看了一下,zipmapDecodeLength的实现还挺巧妙的,直接使用内存操作:
/* Decode the encoded length pointed by 'p' */ static unsigned int zipmapDecodeLength(unsigned char *p) { unsigned int len = *p; if (len < ZIPMAP_BIGLEN) return len; memcpy(&len,p+1,sizeof(unsigned int)); memrev32ifbe(&len); return len; } static unsigned int zipmapGetEncodedLengthSize(unsigned char *p) { return (*p < ZIPMAP_BIGLEN) ? 1: 5; } /* Encode the length 'l' writing it in 'p'. If p is NULL it just returns * the amount of bytes required to encode such a length. */ static unsigned int zipmapEncodeLength(unsigned char *p, unsigned int len) { if (p == NULL) { return ZIPMAP_LEN_BYTES(len); } else { if (len < ZIPMAP_BIGLEN) { p[0] = len; return 1; } else { p[0] = ZIPMAP_BIGLEN; memcpy(p+1,&len,sizeof(len)); memrev32ifbe(p+1); return 1+sizeof(len); } } }