elektra-keyvalue (3) - Linux Manuals
NAME
Key :: Value Manipulation Methods -
Methods to do various operations on Key values.
Functions
const void * keyValue (const Key *key)
ssize_t keyGetValueSize (const Key *key)
ssize_t keyGetString (const Key *key, char *returnedString, size_t maxSize)
ssize_t keySetString (Key *key, const char *newStringValue)
ssize_t keyGetBinary (const Key *key, void *returnedBinary, size_t maxSize)
ssize_t keySetBinary (Key *key, const void *newBinary, size_t dataSize)
const char * keyComment (const Key *key)
ssize_t keyGetCommentSize (const Key *key)
ssize_t keyGetComment (const Key *key, char *returnedComment, size_t maxSize)
ssize_t keySetComment (Key *key, const char *newComment)
Detailed Description
Methods to do various operations on Key values.
A key can contain a value in different format. The most likely situation is, that the value is interpreted as text. Use keyGetString() for that. You can save any Unicode Symbols and Elektra will take care that you get the same back, independent of your current environment.
In some situations this idea fails. When you need exactly the same value back without any interpretation of the characters, there is keySetBinary(). If you use that, its very likely that your Configuration is not according to the standard. Also for Numbers, Booleans and Date you should use keyGetString(). To do so, you might use strtod() strtol() and then atol() or atof() to convert back.
To use them:
#include <kdb.h>
This is a much more efficient version of keyGetComment() and you should use it if you are responsible enough to not mess up things. You are not allowed to change anything in the memory region the returned pointer points to.
keyComment() returns '' when there is no keyComment. The reason is
See keySetComment() for more information on comments.
Note:
Parameters:
Returns:
0 on NULL pointer
See also:
If the type is not binary -1 will be returned.
When the binary data is empty (this is not the same as ''!) 0 will be returned and the returnedBinary will not be changed.
For string values see keyGetString() and keyIsString().
When the returnedBinary is to small to hold the data (its maximum size is given by maxSize), the returnedBinary will not be changed and -1 is returned.
Example:.RS 4
Parameters:
Returns:
0 if the binary is empty
-1 on NULL pointers
-1 when maxSize is 0, too small to hold the value or larger than SSIZE_MAX
-1 on typing error when the key is not binary
See also:
keyGetString() and keySetString() as preferred alternative to binary
keyIsBinary() to see how to check for binary type
A Key comment is description for humans what this key is for. It may be a textual explanation of valid values, when and why a user or administrator changed the key or any other text that helps the user or administrator related to that key.
Don't depend on a comment in your program. A user is always allowed to remove or change it in any way he wants to. But you are allowed or even encouraged to always show the content of the comment to the user and allow him to change it.
Parameters:
Returns:
1 if the string is empty
-1 on NULL pointer
-1 if maxSize is 0, not enough to store the comment or when larger then SSIZE_MAX
See also:
Use this method to know to size for allocated memory to retrieve a key comment.
See keySetComment() for more information on comments.
For an empty key name you need one byte to store the ending NULL. For that reason 1 is returned.
Parameters:
Returns:
1 if there is no comment
-1 on NULL pointer
See also:
When there is no value inside the string, 1 will be returned and the returnedString will be empty '' to avoid programming errors that old strings are shown to the user.
For binary values see keyGetBinary() and keyIsBinary().
Example:.RS 4
Parameters:
Returns:
1 if the string is empty
-1 on NULL pointer
-1 on type mismatch
maxSize is 0, too small for string or is larger than SSIZE_MAX
See also:
keyGetBinary() for working with binary data
It returns the correct size, independent of the Key Type. If it is a binary there might be '\0' values in it.
For an empty string you need one byte to store the ending NULL. For that reason 1 is returned. This is not true for binary data, so there might be returned 0 too.
A binary key has no '\0' termination. String types have it, so to there length will be added 1 to have enough space to store it.
This method can be used with malloc() before keyGetString() or keyGetBinary() is called.
Parameters:
Returns:
1 when there is no data and type is not binary
0 when there is no data and type is binary
-1 on null pointer
See also:
A private copy of newBinary will allocated and saved inside key, so the parameter can be deallocated after the call.
The filesys backend, when used through a kdbSetKey(), will make the value be kdbbEncoded into a human readable hex-digit text format.
Consider using a string key instead.
When newBinary is a NULL pointer the binary will be freed and 0 will be returned.
Note:
Parameters:
Returns:
0 when the internal binary was freed
-1 on NULL pointer
-1 when dataSize is 0 (but newBinary not NULL) or larger than SSIZE_MAX
See also:
keyIsBinary() to check if the type is binary
keyGetString() and keySetString() as preferred alternative to binary
A key comment is like a configuration file comment. See keySetComment() for more information.
