ZipCrc Zig Reference Documentation

ZipCrc

Current Version: 11.6.1

Chilkat.ZipCrc

Calculate ZIP-compatible CRC32 values for files, bytes, strings, and streamed data.

Chilkat.ZipCrc calculates the 32-bit CRC value used in ZIP file headers. It can compute CRC32 values for in-memory byte arrays, BinData, StringBuilder content, strings using a specified character encoding, and entire files. It also supports streaming CRC calculation, allowing applications to process large or incremental data in chunks without holding the full input in memory.

CRC32 for byte data

Use CalculateCrc to calculate a ZIP-style CRC32 value for an in-memory byte array.

BinData support

Use CrcBd when the input bytes are already stored in a Chilkat.BinData object.

String CRCs

Use CrcString or CrcSb to calculate CRC32 for text using a specific charset such as utf-8, utf-16, or windows-1252.

File CRCs

Use FileCrc to calculate the CRC32 of a file while streaming the file contents to keep memory usage small and constant.

Streaming calculation

Call BeginStream, add chunks with MoreData, and finish with EndStream when data arrives incrementally.

Hex formatting

Use ToHex to convert a 32-bit CRC integer into a readable hexadecimal string.

Common pattern: Use FileCrc for files, CalculateCrc or CrcBd for binary data already in memory, and CrcString or CrcSb for text where the byte representation depends on a charset. For large or chunked input, initialize the CRC with BeginStream, feed each block with MoreData, and call EndStream to obtain the final CRC32 value.
ZIP compatibility note: The CRC returned by this class is the same 32-bit CRC value that would appear in a ZIP file header for the same byte content. When calculating CRCs for strings, the selected charset matters because the CRC is computed over bytes, not abstract characters.

Object Creation

// Add the package once:
//     zig fetch --save https://chilkatdownload.com/11.6.1/chilkat-zig-11.6.1.tar.gz
// and in build.zig:
//     const chilkat = b.dependency("chilkat", .{ .target = target, .optimize = optimize });
//     exe.root_module.addImport("chilkat", chilkat.module("chilkat"));
const chilkat = @import("chilkat");

// Once per process, before any other Chilkat call:
try chilkat.unlockBundle("Anything for 30-day trial");

const zip_crc = try chilkat.ZipCrc.init();
defer zip_crc.deinit();
pub fn init() Allocator.Error!ZipCrc

Creates the underlying native Chilkat object. ZipCrc is a one-pointer struct passed by value; copying it copies the handle (two names for one object). Returns error.OutOfMemory if the library could not allocate the object. Use an object from one thread at a time; it may be handed from one thread to another.

pub fn deinit(self: ZipCrc) void

Releases the native object. Call it exactly once per object (usually with defer); the handle is invalid afterwards. Objects returned by methods are owned by the caller too and are released the same way.

pub fn fromHandle(h: *chilkat.c.CkZipCrc.HCkZipCrc) ZipCrc

Wraps a handle obtained from the C API (chilkat.c.CkZipCrc), taking ownership of it. The struct's handle field goes the other way, for anything the Zig API does not cover.

Errors and memory

Methods that can fail return an error union: a method whose only outcome is success or failure returns Error!void; a method producing a string returns (Error || Allocator.Error)![:0]u8; a method producing an object returns Error!T. chilkat.Error is error{ChilkatFailed}; the reason for a failure is in getLastErrorText, and the object remains usable. Properties never fail, and methods that answer a question (hasMember, isUnlocked, ...) return a plain bool.

String arguments are [:0]const u8 (UTF-8; string literals can be passed as is). String results are copies allocated with the allocator argument and owned by the caller, so they stay valid across later calls on the same object.

const text = zip_crc.someMethod(allocator, ...) catch |err| {
    const why = try zip_crc.getLastErrorText(allocator);
    defer allocator.free(why);
    std.debug.print("{s}\n", .{why});
    return err;
};
defer allocator.free(text);

Properties

DebugLogFilePath
// read/write
pub fn getDebugLogFilePath(self: ZipCrc, allocator: Allocator) Allocator.Error![:0]u8
pub fn setDebugLogFilePath(self: ZipCrc, value: [:0]const u8) void

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
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LastErrorHtml
// read-only
pub fn getLastErrorHtml(self: ZipCrc, allocator: Allocator) Allocator.Error![:0]u8

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.

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LastErrorText
// read-only
pub fn getLastErrorText(self: ZipCrc, allocator: Allocator) Allocator.Error![:0]u8

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.

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LastErrorXml
// read-only
pub fn getLastErrorXml(self: ZipCrc, allocator: Allocator) Allocator.Error![:0]u8

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.

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LastMethodSuccess
// read/write
pub fn getLastMethodSuccess(self: ZipCrc) bool
pub fn setLastMethodSuccess(self: ZipCrc, value: bool) void

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.

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VerboseLogging
// read/write
pub fn getVerboseLogging(self: ZipCrc) bool
pub fn setVerboseLogging(self: ZipCrc, value: bool) void

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.

