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channels/Common: only allocate temp buffers for read and write if nec… #49

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channels/Common: only allocate temp buffers for read and write if nec… #49

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27 changes: 19 additions & 8 deletions src/main/java/jnr/enxio/channels/Common.java
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Original file line number Diff line number Diff line change
Expand Up @@ -44,13 +44,19 @@ int getFD() {

int read(ByteBuffer dst) throws IOException {

ByteBuffer buffer = ByteBuffer.allocate(dst.remaining());
int n;
if (!dst.hasArray() && !dst.isDirect()) {
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@huntc huntc Nov 24, 2017 •
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Why do this additional check at all? Why not call Native.read directly with dst. I can't see why the new allocation is required even for non-direct mode. Native.read appears to be agnostic to the type of byte buffer, and if there is something to be done, then the JNI call-site is the best place for those concerns.

ByteBuffer buffer = ByteBuffer.allocate(dst.remaining());

int n = Native.read(_fd, buffer);
n = Native.read(_fd, buffer);

buffer.flip();
buffer.flip();

dst.put(buffer);
} else {
n = Native.read(_fd, dst);
}

dst.put(buffer);

switch (n) {
case 0:
Expand Down Expand Up @@ -92,13 +98,18 @@ long read(ByteBuffer[] dsts, int offset, int length)

int write(ByteBuffer src) throws IOException {

ByteBuffer buffer = ByteBuffer.allocate(src.remaining());
int n;
if (!src.hasArray() && !src.isDirect()) {
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As per my comment for read.

ByteBuffer buffer = ByteBuffer.allocate(src.remaining());

buffer.put(src);
buffer.put(src);
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this is incorrect as per #50 as the src position is updated to limit, which it should be updated by n (bytes written)


buffer.position(0);
buffer.position(0);

int n = Native.write(_fd, buffer);
n = Native.write(_fd, buffer);
} else {
n = Native.write(_fd, src);
}

if (n < 0) {
switch (Native.getLastError()) {
Expand Down