InputStream Manual

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关于
用法
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关于

An input stream is used to read data from a resource defined with a maxon::Url . maxon::InputStreamInterface is based on maxon::BaseStreamInterface .

用法

maxon::InputStreamInterface provides these functions:

maxon::InputStreamInterface::BytesAvailable() : Returns an estimate of the number of bytes that can be read.
maxon::InputStreamInterface::Read() : Reads the given number of bytes into the given buffer.
maxon::InputStreamInterface::ReadEOS() : Reads the given number of bytes into the given buffer or reads until the end of the stream.
maxon::InputStreamInterface::Skip() : Skips over the given number of bytes.

// This example reads a text file and loads the data into a maxon::String.

// construct file URL const maxon::Url url = (targetFolder + maxon::Url ( "textfile.txt" _s)) iferr_return ;

// check if file exists if (url.IoDetect() == maxon::IODETECT::FILE ) { // open input stream and get file size const maxon::InputStreamRef inputStream = url.OpenInputStream() iferr_return ; const maxon::Int length = inputStream.GetStreamLength() iferr_return ;

maxon::BaseArray<maxon::Char> data; data. Resize (length) iferr_return ; inputStream.Read(data) iferr_return ;

// convert to string const maxon::String text { data }; DiagnosticOutput ( "File Content: @" , text); }

// This example loads a file from the web and saves it to the local file system.

// check if the given URL references a file on the web const maxon::UrlScheme scheme = webFile.GetScheme(); const maxon::Bool isHTTP = scheme == maxon::URLSCHEME_HTTP ; const maxon::Bool isHTTPS = scheme == maxon::URLSCHEME_HTTPS ;

if (isHTTP || isHTTPS) { // read data

// input stream const maxon::InputStreamRef inputStream = webFile.OpenInputStream() iferr_return ; const maxon::Int length = inputStream.GetStreamLength() iferr_return ; maxon::BaseArray<maxon::Char> data; data. Resize (length) iferr_return ; inputStream.Read(data) iferr_return ; inputStream.Close() iferr_return ;

// save data to file

// prepare file name const maxon::Url localFile = (targetFolder + webFile.GetName()) iferr_return ; // output stream const maxon::OutputStreamRef outputStream = localFile.OpenOutputStream() iferr_return ; // write to file outputStream.Write(data) iferr_return ; outputStream.Close() iferr_return ; }

The input stream maxon::InputStreamInterface::FromBlock can be used to read data from a memory block.

// This example shows how to access data from a memory block using an InputStreamRef. const auto memblock = maxon::CharToBlock ( "Hello World" ); const maxon::InputStreamRef inputStream = maxon::InputStreamInterface::FromBlock().Create(memblock, false ) iferr_return ;

// read into a maxon::String

// prepare memory const maxon::Int length = inputStream.GetStreamLength() iferr_return ; maxon::BaseArray<maxon::Char> data; data. Resize (length) iferr_return ; inputStream.Read(data) iferr_return ;

// convert to string const maxon::String text { data }; DiagnosticOutput ( "Stream Content: @" , text);

延伸阅读

定义： string.h:1197

maxon::BaseArray::Resize

ResultMem Resize(Int newCnt, COLLECTION_RESIZE_FLAGS resizeFlags=COLLECTION_RESIZE_FLAGS::DEFAULT)

定义： basearray.h:1077

bool Bool

boolean type, possible values are only false/true, 8 bit

定义： apibase.h:177

定义： apibaseid.h:250

#define iferr_return

定义： resultbase.h:1434

maxon::URLSCHEME_HTTPS

static const Id URLSCHEME_HTTPS

定义： url.h:663

maxon::BaseArray

定义： basearray.h:366

DiagnosticOutput

#define DiagnosticOutput(formatString,...)

定义： debugdiagnostics.h:166

定义： url.h:819

maxon::URLSCHEME_HTTP

static const Id URLSCHEME_HTTP

定义： url.h:658

Int64 Int

signed 32/64 bit int, size depends on the platform

定义： apibase.h:184

maxon::IODETECT::FILE

@ FILE

Url is a file.

maxon::CharToBlock

Block< const Char > CharToBlock(const Char *str)

定义： block.h:939