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(Unicode C) S3 Resume DownloadSuppose an S3 download of a very large file failed for some reason and you have a partial file on disk. Rather than restart the entire download, you wish to download the remaining portion. This example demonstrates how to finish a previously failed download. Note: This example requires Chilkat v9.5.0.83 or above.
#include <C_CkRestW.h> #include <C_CkAuthAwsW.h> #include <C_CkFileAccessW.h> #include <C_CkStringBuilderW.h> #include <C_CkStreamW.h> void ChilkatSample(void) { HCkRestW rest; BOOL bTls; int port; BOOL bAutoReconnect; BOOL success; HCkAuthAwsW authAws; HCkFileAccessW fac; const wchar_t *localFilepath; int sz; HCkStringBuilderW sbRange; int responseStatusCode; HCkStreamW bodyStream; const wchar_t *errResponse; // This example requires the Chilkat API to have been previously unlocked. // See Global Unlock Sample for sample code. rest = CkRestW_Create(); // Connect to the Amazon AWS REST server. bTls = TRUE; port = 443; bAutoReconnect = TRUE; success = CkRestW_Connect(rest,L"s3.amazonaws.com",port,bTls,bAutoReconnect); // --------------------------------------------------------------------------- // Important: For buckets created in regions outside us-east-1, // there are three important changes that need to be made. // See Working with S3 Buckets in Non-us-east-1 Regions for the details. // --------------------------------------------------------------------------- // Provide AWS credentials for the REST call. authAws = CkAuthAwsW_Create(); CkAuthAwsW_putAccessKey(authAws,L"AWS_ACCESS_KEY"); CkAuthAwsW_putSecretKey(authAws,L"AWS_SECRET_KEY"); CkAuthAwsW_putServiceName(authAws,L"s3"); success = CkRestW_SetAuthAws(rest,authAws); // Set the bucket name via the HOST header. // In this case, the bucket name is "chilkat100". CkRestW_putHost(rest,L"chilkat100.s3.amazonaws.com"); // We want to continue downloading a file. // The relative local filepath of our previously partially downoaded file is: qa_output/hamlet.xml // Let's find out how many bytes are already downloaded. fac = CkFileAccessW_Create(); localFilepath = L"qa_output/hamlet.xml"; // Note: The FileSize method returns a signed 32-bit integer. If the file is potentially larger than 2GB, call FileSizeStr instead to return // the size of the file as a string, then convert to an integer value. sz = CkFileAccessW_FileSize(fac,localFilepath); if (sz > 0) { wprintf(L"sz = %d\n",sz); // If the sz equals 42375 bytes, then we want to add a Range header that looks like this: // Range: bytes=42375- sbRange = CkStringBuilderW_Create(); CkStringBuilderW_Append(sbRange,L"bytes="); CkStringBuilderW_AppendInt(sbRange,sz); CkStringBuilderW_Append(sbRange,L"-"); CkRestW_AddHeader(rest,L"Range",CkStringBuilderW_getAsString(sbRange)); wprintf(L"Added Range: %s\n",CkStringBuilderW_getAsString(sbRange)); } // Send the request to download the remainder of the file. success = CkRestW_SendReqNoBody(rest,L"GET",L"/hamlet.xml"); if (success != TRUE) { wprintf(L"%s\n",CkRestW_lastErrorText(rest)); CkRestW_Dispose(rest); CkAuthAwsW_Dispose(authAws); CkFileAccessW_Dispose(fac); CkStringBuilderW_Dispose(sbRange); return; } // Read the response header. responseStatusCode = CkRestW_ReadResponseHeader(rest); if (responseStatusCode < 0) { wprintf(L"%s\n",CkRestW_lastErrorText(rest)); CkRestW_Dispose(rest); CkAuthAwsW_Dispose(authAws); CkFileAccessW_Dispose(fac); CkStringBuilderW_Dispose(sbRange); return; } wprintf(L"Response status code = %d\n",responseStatusCode); // We expect a 200 or 206 response status if the file data is coming. // Otherwise, we'll get a string response body with an error message(or no response body). if ((responseStatusCode == 200) || (responseStatusCode == 206)) { bodyStream = CkStreamW_Create(); // The stream's sink will be a file. // We will append to the file.. CkStreamW_putSinkFile(bodyStream,localFilepath); // Indicate that we wish to append to the output file. // The SinkFileAppend property was added in Chilkat v9.50.83 CkStreamW_putSinkFileAppend(bodyStream,TRUE); // Read the response body to the stream. Given that we've // set the stream's sink to a file, it will stream directly // to the file. success = CkRestW_ReadRespBodyStream(rest,bodyStream,TRUE); if (success != TRUE) { wprintf(L"%s\n",CkRestW_lastErrorText(rest)); CkRestW_Dispose(rest); CkAuthAwsW_Dispose(authAws); CkFileAccessW_Dispose(fac); CkStringBuilderW_Dispose(sbRange); CkStreamW_Dispose(bodyStream); return; } wprintf(L"Successfully downloaded the file.\n"); } else { errResponse = CkRestW_readRespBodyString(rest); if (CkRestW_getLastMethodSuccess(rest) != TRUE) { wprintf(L"%s\n",CkRestW_lastErrorText(rest)); } else { wprintf(L"%s\n",errResponse); } } CkRestW_Dispose(rest); CkAuthAwsW_Dispose(authAws); CkFileAccessW_Dispose(fac); CkStringBuilderW_Dispose(sbRange); CkStreamW_Dispose(bodyStream); } |
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