Visual FoxPro

Read the REST Response Body in Chunks

Demonstrates Rest.ReadRespChunkBd, which reads the response body one chunk at a time, appending each chunk to a BinData. A return value of 0 signals the body is complete, while -1 indicates a read failure.

Background. Chunked reading lets an application process a large response incrementally rather than buffering the entire body at once. It is used after ReadResponseHeader within the staged request model.

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LOCAL lnSuccess
LOCAL loRest
LOCAL lnBTls
LOCAL lnBAutoReconnect
LOCAL lnStatusCode
LOCAL loSbError
LOCAL loBdBody
LOCAL lnChunkResult

lnSuccess = 0

loRest = CreateObject('Chilkat.Rest')
lnBTls = 1
lnBAutoReconnect = 1
lnSuccess = loRest.Connect("example.com",443,lnBTls,lnBAutoReconnect)
IF (lnSuccess = 0) THEN
    ? loRest.LastErrorText
    RELEASE loRest
    CANCEL
ENDIF

lnSuccess = loRest.SendReqNoBody("GET","/api/largefile")
IF (lnSuccess = 0) THEN
    ? loRest.LastErrorText
    RELEASE loRest
    CANCEL
ENDIF

lnStatusCode = loRest.ReadResponseHeader()
IF (lnStatusCode < 0) THEN
    ? loRest.LastErrorText
    RELEASE loRest
    CANCEL
ENDIF

*  Check for the expected success status code.  If the response is not 200, the body is likely
*  error text formatted as JSON, XML, or HTML rather than the expected content.  In that case read
*  the body as text, report it, and return.
IF (lnStatusCode <> 200) THEN
    loSbError = CreateObject('Chilkat.StringBuilder')
    lnSuccess = loRest.ReadRespSb(loSbError)
    IF (lnSuccess = 0) THEN
        ? loRest.LastErrorText
        RELEASE loRest
        RELEASE loSbError
        CANCEL
    ENDIF

    ? "Request failed with status code " + STR(lnStatusCode)
    ? loSbError.GetAsString()
    RELEASE loRest
    RELEASE loSbError
    CANCEL
ENDIF

*  The status code is 200.  Read the response body in chunks, appending each chunk to the BinData.
*  Each call waits until at least the requested number of bytes is available, unless the response
*  ends first.  A return value of 0 means the final bytes were returned and the body is complete;
*  -1 indicates a read failure.
loBdBody = CreateObject('Chilkat.BinData')
lnChunkResult = loRest.ReadRespChunkBd(8192,loBdBody)
DO WHILE lnChunkResult > 0
    lnChunkResult = loRest.ReadRespChunkBd(8192,loBdBody)
ENDDO
IF (lnChunkResult < 0) THEN
    ? loRest.LastErrorText
    RELEASE loRest
    RELEASE loSbError
    RELEASE loBdBody
    CANCEL
ENDIF

? "Received " + STR(loBdBody.NumBytes) + " bytes."

RELEASE loRest
RELEASE loSbError
RELEASE loBdBody