Hashtable Tcl Reference Documentation

Hashtable

Current Version: 11.5.0

Chilkat.Hashtable

Store, look up, remove, enumerate, import, and serialize key/value pairs.

Chilkat.Hashtable provides a simple key/value collection for storing string and integer values by key. It can add or replace entries, look up values, test whether keys exist, remove entries, count items, enumerate keys, import URL query parameters, serialize values back to a query string, and save or load the table in XML format.

String and integer values

Store values as strings or integers using straightforward add, replace, and lookup methods.

Fast key lookup

Check whether a key exists and retrieve its value without manually scanning a list or parsing text.

Add, replace, and remove

Maintain a mutable collection by adding new entries, replacing existing values, removing individual keys, or clearing the table.

Enumerate keys

Retrieve the set of keys when application logic needs to loop through the stored entries.

Query string helpers

Import URL query parameters into the table and serialize the table back to a query-string representation.

XML persistence

Save the hashtable to XML or reload it from XML when values need to be persisted or transferred in a simple structured format.

Common pattern: Use Hashtable when application code needs a small mutable key/value table, especially for lookup tables, parsed query parameters, or simple string/integer settings. Add values with AddStr or AddInt, retrieve them with LookupStr or LookupInt, and use XML or query-string methods when the table needs to be saved, loaded, or converted.

For an extended overview, see Hashtable Class Overview.

Object Creation

# 'this' is not a keyword in Tcl. It can freely be used as a variable name.
set this [new CkHashtable]

Properties

Count

integer
set intVal [CkHashtable_get_Count $this]

Introduced in version 9.5.0.97

The number of entries currently stored in the hashtable.

Each key contributes one entry regardless of whether its value is a string or an integer. Adding a new key increases Count; replacing the value of an existing key does not. Removing an entry decreases it, and Clear resets it to 0.

DebugLogFilePath

string
# ckStr is a CkString
CkHashtable_get_DebugLogFilePath $this $ckStr
set strVal [CkHashtable_get_debugLogFilePath $this]
CkHashtable_put_DebugLogFilePath $this $strVal

If set to a file path, this property logs the LastErrorText of each Chilkat method or property call to the specified file. This logging helps identify the context and history of Chilkat calls leading up to any crash or hang, aiding in debugging.

Enabling the VerboseLogging property provides more detailed information. This property is mainly used for debugging rare instances where a Chilkat method call causes a hang or crash, which should generally not happen.

Possible causes of hangs include:

A timeout property set to 0, indicating an infinite timeout.
A hang occurring within an event callback in the application code.
An internal bug in the Chilkat code causing the hang.

More Information and Examples

Example showing how to use DebugLogFilePath.

LastErrorHtml

string
# ckStr is a CkString
CkHashtable_get_LastErrorHtml $this $ckStr
set strVal [CkHashtable_get_lastErrorHtml $this]

Provides HTML-formatted information about the last called method or property. If a method call fails or behaves unexpectedly, check this property for details. Note that information is available regardless of the method call's success.

LastErrorText

string
# ckStr is a CkString
CkHashtable_get_LastErrorText $this $ckStr
set strVal [CkHashtable_get_lastErrorText $this]

Provides plain text information about the last called method or property. If a method call fails or behaves unexpectedly, check this property for details. Note that information is available regardless of the method call's success.

More Information and Examples

Concept of LastErrorText LastErrorText Standard Information

LastErrorXml

string
# ckStr is a CkString
CkHashtable_get_LastErrorXml $this $ckStr
set strVal [CkHashtable_get_lastErrorXml $this]

Provides XML-formatted information about the last called method or property. If a method call fails or behaves unexpectedly, check this property for details. Note that information is available regardless of the method call's success.

LastMethodSuccess

boolean 1/0
set boolVal [CkHashtable_get_LastMethodSuccess $this]
CkHashtable_put_LastMethodSuccess $this $boolVal

Indicates the success or failure of the most recent method call: 1 means success, 0 means failure. This property remains unchanged by property setters or getters. This method is present to address challenges in checking for null or Nothing returns in certain programming languages. Note: This property does not apply to methods that return integer values or to boolean-returning methods where the boolean does not indicate success or failure.

