/*

* Copyright (c) Facebook, Inc. and its affiliates.

*

* This source code is licensed under the MIT license found in the

* LICENSE file in the root directory of this source tree.

*/

#include "hermes/Support/UTF16Stream.h"

#include <cstdlib>

#include "llvh/ADT/ArrayRef.h"

#include "llvh/Support/ConvertUTF.h"

#include "llvh/Support/MathExtras.h"

namespace hermes {

/// Number of char16_t in the internal conversion buffer (if UTF8 input).

static constexpr size_t kChunkChars = 1024;

UTF16Stream::UTF16Stream(llvh::ArrayRef<uint8_t> utf8)

: utf8Begin_(utf8.begin()), utf8End_(utf8.end()), storage_(kChunkChars) {

// Exhaust the buffer and refill it.

cur_ = end_ = storage_.end();

}

bool UTF16Stream::refill() {

assert(cur_ == end_ && "cannot refill when data remains");

if (utf8Begin_ == utf8End_) {

// Pass-through mode, or final chunk already converted.

// Either way, there's nothing (more) to convert.

return false;

}

assert(utf8Begin_ && utf8End_ && "must have input to convert");

// Reset the conversion buffer.

cur_ = storage_.begin();

end_ = storage_.end();

auto out = storage_.begin();

// Fast case for any ASCII prefix...

{

int len = std::min(end_ - cur_, utf8End_ - utf8Begin_);

int index = 0;

while (index < len && utf8Begin_[index] < 128) {

out[index] = utf8Begin_[index];

++index;

}

utf8Begin_ += index;

out += index;

}

// ...and call the library for any non-ASCII remainder. Conversion always

// stops at a code point boundary.

llvh::ConversionResult cRes = ConvertUTF8toUTF16(

&utf8Begin_,

utf8End_,

(llvh::UTF16 **)&out,

(llvh::UTF16 *)const_cast<char16_t *>(end_),

llvh::lenientConversion);

if (cRes != llvh::ConversionResult::targetExhausted) {

// Indicate that we have converted the final chunk.

utf8Begin_ = utf8End_;

}

end_ = out;

// Did we actually convert anything?

return cur_ != end_;

}

} // namespace hermes