Re: [Qemu-devel] [PATCH 03/11] add a generic Error object

[Anthony Liguori <anthony@codemonkey.ws>]

On 03/12/2011 05:05 AM, Blue Swirl wrote:
> On Fri, Mar 11, 2011 at 11:00 PM, Anthony Liguori<aliguori@us.ibm.com>  wrote:
>> The Error class is similar to QError (now deprecated) except that it supports
>> propagation.  This allows for higher quality error handling.  It's losely
>> modeled after glib style GErrors.
>>
>> Signed-off-by: Anthony Liguori<aliguori@us.ibm.com>
>>
>> diff --git a/Makefile.objs b/Makefile.objs
>> index 0ba02c7..da31530 100644
>> --- a/Makefile.objs
>> +++ b/Makefile.objs
>> @@ -15,6 +15,7 @@ oslib-obj-$(CONFIG_POSIX) += oslib-posix.o
>>
>>   block-obj-y = cutils.o cache-utils.o qemu-malloc.o qemu-option.o module.o
>>   block-obj-y += nbd.o block.o aio.o aes.o qemu-config.o
>> +block-obj-y += error.o
>>   block-obj-$(CONFIG_POSIX) += posix-aio-compat.o
>>   block-obj-$(CONFIG_LINUX_AIO) += linux-aio.o
>>
>> diff --git a/error.c b/error.c
>> new file mode 100644
>> index 0000000..5d84106
>> --- /dev/null
>> +++ b/error.c
>> @@ -0,0 +1,122 @@
>> +/*
>> + * QEMU Error Objects
>> + *
>> + * Copyright IBM, Corp. 2011
>> + *
>> + * Authors:
>> + *  Anthony Liguori<aliguori@us.ibm.com>
>> + *
>> + * This work is licensed under the terms of the GNU LGPL, version 2.  See
>> + * the COPYING.LIB file in the top-level directory.
>> + */
>> +#include "error.h"
>> +#include "error_int.h"
>> +#include "qemu-objects.h"
>> +#include "qerror.h"
>> +#include<assert.h>
>> +
>> +struct Error
>> +{
>> +    QDict *obj;
>> +    const char *fmt;
>> +    char *msg;
>> +};
>> +
>> +void error_set(Error **errp, const char *fmt, ...)
>> +{
>> +    Error *err;
>> +    va_list ap;
>> +
>> +    if (errp == NULL) {
>> +        return;
>> +    }
>> +
>> +    err = qemu_mallocz(sizeof(*err));
>> +
>> +    va_start(ap, fmt);
>> +    err->obj = qobject_to_qdict(qobject_from_jsonv(fmt,&ap));
>> +    va_end(ap);
>> +    err->fmt = fmt;
>> +
>> +    *errp = err;
>> +}
>> +
>> +bool error_is_set(Error **errp)
>> +{
>> +    return (errp&&  *errp);
>> +}
>> +
>> +const char *error_get_pretty(Error *err)
>> +{
>> +    if (err->msg == NULL) {
>> +        QString *str;
>> +        str = qerror_format(err->fmt, err->obj);
>> +        err->msg = qemu_strdup(qstring_get_str(str));
>> +    }
>> +
>> +    return err->msg;
>> +}
>> +
>> +const char *error_get_field(Error *err, const char *field)
>> +{
>> +    if (strcmp(field, "class") == 0) {
>> +        return qdict_get_str(err->obj, field);
>> +    } else {
>> +        QDict *dict = qdict_get_qdict(err->obj, "data");
>> +        return qdict_get_str(dict, field);
>> +    }
>> +}
>> +
>> +void error_free(Error *err)
>> +{
>> +    QDECREF(err->obj);
>> +    qemu_free(err->msg);
>> +    qemu_free(err);
>> +}
>> +
>> +bool error_is_type(Error *err, const char *fmt)
>> +{
>> +    char *ptr;
>> +    char *end;
>> +    char classname[1024];
>> +
>> +    ptr = strstr(fmt, "'class': '");
>> +    assert(ptr != NULL);
>> +    ptr += strlen("'class': '");
>> +
>> +    end = strchr(ptr, '\'');
>> +    assert(end != NULL);
>> +
>> +    memcpy(classname, ptr, (end - ptr));
>> +    classname[(end - ptr)] = 0;
>> +
>> +    return strcmp(classname, error_get_field(err, "class")) == 0;
>> +}
>> +
>> +void error_propagate(Error **dst_err, Error *local_err)
>> +{
>> +    if (dst_err) {
>> +        *dst_err = local_err;
>> +    } else if (local_err) {
>> +        error_free(local_err);
>> +    }
>> +}
>> +
>> +QObject *error_get_qobject(Error *err)
>> +{
>> +    QINCREF(err->obj);
>> +    return QOBJECT(err->obj);
>> +}
>> +
>> +void error_set_qobject(Error **errp, QObject *obj)
>> +{
>> +    Error *err;
>> +    if (errp == NULL) {
>> +        return;
>> +    }
>> +    err = qemu_mallocz(sizeof(*err));
>> +    err->obj = qobject_to_qdict(obj);
>> +    qobject_incref(obj);
>> +
>> +    *errp = err;
>> +}
>> diff --git a/error.h b/error.h
>> new file mode 100644
> The name is too generic, it could conflict with system headers. At
> least I have /usr/include/error.h.
>
>> index 0000000..317d487
>> --- /dev/null
>> +++ b/error.h
>> @@ -0,0 +1,65 @@
>> +/*
>> + * QEMU Error Objects
>> + *
>> + * Copyright IBM, Corp. 2011
>> + *
>> + * Authors:
>> + *  Anthony Liguori<aliguori@us.ibm.com>
>> + *
>> + * This work is licensed under the terms of the GNU LGPL, version 2.  See
>> + * the COPYING.LIB file in the top-level directory.
>> + */
>> +#ifndef ERROR_H
>> +#define ERROR_H
> This #define could also conflict with system headers. In my system,
> _ERROR_H is used, but who knows all error.h files out there?

Certainly a good point.  I'll use a different name.

Regards,

Anthony Liguori