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[settings] Make fetch_string_setting_copy() easier to use 

Most callers of functions in the fetch_setting() family treat any
errors as meaning "non-existent setting".  In the case of
fetch_string_setting_copy(), an existent setting can still result in
an error due to memory allocation failure.

Allow the caller to distinguish between a non-existent setting and an
error in allocating memory for the copy, by returning success (and a
NULL buffer pointer) for a non-existent setting.

Signed-off-by: Michael Brown <mcb30@ipxe.org>
This commit is contained in:
Michael Brown 2011-03-03 19:59:31 +00:00
parent 09695f7be9
commit 48a4001152
1 changed files with 10 additions and 1 deletions
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11
src/core/settings.c
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@ -625,6 +625,11 @@ int fetch_string_setting ( struct settings *settings, struct setting *setting,
* The returned length will be the length of the underlying setting
* data. The caller is responsible for eventually freeing the
* allocated buffer.
*
* To allow the caller to distinguish between a non-existent setting
* and an error in allocating memory for the copy, this function will
* return success (and a NULL buffer pointer) for a non-existent
* setting.
*/
int fetch_string_setting_copy ( struct settings *settings,
struct setting *setting,
@ -632,16 +637,20 @@ int fetch_string_setting_copy ( struct settings *settings,
int len;
int check_len = 0;
/* Avoid returning uninitialised data on error */
*data = NULL;
/* Fetch setting length, and return success if non-existent */
len = fetch_setting_len ( settings, setting );
if ( len < 0 )
return len;
return 0;
/* Allocate string buffer */
*data = malloc ( len + 1 );
if ( ! *data )
return -ENOMEM;
/* Fetch setting */
check_len = fetch_string_setting ( settings, setting, *data,
( len + 1 ) );
assert ( check_len == len );