mirror of
https://github.com/CloverHackyColor/CloverBootloader.git
synced 2024-11-27 12:15:19 +01:00
100 lines
3.3 KiB
C++
Executable File
100 lines
3.3 KiB
C++
Executable File
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//#include <posix.h> // use angled, so posix.h will vary depending of the platform
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#include <stdlib.h> // for abort
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#include <stddef.h> // for size_t
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#include <limits.h> // for SIZE_T_MAX
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#include <string.h> // for strlen definition
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#ifdef MAP_TO_EDK_STRLEN
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extern "C" UINTN EFIAPI AsciiStrLen(IN CONST CHAR8 *String);
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#endif
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// Hope that unsigned long long is as big in bits sa a pointer difference.
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#define DOWN_CAST_TO_SIZE_T(a) ( (uintptr_t)(a) > (uintptr_t)(SIZE_T_MAX) ? abort(), 0 : (size_t)(a) )
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/* Return the length of the null-terminated string STR. Scan for
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the null terminator quickly by testing four bytes at a time. */
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size_t clover_strlen(const char *str)
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{
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#ifdef MAP_TO_EDK_STRLEN
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return (size_t)(AsciiStrLen(str));
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#endif
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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; ((uintptr_t) 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 DOWN_CAST_TO_SIZE_T(char_ptr - str);
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}
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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 DOWN_CAST_TO_SIZE_T(cp - str);
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if (cp[1] == 0)
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return DOWN_CAST_TO_SIZE_T(cp - str + 1);
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if (cp[2] == 0)
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return DOWN_CAST_TO_SIZE_T(cp - str + 2);
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if (cp[3] == 0)
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return DOWN_CAST_TO_SIZE_T(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 DOWN_CAST_TO_SIZE_T(cp - str + 4);
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if (cp[5] == 0)
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return DOWN_CAST_TO_SIZE_T(cp - str + 5);
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if (cp[6] == 0)
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return DOWN_CAST_TO_SIZE_T(cp - str + 6);
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if (cp[7] == 0)
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return DOWN_CAST_TO_SIZE_T(cp - str + 7);
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}
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}
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}
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}
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