runtime/native/libcore_util_CharsetUtils.cc

/*
 * Copyright (C) 2010 The Android Open Source Project
 *
 * Licensed under the Apache License, Version 2.0 (the "License");
 * you may not use this file except in compliance with the License.
 * You may obtain a copy of the License at
 *
 *      http://www.apache.org/licenses/LICENSE-2.0
 *
 * Unless required by applicable law or agreed to in writing, software
 * distributed under the License is distributed on an "AS IS" BASIS,
 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
 * See the License for the specific language governing permissions and
 * limitations under the License.
 */

#include "libcore_util_CharsetUtils.h"

#include <string.h>

#include "jni_internal.h"
#include "mirror/string-inl.h"
#include "mirror/string.h"
#include "native_util.h"
#include "nativehelper/scoped_primitive_array.h"
#include "nativehelper/jni_macros.h"
#include "scoped_fast_native_object_access-inl.h"
#include "unicode/utf16.h"

namespace art {

/**
 * Approximates java.lang.UnsafeByteSequence so we don't have to pay the cost of calling back into
 * Java when converting a char[] to a UTF-8 byte[]. This lets us have UTF-8 conversions slightly
 * faster than ICU for large char[]s without paying for the NIO overhead with small char[]s.
 *
 * We could avoid this by keeping the UTF-8 bytes on the native heap until we're done and only
 * creating a byte[] on the Java heap when we know how big it needs to be, but one shouldn't lie
 * to the garbage collector (nor hide potentially large allocations from it).
 *
 * Because a call to append might require an allocation, it might fail. Callers should always
 * check the return value of append.
 */
class NativeUnsafeByteSequence {
 public:
  explicit NativeUnsafeByteSequence(JNIEnv* env)
    : mEnv(env), mJavaArray(nullptr), mRawArray(nullptr), mSize(-1), mOffset(0) {
  }

  ~NativeUnsafeByteSequence() {
    // Release our pointer to the raw array, copying changes back to the Java heap.
    if (mRawArray != nullptr) {
      mEnv->ReleaseByteArrayElements(mJavaArray, mRawArray, 0);
    }
  }

  bool append(jbyte b) {
    if (mOffset == mSize && !resize(mSize * 2)) {
      return false;
    }
    mRawArray[mOffset++] = b;
    return true;
  }

  bool resize(int newSize) {
    if (newSize == mSize) {
      return true;
    }

    // Allocate a new array.
    jbyteArray newJavaArray = mEnv->NewByteArray(newSize);
    if (newJavaArray == nullptr) {
      return false;
    }
    jbyte* newRawArray = mEnv->GetByteArrayElements(newJavaArray, nullptr);
    if (newRawArray == nullptr) {
      return false;
    }

    // Copy data out of the old array and then let go of it.
    // Note that we may be trimming the array.
    if (mRawArray != nullptr) {
      memcpy(newRawArray, mRawArray, mOffset);
      mEnv->ReleaseByteArrayElements(mJavaArray, mRawArray, JNI_ABORT);
      mEnv->DeleteLocalRef(mJavaArray);
    }

    // Point ourselves at the new array.
    mJavaArray = newJavaArray;
    mRawArray = newRawArray;
    mSize = newSize;
    return true;
  }

  jbyteArray toByteArray() {
    // Trim any unused space, if necessary.
    bool okay = resize(mOffset);
    return okay ? mJavaArray : nullptr;
  }

 private:
  JNIEnv* mEnv;
  jbyteArray mJavaArray;
  jbyte* mRawArray;
  jint mSize;
  jint mOffset;

  // Disallow copy and assignment.
  NativeUnsafeByteSequence(const NativeUnsafeByteSequence&);
  void operator=(const NativeUnsafeByteSequence&);
};

static void CharsetUtils_asciiBytesToChars(JNIEnv* env, jclass, jbyteArray javaBytes, jint offset,
                                           jint length, jcharArray javaChars) {
  ScopedByteArrayRO bytes(env, javaBytes);
  if (bytes.get() == nullptr) {
    return;
  }
  ScopedCharArrayRW chars(env, javaChars);
  if (chars.get() == nullptr) {
    return;
  }

  const jbyte* src = &bytes[offset];
  jchar* dst = &chars[0];
  static const jchar REPLACEMENT_CHAR = 0xfffd;
  for (int i = length - 1; i >= 0; --i) {
    jchar ch = static_cast<jchar>(*src++ & 0xff);
    *dst++ = (ch <= 0x7f) ? ch : REPLACEMENT_CHAR;
  }
}

static void CharsetUtils_isoLatin1BytesToChars(JNIEnv* env, jclass, jbyteArray javaBytes,
                                               jint offset, jint length, jcharArray javaChars) {
  ScopedByteArrayRO bytes(env, javaBytes);
  if (bytes.get() == nullptr) {
    return;
  }
  ScopedCharArrayRW chars(env, javaChars);
  if (chars.get() == nullptr) {
    return;
  }

  const jbyte* src = &bytes[offset];
  jchar* dst = &chars[0];
  for (int i = length - 1; i >= 0; --i) {
    *dst++ = static_cast<jchar>(*src++ & 0xff);
  }
}

