meta: move photon/libc to root

libc/stdlib/atof.c

@@ -0,0 +1,42 @@
+#include <ctype.h>
+
+double atof(const char *s)
+{
+    double a = 0.0;
+    int e = 0;
+    int c;
+    while ((c = *s++) != '\0' && isdigit(c)) {
+        a = a*10.0 + (c - '0');
+    }
+    if (c == '.') {
+        while ((c = *s++) != '\0' && isdigit(c)) {
+            a = a*10.0 + (c - '0');
+            e = e-1;
+        }
+    }
+    if (c == 'e' || c == 'E') {
+        int sign = 1;
+        int i = 0;
+        c = *s++;
+        if (c == '+')
+            c = *s++;
+        else if (c == '-') {
+            c = *s++;
+            sign = -1;
+        }
+        while (isdigit(c)) {
+            i = i*10 + (c - '0');
+            c = *s++;
+        }
+        e += i*sign;
+    }
+    while (e > 0) {
+        a *= 10.0;
+        e--;
+    }
+    while (e < 0) {
+        a *= 0.1;
+        e++;
+    }
+    return a;
+}