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#include <stdint.h>
void
encode_varint(uint8_t *data, uint32_t *write, int64_t value, uint32_t left)
{
uint32_t pos = 0;
if (value < 0) {
*write = 0;
return;
}
if (value < 0x80) {
data[pos++] = value & 0xFF;
} else if (value < 0x4000) {
data[pos++] = 0x80 | ((value & 0xFF00 ) >> 8);
data[pos++] = value & 0xFF;
} else if (value < 0x200000) {
data[pos++] = 0xC0 | ((value & 0xFF0000) >> 16);
data[pos++] = ((value & 0xFF00) >> 8) & 0xFF;
data[pos++] = value & 0xFF;
} else if (value < 0x10000000) {
data[pos++] = 0xE0 | ((value ) >> 24);
data[pos++] = (value >> 16) & 0xFF;
data[pos++] = (value >> 8) & 0xFF;
data[pos++] = value & 0xFF;
} else if (value < 0x100000000LL) {
data[pos++] = 0xF0;
data[pos++] = (value >> 24) & 0xFF;
data[pos++] = (value >> 16) & 0xFF;
data[pos++] = (value >> 8) & 0xFF;
data[pos++] = value & 0xFF;
} else {
data[pos++] = 0xF4;
data[pos++] = (value >> 56) & 0xFF;
data[pos++] = (value >> 48) & 0xFF;
data[pos++] = (value >> 40) & 0xFF;
data[pos++] = (value >> 32) & 0xFF;
data[pos++] = (value >> 24) & 0xFF;
data[pos++] = (value >> 16) & 0xFF;
data[pos++] = (value >> 8) & 0xFF;
data[pos++] = value & 0xFF;
}
*write = pos;
}
int64_t
decode_varint(uint8_t *data, uint32_t *read, uint32_t left)
{
int64_t varint = 0;
/* 1 byte with 7 · 8 + 1 leading zeroes */
if ((data[0] & 0x80) == 0x00) {
varint = data[0] & 0x7F;
*read = 1;
/* 2 bytes with 6 · 8 + 2 leading zeroes */
} else if ((data[0] & 0xC0) == 0x80) {
varint = ((data[0] & 0x3F) << 8) | data[1];
*read = 2;
/* 3 bytes with 5 · 8 + 3 leading zeroes */
} else if ((data[0] & 0xE0) == 0xC0) {
varint = (((data[0] & 0x1F) << 16) |
(data[1] << 8) | (data[2]));
*read = 3;
/* 4 bytes with 4 · 8 + 4 leading zeroes */
} else if ((data[0] & 0xF0) == 0xE0) {
varint = (((data[0] & 0x0F) << 24) | (data[1] << 16) |
(data[2] << 8) | (data[3]));
*read = 4;
} else /* if ((data[pos] & 0xF0) == 0xF0) */ {
switch (data[0] & 0xFC) {
/* 32-bit positive number */
case 0xF0:
varint = ((data[1] << 24) | (data[2] << 16) |
(data[3] << 8) | data[4]);
*read = 1 + 4;
break;
/* 64-bit number */
case 0xF4:
varint =
((int64_t)data[1] << 56) | ((int64_t)data[2] << 48) |
((int64_t)data[3] << 40) | ((int64_t)data[4] << 32) |
(data[5] << 24) | (data[6] << 16) |
(data[7] << 8) | (data[8] << 0);
*read = 1 + 8;
break;
/* Negative varint */
case 0xF8:
/* FIXME: handle endless recursion */
varint = -decode_varint(&data[1], read, left - 1);
*read += 1;
break;
/* Negative two bit number */
case 0xFC:
varint = -(int)(data[0] & 0x03);
*read = 1;
break;
}
}
return varint;
}
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