91 lines
1.5 KiB
C++
91 lines
1.5 KiB
C++
#include <bfc/platform/types.h>
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#ifdef _MSC_VER
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#include <intrin.h>
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static uint32_t __inline clz(uint32_t value)
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{
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DWORD leading_zero = 0;
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if (_BitScanReverse(&leading_zero, value))
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{
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return 31 - leading_zero;
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}
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else
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{
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return 32;
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}
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}
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#endif
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uint8_t vint_get_number_bytes(uint8_t first_byte)
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{
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return (uint8_t)clz((uint32_t)first_byte) - 24;
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}
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static uint8_t masks[] =
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{
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0x7F, // 0111 1111
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0x3F, // 0011 1111
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0x1F, // 0001 1111
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0x0F, // 0000 1111
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0x07, // 0000 0111
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0x03, // 0000 0011
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0x01, // 0000 0001
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0x00, // 0000 0000
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};
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/* call if you already know the len (e.g. from vint_get_number_bytes earlier */
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uint64_t vint_read_ptr_len(uint8_t len, const uint8_t *ptr)
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{
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uint64_t ret = masks[len] & ptr[0];
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while (len--)
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{
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ret <<= 8;
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ret |= *++ptr;
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}
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return ret;
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}
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uint64_t vint_read_ptr(const uint8_t *ptr)
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{
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uint8_t len = vint_get_number_bytes(ptr[0]);
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return vint_read_ptr_len(len, ptr);
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}
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bool vint_unknown_length(uint8_t len, const uint8_t *ptr)
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{
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if (masks[len] != (masks[len] & ptr[0]))
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return false;
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while (len--)
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{
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if (*++ptr == 0xFF)
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return false;
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}
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return true;
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}
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static int64_t vsint_substr[] =
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{
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0x3F,
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0x1FFF,
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0x0FFFFF,
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0x07FFFFFF,
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0x03FFFFFFFF,
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0x01FFFFFFFFFF,
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0x00FFFFFFFFFFFF,
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0x007FFFFFFFFFFFFF,
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};
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int64_t vsint_read_ptr_len(uint8_t len, const uint8_t *ptr)
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{
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uint64_t val = vint_read_ptr_len(len, ptr);
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return val - vsint_substr[len];
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}
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int64_t vsint_read_ptr(const uint8_t *ptr)
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{
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uint8_t len = vint_get_number_bytes(ptr[0]);
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uint64_t val = vint_read_ptr(ptr);
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return val - vsint_substr[len];
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} |