GetCurrentContext()).ToLocal(&str))
 return Nothing<size_t>();
 String::ValueView view(isolate, str);

 switch (encoding) {
 case ASCII:
 case LATIN1:
 return Just<size_t>(view.length());

 case BUFFER:
 case UTF8:
 if (view.is_one_byte()) {
 return Just<size_t>(simdutf::utf8_length_from_latin1(
 reinterpret_cast<const char*>(view.data8()), view.length()));
 }
 return Just<size_t>(simdutf::utf8_length_from_utf16(
 reinterpret_cast<const char16_t*>(view.data16()), view.length()));

 case UCS2:
 return Just(view.length() * sizeof(uint16_t));

 case BASE64URL: {
 return Just(simdutf::base64_length_from_binary(view.length(),
 simdutf::base64_url));
 }

 case BASE64: {
 return Just(simdutf::base64_length_from_binary(view.length()));
 }

 case HEX:
 return Just<size_t>(view.length() / 2);
 }

 UNREACHABLE();
}

#define CHECK_BUFLEN_IN_RANGE(len) \
 do { \
 if ((len) > Buffer::kMaxLength) { \
 isolate->ThrowException(node::ERR_BUFFER_TOO_LARGE(isolate)); \
 return MaybeLocal<Value>(); \
 } \
 } while (0)

MaybeLocal<Value> StringBytes::Encode(Isolate* isolate,
 const char* buf,
 size_t buflen,
 enum encoding encoding) {
 CHECK_BUFLEN_IN_RANGE(buflen);

 if (!buflen && encoding != BUFFER) {
 return String::Empty(isolate);
 }

 MaybeLocal<String> val;

 switch (encoding) {
 case BUFFER:
 {
 auto maybe_buf = Buffer::Copy(isolate, buf, buflen);
 Local<v8::Object> buf;
 if (!maybe_buf.ToLocal(&buf)) {
 isolate->ThrowException(node::ERR_MEMORY_ALLOCATION_FAILED(isolate));
 }
 return buf;
 }

 case ASCII:
 buflen = keep_buflen_in_range(buflen);
 if (simdutf::validate_ascii_with_errors(buf, buflen).error) {
 // The input contains non-ASCII bytes.

 return EncodeOneByteString(isolate, buflen, [buf, buflen](char* dst) {
 nbytes::ForceAscii(buf, dst, buflen);
 });
 } else {
 return ExternOneByteString::NewFromCopy(isolate, buf, buflen);
 }

 case UTF8: {
 buflen = keep_buflen_in_range(buflen);

 // ASCII fast path
 // TODO(chalker): remove when String::NewFromUtf8 is fast enough itself
 // This is cheap compared to the benefits though
 if (!simdutf::validate_ascii_with_errors(buf, buflen).error) {
 return ExternOneByteString::NewFromCopy(isolate, buf, buflen);
 }

 // Latin1-fits fast path: one-byte V8 string, half the heap of UTF-16.
 // Capped at 1 MiB (above that the prescan cost erases the win).
 constexpr size_t kLatin1Max = 1u << 20;
 if (buflen >= 256 && buflen <= kLatin1Max) {
 // Skip the allocation when any byte >= 0xC4 (UTF-8 lead for a
 // codepoint > U+FF). Inner loop has no early exit so clang
 // vectorizes it.
 constexpr size_t kChunk = 64;
 bool maybe_latin1 = true;
 size_t i = 0;
 for (; i + kChunk <= buflen; i += kChunk) {
 uint8_t acc = 0;
 for (size_t j = 0; j < kChunk; j++) {
 acc |= static_cast<uint8_t>(buf[i + j]) >= 0xC4 ? 1 : 0;
 }
 if (acc) {
 maybe_latin1 = false;
 break;
 }
 }
 if (maybe_latin1) {
 for (; i < buflen; i++) {
 if (static_cast<uint8_t>(buf[i]) >= 0xC4) {
 maybe_latin1 = false;
 break;
 }
 }
 }
 if (maybe_latin1) {
 MaybeStackBuffer<char, 4096> latin1;
 latin1.AllocateSufficientStorage(buflen);
 simdutf::result l1 = simdutf::convert_utf8_to_latin1_with_errors(
 buf, buflen, latin1.out());
 if (l1.error == simdutf::error_code::SUCCESS) {
 return ExternOneByteString::NewFromCopy(
 isolate, latin1.out(), l1.count);
 }
 }
 }

