Visual FoxPro

Retrieve Metadata from Gzip Data in Memory (BinData)

This example demonstrates how to use the GetGzipInfoBd method to retrieve metadata from Gzip data stored in memory within a BinData object.

The Gzip data is first loaded into the BinData instance. The GetGzipInfoBd method then extracts any available metadata from the Gzip header, including the embedded filename, comment, and optional extra data.

The metadata 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.

Visual FoxPro

LOCAL lnSuccess
LOCAL loGzip
LOCAL loBd
LOCAL loJson
LOCAL lcFilename
LOCAL lcComment
LOCAL lcExtraData

lnSuccess = 0

* This example demonstrates how to retrieve metadata from Gzip data
* stored in a BinData object.

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

* Load a Gzip file into BinData:
lnSuccess = loBd.LoadFile("example.txt.gz")
IF (lnSuccess = 0) THEN
    ? loBd.LastErrorText
    RELEASE loGzip
    RELEASE loBd
    RELEASE loJson
    CANCEL
ENDIF

* Get the metadata information from the in-memory Gzip data:
lnSuccess = loGzip.GetGzipInfoBd(loBd,loJson)
IF (lnSuccess = 0) THEN
    ? loGzip.LastErrorText
    RELEASE loGzip
    RELEASE loBd
    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 loBd
RELEASE loJson