ZipEntry Lua Reference Documentation

chilkat.ZipEntry

Current Version: 11.7.0

Markdown version of this page for AI tools (v 11.7.0) · all AI docs

Chilkat.ZipEntry

Inspect, extract, update, and iterate individual entries inside a ZIP archive.

Chilkat.ZipEntry represents a single item associated with a Chilkat.Zip archive. An entry may be a file already stored in an opened ZIP, a referenced filesystem file waiting to be compressed, an in-memory text or binary entry, or a directory entry. It provides access to entry-level metadata, compressed and uncompressed data, timestamps, attributes, CRC values, encryption information, and extraction or replacement operations for that specific ZIP item.

Entry metadata

Inspect filenames, stored ZIP paths, comments, timestamps, CRC values, attributes, sizes, compression method, and compression level.

Entry type and state

Use EntryType to understand whether the entry comes from an existing ZIP, a filesystem reference, memory data, or a directory.

Extract one entry

Extract a selected file entry to disk, inflate its contents into memory, or read the uncompressed data into Chilkat objects.

Read compressed data

Access the raw compressed entry data when an application needs ZIP-level control rather than only the inflated contents.

Replace or append data

Update an entry's contents from strings, byte data, files, or in-memory data sources before writing the ZIP archive.

Iterate archive entries

Walk through entries returned from Chilkat.Zip methods to inspect, filter, extract, or modify ZIP contents one item at a time.

Common pattern: Open or create a Chilkat.Zip object, obtain a ZipEntry using methods such as EntryAt, EntryOf, EntryMatching, or FirstEntry, then inspect metadata, extract contents, update the entry, or continue iterating through the archive. Use Chilkat.Zip for whole-archive operations and ZipEntry for operations on one specific archive item.

Object Creation

local chilkat = require("chilkat")

local zip_entry = chilkat.ZipEntry.new()
local zip_entry = chilkat.ZipEntry.new()

Creates the object (chilkat.ZipEntry() does the same). Lua's garbage collector frees it when it is no longer referenced; zip_entry:dispose() frees it at once, and in Lua 5.4 and later local zip_entry <close> = chilkat.ZipEntry.new() frees it when the block ends. Calling a method of a disposed object raises an error.

Errors

A method that fails returns nil followed by the error text, as io.open does: local body, err = zip_entry:method(...), where err is the object's last_error_text. Wrap the call in assert() to raise an error with that text instead. Methods that answer a question return true or false, numbers are returned as they are (check last_method_success where the description says a value means failure), and property reads and writes never fail for Chilkat reasons.

Misuse raises a Lua error: a wrong argument type or a missing argument (bad argument #1 to ...), an unknown property name, a write to a read-only property, an out-of-range integer, or an object of the wrong class.

Names are Chilkat's in snake_case: QuickGetStr is quick_get_str, LastErrorText is last_error_text. Properties are fields (zip_entry.verbose_logging = true) and methods use the colon (zip_entry:method(...)). Strings are UTF-8; binary data is a Lua string of bytes. Indexes are 0-based, as in every Chilkat API. Unlocking: call chilkat.unlock_bundle("...") once at startup.

Properties

Comment
-- strVal is a string
local strVal = zip_entry.comment
zip_entry.comment = strVal

Gets or sets the comment stored in the ZIP archive for this entry.

top
CompressedLength
-- intVal is an integer (read-only)
local intVal = zip_entry.compressed_length

The compressed size of this entry, in bytes.

For mapped entries (entries already contained within an opened ZIP archive), this property contains the actual compressed size stored within the ZIP.

For file entries or data entries that have not yet been written to a ZIP archive, compression has not yet occurred. In these cases, this property contains:

  • The current uncompressed data size for data entries.
  • The cached filesystem file size for referenced file entries.

After the ZIP archive is written, the entries become mapped entries, and this property then reflects the actual compressed size stored in the ZIP archive.

top
CompressedLength64
-- intVal is an integer (read-only)
local intVal = zip_entry.compressed_length64

The compressed size of this entry, in bytes, as a 64-bit integer.

For mapped entries (entries already contained within an opened ZIP archive), this property contains the actual compressed size stored within the ZIP.

For file entries or data entries that have not yet been written to a ZIP archive, compression has not yet occurred. In these cases, this property contains:

  • The current uncompressed data size for data entries.
  • The cached filesystem file size for referenced file entries.

After the ZIP archive is written, the entries become mapped entries, and this property then reflects the actual compressed size stored in the ZIP archive.

