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