[libvirt PATCH v5 0/8] Refactor XML parsing boilerplate code

Tim Wiederhake posted 8 patches 5 days, 19 hours ago
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git fetch https://github.com/patchew-project/libvirt tags/patchew/20210408111958.32678-1-twiederh@redhat.com
src/conf/cpu_conf.c      |  14 +-
src/conf/domain_conf.c   |  14 +-
src/conf/network_conf.c  |  16 +--
src/libvirt_private.syms |   5 +
src/util/virxml.c        | 267 +++++++++++++++++++++++++++++++++++++++
src/util/virxml.h        |  31 +++++
6 files changed, 312 insertions(+), 35 deletions(-)

[libvirt PATCH v5 0/8] Refactor XML parsing boilerplate code

Posted by Tim Wiederhake 5 days, 19 hours ago
This series lays the groundwork for replacing some recurring boilerplate code
in src/conf/ regarding the extraction of XML attribute values.

For an on / off attribute, the boilerplate code looks roughly like this,

  g_autofree char *str = NULL;
  if (str = virXMLPropString(node, "x")) {
    int val;
    if ((val = virTristateBoolTypeFromString(str)) <= 0) {
      virReportError(...)
      return -1;
    }
    def->x = val;
  }

with some variations regarding how `str` is free'd in case of later re-use,
the exact error message for invalid values, whether or not
`VIR_TRISTATE_(SWITCH|BOOL)_ABSENT` is explicitly checked for (`val < 0` vs.
`val <= 0`), whether an intermediate variable is used or the value is assigned
directly, and in some cases the conditions in the two if-blocks are merged.

After the refactoring, the above code block looks like this:

  if (virXMLPropTristateBool(node, "x", VIR_XML_PROP_OPTIONAL, &def->x) < 0)
      return -1;

Similar functions are introduced for integer valued attributes, unsigned
integer valued attributes and enum valued attributes.

Patches #6, #7, and #8 demonstrate the application of these function and stand
representative of more patches that I did not sent along yet as to not drown
the mailing list in spam. These patches remove a total of ~ 1000 lines of code
and fix some places, where e.g. `<foo bar="default"/>` would incorrectly be
accepted as virXMLTristateBool.

As an added benefit, this refactoring makes the error messages for invalid
values in these XML attributes much more consistent:

  $ git diff master | grep "^-.*_(\"" | wc -l
  239
  $ git diff master | grep "^+.*_(\"" | wc -l
  21

V1: https://listman.redhat.com/archives/libvir-list/2021-March/msg00853.html
V2: https://listman.redhat.com/archives/libvir-list/2021-March/msg00994.html
V3: https://listman.redhat.com/archives/libvir-list/2021-March/msg01066.html
V4: https://listman.redhat.com/archives/libvir-list/2021-April/msg00209.html

Changes since V4:
* Added custom error message for virXMLProp(Int|UInt) when the attribute value
  is 0 and VIR_XML_PROP_NONZERO is specified.

Cheers,
Tim

Tim Wiederhake (8):
  virxml: Add virXMLPropTristateBool
  virxml: Add virXMLPropTristateSwitch
  virxml: Add virXMLPropInt
  virxml: Add virXMLPropUInt
  virxml: Add virXMLPropEnum
  virNetworkForwardNatDefParseXML: Use virXMLProp*
  virDomainIOThreadIDDefParseXML: Use virXMLProp*
  virCPUDefParseXML: Use virXMLProp*

 src/conf/cpu_conf.c      |  14 +-
 src/conf/domain_conf.c   |  14 +-
 src/conf/network_conf.c  |  16 +--
 src/libvirt_private.syms |   5 +
 src/util/virxml.c        | 267 +++++++++++++++++++++++++++++++++++++++
 src/util/virxml.h        |  31 +++++
 6 files changed, 312 insertions(+), 35 deletions(-)

-- 
2.26.2