picoprintf is a minimal, customizable implementation of sprintf, snprintf, and vsnprintf for embedded platforms.

• Tiny footprint: <1 kB in minimal configuration on most platforms
• No dynamic memory allocation
• Highly customizable via compile-time macros
• Designed for resource-constrained and embedded systems

• %c (char)
• %s (string)
• %d, %i, %u (decimal integers, signed/unsigned). Fill (e.g., %6d or %03i) and forced signs (e.g., %+i) can be enabled at build time by defining PICOFORMAT_HANDLE_FILL and PICOFORMAT_HANDLE_FORCEDSIGN, respectively
• %b (binary) -- can be enabled at build time by defining PICOFORMAT_HANDLE_BIN
• %o (octal) -- can be enabled at build time by defining PICOFORMAT_HANDLE_OCT
• %x/%X (hexadecimal) -- can be enabled at build time by defining PICOFORMAT_HANDLE_HEX
• %p (pointer) -- included with PICOFORMAT_HANDLE_HEX
• %f/%F/%e/%a (floating-point) -- can be enabled at build time by defining PICOFORMAT_HANDLE_FLOATS

1. Copy files: add picoprintf.h, picobool.h, and picoprintf.c to your project
2. Include header: add #include "picoprintf.h" in your source files
3. Configure (optional): adjust the #defines in picoprintf.h to enable or disable features as needed
4. Replace standard functions (optional): use #define snprintf pico_snprintf before including standard headers to override the standard function
5. Build: compile and link as usual

#include "picoprintf.h"

char buf[64];
pico_snprintf(buf, sizeof(buf), "Value: %d", 42);
// buf now contains "Value: 42"

// Enable features in picoprintf.h:
// #define PICOFORMAT_HANDLE_HEX
// #define PICOFORMAT_HANDLE_FILL
// #define PICOFORMAT_HANDLE_FORCEDSIGN

#include "picoprintf.h"

char buf[128];

// Hexadecimal with padding
pico_snprintf(buf, sizeof(buf), "Address: 0x%08X", 0xDEADBEEF);
// buf: "Address: 0xDEADBEEF"

// Decimal with forced sign and padding
pico_snprintf(buf, sizeof(buf), "Temperature: %+6d°C", 23);
// buf: "Temperature:    +23°C"

// Multiple format specifiers
pico_snprintf(buf, sizeof(buf), "User: %s, ID: %04d", "Alice", 42);
// buf: "User: Alice, ID: 0042"

#define snprintf pico_snprintf
#define sprintf  pico_sprintf

// Now `snprintf()` uses picoprintf instead of the standard library
snprintf(buf, sizeof(buf), "Using picoprintf: %d", 123);

Control the code size and feature set by commenting and uncommenting macros in picoprintf.h. Available configuration macros:

Configuration example:

// picoprintf.h - uncomment features you need
#define PICOFORMAT_HANDLE_FILL          // Enable width/padding
#define PICOFORMAT_HANDLE_HEX           // Enable hexadecimal
// #define PICOFORMAT_HANDLE_FLOATS     // Disable floats to save space

picoprintf is compile-time customizable, allowing you to minimize its footprint. The table below compares the code size (in bytes) of this and similar libraries, as measured by .text + .rodata segments in the .map file.

Notes:

• "min": minimal config (chars, strings, ints only)
• "full": all optional features enabled
• all values collected with -Os flag; actual results depend on toolchain version and configuration

Copy the header and C file into your embedded project, build, and inspect the .map file for code size.

To build for native CPU:

clang picoprintf.c picoatox.c picotest.c -Os -Wl,-map,pico.map

Calculate size:

cat pico.map | grep 1\] | grep -o -E '\t0x[0-9A-F]*' | sed 's/\t0x[^0-9A-F]*//' | awk '{ printf "%d\n", "0x" $1 }' | awk '{s+=$1} END {print s}'

gcc picoprintf.c picoatox.c picotest.c -lm -Os -Wl,-Map,pico.map

Calculate size:

cat pico.map | grep pico_v -B 1 | grep -o -E '0x[0-9a-fA-F]{2,4} ' | sed 's/0x[^0-9a-fA-F]*//' | awk '{ printf "%d\n", "0x" $1}' | awk '{s+=$1} END {print s}'

# Compile and run all tests
gcc picoprintf.c picoatox.c picotest.c -lm -DPICOFORMAT_HANDLE_FLOATS -DPICOFORMAT_HANDLE_HEX -o picotest
./picotest

# Test with verbose output
./picotest -v

• all format specifiers (%c, %s, %d, %x, %f, etc.)
• edge cases (negative infinity, NaN, buffer boundaries)
• comparison with standard library snprintf()
• platform-specific behavior verification

int pico_snprintf(char *output_buffer, size_t size, const char *format, ...);
int pico_vsnprintf(char *output_buffer, size_t size, const char *format, va_list args);
int pico_sprintf(char *output_buffer, const char *format, ...);  // risk of buffer overflow, do not use!

Returns the number of characters written (excluding null terminator), or negative on error.

• always use pico_snprintf() instead of pico_sprintf() to prevent buffer overflows
• check return value to verify the string is written in full
• this library does not allocate memory dynamically

Contributions, bug reports, and feature requests are welcome! Please open an issue or submit a pull request.

This project is licensed under the MIT License. See LICENSE for details.