如何使用 Chicken Scheme 读取和写入二进制浮点数？

Question

我正在使用 Chicken 读取二进制数据格式，到目前为止，我已经通过执行类似 (fx+ (fxshl (read-byte) 8) (read-byte)) (Big Endian ）。

如何读取和写入浮点数？我必须能够读取和写入 IEEE 754-2008 32 位和 64 位二进制浮点数。

Answer 1

到目前为止，我还没有找到任何好的库来做到这一点，但我已经将一些可行的东西组合在一起。请注意，我只有 read-byte 和 read-string 可用作输入操作。

  ;;
  ;; These are some unfun C routines to convert 4 int-promoted bytes to a float
  ;; by manually assembling the float using bitwise operators
  ;;
  ;; Caveat! These will only work on platforms in which floats are 32-bit Big
  ;; Endian IEEE754-2008 numbers and doubles are 64-bit Big Endian IEEE754-2008
  ;; numbers! Also, stdint.h.
  ;;
  (define (readFloat)
    (let ([c-read-float
            (foreign-lambda* float
              ((int i1)
               (int i2)
               (int i3)
               (int i4))
               "uint8_t b1 = (uint8_t) i1;
                uint8_t b2 = (uint8_t) i2;
                uint8_t b3 = (uint8_t) i3;
                uint8_t b4 = (uint8_t) i4;

                uint32_t i = 0;

                i = b1;
                i = (i << 8) | b2;
                i = (i << 8) | b3;
                i = (i << 8) | b4;

                float f = *(float*)&i;

                C_return(f);")])
        (let* ([i1 (read-byte)]
               [i2 (read-byte)]
               [i3 (read-byte)]
               [i4 (read-byte)])
          (c-read-float i1 i2 i3 i4))))