(Objective-C) Append Text Data to an Existing ZIP Entry Using ZipEntry.AppendString

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This example demonstrates how to use the ZipEntry.AppendString method to append text data to an existing ZIP entry.

The example opens an existing ZIP archive, locates a text file entry, and appends additional text to the end of the file contents.

An important concept demonstrated by this example is that appending data to a ZIP entry transforms the entry into an in-memory Data Entry (EntryType = 2).

For example:

• If the entry is a mapped entry from an opened ZIP archive (EntryType = 0), the compressed entry is first inflated into memory.
• If the entry is a referenced filesystem file (EntryType = 1), the file contents are first loaded into memory.

The new text is then appended to the uncompressed in-memory data, and the entry becomes a Data Entry.

After the ZIP archive is rewritten, the modified entry again becomes a mapped entry stored within the ZIP archive.

Note: This example requires Chilkat v11.0.0 or greater.

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#import <CkoZip.h>
#import <CkoZipEntry.h>

BOOL success = NO;

CkoZip *zip = [[CkoZip alloc] init];

// ------------------------------------------------------------
// Open an existing ZIP archive.
success = [zip OpenZip: @"c:/temp/notes.zip"];
if (success == NO) {
    NSLog(@"%@",zip.LastErrorText);
    return;
}

// Locate a text file entry within the ZIP archive.
CkoZipEntry *entry = [[CkoZipEntry alloc] init];

success = [zip EntryOf: @"notes/readme.txt" entry: entry];

if (success != NO) {

    // --------------------------------------------------------
    // At this point, the entry is a mapped entry because it
    // originates from an opened ZIP archive.
    // 
    //     EntryType = 0
    // 
    NSLog(@"%@%d",@"Initial EntryType = ",[entry.EntryType intValue]);

    // Append additional text to the ZIP entry.
    // 
    // The existing compressed ZIP entry is first inflated
    // into memory. The new text is then appended.
    // 
    // After AppendString is called, the entry becomes
    // an in-memory Data Entry:
    // 
    //     EntryType = 2
    // 
    success = [entry AppendString: @"\r\nAdditional notes added later." charset: @"utf-8"];

    if (success == NO) {
        NSLog(@"%@",zip.LastErrorText);
        return;
    }

    NSLog(@"%@%d",@"EntryType after AppendString = ",[entry.EntryType intValue]);

    // --------------------------------------------------------
    // Write the modified ZIP archive to a different file.
    // 
    // Changing zip.FileName causes the ZIP archive to be
    // written to a new output file rather than overwriting
    // the original ZIP archive.
    // 
    zip.FileName = @"qa_output/updatedExample.zip";

    // Rewrite the ZIP archive.
    // 
    // The modified in-memory entry is compressed and written
    // into the new ZIP archive.
    // 
    success = [zip WriteZip];
    if (success == NO) {
        NSLog(@"%@",zip.LastErrorText);
        return;
    }

    // After rewriting the ZIP archive, the entry again becomes
    // a mapped entry:
    // 
    //     EntryType = 0
    // 
    NSLog(@"%@%d",@"EntryType after WriteZip = ",[entry.EntryType intValue]);
}

[zip CloseZip];

NSLog(@"%@",@"ZIP entry updated successfully.");