Add files via upload

Author: garyexplains

decode_ieee754.c

@@ -0,0 +1,203 @@
+// Copyright (C) <2024>, Gary Sims
+// All rights reserved.
+//
+// Redistribution and use in source and binary forms, with or without
+// modification, are permitted provided that the following conditions are met:
+//
+// 1. Redistributions of source code must retain the above copyright notice, this
+//   list of conditions and the following disclaimer.
+// 2. Redistributions in binary form must reproduce the above copyright notice,
+//   this list of conditions and the following disclaimer in the documentation
+//   and/or other materials provided with the distribution.
+//
+// THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS "AS IS" AND
+// ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED
+// WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE
+// DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT OWNER OR CONTRIBUTORS BE LIABLE FOR
+// ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES
+// (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES;
+// LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND
+// ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
+// (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF THIS
+// SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
+//
+
+#include <stdio.h>
+#include <stdint.h>
+#include <string.h>
+
+// ------------------------------
+
+#define FIXED_FACTOR 100000000000000000
+#define FIXED_PLACES 17
+
+void print_fixed_point_r(uint64_t n, int i) {
+    uint64_t num = n;
+    int c;
+
+    c = num % 10;
+    num = num / 10;
+    if((i<FIXED_PLACES) || (num>0))
+        print_fixed_point_r(num, i + 1);
+    if (i == FIXED_PLACES) {
+        if(num==0)
+            printf("0");
+        printf(".");
+    }
+    printf("%c", c + '0');
+}
+
+void print_fixed_point(uint64_t n) {
+    print_fixed_point_r(n, 1);
+}
+
+uint64_t set_fixed_point_int(uint64_t n) {
+    return n * FIXED_FACTOR;
+}
+
+// decimal expansion for positive fixed point rational numbers
+uint64_t fixed_point_dec_expansion(uint64_t dividend, uint64_t divisor) {
+    uint64_t result = 0;
+    if (divisor == 0)
+        return 0;
+
+    uint64_t quotient = dividend / divisor;
+    result = result + quotient;
+    result = result * 10;
+
+    // Start calculating the fractional part
+    uint64_t remainder = dividend % divisor;
+    
+    for (int i = 0; i < FIXED_PLACES-1; i++) {
+        // Multiply the remainder by 10 for the next digit
+        remainder = remainder * 10;
+        int digit = remainder / divisor;
+        result = result + digit;
+        result = result * 10;
+        remainder = remainder % divisor;
+    }
+    return result;
+}
+// ---------------------------------
+
+void print_bin32_fraction_expansion(uint32_t frac) {
+    uint32_t p = frac;
+    uint64_t f = 2;
+
+    printf("1 ");
+    for(int i=0;i<23;i++) {
+            if( (p & 0x400000) != 0) {
+                printf(" + ");
+                print_fixed_point(fixed_point_dec_expansion(1, f));
+            }
+            p = (p << 1);
+            f = f << 1;
+    }
+    printf("\n");
+}
+
+
+uint64_t calc_bin32_fraction_fixed(uint32_t frac) {
+    uint32_t p = frac;
+    uint64_t f = 2;
+    uint64_t fraction = set_fixed_point_int(1);
+
+    for(int i=0;i<23;i++) {
+            if( (p & 0x400000) != 0) {
+                fraction = fraction + fixed_point_dec_expansion(1, f);
+            }
+            p = p << 1;
+            f = f << 1;
+    }
+    return fraction;
+}
+
+uint64_t calc_bin32_expo_fixed(uint32_t e) {
+    int32_t shift = e - 127;
+    uint64_t expo = set_fixed_point_int(1);
+
+    if(shift > 0) {
+        for(int i=0;i<shift;i++) {
+            expo = expo << 1;
+        }
+    } else {
+        int f = 1;
+        for(int i=0;i<shift*-1;i++) {
+            f = f << 1;
+        }
+        expo = fixed_point_dec_expansion(1, f);
+    }
+    return expo;
+}
+
+uint64_t calc_expo_fixed(uint64_t f, int e) {
+
+    if(e > 0) {
+        for(int i=0;i<e;i++) {
+            f = f << 1;
+        }
+    } else {
+        for(int i=0;i<e*-1;i++) {
+            f = f >> 1;
+        }
+    }
+    return f;
+}
+
+void decode_binary32(float f) {
+    uint32_t p;
+    uint32_t sign;
+    uint32_t expo=0;
+    uint32_t fraction=0;
+
+    printf("\n%f decodes to:\nBinary Representation: ", f);
+    memcpy(&p, &f, 4);
+    sign = (p & 0x80000000);
+    printf("%c", (sign == 0) ? '0' : '1');
+    p = (p << 1);
+
+    for(int i=0;i<8;i++) {
+        if( (p & 0x80000000) == 0) {
+            printf("0");
+        } else {
+            printf("1");
+            expo = expo | 0x1;
+        }
+        expo = (expo << 1);
+        p = (p << 1);
+    }
+    expo = (expo >> 1);
+
+   for(int i=0;i<23;i++) {
+        if( (p & 0x80000000) == 0) {
+            printf("0");
+        } else {
+            printf("1");
+            fraction = fraction | 0x1;
+        }
+        fraction = (fraction << 1);
+        p = (p << 1);
+    }
+    fraction = (fraction >> 1);
+
+    printf("\nSign: %c\n", (sign == 0) ? '+' : '-');
+    printf("Expo: %d\n", (int) (expo - 127));
+    printf("Frac: ");
+    print_bin32_fraction_expansion(fraction);
+    printf("Fixed point fraction: ");
+    print_fixed_point(calc_bin32_fraction_fixed(fraction));
+    printf("\n");
+    printf("Fixed point expo: ");
+    print_fixed_point(calc_bin32_expo_fixed(expo));
+    printf("\n");
+    printf("Fixed point reconstructed float is: ");
+    print_fixed_point(calc_expo_fixed(calc_bin32_fraction_fixed(fraction), (int) (expo - 127)));
+    printf("\n");
+}
+
+void main(void) {
+    decode_binary32((float) 0.15625);
+    decode_binary32((float) 0.12);
+    decode_binary32((float) 12.334);
+    decode_binary32((float) 121.009);
+}