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Version
// read-only
pub fn getVersion(self: ZipCrc, allocator: Allocator) Allocator.Error![:0]u8

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

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Methods

BeginStream
pub fn beginStream(self: ZipCrc) void

Provides a way to calculate a CRC by streaming the data a chunk at a time. An application would start by calling BeginStream. Then it would add data by calling MoreData for each additional chunk. After the last chunk has been processed, the EndStream method is called to return the CRC.

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CrcBd
pub fn crcBd(self: ZipCrc, bd: chilkat.BinData) u32
Introduced in version 9.5.0.75

Calculates a CRC32 for the bytes contained in bd.

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CrcSb
pub fn crcSb(self: ZipCrc, sb: chilkat.StringBuilder, charset: [:0]const u8) u32
Introduced in version 9.5.0.75

Calculates a CRC32 for the string contained in sb. The charset is the byte representation to be used for the sb when calculating the CRC32. It can be utf-8, utf-16, windows-1252, iso-8859-1, or any of the character encodings (charsets) listed at the link below.

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CrcString
pub fn crcString(self: ZipCrc, str: [:0]const u8, charset: [:0]const u8) u32
Introduced in version 9.5.0.75

Calculates a CRC32 for a string. The charset is the byte representation to be used for the str when calculating the CRC32. It can be utf-8, utf-16, windows-1252, iso-8859-1, or any of the character encodings (charsets) listed at the link below.

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EndStream
pub fn endStream(self: ZipCrc) u32

Finalizes and returns the Zip CRC value calculated by calling BeginStream followed by multiple calls to MoreData.

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FileCrc
pub fn fileCrc(self: ZipCrc, path: [:0]const u8) u32

Calculates the CRC32 of a file. The data contained in the file is streamed for the calculation to keep the memory footprint small and constant. Returns the CRC32 of the file.

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ToHex
pub fn toHex(self: ZipCrc, allocator: Allocator, crc: u32) (Error || Allocator.Error)![:0]u8

Converts a 32-bit integer to a hex string.

Returns error.ChilkatFailed on failure; getLastErrorText explains why. The string is allocated with allocator and owned by the caller (defer allocator.free(s)).

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Events

All Chilkat methods are synchronous: the call returns when the work is done. During a call, ZipCrc raises three events so your program can show progress and offer a way out. Declare any subset of abortCheck, percentDone and progressInfo in a struct of your own and install a pointer to it with setEventHandler:

const Progress = struct {
    pub fn percentDone(_: *Progress, pct: i32) bool {
        std.debug.print("{d}%\n", .{pct});
        return false; // return true to abort the method in progress
    }
    pub fn progressInfo(_: *Progress, name: [:0]const u8, value: [:0]const u8) void {
        std.debug.print("{s}: {s}\n", .{ name, value });
    }
};

var progress = Progress{};
zip_crc.setEventHandler(&progress); // progress must outlive the installation
defer zip_crc.clearEventHandler();
zip_crc.setHeartbeatMs(250); // abortCheck 4 times per second during Chilkat calls
pub fn setEventHandler(self: ZipCrc, handler: anytype) void

Installs handler, a pointer to any struct, as the receiver of this object's events, replacing any handler installed earlier. The dispatch is resolved at compile time: only the methods the struct declares are called, and a struct declaring none of the three is a compile error. The struct must stay alive, at the same address, until clearEventHandler or deinit.

pub fn clearEventHandler(self: ZipCrc) void

Removes the handler; events are no longer delivered.

AbortCheck fires at regular intervals controlled by the HeartbeatMs property (0, the default, disables it); PercentDone fires when an operation's completion percentage is known; ProgressInfo delivers named progress values. Returning true from abortCheck or percentDone aborts the running method, which then returns error.ChilkatFailed.

Events fire on the thread that called the method, before that method returns. To abort a long operation from another thread, have abortCheck read a std.atomic.Value(bool), or set the object's AbortCurrent property.

AbortCheck
// handler struct method (optional); install with setEventHandler
pub fn abortCheck(self: *T) bool

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

const Abort = struct {
    stop: std.atomic.Value(bool) = .init(false),
    pub fn abortCheck(self: *Abort) bool {
        return self.stop.load(.acquire); // another thread may call abort.stop.store(true, .release)
    }
};

var abort = Abort{};
zip_crc.setHeartbeatMs(250); // call abortCheck 4 times per second
zip_crc.setEventHandler(&abort);
defer zip_crc.clearEventHandler();
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PercentDone
// handler struct method (optional); install with setEventHandler
pub fn percentDone(self: *T, pct: i32) bool

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

const Progress = struct {
    pub fn percentDone(_: *Progress, pct: i32) bool {
        // pct ranges from 1 to 100.
        std.debug.print("Percent done: {d}\n", .{pct});
        return false; // return true to abort the method in progress
    }
};

var progress = Progress{};
zip_crc.setEventHandler(&progress);
defer zip_crc.clearEventHandler();
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ProgressInfo
// handler struct method (optional); install with setEventHandler
pub fn progressInfo(self: *T, name: [:0]const u8, value: [:0]const u8) void

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

const Info = struct {
    pub fn progressInfo(_: *Info, name: [:0]const u8, value: [:0]const u8) void {
        std.debug.print("{s}: {s}\n", .{ name, value });
    }
};

var info = Info{};
zip_crc.setEventHandler(&info);
defer zip_crc.clearEventHandler();
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