Parameters:
Returns:
1 when the comment was freed
-1 on NULL pointer or memory problems
See also:
The function will allocate and save a private copy of newStringValue, so the parameter can be freed after the call.
String values will be saved in backend storage, when kdbSetKey() will be called, in UTF-8 universal encoding, regardless of the program's current encoding, when compiled with --enable-iconv.
The type will be set to KEY_TYPE_STRING. When the type of the key is already a string type it won't be changed.
Parameters:
Returns:
-1 on NULL pointer
See also:
This is a much more efficient version of keyGetString() keyGetBinary(), and you should use it if you are responsible enough to not mess up things. You are not allowed to modify anything in the returned string. If you need a copy of the Value, consider to use keyGetString() or keyGetBinary() instead.
If key is string (keyIsString()), you may cast the returned as a 'char *' because you'll get a NULL terminated regular string.
keyValue() returns '' in string mode when there is no value. The reason is
If the data is binary, the size of the value must be determined by keyGetValueSize(), any strlen() operations are not suitable to determine the size.
keyValue() returns 0 in binary mode when there is no value. The reason is
Note:
Warning:
Example:.RS 4
Parameters:
Returns:
0 where there is no data and key is binary
0 on NULL pointer
See also:
Generated automatically by Doxygen for Elektra Projekt from the source code.
Function Documentation
const char* keyComment (const Key * key)Return a pointer to the real internal key comment.
key=keyNew(0);
keySetComment(key,'');
keyComment(key); // you would expect '' here
keyDel(key);
ssize_t keyGetBinary (const Key * key, void * returnedBinary, size_t maxSize)Get the value of a key as a binary.
Key *key = keyNew ('user/keyname', KEY_TYPE, KEY_TYPE_BINARY, KEY_END);
char buffer[300];
if (keyGetBinary(key,buffer,sizeof(buffer)) == -1)
{
// handle error
}
returnedBinary pre-allocated memory to store a copy of the key value
maxSize number of bytes of pre-allocated memory in returnedBinary
ssize_t keyGetComment (const Key * key, char * returnedComment, size_t maxSize)Get the key comment.
Comments
returnedComment pre-allocated memory to copy the comments to
maxSize number of bytes that will fit returnedComment
ssize_t keyGetCommentSize (const Key * key)Calculates number of bytes needed to store a key comment, including final NULL.
char *buffer;
buffer = malloc (keyGetCommentSize (key));
// use this buffer to store the comment
// pass keyGetCommentSize (key) for maxSize
ssize_t keyGetString (const Key * key, char * returnedString, size_t maxSize)Get the value of a key as a string.
Key *key = keyNew ('user/keyname', KEY_END);
char buffer[300];
if (keyGetString(key,buffer,sizeof(buffer)) == -1)
{
// handle error
} else {
printf ('buffer: %s, buffer);
}
returnedString pre-allocated memory to store a copy of the key value
maxSize number of bytes of allocated memory in returnedString
ssize_t keyGetValueSize (const Key * key)Returns the number of bytes needed to store the key value, including the NULL terminator.
char *buffer;
buffer = malloc (keyGetValueSize (key));
// use this buffer to store the value (binary or string)
// pass keyGetValueSize (key) for maxSize
ssize_t keySetBinary (Key * key, const void * newBinary, size_t dataSize)Set the value of a key as a binary.
newBinary is a pointer to any binary data or NULL to free the previous set data
dataSize number of bytes to copy from newBinary
ssize_t keySetComment (Key * key, const char * newComment)Set a comment for a key.
newComment the comment, that can be freed after this call.
ssize_t keySetString (Key * key, const char * newStringValue)Set the value for key as newStringValue.
newStringValue NULL-terminated text string to be set as key's value
const void* keyValue (const Key * key)Return a pointer to the real internal key value.
String Handling
key=keyNew(0);
keySetString(key,'');
keyValue(key); // you would expect '' here
keyDel(key);
Binary Data Handling
int i=23;
key=keyNew(0);
keySetBinary(key, 0, 0);
keyValue(key); // you would expect 0 here
keySetBinary(key,'', 1);
keyValue(key); // you would expect '' (a pointer to '
KDB *handle = kdbOpen();
KeySet *ks=ksNew(0);
Key *current=0;
kdbGetByName(handle,ks,'system/sw/my',KDB_O_SORT|KDB_O_RECURSIVE);
ksRewind(ks);
while(current=ksNext(ks)) {
size_t size=0;
if (keyIsBin(current)) {
size=keyGetValueSize(current);
printf('Key %s has a value of size %d bytes. Value: <BINARY>omment: %s',
keyName(current),
size,
keyComment(current));
} else {
size=kdbiStrLen((char *)keyValue(current));
printf('Key %s has a value of size %d bytes. Value: %somment: %s',
keyName(current),
size,
(char *)keyValue(current),
keyComment(current));
}
}
ksDel (ks);
kdbClose (handle);
Author