Initial community commit

Src/nsmkv/vint.cpp

@@ -0,0 +1,91 @@
+#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];
+}