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109 lines
3.4 KiB
109 lines
3.4 KiB
#include "crt.h"
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int strcmp(const char* p1, const char* p2)
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{
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const unsigned char* s1 = (const unsigned char*)p1;
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const unsigned char* s2 = (const unsigned char*)p2;
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unsigned char c1, c2;
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do
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{
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c1 = (unsigned char)*s1++;
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c2 = (unsigned char)*s2++;
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if (c1 == '\0')
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return c1 - c2;
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} while (c1 == c2);
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return c1 - c2;
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}
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size_t strlen(const char* str)
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{
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const char* char_ptr;
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const unsigned long int* longword_ptr;
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unsigned long int longword, himagic, lomagic;
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/* Handle the first few characters by reading one character at a time.
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Do this until CHAR_PTR is aligned on a longword boundary. */
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for (char_ptr = str; ((unsigned long int) char_ptr
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& (sizeof(longword) - 1)) != 0;
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++char_ptr)
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if (*char_ptr == '\0')
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return char_ptr - str;
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/* All these elucidatory comments refer to 4-byte longwords,
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but the theory applies equally well to 8-byte longwords. */
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longword_ptr = (unsigned long int*) char_ptr;
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/* Bits 31, 24, 16, and 8 of this number are zero. Call these bits
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the "holes." Note that there is a hole just to the left of
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each byte, with an extra at the end:
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bits: 01111110 11111110 11111110 11111111
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bytes: AAAAAAAA BBBBBBBB CCCCCCCC DDDDDDDD
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The 1-bits make sure that carries propagate to the next 0-bit.
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The 0-bits provide holes for carries to fall into. */
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himagic = 0x80808080L;
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lomagic = 0x01010101L;
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if (sizeof(longword) > 4)
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{
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/* 64-bit version of the magic. */
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/* Do the shift in two steps to avoid a warning if long has 32 bits. */
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himagic = ((himagic << 16) << 16) | himagic;
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lomagic = ((lomagic << 16) << 16) | lomagic;
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}
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if (sizeof(longword) > 8)
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abort();
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/* Instead of the traditional loop which tests each character,
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we will test a longword at a time. The tricky part is testing
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if *any of the four* bytes in the longword in question are zero. */
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for (;;)
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{
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longword = *longword_ptr++;
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if (((longword - lomagic) & ~longword & himagic) != 0)
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{
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/* Which of the bytes was the zero? If none of them were, it was
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a misfire; continue the search. */
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const char* cp = (const char*)(longword_ptr - 1);
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if (cp[0] == 0)
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return cp - str;
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if (cp[1] == 0)
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return cp - str + 1;
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if (cp[2] == 0)
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return cp - str + 2;
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if (cp[3] == 0)
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return cp - str + 3;
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if (sizeof(longword) > 4)
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{
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if (cp[4] == 0)
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return cp - str + 4;
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if (cp[5] == 0)
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return cp - str + 5;
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if (cp[6] == 0)
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return cp - str + 6;
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if (cp[7] == 0)
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return cp - str + 7;
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}
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}
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}
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}
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void* operator new(std::size_t size)
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{
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return VirtualAlloc(NULL, size, MEM_COMMIT | MEM_RESERVE, PAGE_READWRITE);
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}
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void operator delete(void* addr, std::size_t size)
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{
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VirtualFree(addr, size, NULL);
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}
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size_t wcslen(const wchar_t* s)
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{
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size_t len = 0;
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while (s[len] != L'\0')
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{
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if (s[++len] == L'\0')
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return len;
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if (s[++len] == L'\0')
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return len;
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if (s[++len] == L'\0')
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return len;
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++len;
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}
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return len;
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} |