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printf-like formatted output for streams More...
#include <cmnPrintf.h>
Public Member Functions | |
| cmnPrintf (const std::string &formatStr) | |
| ~cmnPrintf () | |
| cmnPrintf (const cmnPrintf &other) | |
Friends | |
| class | cmnPrintfParser |
printf-like formatted output for streams
This is the user interface for output formatting with C++ streams after the fashion of printf.
A usage example:
prints the text (followed by a
newline)
Hello 12.3450 World
cmnPrintf can be "streamed" into any object derived from the std::ostream base class. The formatting rules are the same as in the standard C routines printf, sprintf, etc. Note that if a cmnPrintf object is streamed out, the rest of the expression no longer behaves like an ordinary "ostream <<", but the cmnPrintf object takes precedence.
In behavior, the format string is parsed and whenever a '' sequence is encountered, a single object is fetched from the corresponding '<<'. That object is formatted and printed. If there are more inputs in the '<<' sequence than `' sequences in the format string, then only the objects that correspond to '' sequences are printed, and the rest are ignored. For example,
will print:
One (1), two and a half (2.5), text (text-input)
and ignore the input 10.
If there are fewer inputs in the '<<' sequence, then the formatting occurs until the '' sequence that follows the last input object, and stops there. For example,
will print:
One (1), two and a half (2.5), text(
Default formatting is provided for the types double ("%f"), int ("%d") and const char * ("%s"). Other basic types are automatically converted by the compiler to one of these and printed. However, the model can be extended to include more output types. See the documentation of cmnPrintfParser for more information.
Note that special ios manipulators and functions, such as endl, flush, setw, setprecision, etc., have no '' sequence, and therefore CANNOT be used with with cmnPrintf. To print a newline (without flush), one may, for example, include a '
' character in the format stream, as done with the C printf function. To flush, a flush method must be called outside of the cmnPrintf expression.
cmnPrintf is stateless, which means that it does not affect any of the state variables in the output stream, such as width, precision, etc. All the output is done through conversion to character strings.
The allocated space for each output element is defined in cmnPrintfParser::BUFFER_SIZE. If the length of the formatted element is larger than this number, then the output is truncated, and the text '(truncated)' is appended following the first BUFFER_SIZE characters. Unfortunately, there is no standard way to compute the length of a formatted string (snprintf is not portable to Visual Studio), and hence to way for our code to know how much memory to allocate for the result of the formatting.
Implementation-wise, this is a dummy class that just stores a copy of the format string. The real work is done by a cmnPrintfParser object which is returned from operator <<.
The expression
creates a cmnPrintf object, which is streamed into std::cout. The result of the expression is an invisible cmnPrintfParser object, into which all the following elements are streamed. The cmnPrintfParser object parses the format string, formats the streamed objects, and forwards the formatted result to std::cout.
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inline |
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inline |
Destructor. Delete any internally allocated memory
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inline |
Copy constructor. We would like to have this constructor private but gcc-4.0.2 complains if it is private even thought is doesn't use it.
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friend |
1.8.6