Re: casting typed array to java byte[] is it possible?
Hi, Yes, I reproduced the issue with jdk8 (haven't tried graal.js though). Please file bug(s). -Sundar On 12/10/18, 7:29 PM, Paulo Lopes wrote: Interesting enough, with Java>=9 the length is reported correctly, so in the case of: var bb = java.nio.ByteBuffer.allocateDirect(12) var ab = new ArrayBuffer(bb) var ia = new Int8Array(ab) ia.length // prints 12 ab.byteLength // prints 12 This fails now on JDK8 and Graal.js (is Graal.js supposed to allow this? (setting a ByteBuffer as the underlying buffer of a js ArrayBuffer?) I can imagine that for embedded applications this could make sense...
Re: casting typed array to java byte[] is it possible?
Hi Sundar, Yes indeed that helps and it really gets close to my needs, I notice however, if I do that, then: var ia = new Int8Array(ab) ia.length will never have a valid value, it will be zero regardless of the underlying ArrayBuffer, since the property is read only I cannot assign it myself (since I know the size at construction time) either. Trying to specify the size: var bb = java.nio.ByteBuffer.allocateDirect(12) var ab = new ArrayBuffer(bb) var ia = new Int8Array(ab, 0, 12) it's all 8 bit ints so (bytes) fails with: java.lang.RuntimeException: byteOffset + byteLength out of range, byteOffset=0, elementLength=12, bytesPerElement=1 Is this expected? Or can I specify the length somewhere? Also ab.byteLength prints 0 instead of 12... On Fri, 2018-10-12 at 17:34 +0530, Sundararajan Athijegannathan wrote: > Hi Paulo Lopes, > > ArrayBuffer can be created using a nio ByteBuffer. > > // you could create a ByteBuffer in Java & pass > var bb = java.nio.ByteBuffer.allocateDirect(100) > > // create JS ArrayBuffer backed by Java ByteBuffer instance > var ab = new ArrayBuffer(bb) > > var ia = new Int8Array(ab) > ia[0] = 10 > print(bb.get(0)) > > Hope this helps, > -Sundar > > On 12/10/18, 5:04 PM, Paulo Lopes wrote: > > Hi Hannes, > > > > Thanks for the tip, knowing that the convention isn't possible as > > is, are there any alternatives to get the JVM buffer that backs a > > typed array? > > > > I wanted to perform some work on a given buffer and then pass it to > > the JVM for further processing. Having to copy the buffer byte by > > byte will introduce a penalty that kind of defeats the whole > > purpose of using typed arrays to start with. > > > > > > Paulo Lopes > > Principal Software Engineer > > > > > >Original Message > > From: hannes.wallnoe...@oracle.com > > Sent: October 12, 2018 10:10 AM > > To: pmart...@redhat.com > > Cc: nashorn-dev@openjdk.java.net > > Subject: Re: casting typed array to java byte[] is it possible? > > > > Hi Paulo, > > > > Java.to() would be the way to go, but as you found out it does not > > support typed arrays. > > > > What works is to convert the typed array to an ordinary JS array > > and convert to byte[] from there: > > > >Java.to(Array.prototype.slice.call(arr), 'byte[]‘); > > > > That’s obviously not very elegant nor efficient, but it’s the only > > workaround I can think of. > > > > Hannes > > > > > > > Am 11.10.2018 um 20:21 schrieb Paulo Lopes: > > > > > > Hi, > > > > > > I'm trying to handle a case where a Uint8Array is being passed to > > > a > > > method, that has the signature: > > > > > > String encode(byte[]); > > > > > > Sadly nashorn fails with: > > > > > > java.lang.ClassCastException: Cannot cast > > > jdk.nashorn.internal.objects.NativeUint8Array to [B > > > > > > And trying to help the cast with: > > > > > > javaObj.encode(Java.to(arr, 'byte[]')); > > > > > > Does not help either. The documentation on typed arrays is quite > > > scarce > > > so I cannot see how to handle this, does anyone have a clue? > > > > > > Thanks! > > > Paulo > > >
Re: casting typed array to java byte[] is it possible?
