SIMPLE SAMPLE in VB.NET

Maker PDF-417 2d barcode in VB.NET SIMPLE SAMPLE

CHAPTER 1 SIMPLE SAMPLE
Generate PDF-417 2d Barcode In VB.NET
Using Barcode generator for .NET Control to generate, create PDF 417 image in VS .NET applications.
www.OnBarcode.com
PDF417 Decoder In Visual Basic .NET
Using Barcode decoder for VS .NET Control to read, scan read, scan image in .NET framework applications.
www.OnBarcode.com
The numbers in parentheses represent the Unicode characters o, d, d, and ! and the zero terminator. When you use ILDASM, you can see bytearrays everywhere. A bytearray is a universal, type-neutral form of data representation, and ILDASM uses it whenever it cannot identify the type associated with the data as one of the elementary types, such as int32. On the other hand, you could define the data FormatData as follows: .data FormatData = int64(0x0000000000006425) This would result in the same data segment size and contents. When you specify a type declaring a data segment (for instance, int64), no record concerning this type is entered into metadata or anywhere else. The ILAsm compiler uses the specified type for two purposes only: to identify the size of the data segment being allocated and to identify the byte layout within this segment.
Encoding Matrix 2D Barcode In Visual Basic .NET
Using Barcode maker for .NET framework Control to generate, create 2D Barcode image in .NET framework applications.
www.OnBarcode.com
Encoding Code 128C In Visual Basic .NET
Using Barcode creator for .NET framework Control to generate, create Code 128 Code Set C image in .NET applications.
www.OnBarcode.com
Value Type As Placeholder
Code39 Generation In Visual Basic .NET
Using Barcode encoder for .NET Control to generate, create ANSI/AIM Code 39 image in VS .NET applications.
www.OnBarcode.com
Encode Barcode In Visual Basic .NET
Using Barcode maker for VS .NET Control to generate, create Barcode image in VS .NET applications.
www.OnBarcode.com
This is the value type used as a placeholder: .field public static valuetype CharArray8 Format at FormatData .data FormatData = bytearray(25 64 00 00 00 00 00 00) .class public explicit CharArray8 extends [mscorlib]System.ValueType { .size 8 } .class public explicit CharArray8 extends [mscorlib]System.ValueType { .size 8 } declares a value type that has no members but has an explicitly specified size, 8 bytes. Declaring such a value type is a common way to declare just a piece of memory. In this case, you don t need to declare any members of this value type because you aren t interested in the internal structure of this piece of memory; you simply want to use it as a type of your global field Format to specify the field s size. In a sense, this value type is nothing but a placeholder. Could you use an array of 8 bytes instead and save yourself the declaration of another value type You could if you did not intend to map the field to the data. Because arrays are subject to garbage collection, they are not allowed as types of mapped fields. Using value types as placeholders is popular with managed C/C++ compilers because of the need to store and address numerous ANSI string constants. The Visual C# and Visual Basic .NET compilers, which deal mostly with Unicode strings, are less enthusiastic about this technique because they can directly use the common language runtime string constants, which are stored in metadata in Unicode format.
Encoding Barcode In Visual Basic .NET
Using Barcode printer for .NET framework Control to generate, create Barcode image in .NET framework applications.
www.OnBarcode.com
Making Bookland EAN In VB.NET
Using Barcode maker for .NET framework Control to generate, create ISBN - 10 image in .NET framework applications.
www.OnBarcode.com
Calling Unmanaged Code
PDF417 Reader In VS .NET
Using Barcode scanner for .NET framework Control to read, scan read, scan image in .NET applications.
www.OnBarcode.com
PDF 417 Creation In None
Using Barcode printer for Office Word Control to generate, create PDF 417 image in Microsoft Word applications.
www.OnBarcode.com
This is how the OddOrEven application declares the unmanaged method, which is called from the managed method check: .method public static pinvokeimpl("msvcrt.dll" cdecl) vararg int32 sscanf(string,int8*) cil managed { } The line .method public static pinvokeimpl("msvcrt.dll" cdecl) vararg int32 sscanf(string, int8*) cil managed { } declares an unmanaged method, to be called from managed code. The attribute pinvokeimpl("msvcrt.dll" cdecl) indicates that this is an unmanaged method, called using the mechanism known as platform invocation or P/Invoke.
