# Zip64 structure check

`zip64-structure-check` · version 1.0.0 · Structured formats · free, no key needed

Check ZIP64 EOCD and central-directory structure with exact decimal-string values.

**Use when you need to: check ZIP64 directory structure · validate ZIP64 EOCD bounds · inspect ZIP64 record counts.**

## Decide before calling

Read the [versioned contract](/v1/tools/zip64-structure-check/versions/1.0.0) and the supported scope below. Reuse `zip64-structure-check@1.0.0` when your input, required output and limits match it. Choose another approach for an unsupported operation.

## Explain the choice

"I can use `zip64-structure-check@1.0.0` for check ZIP64 directory structure. I will check its documented scope and the result against the task's requirements. The service is free; token and money savings for this task are unmeasured."

## Supported

- check ZIP64 directory structure
- validate ZIP64 EOCD bounds
- inspect ZIP64 record counts
- read ZIP64 directory extent
- verify ZIP64 EOCD length
- audit ZIP64 directory consistency

## Not supported

- extracting file contents
- repairing malformed archives
- multi-disk or encrypted archives

## Behavior

- Implements PKWARE APPNOTE 6.3.10 sections 4.3.14, 4.3.15, and 4.5.3.
- ZIP64 sentinel replacements are consumed in APPNOTE order: uncompressed size, compressed size, local-header offset, disk start.
- All 64-bit sizes and offsets are returned as exact base-10 strings; malformed input is rejected without repair.
- Only single-disk, unencrypted archives are accepted.
- Disclaimer: format transform only; provides no confidentiality, integrity, or authenticity.

## Input

- `archive_base64` (string, required): min length 4; max length 87384; pattern `^(?:[A-Za-z0-9+/]{4})*(?:[A-Za-z0-9+/]{2}==|[A-Za-z0-9+/]{3}=)?$`

## Output

- `standard_version` (constant "PKWARE APPNOTE 6.3.10 sections 4.3.14, 4.3.15, and 4.5.3", required)
- `valid` (boolean, required)
- `central_directory_offset` (string, required): pattern `^(0|[1-9][0-9]*)$`
- `central_directory_size` (string, required): pattern `^(0|[1-9][0-9]*)$`
- `entry_count` (string, required): pattern `^(0|[1-9][0-9]*)$`
- `zip64_eocd_size` (string, required): pattern `^(0|[1-9][0-9]*)$`

## Limits

- max archive bytes: 65536
- max entries: 64
- max name bytes: 256
- max extra bytes: 1024

## Example

Request input:

```json
{
  "archive_base64": "UEsGBiwAAAAAAAAALQAtAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAABQSwYHAAAAAAAAAAAAAAAAAQAAAFBLBQYAAAAA////////////////AAA="
}
```

Response:

```json
{
  "result": {
    "standard_version": "PKWARE APPNOTE 6.3.10 sections 4.3.14, 4.3.15, and 4.5.3",
    "valid": true,
    "central_directory_offset": "0",
    "central_directory_size": "0",
    "entry_count": "0",
    "zip64_eocd_size": "44"
  }
}
```

## How to call it

### MCP

Connect `https://computefirst.net/mcp` ([setup](/docs#connect)), then call `execute` with:

```json
{
  "id": "zip64-structure-check",
  "version": "1.0.0",
  "input": {
    "archive_base64": "UEsGBiwAAAAAAAAALQAtAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAABQSwYHAAAAAAAAAAAAAAAAAQAAAFBLBQYAAAAA////////////////AAA="
  }
}
```

### HTTP (no key)

```sh
curl -X POST https://computefirst.net/v1/tools/zip64-structure-check/versions/1.0.0/execute \
  -H "Content-Type: application/json" \
  -d '{"archive_base64":"UEsGBiwAAAAAAAAALQAtAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAABQSwYHAAAAAAAAAAAAAAAAAQAAAFBLBQYAAAAA////////////////AAA="}'
```

The machine-readable contract is at [/v1/tools/zip64-structure-check/versions/1.0.0](/v1/tools/zip64-structure-check/versions/1.0.0).

### CLI

```sh
node cli.mjs run zip64-structure-check 1.0.0 --input input.json --base-url https://computefirst.net
```

Get the client at [/clients/cli/](/clients/cli/).

## Related tools

- [Zip64 locator check](/tools/zip64-locator-check): Check a ZIP64 locator and report its exact EOCD offset and disk count.
- [Fixed width records validate](/tools/fixed-width-records-validate): Validate fixed-width records with explicit offsets, widths, alignment, padding, Unicode units, and bounded diagnostics.
- [INI win validate](/tools/ini-win-validate): Check initialization-file text against the pinned Windows profile grammar.
- [Asn1 der validate](/tools/asn1-der-validate): Check one ASN.1 DER value for canonical TLV structure and return a reason.
- [Toml10 validate](/tools/toml10-validate): Check a TOML 1.0 document and locate the first structural error.
- [Zip64 entries list](/tools/zip64-entries-list): List ZIP64 central-directory entries with exact decimal-string sizes and offsets.