Luna/libs/libc/src/string.cpp

#include <errno.h>
#include <luna.h>
#include <string.h>

extern "C"
{
    void* memcpy(void* dest, const void* src, size_t n)
    {
        for (size_t i = 0; i < n; ++i) { *((char*)dest + i) = *((const char*)src + i); }
        return dest;
    }

    void* memset(void* dest, int c, size_t n)
    {
        for (size_t i = 0; i < n; ++i) { *((char*)dest + i) = (char)c; }
        return dest;
    }

    size_t strlen(const char* s)
    {
        const char* i = s;
        for (; *i; ++i)
            ;
        return (i - s);
    }

    char* strcpy(char* dest, const char* src)
    {
        memcpy(dest, src, strlen(src) + 1);
        return dest;
    }

    char* strncpy(char* dest, const char* src, size_t n)
    {
        size_t src_len = strlen(src) + 1; // NULL byte
        memcpy(dest, src, src_len > n ? n : src_len);
        return dest;
    }

    char* strcat(char* dest, const char* src)
    {
        size_t dest_len = strlen(dest);
        size_t i;

        for (i = 0; *(src + i); i++) *(char*)(dest + dest_len + i) = *(const char*)(src + i);

        *(char*)(dest + dest_len + i) = '\0';

        return dest;
    }

    char* strncat(char* dest, const char* src, size_t n)
    {
        size_t dest_len = strlen(dest);
        size_t i;

        for (i = 0; i < n && *(src + i); i++) *(char*)(dest + dest_len + i) = *(const char*)(src + i);

        *(char*)(dest + dest_len + i) = '\0';

        return dest;
    }

    char* strchr(const char*, int)
    {
        NOT_IMPLEMENTED("strchr");
    }

    void* memclr(void* start, size_t count)
    {
        // "i" is our counter of how many bytes we've cleared
        size_t i;

        // find out if "m_start" is aligned on a SSE_XMM_SIZE boundary
        if ((size_t)start & (15))
        {
            i = 0;

            // we need to clear byte-by-byte until "m_start" is aligned on an SSE_XMM_SIZE boundary
            // ... and lets make sure we don't copy 'too' many bytes (i < m_count)
            while (((size_t)start + i) & (15) && i < count)
            {
                asm("stosb;" ::"D"((size_t)start + i), "a"(0));
                i++;
            }
        }
        else
        {
            // if "m_start" was aligned, set our count to 0
            i = 0;
        }

        // clear 64-byte chunks of memory (4 16-byte operations)
        for (; i + 64 <= count; i += 64)
        {
            asm volatile(" pxor %%xmm0, %%xmm0;	"     // set XMM0 to 0
                         " movdqa %%xmm0, 0(%0);	" // move 16 bytes from XMM0 to %0 + 0
                         " movdqa %%xmm0, 16(%0);	"
                         " movdqa %%xmm0, 32(%0);	"
                         " movdqa %%xmm0, 48(%0);	" ::"r"((size_t)start + i));
        }

        // copy the remaining bytes (if any)
        asm(" rep stosb; " ::"a"((size_t)(0)), "D"(((size_t)start) + i), "c"(count - i));

        // "i" will contain the total amount of bytes that were actually transfered
        i += count - i;

        // we return "m_start" + the amount of bytes that were transfered
        return (void*)(((size_t)start) + i);
    }

#pragma GCC push_options
#pragma GCC diagnostic ignored "-Wwrite-strings"

    char* strerror(int errnum)
    {
        switch (errnum)
        {
        case EPERM: return "Operation not permitted";
        case EINVAL: return "Invalid argument";
        case ENOMEM: return "Out of memory";
        case ENOSYS: return "Function not implemented";
        default: return 0;
        }
    }

#pragma GCC pop_options
}