Visual FoxPro

Retrieve Metadata from a Gzip File

See more Gzip Examples

This example demonstrates how to use the GetGzipInfo method to retrieve metadata embedded within a Gzip file.

The method reads the Gzip header and extracts any available metadata, including the embedded filename, comment, and optional extra data. The extracted information is returned in a JsonObject.

Because these fields are optional, the example checks for the existence of each JSON member using HasMember before retrieving its value. This avoids attempting to access values that may not be present.

Visual FoxPro

LOCAL lnSuccess
LOCAL loGzip
LOCAL loJson
LOCAL lcGzPath
LOCAL lcFilename
LOCAL lcComment
LOCAL lcExtraData

lnSuccess = 0

* This example demonstrates how to retrieve metadata embedded in a Gzip file.

loGzip = CreateObject('Chilkat.Gzip')
loJson = CreateObject('Chilkat.JsonObject')

* The Gzip file to examine:
lcGzPath = "example.txt.gz"

* Get the metadata information:
lnSuccess = loGzip.GetGzipInfo(lcGzPath,loJson)
IF (lnSuccess = 0) THEN
    ? loGzip.LastErrorText
    RELEASE loGzip
    RELEASE loJson
    CANCEL
ENDIF

* Output the JSON containing metadata:
? "Gzip metadata JSON:"
? loJson.Emit()

* Access individual fields only if they exist:

IF (loJson.HasMember("filename") = 1) THEN
    lcFilename = loJson.StringOf("filename")
    ? "Filename: " + lcFilename
ENDIF

IF (loJson.HasMember("comment") = 1) THEN
    lcComment = loJson.StringOf("comment")
    ? "Comment: " + lcComment
ENDIF

IF (loJson.HasMember("extraData") = 1) THEN
    lcExtraData = loJson.StringOf("extraData")
    ? "ExtraData (Base64): " + lcExtraData
ENDIF

RELEASE loGzip
RELEASE loJson