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114 lines
2.5 KiB
114 lines
2.5 KiB
3 months ago
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/*
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* UCW Library -- Coding of u64 into variable length bytecode.
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*
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* (c) 2013 Tomas Valla <tom@ucw.cz>
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*
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* This software may be freely distributed and used according to the terms
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* of the GNU Lesser General Public License.
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*/
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#include <ucw/lib.h>
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#include <ucw/varint.h>
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#define PUTB(j,i) p[j] = (byte)((u >> (8*(i))));
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#define PUTB4(b) PUTB(0,b-1) PUTB(1,b-2) PUTB(2,b-3) PUTB(3,b-4)
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uint varint_put_big(byte *p, u64 u)
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{
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ASSERT(u >= VARINT_SHIFT_L4);
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if (u < VARINT_SHIFT_L5) {
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u -= VARINT_SHIFT_L4;
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PUTB4(5)
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p[0] |= 0xf0;
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PUTB(4,0);
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return 5;
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}
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if (u < VARINT_SHIFT_L6) {
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u -= VARINT_SHIFT_L5;
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PUTB4(6)
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PUTB(4,1) PUTB(5,0)
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p[0] |= 0xf8;
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return 6;
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}
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if (u < VARINT_SHIFT_L7) {
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u -= VARINT_SHIFT_L6;
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PUTB4(7)
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p[0] |= 0xfc;
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PUTB(4,2) PUTB(5,1) PUTB(6,0)
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return 7;
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}
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if (u < VARINT_SHIFT_L8) {
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u -= VARINT_SHIFT_L7;
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p[0] = 0xfe;
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PUTB(1,6) PUTB(2,5) PUTB(3,4) PUTB(4,3)
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PUTB(5,2) PUTB(6,1) PUTB(7,0)
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return 8;
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}
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u -= VARINT_SHIFT_L8;
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p[0] = 0xff;
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PUTB(1,7) PUTB(2,6) PUTB(3,5) PUTB(4,4)
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PUTB(5,3) PUTB(6,2) PUTB(7,1) PUTB(8,0)
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return 9;
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}
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const byte *varint_get_big(const byte *p, u64 *r)
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{
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ASSERT((*p & 0xf0) == 0xf0);
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byte h = ~*p;
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if (h & 0x08) {
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*r = (u64)(p[0] & 7)<<32 | (u64)p[1]<<24 | (u64)p[2]<<16 | (u64)p[3]<<8 | (u64)p[4];
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*r += VARINT_SHIFT_L4;
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return p+5;
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}
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if (h & 0x04) {
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*r = (u64)(p[0] & 3)<<40 | (u64)p[1]<<32 | (u64)p[2]<<24 | (u64)p[3]<<16 | (u64)p[4]<<8 | (u64)p[5];
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*r += VARINT_SHIFT_L5;
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return p+6;
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}
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if (h & 0x02) {
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*r = (u64)(p[0] & 1)<<48 | (u64)p[1]<<40 | (u64)p[2]<<32 | (u64)p[3]<<24 | (u64)p[4]<<16 | (u64)p[5]<<8 | (u64)p[6];
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*r += VARINT_SHIFT_L6;
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return p+7;
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}
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if (h & 0x01) {
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*r = (u64)p[1]<<48 | (u64)p[2]<<40 | (u64)p[3]<<32 | (u64)p[4]<<24 | (u64)p[5]<<16 | (u64)p[6]<<8 | (u64)p[7];
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*r += VARINT_SHIFT_L7;
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return p+8;
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}
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*r = ((u64)p[1] << 56) | ((u64)p[2] << 48) | ((u64)p[3] << 40) | ((u64)p[4] << 32) | ((u64)p[5] << 24) | ((u64)p[6] << 16) | ((u64)p[7] << 8) | (u64)p[8];
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*r += VARINT_SHIFT_L8;
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return p+9;
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}
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#ifdef TEST
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#include <string.h>
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#include <stdio.h>
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#include <inttypes.h>
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int main(int argc, char **argv UNUSED)
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{
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byte buf[16] = { 0xaa, 0xaa, 0xaa, 0xaa, 0xaa, 0xaa, 0xaa, 0xaa, 0xaa, 0xaa, 0xaa };
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u64 u;
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if (scanf("%"SCNx64, &u) != 1) {
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fprintf(stderr, "Invalid usage!\n");
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return 1;
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}
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varint_put(buf, u);
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int l = varint_len(buf[0]);
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varint_get(buf, &u);
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printf("%u %d %jx", varint_space(u), l, (uintmax_t) u);
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if (argc > 1) {
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for (int i=0; i<l; i++)
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printf(" %x", buf[i]);
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}
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printf("\n");
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return 0;
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}
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#endif
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