Use this property when sizes may exceed the range of a 32-bit integer.

top
CompressedLengthStr
-- strVal is a string (read-only)
local strVal = zip_entry.compressed_length_str

The compressed size of this entry as a decimal string.

For mapped entries (entries already contained within an opened ZIP archive), this property contains the actual compressed size stored within the ZIP.

For file entries or data entries that have not yet been written to a ZIP archive, compression has not yet occurred. In these cases, this property contains:

  • The current uncompressed data size for data entries.
  • The cached filesystem file size for referenced file entries.

After the ZIP archive is written, the entries become mapped entries, and this property then reflects the actual compressed size stored in the ZIP archive.

This property is useful when sizes may exceed the range of a 32-bit integer.

top
CompressionLevel
-- intVal is an integer
local intVal = zip_entry.compression_level
zip_entry.compression_level = intVal

Gets or sets the compression level for this entry.

A value of 0 means no compression, and a value of 9 means maximum compression.

The default value is 6.

top
CompressionMethod
-- intVal is an integer
local intVal = zip_entry.compression_method
zip_entry.compression_method = intVal

Gets or sets the compression method used for this entry.

  • 0 means no compression.
  • 8 means Deflate compression.

Deflate is the standard compression algorithm used by common ZIP utilities such as WinZip.

top
Crc
-- intVal is an integer (read-only)
local intVal = zip_entry.crc

The CRC value for this ZIP entry.

For AES-encrypted entries, the CRC value is 0.

top
DebugLogFilePath
-- strVal is a string
local strVal = zip_entry.debug_log_file_path
zip_entry.debug_log_file_path = 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
top
EncryptionKeyLen
-- intVal is an integer (read-only)
local intVal = zip_entry.encryption_key_len
Introduced in version 9.5.0.69

The AES encryption key length for this entry.

If this entry is AES encrypted, the value is 128, 192, or 256.

If this entry is not AES encrypted, the value is 0.

top
EntryID
-- intVal is an integer (read-only)
local intVal = zip_entry.entry_id

A unique identifier assigned to this entry while the ZIP object is instantiated in memory.

This ID can be used to retrieve the same entry later with Zip.EntryById.

top
EntryType
-- intVal is an integer (read-only)
local intVal = zip_entry.entry_type

Indicates the origin and current state of this ZIP entry.

  • 0 — Mapped Entry: an entry that already exists in an open ZIP file.
  • 1 — File Entry: a file in the local filesystem that has been referenced, but not yet read or compressed.
  • 2 — Data Entry: an entry containing uncompressed data already held in memory.
  • 3 — Null Entry: an entry that no longer exists in the ZIP archive.
  • 4 — New Directory Entry: a directory entry added to the ZIP object.

When the ZIP archive is written by calling WriteZip or WriteToMemory, entries are transformed into mapped entries. In other words, after writing, they point to compressed data contained in the newly created or rewritten ZIP archive.

top
FileDateTimeStr
-- strVal is a string
local strVal = zip_entry.file_date_time_str
zip_entry.file_date_time_str = strVal

Gets or sets the local last-modified date/time for this ZIP entry in RFC 822 string format.

Example RFC 822 date/time strings:

Tue, 15 Nov 1994 12:45:26 GMT
Fri, 05 Jan 2024 18:30:00 -0500

The timezone may be specified either as a named timezone such as GMT, or as a numeric UTC offset such as -0500.

top
FileName
-- strVal is a string
local strVal = zip_entry.file_name
zip_entry.file_name = strVal

Gets or sets the filename, including any relative path, stored for this entry inside the ZIP archive.

Changing this property changes the path/name that will appear in the ZIP archive. It does not rename a source file in the local filesystem.

top
FileNameHex
-- strVal is a string (read-only)
local strVal = zip_entry.file_name_hex

Returns the raw filename bytes found in the ZIP entry, encoded as a hexadecimal string.

This can be useful for diagnosing filename encoding issues.

top
HeartbeatMs
-- intVal is an integer
local intVal = zip_entry.heartbeat_ms
zip_entry.heartbeat_ms = intVal

The interval in milliseconds between each AbortCheck event callback, which enables an application to abort certain method calls before they complete. By default, HeartbeatMs is set to 0, meaning no AbortCheck event callbacks will trigger.

More Information and Examples
top
IsAesEncrypted
-- boolVal is a boolean (read-only)
local boolVal = zip_entry.is_aes_encrypted
Introduced in version 9.5.0.69

Indicates whether this ZIP entry is AES encrypted.

