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lvm2app: Add signed numerical property values

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Currently lvm2app properties have the following structure:

typedef struct lvm_property_value {
        uint32_t is_settable:1;
        uint32_t is_string:1;
        uint32_t is_integer:1;
        uint32_t is_valid:1;
        uint32_t padding:28;
        union {
                const char *string;
                uint64_t integer;
        } value;
} lvm_property_value_t;

which assumes that numerical values were in the range of 0 to 2**64-1.  However,
some of the properties were 'signed', like LV major/minor numbers and some
reserved values for properties that represent percentages.  Thus when the
values were retrieved they were in two's complement notation.  So for a -1
major number the API user would get a value of 18446744073709551615.  The
API user could cast the returned value to an int64_t to handle this, but that
requires the API developer to look at the source code and determine when it
should be done.

This change modifies the return property structure to:

typedef struct lvm_property_value {
        uint32_t is_settable:1;
        uint32_t is_string:1;
        uint32_t is_integer:1;
        uint32_t is_valid:1;
        uint32_t is_signed:1;
        uint32_t padding:27;
        union {
                const char *string;
                uint64_t integer;
                int64_t signed_integer;
        } value;
} lvm_property_value_t;

With this addition the API user can interrogate that the value is numerical,
(is_integer = 1) and subsequently check if it's signed (is_signed = 1) too.
If signed, then the API developer should use the union's signed_integer to
avoid casting.

This change maintains backwards compatibility as the structure size remains
unchanged and integer value remains unchanged.  Only the additional bit
taken from the pad is utilized.

Bugzilla reference:
https://bugzilla.redhat.com/show_bug.cgi?id=838257

Signed-off-by: Tony Asleson <tasleson@redhat.com>
This commit is contained in:
Tony Asleson
2015-05-04 14:51:41 -05:00
parent 5bbf083cd1
commit 91f737383c
7 changed files with 17 additions and 8 deletions
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5
lib/properties/prop_common.h
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@@ -26,9 +26,11 @@ struct lvm_property_type {
unsigned is_settable:1;
unsigned is_string:1;
unsigned is_integer:1;
unsigned is_signed:1;
union {
const char *string;
uint64_t integer;
int64_t signed_integer;
} value;
int (*get) (const void *obj, struct lvm_property_type *prop);
int (*set) (void *obj, struct lvm_property_type *prop);
@@ -126,9 +128,10 @@ static int _ ## NAME ## _get (const void *obj, struct lvm_property_type *prop) \
#define SIZ 4
#define PCT 5
#define STR_LIST 6
#define SNUM 7 /* Signed Number */
#define FIELD_MODIFIABLE 0x00000001
#define FIELD(type, strct, field_type, head, field, width, fn, id, desc, settable) \
{ type, #id, settable, field_type == STR, ((field_type == NUM) || (field_type == BIN) || (field_type == SIZ) || (field_type == PCT)), { .integer = 0 }, _ ## id ## _get, _ ## id ## _set },
{ type, #id, settable, field_type == STR, ((field_type == NUM) || (field_type == BIN) || (field_type == SIZ) || (field_type == PCT) || (field_type == SNUM)), ((field_type == SNUM) || (field_type == PCT)), { .integer = 0 }, _ ## id ## _get, _ ## id ## _set },
#endif