public int read(byte[] dst, int offset, int len) throws IOException {
// guard agains buffer overflows
if (len > dst.length - offset) {
throw new IndexOutOfBoundsException(
"Requested lenght "
+ len
+ " exceeds the buffer size "
+ dst.length
+ " from offset "
+ offset);
}
// the buffer is empty
while (oEnd == oPos) {
int iPos = 0;
long toRead = nextSrcSizeToDecompress(ctx);
// Reached end of stream (-1) if there is anything more to read
if (toRead == 0) {
return -1;
}
// Start from the beginning if we have reached the end of the oBuff
if (oBuffSize - oPos < blockSize) {
oPos = 0;
oEnd = 0;
}
// in.read is not guaranteed to return the requested size in one go
while (iPos < toRead) {
long read = in.read(iBuff, iPos, (int) toRead - iPos);
if (read > 0) {
iPos += read;
} else {
throw new IOException("Read error or truncated source");
}
}
// Decode
long decoded = decompressContinue(ctx, oBuff, oPos, oBuffSize - oPos, iBuff, iPos);
if (Zstd.isError(decoded)) {
throw new IOException("Decode Error: " + Zstd.getErrorName(decoded));
}
oEnd += (int) decoded;
}
// return size is min(requested, available)
int size = Math.min(len, oEnd - oPos);
oBuff.position(oPos);
oBuff.get(dst, offset, size);
oPos += size;
return size;
}
// The main constuctor
public ZstdInputStream(InputStream inStream) throws IOException {
// FilterInputStream constructor
super(inStream);
// create decompression context
ctx = createDCtx();
/* allocate input buffer memory */
iBuff = ByteBuffer.allocate(iBuffSize).array();
if (iBuff == null) {
throw new IOException("Error allocating the input buffer of size " + iBuffSize);
}
long toRead = nextSrcSizeToDecompress(ctx);
// read the header - we need it in order know the size of the output buffer
// in.read is not guaranteed to return the requested size in one go
int iPos = in.read(iBuff, 0, (int) toRead);
// find the size and allocate the output buffer
while (oBuffSize < 0) {
oBuffSize = findOBuffSize(iBuff, iPos);
if (oBuffSize < 0) {
iPos += in.read(iBuff, iPos, -oBuffSize - iPos);
}
}
// allocate the output buffer
oBuff = ByteBuffer.allocateDirect(oBuffSize);
if (oBuff == null) {
throw new IOException("Error allocating the output buffers of size " + oBuffSize);
}
// decode the first frame
long decoded = decompressContinue(ctx, oBuff, oPos, oBuffSize - oPos, iBuff, iPos);
if (Zstd.isError(decoded)) {
throw new IOException("Decode Error: " + Zstd.getErrorName(decoded));
}
oEnd += (int) decoded;
}