This property can be true only for entries already contained in a ZIP archive, such as entries obtained after calling OpenZip, OpenBd, or OpenFromMemory.

If the entry is not AES encrypted, the property is false.

top
IsDirectory
-- boolVal is a boolean (read-only)
local boolVal = zip_entry.is_directory

Indicates whether this ZIP entry is a directory entry.

The value is true if the entry represents a directory, and false if it represents a file.

top
LastErrorHtml
-- strVal is a string (read-only)
local strVal = zip_entry.last_error_html

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.

top
LastErrorText
-- strVal is a string (read-only)
local strVal = zip_entry.last_error_text

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.

top
LastErrorXml
-- strVal is a string (read-only)
local strVal = zip_entry.last_error_xml

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.

top
LastMethodSuccess
-- boolVal is a boolean
local boolVal = zip_entry.last_method_success
zip_entry.last_method_success = boolVal

Indicates the success or failure of the most recent method call: true means success, false 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.

top
TextFlag
-- boolVal is a boolean
local boolVal = zip_entry.text_flag
zip_entry.text_flag = boolVal

Gets or sets the text flag in the internal file attributes for this ZIP entry.

This flag indicates whether the entry contents should be considered text rather than binary data.

The flag is informational and does not need to be accurate for normal ZIP processing. It is provided for compatibility with applications that may be sensitive to this attribute.

top
UncompressedLength
-- intVal is an integer (read-only)
local intVal = zip_entry.uncompressed_length

The uncompressed size of this entry, in bytes.

top
UncompressedLength64
-- intVal is an integer (read-only)
local intVal = zip_entry.uncompressed_length64

The uncompressed size of this entry, in bytes, as a 64-bit integer.

Use this property when the uncompressed size may exceed the range of a 32-bit integer.

top
UncompressedLengthStr
-- strVal is a string (read-only)
local strVal = zip_entry.uncompressed_length_str

The uncompressed size of this ZIP entry as a decimal string.

This is useful when the uncompressed size may be larger than what can safely be represented by a 32-bit integer.

top
VerboseLogging
-- boolVal is a boolean
local boolVal = zip_entry.verbose_logging
zip_entry.verbose_logging = boolVal

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

top
Version
-- strVal is a string (read-only)
local strVal = zip_entry.version

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

More Information and Examples
top

Methods

AppendString
-- str_content is a string
-- charset is a string
-- ok is true, or nil and err on failure
local ok, err = zip_entry:append_string(str_content, charset)

Appends text data to this ZIP entry's file contents.

The text is converted to bytes using the character encoding specified by charset, such as utf-8, utf-16, or ansi.

If this entry is already a Data Entry (EntryType = 2), then the encoded bytes are appended directly to the existing uncompressed in-memory data.

If this entry is not already a Data Entry, then the entry is first converted into a Data Entry before the new text data is appended.

  • If the entry is a mapped entry (EntryType = 0), the compressed ZIP entry data is first inflated into memory. The new text data is then appended, and the entry becomes a Data Entry containing the combined uncompressed data.
  • If the entry is a file entry (EntryType = 1), the referenced filesystem file is first loaded into memory. The new text data is then appended, and the entry becomes a Data Entry containing the combined data.

After this method is called, the entry contents exist entirely as uncompressed in-memory data associated with the ZipEntry object.

Returns true on success, nil, err on failure. The second return value, err, is the object's last_error_text; wrap the call in assert() to raise an error instead.

top
CopyToBase64
-- str is a string, or nil and err on failure
local str, err = zip_entry:copy_to_base64()

Returns the compressed data for this ZIP entry as a Base64-encoded string.

This method can only be used when the entry already contains compressed data, meaning the entry is a mapped entry.

This is possible for entries from a ZIP archive that has already been opened, or after writing a ZIP archive while it remains open.

Returns the string, or nil, err on failure (or when nothing is found). The second return value, err, is the object's last_error_text; wrap the call in assert() to raise an error instead.

top
CopyToHex
-- str is a string, or nil and err on failure
local str, err = zip_entry:copy_to_hex()

Returns the compressed data for this ZIP entry as a hexadecimal encoded string.

This method can only be used when the entry already contains compressed data, meaning the entry is a mapped entry.

This is possible for entries from a ZIP archive that has already been opened, or after writing a ZIP archive while it remains open.