/**
 * Translates the given characters to US-ASCII or ISO-8859-1 bytes, using the fact that
 * Unicode code points between U+0000 and U+007f inclusive are identical to US-ASCII, while
 * U+0000 to U+00ff inclusive are identical to ISO-8859-1.
 */
static jbyteArray charsToBytes(JNIEnv* env, jstring java_string, jint offset, jint length,
                               jchar maxValidChar) {
  ScopedObjectAccess soa(env);
  StackHandleScope<1> hs(soa.Self());
  Handle<mirror::String> string(hs.NewHandle(soa.Decode<mirror::String>(java_string)));
  if (string == nullptr) {
    return nullptr;
  }

  jbyteArray javaBytes = env->NewByteArray(length);
  ScopedByteArrayRW bytes(env, javaBytes);
  if (bytes.get() == nullptr) {
    return nullptr;
  }

  jbyte* dst = &bytes[0];
  for (int i = 0; i < length; ++i) {
    jchar ch = string->CharAt(offset + i);
    if (ch > maxValidChar) {
      ch = '?';
    }
    *dst++ = static_cast<jbyte>(ch);
  }

  return javaBytes;
}

static jbyteArray CharsetUtils_toAsciiBytes(JNIEnv* env, jclass, jstring java_string, jint offset,
                                            jint length) {
    return charsToBytes(env, java_string, offset, length, 0x7f);
}

static jbyteArray CharsetUtils_toIsoLatin1Bytes(JNIEnv* env, jclass, jstring java_string,
                                                jint offset, jint length) {
    return charsToBytes(env, java_string, offset, length, 0xff);
}

static jbyteArray CharsetUtils_toUtf8Bytes(JNIEnv* env, jclass, jstring java_string, jint offset,
                                           jint length) {
  ScopedObjectAccess soa(env);
  StackHandleScope<1> hs(soa.Self());
  Handle<mirror::String> string(hs.NewHandle(soa.Decode<mirror::String>(java_string)));
  if (string == nullptr) {
    return nullptr;
  }

  NativeUnsafeByteSequence out(env);
  if (!out.resize(length)) {
    return nullptr;
  }

  const int end = offset + length;
  for (int i = offset; i < end; ++i) {
    jint ch = string->CharAt(i);
    if (ch < 0x80) {
      // One byte.
      if (!out.append(ch)) {
        return nullptr;
      }
    } else if (ch < 0x800) {
      // Two bytes.
      if (!out.append((ch >> 6) | 0xc0) || !out.append((ch & 0x3f) | 0x80)) {
        return nullptr;
      }
    } else if (U16_IS_SURROGATE(ch)) {
      // A supplementary character.
      jchar high = static_cast<jchar>(ch);
      jchar low = (i + 1 != end) ? string->CharAt(i + 1) : 0;
      if (!U16_IS_SURROGATE_LEAD(high) || !U16_IS_SURROGATE_TRAIL(low)) {
        if (!out.append('?')) {
          return nullptr;
        }
        continue;
      }
      // Now we know we have a *valid* surrogate pair, we can consume the low surrogate.
      ++i;
      ch = U16_GET_SUPPLEMENTARY(high, low);
      // Four bytes.
      jbyte b1 = (ch >> 18) | 0xf0;
      jbyte b2 = ((ch >> 12) & 0x3f) | 0x80;
      jbyte b3 = ((ch >> 6) & 0x3f) | 0x80;
      jbyte b4 = (ch & 0x3f) | 0x80;
      if (!out.append(b1) || !out.append(b2) || !out.append(b3) || !out.append(b4)) {
        return nullptr;
      }
    } else {
      // Three bytes.
      jbyte b1 = (ch >> 12) | 0xe0;
      jbyte b2 = ((ch >> 6) & 0x3f) | 0x80;
      jbyte b3 = (ch & 0x3f) | 0x80;
      if (!out.append(b1) || !out.append(b2) || !out.append(b3)) {
        return nullptr;
      }
    }
  }
  return out.toByteArray();
}

static JNINativeMethod gMethods[] = {
  FAST_NATIVE_METHOD(CharsetUtils, asciiBytesToChars, "([BII[C)V"),
  FAST_NATIVE_METHOD(CharsetUtils, isoLatin1BytesToChars, "([BII[C)V"),
  FAST_NATIVE_METHOD(CharsetUtils, toAsciiBytes, "(Ljava/lang/String;II)[B"),
  FAST_NATIVE_METHOD(CharsetUtils, toIsoLatin1Bytes, "(Ljava/lang/String;II)[B"),
  FAST_NATIVE_METHOD(CharsetUtils, toUtf8Bytes, "(Ljava/lang/String;II)[B"),
};

void register_libcore_util_CharsetUtils(JNIEnv* env) {
  REGISTER_NATIVE_METHODS("libcore/util/CharsetUtils");
}

}  // namespace art