bad_apple_os/src/cstdlib/stdio.cpp

#include <stdio.h>

#include <cassert>
#include <cstring>
#include <stdarg.h>
#include "os/tty.hpp"

extern "C"
{
namespace
{
int printInt(int value)
{
    if (value == 0)
    {
        putchar('0');
        return 1;
    }
    if (value < 0)
    {
        putchar('-');
        return printInt(-value) + 1;
    }

    char digits[10]; // 2147483647 has 10 digits
    char* pos = &digits[0];

    while (value > 0)
    {
        *pos = static_cast<char>('0' + (value % 10));
        value /= 10;
        ++pos;
    }
    for (char* chr = pos - 1; chr >= digits; --chr)
    {
        putchar(*chr);
    }
    return pos - digits;
}

int printUInt(uint64_t value)
{
    if (value == 0)
    {
        putchar('0');
        return 1;
    }

    char digits[20]; // 18,446,744,073,709,551,615 has 20 digits
    char* pos = &digits[0];

    while (value > 0)
    {
        *pos = static_cast<char>('0' + (value % 10));
        value /= 10;
        ++pos;
    }
    for (char* chr = pos - 1; chr >= digits; --chr)
    {
        putchar(*chr);
    }
    return pos - digits;
}

int printHexInt(uint64_t value)
{
    if (value == 0)
    {
        putchar('0');
        return 1;
    }

    char digits[16]; // FFFFFFFFFFFFFFFF has 16 digits
    char* pos = &digits[0];

    while (value > 0)
    {
        const uint64_t digit = (value % 16);
        if (digit < 10)
        {
            *pos = static_cast<char>('0' + digit);
        }
        else
        {
            *pos = static_cast<char>('A' + digit - 10);
        }
        value /= 16;
        ++pos;
    }
    for (char* chr = pos - 1; chr >= digits; --chr)
    {
        putchar(*chr);
    }
    return pos - digits;
}

int printPointer(void* ptr)
{
    return printHexInt(reinterpret_cast<uint64_t>(ptr));
}

int printString(const char* str)
{
    const size_t len = std::strlen(str);

    for (size_t idx = 0; idx < len; ++idx)
    {
        putchar(str[idx]);
    }
    return static_cast<int>(len);
}

int printByteSize(size_t bytes)
{
    const char* suffixes[] = {
        "B", "KiB", "MiB", "GiB", "TiB"
    };
    int suffixIdx = 0;
    for (; suffixIdx < sizeof(suffixes) / sizeof(suffixes[0]); ++suffixIdx)
    {
        if (bytes < 1024) {
            break;
        }
        bytes /= 1024;
    }
    return printUInt(bytes) + printString(suffixes[suffixIdx]);
}
}

int putchar(int chr) noexcept
{
    tty::putChar(static_cast<char>(chr));
    return 0;
}

int puts(const char* str) noexcept
{
    tty::write(str);
    tty::putChar('\n');
    return 0;
}

int printf(const char* format, ...) noexcept
{
    va_list parameters;
    va_start(parameters, format);
    const int result = vprintf(format, parameters);
    va_end(parameters);
    return result;
}

int vprintf(const char* format, std::va_list vlist) BA_CXX_NOEXCEPT
{
    int result = 0;
    const char* pos = format;
    while (*pos != '\0')
    {
        if (*pos == '%')
        {
            ++pos;
            switch (*pos)
            {
                case '%':
                    putchar('%');
                    ++result;
                    break;
                case '\0':
                    // TODO: invalid format string, do something
                    assert(!"Invalid format string, ends with %.");
                    return -1;
                case 'b':
                    result += printByteSize(va_arg(vlist, size_t));
                    break;
                case 'c':
                {
                    const char chr = static_cast<char>(va_arg(vlist, int));
                    putchar(chr);
                    ++result;
                    break;
                }
                case 's':
                    result += printString(va_arg(vlist, const char*));
                    break;
                case 'd':
                    result += printInt(va_arg(vlist, int));
                    break;
                case 'p':
                    result += printPointer(va_arg(vlist, void*));
                    break;
                case 'X':
                    result += printHexInt(va_arg(vlist, unsigned));
                    break;
                default:
                    assert(!"Invalid format string, unknown format identifier.");
                    return -1;
            }
        } else
        {
            putchar(*pos);
        }
        ++pos;
    }
    ++result;
    return result;
}
} // extern "C"