Returns the string, or nil, err on failure (or when nothing is found). The second return value, err, is the object's last_error_text; wrap the call in assert() to raise an error instead.

top
Extract
-- dir_path is a string
-- ok is true, or nil and err on failure
local ok, err = zip_entry:extract(dir_path)

Extracts this ZIP entry beneath the specified base directory.

The entry is extracted according to the relative path stored in the ZIP archive.

For example, if the entry filename is docs/readme.txt and dirPath is c:/temp/output, the file is extracted to c:/temp/output/docs/readme.txt.

Use ExtractInto instead if the file should be extracted directly into a specific directory regardless of the path stored in the ZIP archive.

Returns true on success, nil, err on failure. The second return value, err, is the object's last_error_text; wrap the call in assert() to raise an error instead.

top
ExtractInto
-- dir_path is a string
-- ok is true, or nil and err on failure
local ok, err = zip_entry:extract_into(dir_path)

Extracts this entry directly into the specified directory, ignoring any path information stored in the ZIP entry.

For example, if the entry filename is docs/readme.txt and dirPath is c:/temp/output, the file is extracted to c:/temp/output/readme.txt.

If this entry is a directory entry, nothing is extracted. To create the directory represented by a directory entry, use Extract instead.

Returns true on success, nil, err on failure. The second return value, err, is the object's last_error_text; wrap the call in assert() to raise an error instead.

top
GetNext
-- flag is true or false
local flag = zip_entry:get_next()
Introduced in version 11.0.0

Updates this ZipEntry object so that it represents the next entry in the same ZIP archive.

The next entry may be either a file entry or a directory entry.

Returns true if the object was advanced to the next entry. Returns false if there are no more entries.

Returns true or false: an answer, not a success flag.

top
GetNextMatch
-- pattern is a string
-- flag is true or false
local flag = zip_entry:get_next_match(pattern)
Introduced in version 11.0.0

Updates this ZipEntry object so that it represents the next entry in the ZIP archive matching the specified wildcard pattern.

The wildcard character * matches zero or more characters. Matching is performed against the full stored filename, including any relative path.

The matching entry may be either a file entry or a directory entry.

Returns true if a matching entry is found. Returns false if no further matching entry exists.

Returns true or false: an answer, not a success flag.

top
ReplaceString
-- str_content is a string
-- charset is a string
-- ok is true, or nil and err on failure
local ok, err = zip_entry:replace_string(str_content, charset)

Replaces this ZIP entry's existing contents with new text data.

The text is converted to bytes using the character encoding specified by charset, such as utf-8 or ansi.

The resulting bytes become the complete contents of the entry.

Returns true on success, nil, err on failure. The second return value, err, is the object's last_error_text; wrap the call in assert() to raise an error instead.

More Information and Examples
top
SetDt
-- dt is a chilkat.DateTime
zip_entry:set_dt(dt)

Sets the last-modified date/time for this ZIP entry.

The dt argument is a CkDateTime object containing the date/time to store for the entry.

top
UnzipToBd
-- bin_data is a chilkat.BinData
-- ok is true, or nil and err on failure
local ok, err = zip_entry:unzip_to_bd(bin_data)
Introduced in version 9.5.0.67

Unzips this entry directly into a BinData object.

The uncompressed bytes are written to binData.

Returns true on success, nil, err on failure. The second return value, err, is the object's last_error_text; wrap the call in assert() to raise an error instead.

top
UnzipToSb
-- line_ending_behavior is an integer
-- src_charset is a string
-- sb is a chilkat.StringBuilder
-- ok is true, or nil and err on failure
local ok, err = zip_entry:unzip_to_sb(line_ending_behavior, src_charset, sb)
Introduced in version 9.5.0.67

Unzips this entry as text and appends the result to a StringBuilder.

The srcCharset argument specifies how the uncompressed bytes should be interpreted, such as utf-8, utf-16, or windows-1252.

The lineEndingBehavior argument controls line-ending conversion:

  • 0 — leave line endings unchanged.
  • 1 — convert all line endings to bare LF.
  • 2 — convert all line endings to CRLF.

Returns true on success, nil, err on failure. The second return value, err, is the object's last_error_text; wrap the call in assert() to raise an error instead.

top
UnzipToStream
-- to_stream is a chilkat.Stream
-- ok is true, or nil and err on failure
local ok, err = zip_entry:unzip_to_stream(to_stream)
Introduced in version 9.5.0.67

Unzips this entry to a stream.