Utf8

boolean 1/0
set boolVal [CkHashtable_get_Utf8 $this]
CkHashtable_put_Utf8 $this $boolVal

When set to 1, all string arguments and return values are interpreted as UTF-8 strings. When set to 0, they are interpreted as ANSI strings.

In Chilkat v11.0.0 and later, the default value is 1. Before v11.0.0, it was 0.

More Information and Examples

Strings in TCL: Encoding, UTF-8, and Source File Format Considerations

VerboseLogging

boolean 1/0
set boolVal [CkHashtable_get_VerboseLogging $this]
CkHashtable_put_VerboseLogging $this $boolVal

If set to 1, then the contents of LastErrorText (or LastErrorXml, or LastErrorHtml) may contain more verbose information. The default value is 0. Verbose logging should only be used for debugging. The potentially large quantity of logged information may adversely affect peformance.

Version

string
# ckStr is a CkString
CkHashtable_get_Version $this $ckStr
set strVal [CkHashtable_get_version $this]

Version of the component/library, such as "10.1.0"

More Information and Examples

How to get the Chilkat version at runtime.

Methods

AddFromXmlSb

# sbXml is a CkStringBuilder
set status [CkHashtable_AddFromXmlSb $this $sbXml]

Introduced in version 9.5.0.64

Reads hashtable XML previously produced by ToXmlSb from the StringBuilder passed in sbXml and adds the entries to this table.

The operation merges with the existing table: keys not present in the XML remain, and an imported entry replaces the current value for the same key. Call Clear first when the XML should completely replace the current contents.

Returns 1 when the XML is parsed and imported successfully; otherwise returns 0.

Returns 1 for success, 0 for failure.

More Information and Examples

Serialize / Deserialize Hashtable to/from XML

AddInt

# key is a string
# value is an integer
set status [CkHashtable_AddInt $this $key $value]

Introduced in version 9.5.0.51

Adds an entry whose string key is key and whose value is the integer value. If the key already exists, its previous value is replaced.

Returns 1 when the entry is added or replaced. Returns 0 if the operation cannot be completed, such as because memory could not be allocated.

One entry per key: Adding the same key again replaces the existing value; it does not create a second entry. Replacing a value does not increase Count. Use LookupInt to retrieve an integer value.

Returns 1 for success, 0 for failure.

AddQueryParams

# queryParams is a string
set status [CkHashtable_AddQueryParams $this $queryParams]

Introduced in version 9.5.0.62

Parses URL query parameters from queryParams and adds them to the hashtable as string entries. Pass the query component in the following form:

field1=value1&field2=value2&field3=value3

Each value is expected to be URL encoded and is URL decoded before being stored. If an imported key already exists, its previous value is replaced. Returns 1 on success and 0 if the query parameters cannot be imported.

Repeated parameter names: A hashtable stores one value per key. It cannot preserve a query string containing several independent values with the same field name. Use a list-oriented parser when repeated names must remain distinct.

Returns 1 for success, 0 for failure.

More Information and Examples

Keeping Query Params in a Hashtable

AddStr

# key is a string
# value is a string
set status [CkHashtable_AddStr $this $key $value]

Introduced in version 9.5.0.51

Adds an entry whose string key is key and whose value is the string value. If the key already exists, its previous value is replaced.

Returns 1 when the entry is added or replaced. Returns 0 if the operation cannot be completed, such as because memory could not be allocated.

One entry per key: Adding the same key again replaces the existing value; it does not create a second entry. Replacing a value does not increase Count. Use LookupStr to retrieve a string value.

Returns 1 for success, 0 for failure.

Clear

CkHashtable_Clear $this

Introduced in version 9.5.0.51

Removes every entry from the hashtable. After this call, Count is 0.

The current hash-table capacity is retained. To clear the entries and also select a different bucket capacity, call ClearWithNewCapacity.

ClearWithNewCapacity

# capacity is an integer
set status [CkHashtable_ClearWithNewCapacity $this $capacity]

Introduced in version 9.5.0.51

Removes every entry and reinitializes the hashtable with capacity buckets. The initial default capacity of a new Hashtable object is 521.

Returns 1 on success and 0 if the table cannot be reinitialized.

Term	Meaning
`Count`	The number of stored entries.
Capacity	The number of hash buckets, not a maximum entry count.

Performance note: More buckets can reduce collisions for a large table, but use more memory. Choosing roughly twice the expected number of entries and using a prime number are tuning guidelines, not correctness requirements.

