如何将整个输入流读到字节数组?
当前回答
public static byte[] getBytesFromInputStream(InputStream is) throws IOException {
ByteArrayOutputStream os = new ByteArrayOutputStream();
byte[] buffer = new byte[0xFFFF];
for (int len = is.read(buffer); len != -1; len = is.read(buffer)) {
os.write(buffer, 0, len);
}
return os.toByteArray();
}
其他回答
如果您不想使用Apache common -io库,则此代码片段取自sun.misc.IOUtils类。它的速度几乎是使用ByteBuffers的普通实现的两倍:
public static byte[] readFully(InputStream is, int length, boolean readAll)
throws IOException {
byte[] output = {};
if (length == -1) length = Integer.MAX_VALUE;
int pos = 0;
while (pos < length) {
int bytesToRead;
if (pos >= output.length) { // Only expand when there's no room
bytesToRead = Math.min(length - pos, output.length + 1024);
if (output.length < pos + bytesToRead) {
output = Arrays.copyOf(output, pos + bytesToRead);
}
} else {
bytesToRead = output.length - pos;
}
int cc = is.read(output, pos, bytesToRead);
if (cc < 0) {
if (readAll && length != Integer.MAX_VALUE) {
throw new EOFException("Detect premature EOF");
} else {
if (output.length != pos) {
output = Arrays.copyOf(output, pos);
}
break;
}
}
pos += cc;
}
return output;
}
我试图编辑@numan的答案,修复了写垃圾数据,但编辑被拒绝。虽然这段简短的代码并不出色,但我看不到其他更好的答案。以下是我认为最有意义的建议:
ByteArrayOutputStream out = new ByteArrayOutputStream();
byte[] buffer = new byte[1024]; // you can configure the buffer size
int length;
while ((length = in.read(buffer)) != -1) out.write(buffer, 0, length); //copy streams
in.close(); // call this in a finally block
byte[] result = out.toByteArray();
ByteArrayOutputStream不需要关闭。为了可读性,省略了一些结构
Kotlin中的解决方案(当然也可以在Java中工作),其中包括当你知道大小时的两种情况:
fun InputStream.readBytesWithSize(size: Long): ByteArray? {
return when {
size < 0L -> this.readBytes()
size == 0L -> ByteArray(0)
size > Int.MAX_VALUE -> null
else -> {
val sizeInt = size.toInt()
val result = ByteArray(sizeInt)
readBytesIntoByteArray(result, sizeInt)
result
}
}
}
fun InputStream.readBytesIntoByteArray(byteArray: ByteArray,bytesToRead:Int=byteArray.size) {
var offset = 0
while (true) {
val read = this.read(byteArray, offset, bytesToRead - offset)
if (read == -1)
break
offset += read
if (offset >= bytesToRead)
break
}
}
如果您知道大小,那么与其他解决方案相比,它可以节省两倍的内存(在很短的时间内,但仍然可能有用)。这是因为您必须将整个流读到末尾,然后将其转换为字节数组(类似于将数组转换为数组的ArrayList)。
例如,如果你在Android上,你有一些Uri要处理,你可以尝试用这个来获取大小:
fun getStreamLengthFromUri(context: Context, uri: Uri): Long {
context.contentResolver.query(uri, arrayOf(MediaStore.MediaColumns.SIZE), null, null, null)?.use {
if (!it.moveToNext())
return@use
val fileSize = it.getLong(it.getColumnIndex(MediaStore.MediaColumns.SIZE))
if (fileSize > 0)
return fileSize
}
//if you wish, you can also get the file-path from the uri here, and then try to get its size, using this: https://stackoverflow.com/a/61835665/878126
FileUtilEx.getFilePathFromUri(context, uri, false)?.use {
val file = it.file
val fileSize = file.length()
if (fileSize > 0)
return fileSize
}
context.contentResolver.openInputStream(uri)?.use { inputStream ->
if (inputStream is FileInputStream)
return inputStream.channel.size()
else {
var bytesCount = 0L
while (true) {
val available = inputStream.available()
if (available == 0)
break
val skip = inputStream.skip(available.toLong())
if (skip < 0)
break
bytesCount += skip
}
if (bytesCount > 0L)
return bytesCount
}
}
return -1L
}
我知道已经太迟了,但我认为这里有更清晰的解决方案,更易于阅读……
/**
* method converts {@link InputStream} Object into byte[] array.
*
* @param stream the {@link InputStream} Object.
* @return the byte[] array representation of received {@link InputStream} Object.
* @throws IOException if an error occurs.
*/
public static byte[] streamToByteArray(InputStream stream) throws IOException {
byte[] buffer = new byte[1024];
ByteArrayOutputStream os = new ByteArrayOutputStream();
int line = 0;
// read bytes from stream, and store them in buffer
while ((line = stream.read(buffer)) != -1) {
// Writes bytes from byte array (buffer) into output stream.
os.write(buffer, 0, line);
}
stream.close();
os.flush();
os.close();
return os.toByteArray();
}
Java 7及以上版本:
import sun.misc.IOUtils;
...
InputStream in = ...;
byte[] buf = IOUtils.readFully(in, -1, false);
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