Encoding Matrix In Visual C#
Using Barcode drawer for .NET Control to generate, create Matrix Barcode image in VS .NET applications.
www.OnBarcode.com
Code 128 Code Set A Generation In .NET
Using Barcode generation for Reporting Service Control to generate, create Code 128C image in Reporting Service applications.
www.OnBarcode.com
CHAPTER 1 SIMPLE SAMPLE
Generating Barcode In Objective-C
Using Barcode encoder for iPhone Control to generate, create Barcode image in iPhone applications.
www.OnBarcode.com
Reading Barcode In Java
Using Barcode recognizer for Java Control to read, scan read, scan image in Java applications.
www.OnBarcode.com
This attribute also indicates that this method resides in the unmanaged DLL Msvcrt.dll and has the calling convention cdecl. This calling convention means the unmanaged method handles the arguments the same way an ANSI C function does. The method takes two mandatory parameters of types string and int8* (the equivalent of C/C++ char*) and returns int32. Being a vararg method, sscanf can take any number of optional parameters of any type, but as you know already, neither the optional parameters nor a sentinel is specified when a vararg method is declared. Platform invocation is the mechanism the common language runtime provides to facilitate the calls from the managed code to unmanaged functions. Behind the scenes, the runtime constructs the so-called stub, or thunk, which allows the addressing of the unmanaged function and conversion of managed argument types to the appropriate unmanaged types and back. This conversion is known as parameter marshaling. What is being declared here is not an actual unmanaged method to be called but a stub generated by the runtime, as it is seen from the managed code, which explains the implementation flags cil managed. Specifying the method signature as int32(string, int8*), you specify the managed side of parameter marshaling. The unmanaged side of the parameter marshaling is defined by the actual signature of the unmanaged method being invoked. The actual signature of the unmanaged function sscanf in C is int sscanf(const char*, const char*, ). So, the first parameter is marshaled from managed type string to unmanaged type char*. Recall that when I declared the class Odd.or.Even, I specified the ansi flag, which means the managed strings by default are marshaled as ANSI C strings, that is, char*. And because the call to sscanf is made from a member method of class Odd.or.Even, you don t need to provide special information about marshaling the managed strings. The second parameter of the sscanf declaration is int8*, which is a direct equivalent of char*; as a result, little marshaling is required. (ILAsm has type char as well, but it indicates a Unicode character rather than ANSI, equivalent to unsigned short in C, so you cannot use this type here.) The optional parameters of the original (unmanaged) sscanf are supposed to be the pointers to items (variables) you want to fill while parsing the buffer string. The number and base types of these pointers are defined according to the format specification string (the second argument of sscanf). In this case, given the format specification string "%d", sscanf will expect a single optional argument of type int*. When I call the managed thunk of sscanf, I provide the optional argument of type int32*, which might require marshaling to a native integer pointer only if you are dealing with a platform other than a 32-bit Intel platform (for example, an AMD or Intel 64-bit platform). The P/Invoke mechanism is very useful because it gives you full access to rich and numerous native libraries and platform APIs. But don t overestimate the ubiquity of P/Invoke. Different platforms tend to have different APIs, so overtaxing P/Invoke can easily limit the portability of your applications. It s better to stick with the .NET Framework class library and take some consolation in the thought that by now you can make a fair guess about what lies at the bottom of this library. Now that I ve finished showing you the source code, find the sample file Simple.il on the Apress Web site, copy it into your working directory, compile it using the console command ilasm simple (assuming you have installed the .NET Framework and the Platform software development kit [SDK]), and try running the resulting Simple.exe.
Encoding Code 128 Code Set A In None
Using Barcode encoder for Online Control to generate, create Code128 image in Online applications.
www.OnBarcode.com
Quick Response Code Maker In .NET Framework
Using Barcode creation for Reporting Service Control to generate, create QR Code JIS X 0510 image in Reporting Service applications.
www.OnBarcode.com
QR Code JIS X 0510 Creator In Java
Using Barcode maker for Java Control to generate, create QR Code ISO/IEC18004 image in Java applications.
www.OnBarcode.com
ANSI/AIM Code 128 Creator In Objective-C
Using Barcode drawer for iPhone Control to generate, create Code 128 image in iPhone applications.
www.OnBarcode.com
Barcode Recognizer In None
Using Barcode recognizer for Software Control to read, scan read, scan image in Software applications.
www.OnBarcode.com
Barcode Recognizer In C#
Using Barcode recognizer for .NET framework Control to read, scan read, scan image in Visual Studio .NET applications.
www.OnBarcode.com
Copyright © OnBarcode.com . All rights reserved.