Hi Paulo Lopes, ArrayBuffer can be created using a nio ByteBuffer. // you could create a ByteBuffer in Java & pass var bb = java.nio.ByteBuffer.allocateDirect(100) // create JS ArrayBuffer backed by Java ByteBuffer instance var ab = new ArrayBuffer(bb) var ia = new Int8Array(ab) ia[0] = 10 print(bb.get(0)) Hope this helps, -Sundar On 12/10/18, 5:04 PM, Paulo Lopes wrote: Hi Hannes, Thanks for the tip, knowing that the convention isn't possible as is, are there any alternatives to get the JVM buffer that backs a typed array? I wanted to perform some work on a given buffer and then pass it to the JVM for further processing. Having to copy the buffer byte by byte will introduce a penalty that kind of defeats the whole purpose of using typed arrays to start with. Paulo Lopes Principal Software Engineer Original Message From: hannes.wallnoe...@oracle.com Sent: October 12, 2018 10:10 AM To: pmart...@redhat.com Cc: nashorn-dev@openjdk.java.net Subject: Re: casting typed array to java byte[] is it possible? Hi Paulo, Java.to() would be the way to go, but as you found out it does not support typed arrays. What works is to convert the typed array to an ordinary JS array and convert to byte[] from there: Java.to(Array.prototype.slice.call(arr), 'byte[]‘); That’s obviously not very elegant nor efficient, but it’s the only workaround I can think of. Hannes Am 11.10.2018 um 20:21 schrieb Paulo Lopes: Hi, I'm trying to handle a case where a Uint8Array is being passed to a method, that has the signature: String encode(byte[]); Sadly nashorn fails with: java.lang.ClassCastException: Cannot cast jdk.nashorn.internal.objects.NativeUint8Array to [B And trying to help the cast with: javaObj.encode(Java.to(arr, 'byte[]')); Does not help either. The documentation on typed arrays is quite scarce so I cannot see how to handle this, does anyone have a clue? Thanks! Paulo
Re: casting typed array to java byte[] is it possible?
Hi Hannes, Thanks for the tip, knowing that the convention isn't possible as is, are there any alternatives to get the JVM buffer that backs a typed array? I wanted to perform some work on a given buffer and then pass it to the JVM for further processing. Having to copy the buffer byte by byte will introduce a penalty that kind of defeats the whole purpose of using typed arrays to start with. Paulo Lopes Principal Software Engineer Original Message From: hannes.wallnoe...@oracle.com Sent: October 12, 2018 10:10 AM To: pmart...@redhat.com Cc: nashorn-dev@openjdk.java.net Subject: Re: casting typed array to java byte[] is it possible? Hi Paulo, Java.to() would be the way to go, but as you found out it does not support typed arrays. What works is to convert the typed array to an ordinary JS array and convert to byte[] from there: Java.to(Array.prototype.slice.call(arr), 'byte[]‘); That’s obviously not very elegant nor efficient, but it’s the only workaround I can think of. Hannes > Am 11.10.2018 um 20:21 schrieb Paulo Lopes : > > Hi, > > I'm trying to handle a case where a Uint8Array is being passed to a > method, that has the signature: > > String encode(byte[]); > > Sadly nashorn fails with: > > java.lang.ClassCastException: Cannot cast > jdk.nashorn.internal.objects.NativeUint8Array to [B > > And trying to help the cast with: > > javaObj.encode(Java.to(arr, 'byte[]')); > > Does not help either. The documentation on typed arrays is quite scarce > so I cannot see how to handle this, does anyone have a clue? > > Thanks! > Paulo >
Re: casting typed array to java byte[] is it possible?
Hi Paulo, Java.to() would be the way to go, but as you found out it does not support typed arrays. What works is to convert the typed array to an ordinary JS array and convert to byte[] from there: Java.to(Array.prototype.slice.call(arr), 'byte[]‘); That’s obviously not very elegant nor efficient, but it’s the only workaround I can think of. Hannes > Am 11.10.2018 um 20:21 schrieb Paulo Lopes : > > Hi, > > I'm trying to handle a case where a Uint8Array is being passed to a > method, that has the signature: > > String encode(byte[]); > > Sadly nashorn fails with: > > java.lang.ClassCastException: Cannot cast > jdk.nashorn.internal.objects.NativeUint8Array to [B > > And trying to help the cast with: > > javaObj.encode(Java.to(arr, 'byte[]')); > > Does not help either. The documentation on typed arrays is quite scarce > so I cannot see how to handle this, does anyone have a clue? > > Thanks! > Paulo >
casting typed array to java byte[] is it possible?
Hi, I'm trying to handle a case where a Uint8Array is being passed to a method, that has the signature: String encode(byte[]); Sadly nashorn fails with: java.lang.ClassCastException: Cannot cast jdk.nashorn.internal.objects.NativeUint8Array to [B And trying to help the cast with: javaObj.encode(Java.to(arr, 'byte[]')); Does not help either. The documentation on typed arrays is quite scarce so I cannot see how to handle this, does anyone have a clue? Thanks! Paulo
