The return value for virStreamRecvHole is slightly different to its C counterpart. In python, either it returns the hole size or None if C API fails. Signed-off-by: Michal Privoznik <mprivozn(a)redhat.com&gt; --- generator.py | 2 ++ libvirt-override-virStream.py | 21 +++++++++++++++ libvirt-override.c | 63 +++++++++++++++++++++++++++++++++++++++++++ 3 files changed, 86 insertions(+) diff --git a/generator.py b/generator.py index 5dfa73e..ca1df35 100755 --- a/generator.py +++ b/generator.py @@ -543,6 +543,8 @@ skip_function = ( 'virStreamSendAll', # Pure python libvirt-override-virStream.py 'virStreamRecv', # overridden in libvirt-override-virStream.py 'virStreamSend', # overridden in libvirt-override-virStream.py + 'virStreamRecvHole', # overridden in libvirt-override-virStream.py + 'virStreamSendHole', # overridden in libvirt-override-virStream.py 'virConnectUnregisterCloseCallback', # overridden in virConnect.py 'virConnectRegisterCloseCallback', # overridden in virConnect.py diff --git a/libvirt-override-virStream.py b/libvirt-override-virStream.py index 2e77cc7..62c1328 100644 --- a/libvirt-override-virStream.py +++ b/libvirt-override-virStream.py @@ -125,3 +125,24 @@ ret = libvirtmod.virStreamSend(self._o, data) if ret == -1: raise libvirtError ('virStreamSend() failed') return ret + + def recvHole(self, flags = 0): + """This method is used to determine the length in bytes + of the empty space to be created in a stream's target + file when uploading or downloading sparsely populated + files. This is the counterpart to sendHole. + """ + ret = libvirtmod.virStreamRecvHole(self._o, flags) + if ret is None: raise libvirtError ('virStreamRecvHole() failed') + return ret + + def sendHole(self, length, flags = 0): + """Rather than transmitting empty file space, this method + directs the stream target to create length bytes of empty + space. This method would be used when uploading or + downloading sparsely populated files to avoid the + needless copy of empty file space. + """ + ret = libvirtmod.virStreamSendHole(self._o, length, flags) + if ret == -1: raise libvirtError('virStreamSendHole() failed') + return ret diff --git a/libvirt-override.c b/libvirt-override.c index a762941..a6ef49e 100644 --- a/libvirt-override.c +++ b/libvirt-override.c @@ -9463,6 +9463,65 @@ libvirt_virConnectSecretEventDeregisterAny(PyObject *self ATTRIBUTE_UNUSED, } #endif /* LIBVIR_CHECK_VERSION(3, 0, 0)*/ + +#if LIBVIR_CHECK_VERSION(3, 4, 0) +static PyObject * +libvirt_virStreamRecvHole(PyObject *self ATTRIBUTE_UNUSED, + PyObject *args) +{ + PyObject *pyobj_stream; + virStreamPtr stream; + long long length = -1; + unsigned int flags; + int ret; + + if (!PyArg_ParseTuple(args, (char *) "OI:virStreamRecvHole", + &pyobj_stream, &flags)) + return NULL; + + stream = PyvirStream_Get(pyobj_stream); + + LIBVIRT_BEGIN_ALLOW_THREADS; + ret = virStreamRecvHole(stream, &length, flags); + LIBVIRT_END_ALLOW_THREADS; + + DEBUG("StreamRecvHole ret=%d length=%lld\n", ret, length); + + if (ret < 0) + return VIR_PY_NONE; + + return libvirt_longlongWrap(length); +} + + +static PyObject * +libvirt_virStreamSendHole(PyObject *self ATTRIBUTE_UNUSED, + PyObject *args) +{ + PyObject *pyobj_stream; + virStreamPtr stream; + long long length; + unsigned int flags; + int ret; + + if (!PyArg_ParseTuple(args, (char *) "OLI:virStreamSendHole", + &pyobj_stream, &length, &flags)) + return NULL; + + stream = PyvirStream_Get(pyobj_stream); + + LIBVIRT_BEGIN_ALLOW_THREADS; + ret = virStreamSendHole(stream, length, flags); + LIBVIRT_END_ALLOW_THREADS; + + DEBUG("StreamSendHole ret=%d\n", ret); + + return libvirt_intWrap(ret); +} + +#endif /* LIBVIR_CHECK_VERSION(3, 4, 0) */ + + /************************************************************************ * * * The registration stuff * @@ -9687,6 +9746,10 @@ static PyMethodDef libvirtMethods[] = { {(char *) "virConnectSecretEventRegisterAny", libvirt_virConnectSecretEventRegisterAny, METH_VARARGS, NULL}, {(char *) "virConnectSecretEventDeregisterAny", libvirt_virConnectSecretEventDeregisterAny, METH_VARARGS, NULL}, #endif /* LIBVIR_CHECK_VERSION(3, 0, 0) */ +#if LIBVIR_CHECK_VERSION(3, 4, 0) + {(char *) "virStreamRecvHole", libvirt_virStreamRecvHole, METH_VARARGS, NULL}, + {(char *) "virStreamSendHole", libvirt_virStreamSendHole, METH_VARARGS, NULL}, +#endif /* LIBVIR_CHECK_VERSION(3, 4, 0) */ {NULL, NULL, 0, NULL} }; -- 2.13.0

Yet again, our parser is not capable of generating proper wrapper. To be fair, this one wold be really tough anyway. Signed-off-by: Michal Privoznik <mprivozn(a)redhat.com&gt; --- generator.py | 2 + libvirt-override-virStream.py | 107 ++++++++++++++++++++++++++++++++++++++++++ sanitytest.py | 6 ++- 3 files changed, 113 insertions(+), 2 deletions(-) diff --git a/generator.py b/generator.py index 0e07fc8..93d1dc3 100755 --- a/generator.py +++ b/generator.py @@ -546,6 +546,8 @@ skip_function = ( 'virStreamRecvHole', # overridden in libvirt-override-virStream.py 'virStreamSendHole', # overridden in libvirt-override-virStream.py 'virStreamRecvFlags', # overridden in libvirt-override-virStream.py + 'virStreamSparseRecvAll', # overridden in libvirt-override-virStream.py + 'virStreamSparseSendAll', # overridden in libvirt-override-virStream.py 'virConnectUnregisterCloseCallback', # overridden in virConnect.py 'virConnectRegisterCloseCallback', # overridden in virConnect.py diff --git a/libvirt-override-virStream.py b/libvirt-override-virStream.py index 66d2bf6..0ab7815 100644 --- a/libvirt-override-virStream.py +++ b/libvirt-override-virStream.py @@ -164,3 +164,110 @@ ret = libvirtmod.virStreamRecvFlags(self._o, nbytes, flags) if ret is None: raise libvirtError ('virStreamRecvFlags() failed') return ret + + def sparseRecvAll(self, handler, holeHandler, opaque): + """Receive the entire data stream, sending the data to + the requested data sink handler and calling the skip + holeHandler to generate holes for sparse stream targets. + This is simply a convenient alternative to recvFlags, for + apps that do blocking-I/O and want to preserve sparseness. + + Hypothetical callbacks can look like this: + + def handler(stream, # virStream instance + buf, # string containing received data + opaque): # extra data passed to sparseRecvAll as opaque + fd = opaque + return os.write(fd, buf) + + def holeHandler(stream, # virStream instance + length, # number of bytes to skip + opaque): # extra data passed to sparseRecvAll as opaque + fd = opaque + cur = os.lseek(fd, length, os.SEEK_CUR) + return os.ftruncate(fd, cur) # take this extra step to + # actually allocate the hole + """ + while True: + want = 64 * 1024 + got = self.recvFlags(want, VIR_STREAM_RECV_STOP_AT_HOLE) + if got == -2: + raise libvirtError("cannot use sparseRecvAll with " + "nonblocking stream") + if got == -3: + length = self.recvHole() + if