BufIterFromBuf

        BufWriteU64LE(&b, 0xFEEDFACECAFEBEEFull);
    
        BufIter it = BufIterFromBuf(&b);
        u16     v16;
        u32     v32;

        BufWriteSLeb128(&b, -123456);
    
        BufIter it = BufIterFromBuf(&b);
        u64     uv;
        i64     sv;

        BufWriteCstr(&b, "world");
    
        BufIter     it = BufIterFromBuf(&b);
        const char *s1 = BufReadCstr(&it);
        const char *s2 = BufReadCstr(&it);

        BufAppendFmt(&b, "{<2r}{>4r}{<8r}", (u16)0x1234, (u32)0xDEADBEEF, (u64)0x0102030405060708ull);
    
        BufIter it = BufIterFromBuf(&b);
        u16     v16;
        u32     v32;

        BufAppendFmt(&b, "{<2r}", (u16)0xABCD); // only 2 bytes; reader wants 6
    
        BufIter it    = BufIterFromBuf(&b);
        size    entry = it.pos;
        u16     v16   = 0;