Output Streams and Formating

Overview

fiber::OStream provides a lightweight and flexible output streaming interface, optimized for embedded systems with limited resources. It offers:

• Minimal FLASH memory usage compared to alternatives like std::ostream or {fmt}.
• Formatted output for various types: strings, integers, floating points, booleans, pointers, and chrono durations.
• Extendable and customizable formatting.

Getting Started

Basic example:

fiber::cout << "Hello World!" << fiber::endl;

Predefined default output streams:

• fiber::cout — Standard output
• fiber::cerr — Error output

These must be initialized by the user to point to a concrete OStream implementation. Creating a Custom Output Stream.

class MyCout : public OStream {/*...*/};
class MyCerr : public OStream {/*...*/};
 
MyCout my_cout;
MyCerr my_cerr;
 
int main(){
    fiber::cout = my_cout;
    fiber::cerr = my_cerr;
}

To create your own output stream (e.g., UART, USB), derive from fiber::OStream:

class MyStream : public fiber::OStream {
public:
    void put(char c) final {
        // Output one character
    }
 
    void flush() final {
        // Flush buffer if necessary
    }
 
    void write(const char* str, size_t len) final {
        // (Optional) Optimized multi-character output
    }
};

Mandatory methods to override:

• void put(char c)
• void flush()

Recommended for performance:

• void write(const char* str, size_t len)

Optional:

• void newl() define how to end a line (default: \n)
• void endl() default: newline + flush

Formating and Streaming Capabilities

Stream the following types naturally with operator<<:

• Characters and strings (char, const char*)
• Booleans (bool) — configurable textual/numeric output
• Integers and unsigned integers (all standard sizes + units)
• Floating point numbers (float, double, long double)
• Pointers and nullptr

Example:

fiber::cout << "Answer: " << 42 << fiber::newl;
fiber::cout << "Result: " << true << fiber::endl;
fiber::cout << "Address: " << myPtr << fiber::endl;

Special Stream Functions

You can use the following functions inside streaming expressions:

• fiber::newl(stream): Write newline (\n) - may be overridden by the user by overrideing OStream::newl()
• fiber::flush(stream): Flush the stream
• fiber::endl(stream): Write newline and flush

String Formatting (FormatStr)

Format strings with padding, minimum width, alignment:

fiber::cout << "[" << fiber::FormatStr("OK").mwidth(6).left() << "]" << fiber::endl;
// Output: [OK    ]

All following formating types use and provide the functionalities of fiber::FormatStr.

See also

fiber::FormatStr

Boolean Formatting (FormatBool)

Configure booleans to print as true/false or 1/0:

fiber::cout << FormatBool(true).text() << fiber::endl; // "true"
fiber::cout << FormatBool(false).num() << fiber::endl; // "0"

See also

fiber::FormatBool

Integer Formatting (FormatInt)

Enhanced integer output, with thousands, alignment, and sign padding

fiber::cout << FormatInt(123456).use_thousands().thousands('.') << fiber::endl; // "123.456"
fiber::cout << FormatInt(42).fsign().mwidth(6) << fiber::endl; // "  +42"

See also

fiber::FormatInt

Integer with Suffix (FormatIntSuffix)

Allows to add a suffix to integers that will be aligned with the integer.

fiber::cout << FormatIntSuffix(64, "kB").left().mwidth(6) << fiber::endl; // "64kB  "

See also

FormatIntSuffix

Floating-Point Formatting (FormatFloat)

Flexible floating-point output in scientific, engineering and full formating:

fiber::cout << FormatFloat(3.14f).decimals(2).full() << fiber::endl; // "3.14"
fiber::cout << FormatFloat(12345.6).sci() << fiber::endl; // "1.2356e4"
fiber::cout << FormatFloat(12345.6).eng() << fiber::endl; // "12.356e3"

See also

fiber::FormatFloat

Hexadecimal Formatting (FormatHex)

Custom FormatHex options allows including or excluding the hex header 0x as well as upper/lower case and optional leading zeros or compact notation.

int a;
fiber::cout << FormatHex(&a).upper << fiber::endl; // possible output: 0x21F56D

See also

fiber::FormatHex

Note: Pointers are automatically formatted as hexadecimal.

Chrono Durations

Using format_chrono(duration) you can create an fiber::FormatIntSuffix from std::chrono::duration types with automatically appropriate units (determined at compile time).

See also

fiber::format_chrono

fiber::FormatIntSuffix

Customization with Compiler Flags

You can customize the formatting behavior at compile time by defining multiple compiler macros or CMake options.

For a complete overview of available compile options and their effect on formatting, refer to the page: Compile Options & Flags, specifically section Formatting