Returns 1 for success, 0 for failure.

Contains

# key is a string
set retBool [CkHashtable_Contains $this $key]

Introduced in version 9.5.0.51

Returns 1 if the hashtable contains the string key key; otherwise returns 0. The result tests key existence regardless of the value stored for that key.

Useful before lookup: Call Contains when a lookup result could be ambiguous. For example, LookupInt returns 0 both for a missing key and for an entry whose value is actually zero.

ContainsIntKey

# key is an integer
set retBool [CkHashtable_ContainsIntKey $this $key]

Introduced in version 9.5.0.64

Returns 1 if the hashtable contains the integer key key; otherwise returns 0.

Key type: This method accepts an integer key. It is distinct from Contains, which tests for a string key, and from AddInt, whose key is a string and whose value is an integer.

GetKeys

# strTable is a CkStringTable
set status [CkHashtable_GetKeys $this $strTable]

Introduced in version 9.5.0.62

Appends all hashtable key strings to the StringTable passed in strTable. Existing strings already contained in strTable are not cleared.

Returns 1 on success and 0 on failure.

Enumeration order: Hashtable keys may be returned in any order. Do not depend on insertion order or sorted order. Clear the destination StringTable first when it should contain only the current hashtable keys.

Returns 1 for success, 0 for failure.

More Information and Examples

Serialize / Deserialize Hashtable to/from XML

LookupInt

# key is a string
set retInt [CkHashtable_LookupInt $this $key]

Introduced in version 9.5.0.51

Returns the integer value associated with the string key key. This method is intended for entries stored with AddInt.

If the key does not exist, the return value is 0.

Missing key versus zero: Because 0 is also a valid stored value, call Contains first when the application must distinguish a missing key from an entry containing zero.

LookupStr

# key is a string
# outStr is a CkString (output)
set status [CkHashtable_LookupStr $this $key $outStr]
set retStr [CkHashtable_lookupStr $this $key]

Introduced in version 9.5.0.51

Returns the string value associated with the string key key. This method is intended for entries stored as strings, including entries added by AddStr or AddQueryParams.

Check lookup success: The representation of a failed string-returning call varies by programming language and may be null, Nothing, or an empty string. An empty string may also be a legitimate value. Use Contains or LastMethodSuccess when the distinction matters.

Returns 1 for success, 0 for failure.

Remove

# key is a string
set retBool [CkHashtable_Remove $this $key]

Introduced in version 9.5.0.51

Removes the entry whose string key is key.

Returns 1 if the key existed and the entry was removed.
Returns 0 if the key was not present.

A 0 result caused by an absent key is a normal lookup outcome, not an indication that the hashtable was damaged. Removing an existing entry decreases Count by one.

ToQueryString

# outStr is a CkString (output)
set status [CkHashtable_ToQueryString $this $outStr]
set retStr [CkHashtable_toQueryString $this]

Introduced in version 9.5.0.92

Serializes the hashtable as a URL query string in the following form:

key1=value1&key2=value2&key3=value3

Each value is URL encoded. The returned string does not include a leading ?.

Important limitations: Key order is not defined, and a hashtable contains only one value per key. Therefore the output is not suitable when parameter order is significant or repeated field names must be preserved. In language bindings where string-return failure is ambiguous, check LastMethodSuccess.

Returns 1 for success, 0 for failure.

More Information and Examples

Keeping Query Params in a Hashtable

ToXmlSb

# sbXml is a CkStringBuilder
set status [CkHashtable_ToXmlSb $this $sbXml]

Introduced in version 9.5.0.64

Serializes the current hashtable to Chilkat's hashtable XML format and appends the XML to the StringBuilder passed in sbXml. Existing content in the StringBuilder is preserved.

Returns 1 on success and 0 on failure. The generated XML can be loaded by AddFromXmlSb.

&lt;hashtable&gt;
  &lt;e&gt;&lt;k&gt;key&lt;/k&gt;&lt;v&gt;value&lt;/v&gt;&lt;/e&gt;
&lt;/hashtable&gt;

Ordering: Because hashtable enumeration order is not defined, do not rely on entries appearing in insertion order or use the serialized text as a canonical, byte-for-byte representation.

Returns 1 for success, 0 for failure.

More Information and Examples

Serialize / Deserialize Hashtable to/from XML