nuttx/libs/libc/stdio

lib_libbsprintf

This function is mainly used to output the contents of the input structure. Most standards follow the standards of printf and scanf. For detailed parameters, see:

1. https://en.cppreference.com/w/c/io/fprintf
2. https://en.cppreference.com/w/c/io/fscanf

• special:
  1. Float use %hf, and double for all others.
  2. The char array is specified with %.xs. for example: "char t[30]" is specified with "%.30s", char a [20] - " %.20s "
  3. "%u" is unsigned int.
  4. "%d" is int.
  5. When using %f to format a double data type, the double is truncated to 6 decimal places by default.
  6. It is recommended that the "char[]" array be placed at the end of the structure to prevent parameter configuration errors such as "%.20s" from causing problems in parsing the entire buffer.
• demo
  1. struct:

  begin_packed_struct
  struct test
  {
    uint8_t a;
    uint16_t b;
    uint32_t c;
    int8_t d;
    int16_t e;
    int32_t f;
    float g;
    double h;
    char i[32];
    uint64_t j;
    int64_t k;
    char l;
    unsigned char m;
    short int n;
    unsigned short int o;
    int p;
    unsigned int q;
    long r;
    unsigned long s;
    long long t;
    unsigned long long u;
    size_t v;
    long double w;
  }end_packed_struct;
  

  1. format string:

  const char* sg = "           uint8_t:[%hhu]\n" \
                   "          uint16_t:[%hu]\n" \
                   "          uint32_t:[%u]\n" \
                   "            int8_t:[%hhd]\n" \
                   "           int16_t:[%hd]\n" \
                   "           int32_t:[%d]\n" \
                   "             float:[%hf]\n" \
                   "            double:[%f]\n" \
                   "            char[]:[%.32s]\n" \
                   "          uint64_t:[%lu]\n" \
                   "           int64_t:[%ld]\n" \
                   "              char:[%hhd]\n" \
                   "     unsigned char:[%hhu]\n" \
                   "         short int:[%hd]\n" \
                   "unsigned short int:[%hu]\n" \
                   "               int:[%d]\n" \
                   "      unsigned int:[%u]\n" \
                   "              long:[%ld]\n" \
                   "     unsigned long:[%lu]\n" \
                   "         long long:[%lld]\n" \
                   "unsigned long long:[%llu]\n" \
                   "            size_t:[%uz]\n" \
                   "       long double:[%Lf]\n";
  

  1. use:
  • output to terminal:

  #ifdef CONFIG_FILE_STREAM
   struct lib_stdoutstream_s stdoutstream;
  
   lib_stdoutstream(&stdoutstream, stdout);
  
   flockfile(stdout);
   lib_bsprintf(&stdoutstream.common, sv, &test_v);
   lib_bsprintf(&stdoutstream.common, sg, &test_g);
   funlockfile(stdout);
  #else
   struct lib_rawoutstream_s rawoutstream;
   struct lib_bufferedoutstream_s outstream;
  
   lib_rawoutstream(&rawoutstream, STDOUT_FILENO);
   lib_bufferedoutstream(&outstream, &rawoutstream.common);
  
   lib_bsprintf(&outstream.common, sv, &test_v);
   lib_bsprintf(&outstream.common, sg, &test_g);
  
   lib_stream_flush(&outstream.common);
  #endif