length is None: + self.abort() + raise RuntimeError("recvHole handler failed") + ret = holeHandler(self, length, opaque) + if type(ret) is int and ret < 0: + self.abort() + raise RuntimeError("holeHandler handler returned %d" % ret) + continue + + if len(got) == 0: + break + + try: + ret = handler(self, got, opaque) + if type(ret) is int and ret < 0: + raise RuntimeError("sparseRecvAll handler returned %d" % ret) + except Exception as e: + self.abort() + raise e + + def sparseSendAll(self, handler, holeHandler, skipHandler, opaque): + """Send the entire data stream, reading the data from the + requested data source. This is simply a convenient + alternative to virStreamSend, for apps that do + blocking-I/O and want to preserve sparseness. + + Hypothetical callbacks can look like this: + + def handler(stream, # virStream instance + nbytes, # int amt of data to read + opaque): # extra data passed to sparseSendAll as opaque + fd = opaque + return os.read(fd, nbytes) + + def holeHandler(stream, # virStream instance + opaque): # extra data passed to sparseSendAll as opaque + fd = opaque + cur = os.lseek(fd, 0, os.SEEK_CUR) + # ... find out current section and its boundaries + # and set inData = True/False and sectionLen correspondingly + os.lseek(fd, cur, os.SEEK_SET) + return [inData, sectionLen] + + def skipHandler(stream, # virStream instance + length, # number of bytes to skip + opaque): # extra data passed to sparseSendAll as opaque + fd = opaque + return os.lseek(fd, length, os.SEEK_CUR) + + """ + while True: + [inData, sectionLen] = holeHandler(self, opaque) + if (inData == False and sectionLen > 0): + if (self.sendHole(sectionLen) < 0 or + skipHandler(self, sectionLen, opaque) < 0): + self.abort() + continue + + want = 64 * 1024 + if (want > sectionLen): + want = sectionLen + + try: + got = handler(self, want, opaque) + except Exception as e: + self.abort() + raise e + + if not got: + break + + ret = self.send(got) + if ret == -2: + raise libvirtError("cannot use sparseSendAll with " + "nonblocking stream") diff --git a/sanitytest.py b/sanitytest.py index 7183baa..deec200 100644 --- a/sanitytest.py +++ b/sanitytest.py @@ -167,7 +167,8 @@ for cname in wantfunctions: # These aren't functions, they're callback signatures if name in ["virConnectAuthCallbackPtr", "virConnectCloseFunc", "virStreamSinkFunc", "virStreamSourceFunc", "virStreamEventCallback", - "virEventHandleCallback", "virEventTimeoutCallback", "virFreeCallback"]: + "virEventHandleCallback", "virEventTimeoutCallback", "virFreeCallback", + "virStreamSinkHoleFunc", "virStreamSourceHoleFunc", "virStreamSourceSkipFunc"]: continue if name[0:21] == "virConnectDomainEvent" and name[-8:] == "Callback": continue @@ -373,7 +374,8 @@ for name in sorted(finalklassmap): # These exist in C and exist in python, but we've got # a pure-python impl so don't check them - if name in ["virStreamRecvAll", "virStreamSendAll"]: + if name in ["virStreamRecvAll", "virStreamSendAll", + "virStreamSparseRecvAll", "virStreamSparseSendAll"]: continue try: -- 2.13.0

