Initial commit: Add starter code for Datalab

1 files changed, 140 insertions, 0 deletions

diff --git a/fshow.c b/fshow.c
new file mode 100644
index 0000000..bac7318
--- /dev/null
+++ b/fshow.c
@@ -0,0 +1,140 @@
+/* Display structure of floating-point numbers */
+
+#include <stdio.h>
+#include <stdlib.h>
+float strtof(const char* nptr, char** endptr);
+
+#define FLOAT_SIZE 32
+#define FRAC_SIZE 23
+#define EXP_SIZE 8
+#define BIAS ((1 << (EXP_SIZE - 1)) - 1)
+#define FRAC_MASK ((1 << FRAC_SIZE) - 1)
+#define EXP_MASK ((1 << EXP_SIZE) - 1)
+
+/* Floating point helpers */
+unsigned f2u(float f) {
+    union {
+        unsigned u;
+        float f;
+    } v;
+    v.u = 0;
+    v.f = f;
+    return v.u;
+}
+
+static float u2f(unsigned u) {
+    union {
+        unsigned u;
+        float f;
+    } v;
+    v.u = u;
+    return v.f;
+}
+
+/* Get exponent */
+unsigned get_exp(unsigned uf) {
+    return (uf >> FRAC_SIZE) & EXP_MASK;
+}
+
+/* Get fraction */
+unsigned get_frac(unsigned uf) {
+    return uf & FRAC_MASK;
+}
+
+/* Get sign */
+unsigned get_sign(unsigned uf) {
+    return (uf >> (FLOAT_SIZE - 1)) & 0x1;
+}
+
+void show_float(unsigned uf) {
+    float f = u2f(uf);
+    unsigned exp = get_exp(uf);
+    unsigned frac = get_frac(uf);
+    unsigned sign = get_sign(uf);
+
+    printf("\nFloating point value %.10g\n", f);
+    printf("Bit Representation 0x%.8x, sign = %x, exponent = 0x%.2x, fraction = 0x%.6x\n",
+           uf, sign, exp, frac);
+    if (exp == EXP_MASK) {
+        if (frac == 0) {
+            printf("%cInfinity\n", sign ? '-' : '+');
+        } else
+            printf("Not-A-Number\n");
+    } else {
+        int denorm = (exp == 0);
+        int uexp = denorm ? 1 - BIAS : exp - BIAS;
+        int mantissa = denorm ? frac : frac + (1 << FRAC_SIZE);
+        float fman = (float)mantissa / (float)(1 << FRAC_SIZE);
+        printf("%s.  %c%.10f X 2^(%d)\n",
+               denorm ? "Denormalized" : "Normalized",
+               sign ? '-' : '+',
+               fman, uexp);
+    }
+}
+
+/* Extract hex/decimal/or float value from string */
+static int get_num_val(char* sval, unsigned* valp) {
+    char* endp;
+    /* See if it's an integer or floating point */
+    int ishex = 0;
+    int isfloat = 0;
+    int i;
+    for (i = 0; sval[i]; i++) {
+        switch (sval[i]) {
+            case 'x':
+            case 'X':
+                ishex = 1;
+                break;
+            case 'e':
+            case 'E':
+                if (!ishex)
+                    isfloat = 1;
+                break;
+            case '.':
+                isfloat = 1;
+                break;
+            default:
+                break;
+        }
+    }
+    if (isfloat) {
+        float fval = strtof(sval, &endp);
+        if (!*endp) {
+            *valp = *(unsigned*)&fval;
+            return 1;
+        }
+        return 0;
+    } else {
+        long long int llval = strtoll(sval, &endp, 0);
+        long long int upperbits = llval >> 31;
+        /* will give -1 for negative, 0 or 1 for positive */
+        if (valp && (upperbits == 0 || upperbits == -1 || upperbits == 1)) {
+            *valp = (unsigned)llval;
+            return 1;
+        }
+        return 0;
+    }
+}
+
+void usage(char* fname) {
+    printf("Usage: %s val1 val2 ...\n", fname);
+    printf("Values may be given as hex patterns or as floating point numbers\n");
+    exit(0);
+}
+
+int main(int argc, char* argv[]) {
+    int i;
+    unsigned uf;
+    if (argc < 2)
+        usage(argv[0]);
+    for (i = 1; i < argc; i++) {
+        char* sval = argv[i];
+        if (get_num_val(sval, &uf)) {
+            show_float(uf);
+        } else {
+            printf("Invalid 32-bit number: '%s'\n", sval);
+            usage(argv[0]);
+        }
+    }
+    return 0;
+}