 if (buflen >= 32) {
 // Single-pass UTF-16: over-allocate (1 char16_t per byte), then
 // shrink. Above 1 MiB the exact-size 3-pass below is cheaper.
 constexpr size_t kSinglePassMax = 1u << 20;
 if (buflen <= kSinglePassMax) {
 MaybeStackBuffer<uint16_t, 256> u16;
 u16.AllocateSufficientStorage(buflen);
 simdutf::result r = simdutf::convert_utf8_to_utf16_with_errors(
 buf, buflen, reinterpret_cast<char16_t*>(u16.out()));
 if (r.error == simdutf::error_code::SUCCESS) {
 if (r.count > static_cast<size_t>(v8::String::kMaxLength)) {
 isolate->ThrowException(ERR_STRING_TOO_LONG(isolate));
 return MaybeLocal<Value>();
 }
 if (u16.IsAllocated()) {
 uint16_t* data = u16.out();
 u16.Release();
 uint16_t* shrunk = static_cast<uint16_t*>(
 realloc(data, r.count * sizeof(uint16_t)));
 if (shrunk == nullptr) shrunk = data;
 return ExternTwoByteString::New(isolate, shrunk, r.count);
 }
 return String::NewFromTwoByte(isolate,
 u16.out(),
 v8::NewStringType::kNormal,
 static_cast<int>(r.count));
 }
 } else if (simdutf::validate_utf8(buf, buflen)) {
 size_t u16size = simdutf::utf16_length_from_utf8(buf, buflen);
 if (u16size > static_cast<size_t>(v8::String::kMaxLength)) {
 isolate->ThrowException(ERR_STRING_TOO_LONG(isolate));
 return MaybeLocal<Value>();
 }
 return EncodeTwoByteString(
 isolate, u16size, [buf, buflen, u16size](uint16_t* dst) {
 size_t written = simdutf::convert_valid_utf8_to_utf16(
 buf, buflen, reinterpret_cast<char16_t*>(dst));
 CHECK_EQ(written, u16size);
 });
 }
 }

 val =
 String::NewFromUtf8(isolate, buf, v8::NewStringType::kNormal, buflen);
 Local<String> str;
 if (!val.ToLocal(&str)) {
 isolate->ThrowException(node::ERR_STRING_TOO_LONG(isolate));
 }
 return str;
 }

 case LATIN1:
 buflen = keep_buflen_in_range(buflen);
 return ExternOneByteString::NewFromCopy(isolate, buf, buflen);

 case BASE64: {
 buflen = keep_buflen_in_range(buflen);
 size_t dlen = simdutf::base64_length_from_binary(buflen);
 return EncodeOneByteString(isolate, dlen, [buf, buflen, dlen](char* dst) {
 size_t written = simdutf::binary_to_base64(buf, buflen, dst);
 CHECK_EQ(written, dlen);
 });
 }

 case BASE64URL: {
 buflen = keep_buflen_in_range(buflen);
 size_t dlen =
 simdutf::base64_length_from_binary(buflen, simdutf::base64_url);
 return EncodeOneByteString(isolate, dlen, [buf, buflen, dlen](char* dst) {
 size_t written =
 simdutf::binary_to_base64(buf, buflen, dst, simdutf::base64_url);
 CHECK_EQ(written, dlen);
 });
 }

