如何讀取和寫入Chicken計劃的二進制浮點數？

Question

我正在閱讀使用雞的二進制數據格式，到目前爲止，我已通過執行類似(fx+ (fxshl (read-byte) 8) (read-byte))（Big Endian）的工作來獲取整數。

我該如何讀寫浮動塊？我必須能夠讀寫IEEE 754-2008 32位和64位二進制浮點數。

Answer 1

到目前爲止，我還沒有找到任何好的庫來做到這一點，但我一起黑了一些有效的東西。請注意，我只有read-byte和read-string可供我作爲輸入操作。

;; 
    ;; 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))))