Sparse streams are not that straight forward to use for the very first time. Especially the sparseRecvAll() and sparseSendAll() methods which expects callbacks. What we can do to make it easier for developers is to have an example where they can take an inspiration from. Signed-off-by: Michal Privoznik <mprivozn(a)redhat.com&gt; --- examples/sparsestream.py | 117 +++++++++++++++++++++++++++++++++++++++++++++++ 1 file changed, 117 insertions(+) create mode 100755 examples/sparsestream.py diff --git a/examples/sparsestream.py b/examples/sparsestream.py new file mode 100755 index 0000000..e960c40 --- /dev/null +++ b/examples/sparsestream.py @@ -0,0 +1,117 @@ +#!/usr/bin/env python +# Example of sparse streams usage +# +# Authors: +# Michal Privoznik <mprivozn(a)redhat.com&gt; + +import libvirt, sys, os + +def bytesWriteHandler(stream, buf, opaque): + fd = opaque + return os.write(fd, buf) + +def bytesReadHandler(stream, nbytes, opaque): + fd = opaque + return os.read(fd, nbytes) + +def recvSkipHandler(stream, length, opaque): + fd = opaque + cur = os.lseek(fd, length, os.SEEK_CUR) + return os.ftruncate(fd, cur) + +def sendSkipHandler(stream, length, opaque): + fd = opaque + return os.lseek(fd, length, os.SEEK_CUR) + +def holeHandler(stream, opaque): + fd = opaque + cur = os.lseek(fd, 0, os.SEEK_CUR) + + try: + data = os.lseek(fd, cur, os.SEEK_DATA) + except OSError as e: + if e.errno != 6: + raise e + else: + data = -1; + # There are three options: + # 1) data == cur; @cur is in data + # 2) data > cur; @cur is in a hole, next data at @data + # 3) data < 0; either @cur is in trailing hole, or @cur is beyond EOF. + if data < 0: + # case 3 + inData = False + eof = os.lseek(fd, 0, os.SEEK_END) + if (eof < cur): + raise RuntimeError("Current position in file after EOF: %d" % cur) + sectionLen = eof - cur + else: + if (data > cur): + # case 2 + inData = False + sectionLen = data - cur + else: + # case 1 + inData = True + + # We don't know where does the next hole start. Let's find out. + # Here we get the same options as above + hole = os.lseek(fd, data, os.SEEK_HOLE) + if hole < 0: + # case 3. But wait a second. There is always a trailing hole. + # Do the best what we can here + raise RuntimeError("No trailing hole") + + if (hole == data): + # case 1. Again, this is suspicious. The reason we are here is + # because we are in data. But at the same time we are in a + # hole. WAT? + raise RuntimeError("Impossible happened") + else: + # case 2 + sectionLen = hole - data + os.lseek(fd, cur, os.SEEK_SET) + return [inData, sectionLen] + +def download(vol, st, filename): + offset = 0 + length = 0 + + fd = os.open(filename, os.O_WRONLY | os.O_CREAT | os.O_TRUNC, mode=0o0660) + vol.download(st, offset, length, libvirt.VIR_STORAGE_VOL_DOWNLOAD_SPARSE_STREAM) + st.sparseRecvAll(bytesWriteHandler, recvSkipHandler, fd) + + os.close(fd) + +def upload(vol, st, filename): + offset = 0 + length = 0 + + fd = os.open(filename, os.O_RDONLY) + vol.upload(st, offset, length, libvirt.VIR_STORAGE_VOL_UPLOAD_SPARSE_STREAM) + st.sparseSendAll(bytesReadHandler, holeHandler, sendSkipHandler, fd) + + os.close(fd) + +# main +if len(sys.argv) != 5: + print("Usage: ", sys.argv[0], " URI --upload/--download VOLUME FILE") + print("Either uploads local FILE to libvirt VOLUME, or downloads libvirt ") + print("VOLUME into local FILE while preserving FILE/VOLUME sparseness") + sys.exit(1) + +conn = libvirt.open(sys.argv[1]) +vol = conn.storageVolLookupByKey(sys.argv[3]) + +st = conn.newStream() + +if sys.argv[2] == "--download": + download(vol, st, sys.argv[4]) +elif sys.argv[2] == "--upload": + upload(vol, st, sys.argv[4]) +else: + print("Unknown operation: %s " % sys.argv[1]) + sys.exit(1) + +st.finish() +conn.close() -- 2.13.0