If called synchronously, the toStream must have a sink, such as a file or another stream object.

If called asynchronously, the foreground thread can read from the stream while the unzip operation writes to it.

Returns true on success, nil, err on failure. The second return value, err, is the object's last_error_text; wrap the call in assert() to raise an error instead.

top
UnzipToString
-- line_ending_behavior is an integer
-- src_charset is a string
-- str is a string, or nil and err on failure
local str, err = zip_entry:unzip_to_string(line_ending_behavior, src_charset)

Inflates this entry and returns the uncompressed data as a string.

The srcCharset argument specifies how the uncompressed bytes should be interpreted, such as utf-8, utf-16, or windows-1252.

The lineEndingBehavior argument controls line-ending conversion:

  • 0 — leave line endings unchanged.
  • 1 — convert all line endings to bare LF.
  • 2 — convert all line endings to CRLF.

Returns the string, or nil, err on failure (or when nothing is found). The second return value, err, is the object's last_error_text; wrap the call in assert() to raise an error instead.

top

Events

All Chilkat methods are synchronous: the call returns when the work is done. During a long-running call, chilkat.ZipEntry reports progress to the functions given to set_event_handler, in a table keyed by event name (plain functions, not methods: closures carry whatever state they need):

zip_entry:set_event_handler({
    percent_done  = function(pct) print(pct .. "%") end,              -- return true to abort
    progress_info = function(name, value) print(name, value) end,
})
zip_entry.heartbeat_ms = 250   -- abort_check is called 4 times per second
zip_entry:set_event_handler({ event_name = function(...) ... end, ... })

Installs the handlers, replacing any installed before; zip_entry:set_event_handler(nil) removes them. The event names are checked when the table is installed: a misspelled one raises an error.

The abort_check handler is called at the interval set by the heartbeat_ms property (0, the default, disables it); percent_done is called when an operation's completion percentage is known; progress_info delivers named progress values. A true return from abort_check or percent_done aborts the running method, which then fails in the usual way (nil, err). An error raised in a handler aborts the method and is raised again from the method call; the object remains usable.

AbortCheck
-- handler: function() ... return abort end -- a true return aborts the method in progress
zip_entry:set_event_handler({ abort_check = function() ... end })

Enables a method call to be aborted by triggering the AbortCheck event at intervals defined by the HeartbeatMs property. If HeartbeatMs is set to its default value of 0, no events will occur. For instance, set HeartbeatMs to 200 to trigger 5 AbortCheck events per second.

More Information and Examples

Example

local deadline = os.time() + 30                  -- give up after 30 seconds
zip_entry.heartbeat_ms = 250                      -- call the handler 4 times per second
zip_entry:set_event_handler({ abort_check = function() return os.time() > deadline end })
top
PercentDone
-- handler: function(pct_done) ... return abort end -- a true return aborts
zip_entry:set_event_handler({ percent_done = function(pct_done) ... end })

This provides the percentage completion for any method involving network communications or time-consuming processing, assuming the progress can be measured as a percentage. This event is triggered only when it's possible and logical to express the operation's progress as a percentage. The pctDone argument will range from 1 to 100. For methods that finish quickly, the number of PercentDone callbacks may vary, but the final callback will have pctDone equal to 100. For longer operations, callbacks will not exceed one per percentage point (e.g., 1, 2, 3, ..., 98, 99, 100).

The PercentDone callback also acts as an AbortCheck event. For fast methods where PercentDone fires, an AbortCheck event may not trigger since the PercentDone callback already provides an opportunity to abort. For longer operations, where time between PercentDone callbacks is extended, AbortCheck callbacks enable more responsive operation termination.

To abort the operation, set the abort output argument to true. This will cause the method to terminate and return a failure status or corresponding failure value.

More Information and Examples

Example

zip_entry:set_event_handler({
    percent_done = function(pct_done)     -- 0 to 100
        print("Percent done: " .. pct_done)
        return false                       -- return true to abort the method in progress
    end,
})
top
ProgressInfo
-- handler: function(name, value) ... end
zip_entry:set_event_handler({ progress_info = function(name, value) ... end })

This event callback provides tag name/value pairs that detail what occurs during a method call. To discover existing tag names, create code to handle the event, emit the pairs, and review them. Most tag names are self-explanatory.

Note: Some Chilkat methods don't fire any ProgressInfo events.

More Information and Examples

Example

zip_entry:set_event_handler({
    progress_info = function(name, value) print(name .. ": " .. value) end,
})
top