StringPlus

A comprehensive C library implementing string manipulation functions with custom implementations of sprintf and sscanf.

Overview

StringPlus is a feature-rich string processing library written in C11. It provides a complete reimplementation of the standard string.h library functions, along with custom implementations of sprintf and sscanf from stdio.h, plus additional utility functions inspired by C#'s String class.

Features

Standard String Functions

Complete implementation of standard C string manipulation functions:

• Memory operations: memchr, memcmp, memcpy, memset
• String operations: strlen, strchr, strrchr, strcmp, strcpy, strcat, strncat, strncpy, strncmp
• Search functions: strstr, strpbrk, strcspn, strspn, strtok
• Error handling: strerror with platform-specific error messages

Custom Formatted I/O Functions

• sprintf: Full implementation supporting all standard format specifiers

  • Specifiers: c, d, i, f, e, E, g, G, s, u, x, X, o, p, n, %
  • Flags: -, +, (space), #, 0
  • Width and precision modifiers
  • Length modifiers: h, l, L

• sscanf: Complete implementation for parsing formatted input

  • All standard format specifiers
  • Width and length modifiers
  • Suppression flag *

Additional Utility Functions

Inspired by C# String class:

• to_upper: Convert string to uppercase
• to_lower: Convert string to lowercase
• insert: Insert substring at specified position
• trim: Remove leading and trailing characters

Technical Details

• Language: C11 standard
• Compiler: GCC
• Code Style: Google C++ Style Guide adapted for C
• Testing: Unit tests with Check library
• Test Coverage: 80%+ for all functions
• Platform Support: Cross-platform (Linux, macOS)

Building

# Build the library
make

# Run tests
make test

# Generate coverage report
make gcov_report

# Clean build artifacts
make clean

Project Structure

StringPlus/
├── .gitignore
├── LICENSE
├── README.md
└── src/
    ├── Makefile
    ├── string_plus.h               # Main header file
    ├── plus_sprintf.h              # sprintf header
    │
    ├── plus_memchr.c               # Memory functions
    ├── plus_memcmp.c
    ├── plus_memcpy.c
    ├── plus_memset.c
    │
    ├── plus_strlen.c               # String functions
    ├── plus_strchr.c
    ├── plus_strrchr.c
    ├── plus_strcmp.c
    ├── plus_strncmp.c
    ├── plus_strcpy.c
    ├── plus_strncpy.c
    ├── plus_strcat.c
    ├── plus_strncat.c
    ├── plus_strcspn.c
    ├── plus_strspn.c
    ├── plus_strpbrk.c
    ├── plus_strstr.c
    ├── plus_strtok.c
    ├── plus_strerror.c
    │
    ├── plus_sprintf.c              # Formatted output
    ├── plus_sscanf.c               # Formatted input
    │
    ├── plus_to_upper.c             # Utility functions
    ├── plus_to_lower.c
    ├── plus_insert.c
    ├── plus_trim.c
    │
    ├── plus_assign_char_value.c    # sscanf helpers
    ├── plus_assign_float_value.c
    ├── plus_assign_integer_value.c
    ├── plus_assign_pointer_value.c
    ├── plus_assign_string_value.c
    ├── plus_char_to_digit.c
    ├── plus_handle_literal_match.c
    ├── plus_parse_exponent.c
    ├── plus_parse_float.c
    ├── plus_parse_format_spec.c
    ├── plus_parse_fraction_part.c
    ├── plus_parse_integer.c
    ├── plus_parse_integer_part.c
    ├── plus_parse_sign.c
    ├── plus_process_percent.c
    ├── plus_process_specifier.c
    ├── plus_scan_char.c
    ├── plus_scan_float.c
    ├── plus_scan_integer.c
    ├── plus_scan_pointer.c
    ├── plus_scan_string.c
    ├── plus_skip_whitespace.c
    │
    ├── test_string_plus.c          # Unit tests
    └── utils.c                     # Utility functions

Implementation Highlights

Memory Safety

All functions implement proper bounds checking and handle edge cases to prevent buffer overflows and undefined behavior.

Platform Compatibility

Error message handling (strerror) includes platform-specific implementations for both macOS and Linux systems.

Formatted Output Precision

The sprintf implementation matches the standard library's output precision (up to 1e-6 for floating-point numbers).

Comprehensive Testing

Unit tests compare implementation results against the standard library to ensure correctness and compatibility.

Skills Demonstrated

• Low-level C programming: Direct memory manipulation, pointer arithmetic
• Standard library implementation: Deep understanding of C standard library internals
• Parsing and formatting: Complex format string parsing and number formatting algorithms
• Cross-platform development: Platform-specific code with preprocessor directives
• Testing and quality assurance: Comprehensive unit testing with high code coverage
• Software engineering practices: Clean code, modular design, documentation

Usage Example

#include "string_plus.h"

int main() {
    // Using standard string functions with plus_ prefix
    char str[100] = "Hello, ";
    plus_strncat(str, "World!", 10);
    printf("Length: %zu\n", plus_strlen(str));

    // Using sprintf implementation
    char buffer[100];
    plus_sprintf(buffer, "Number: %d, Float: %.2f", 42, 3.14);

    // Using sscanf implementation
    int num;
    float flt;
    plus_sscanf("42 3.14", "%d %f", &num, &flt);

    // Using utility functions
    char *upper = plus_to_upper("hello");
    char *trimmed = plus_trim("  spaces  ", " ");

    free(upper);
    free(trimmed);

    return 0;
}

API Reference

All functions use the plus_ prefix to avoid naming conflicts with standard library functions.

String Functions

• plus_size_t plus_strlen(const char *str) - Calculate string length
• char *plus_strchr(const char *str, int c) - Find first occurrence of character
• char *plus_strstr(const char *haystack, const char *needle) - Find substring
• char *plus_strncpy(char *dest, const char *src, plus_size_t n) - Copy string
• And many more...

Memory Functions

• void *plus_memchr(const void *str, int c, plus_size_t n) - Find byte in memory
• int plus_memcmp(const void *str1, const void *str2, plus_size_t n) - Compare memory blocks
• void *plus_memcpy(void *dest, const void *src, plus_size_t n) - Copy memory
• void *plus_memset(void *str, int c, plus_size_t n) - Fill memory with byte

Formatted I/O

• int plus_sprintf(char *str, const char *format, ...) - Format string output
• int plus_sscanf(const char *str, const char *format, ...) - Parse formatted input

Utility Functions

• void *plus_to_upper(const char *str) - Convert to uppercase (allocates new string)
• void *plus_to_lower(const char *str) - Convert to lowercase (allocates new string)
• void *plus_insert(const char *src, const char *str, plus_size_t start_index) - Insert substring
• void *plus_trim(const char *src, const char *trim_chars) - Trim characters

Testing

The project includes comprehensive unit tests covering:

• Boundary conditions and edge cases
• Comparison with standard library behavior
• Memory safety and error handling
• Format string parsing accuracy
• Cross-platform compatibility

Run tests with:

cd src
make test

Generate coverage report:

cd src
make gcov_report

Contributing

This is a personal portfolio project demonstrating C programming skills. However, if you find bugs or have suggestions, feel free to open an issue.

License

MIT License - see LICENSE file for details.