 case HEX: {
 buflen = keep_buflen_in_range(buflen);
 size_t dlen = buflen * 2;
 return EncodeOneByteString(isolate, dlen, [buf, buflen, dlen](char* dst) {
 size_t written = nbytes::HexEncode(buf, buflen, dst, dlen);
 CHECK_EQ(written, dlen);
 });
 }

 case UCS2: {
 buflen = keep_buflen_in_range(buflen);
 size_t str_len = buflen / 2;
 if constexpr (IsBigEndian()) {
 return EncodeTwoByteString(
 isolate, str_len, [buf, str_len](uint16_t* dst) {
 for (size_t i = 0, k = 0; k < str_len; i += 2, k += 1) {
 // The input is in *little endian*, because that's what Node.js
 // expects, so the high byte comes after the low byte.
 const uint8_t hi = static_cast<uint8_t>(buf[i + 1]);
 const uint8_t lo = static_cast<uint8_t>(buf[i + 0]);
 dst[k] = static_cast<uint16_t>(hi) << 8 | lo;
 }
 });
 }
 if (reinterpret_cast<uintptr_t>(buf) % 2 != 0) {
 return EncodeTwoByteString(
 isolate, str_len, [buf, buflen](uint16_t* dst) {
 memcpy(dst, buf, buflen);
 });
 }
 return ExternTwoByteString::NewFromCopy(
 isolate, reinterpret_cast<const uint16_t*>(buf), str_len);
 }

 default:
 UNREACHABLE("unknown encoding");
 }
}

MaybeLocal<Value> StringBytes::EncodeValidUtf8(Isolate* isolate,
 const char* buf,
 size_t buflen) {
 CHECK_BUFLEN_IN_RANGE(buflen);
 if (!buflen) return String::Empty(isolate);
 buflen = keep_buflen_in_range(buflen);

 // ASCII fast path
 if (!simdutf::validate_ascii_with_errors(buf, buflen).error) {
 return ExternOneByteString::NewFromCopy(isolate, buf, buflen);
 }

 if (buflen >= 32) {
 size_t u16size = simdutf::utf16_length_from_utf8(buf, buflen);
 if (u16size > static_cast<size_t>(v8::String::kMaxLength)) {
 isolate->ThrowException(ERR_STRING_TOO_LONG(isolate));
 return MaybeLocal<Value>();
 }
 return EncodeTwoByteString(
 isolate, u16size, [buf, buflen, u16size](uint16_t* dst) {
 size_t written = simdutf::convert_valid_utf8_to_utf16(
 buf, buflen, reinterpret_cast<char16_t*>(dst));
 CHECK_EQ(written, u16size);
 });
 }

 Local<String> str;
 if (!String::NewFromUtf8(isolate, buf, v8::NewStringType::kNormal, buflen)
 .ToLocal(&str)) {
 isolate->ThrowException(node::ERR_STRING_TOO_LONG(isolate));
 }
 return str;
}

MaybeLocal<Value> StringBytes::Encode(Isolate* isolate,
 const uint16_t* buf,
 size_t buflen) {
 if (buflen == 0) return String::Empty(isolate);
 CHECK_BUFLEN_IN_RANGE(buflen);

 // Node's "ucs2" encoding expects LE character data inside a
 // Buffer, so we need to reorder on BE platforms. See
 // https://nodejs.org/api/buffer.html regarding Node's "ucs2"
 // encoding specification
 if constexpr (IsBigEndian()) {
 return EncodeTwoByteString(isolate, buflen, [buf, buflen](uint16_t* dst) {
 size_t nbytes = buflen * sizeof(uint16_t);
 memcpy(dst, buf, nbytes);
 CHECK(nbytes::SwapBytes16(reinterpret_cast<char*>(dst), nbytes));
 });
 } else {
 return ExternTwoByteString::NewFromCopy(isolate, buf, buflen);
 }
}

MaybeLocal<Value> StringBytes::Encode(Isolate* isolate,
 const char* buf,
 enum encoding encoding) {
 const size_t len = strlen(buf);
 return Encode(isolate, buf, len, encoding);
}

} // namespace node