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Vely 15.2.0 released on Jan 18, 2023
Articles updated Jan 17, 2023

write-hash


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Purpose:


Store key/value pair into a hash table.

Syntax:



write-hash <hash> \
    key <key> \
    value <value> \
    [ status [ define ] <status> ] \
    [ old-value [ define ] <old value> ]


Description:


write-hash will store <key> (in "key" clause) with <value> (specified in "value" clause) into hash table <hash>, which must be created with new-hash. <key> is a string and <value> can be a pointer of any type, allowing storage of any kind of data. <key> and <value> must not go out of scope or be freed while the hash is used - if necessary, store a copy (see copy-string for strings).

If <key> already exists in the hash table, then the pointer to old value associated with it is returned in the optional <old value> (in "old-value" clause) - in this case the optional number <status> (in "status" clause) has a value of VV_ERR_EXIST. If <key> did not exist, <status> will be VV_OKAY and <old value> is NULL. Both <status> and <old value> can be created with "define" clause.

Examples:


Writing data to hash:

new-hash define h size 1000
write-hash h key "mykey" value "some data"

Writing new value with the same key and obtaining the previous value (which is "some data"):

write-hash h key "mykey" value "new data" status define st old-value define od
if (st == VV_ERR_EXIST) {
    @Previous value for this key is <<p-out od>>
}

See read-hash for more examples.

See also:


Hash table ( get-hash   new-hash   purge-hash   read-hash   resize-hash   write-hash  )  SEE ALL (documentation)



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