ref: 9e09742e9b5789a94b7676ff5f4e01468d2f2d88
dir: /sys/src/liboventi/zero.c/
#include <u.h> #include <libc.h> #include <oventi.h> /* score of a zero length block */ uchar vtZeroScore[VtScoreSize] = { 0xda, 0x39, 0xa3, 0xee, 0x5e, 0x6b, 0x4b, 0x0d, 0x32, 0x55, 0xbf, 0xef, 0x95, 0x60, 0x18, 0x90, 0xaf, 0xd8, 0x07, 0x09 }; int vtZeroExtend(int type, uchar *buf, int n, int nn) { uchar *p, *ep; switch(type) { default: memset(buf+n, 0, nn-n); break; case VtPointerType0: case VtPointerType1: case VtPointerType2: case VtPointerType3: case VtPointerType4: case VtPointerType5: case VtPointerType6: case VtPointerType7: case VtPointerType8: case VtPointerType9: p = buf + (n/VtScoreSize)*VtScoreSize; ep = buf + (nn/VtScoreSize)*VtScoreSize; while(p < ep) { memmove(p, vtZeroScore, VtScoreSize); p += VtScoreSize; } memset(p, 0, buf+nn-p); break; } return 1; } int vtZeroTruncate(int type, uchar *buf, int n) { uchar *p; switch(type) { default: for(p = buf + n; p > buf; p--) { if(p[-1] != 0) break; } return p - buf; case VtRootType: if(n < VtRootSize) return n; return VtRootSize; case VtPointerType0: case VtPointerType1: case VtPointerType2: case VtPointerType3: case VtPointerType4: case VtPointerType5: case VtPointerType6: case VtPointerType7: case VtPointerType8: case VtPointerType9: /* ignore slop at end of block */ p = buf + (n/VtScoreSize)*VtScoreSize; while(p > buf) { if(memcmp(p - VtScoreSize, vtZeroScore, VtScoreSize) != 0) break; p -= VtScoreSize; } return p - buf; } }