Write hash
Purpose: Store key/value pair into a hash.

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

write-hash will store string <key> (in "key" clause) and <value> (in "value" clause) into <hash>, which must be created with new-hash.

<key> and <value> are collectively called an "element".

If <key> already exists in the hash, then the old value associated with it is returned in string <old value> (in "old-value" clause) and <value> will replace the old value - in this case <status> number (in "status" clause) has a value of GG_INFO_EXIST.

If <key> did not exist, <status> will be GG_OKAY and <old value> is unchanged.

If a <hash> was created with "process-scope" clause (see new-hash), then the element (including <key> and <value>) will not be freed when the current request ends, rather it will persist while the process runs, unless deleted (see read-hash with delete clause).
Examples
Writing data to a hash:
 new-hash h
 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 st old-value od
 if-true st equal GG_INFO_EXIST
     @Previous value for this key is <<print-out od>>
 end-if

The following is a key/value service, where a process-scoped hash is created. It provides inserting, deleting and querying key/value pairs. Such a service process can run indefinitely. Create file keysrv.golf:
 %% /keysrv public
     do-once
     new-hash h hash-size 1024 process-scope
     end-do-once

     // Get input parameters
     get-param op
     get-param key
     get-param data

     if-true op equal "add" // Add data to hash 
         write-hash h key key value data old-value old_data status st
         if-true st equal GG_INFO_EXIST
             delete-string old_data
         end-if
         @Added [<<print-out key>>]
     else-if op equal "delete" // Delete data and obtain the value deleted
         read-hash h key (key) value val delete status st
         if-true st equal GG_ERR_EXIST
             @Not found [<<print-out key>>]
         else-if
             // If found, then delete key and value
             @Deleted [<<print-out val>>]
             delete-string val
         end-if
     else-if op equal "query" // Query hash based on key value
         read-hash h key (key) value val status st
         if-true st equal GG_ERR_EXIST
             @Not found, queried [<<print-out key>>]
         else-if
             @Value [<<print-out val>>]
         end-if
     end-if
 %%

Create and make the application, then run it as service:
// Create application
gg -k hash
// Make application
gg -q
// Start application (single process key service)
mgrg -w 1 hash

Try it from a command line client (see gg):
// Add data
gg -r --req="/keysrv/op=add/key=15/data=15" --service --app="/hash" --exec
// Query data
gg -r --req="/keysrv/op=query/key=15" --service --app="/hash" --exec
// Delete data
gg -r --req="/keysrv/op=delete/key=15" --service --app="/hash" --exec

See read-hash for more examples.

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