Initial Upload

printf.c

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+#include "types.h"
+#include "stat.h"
+#include "user.h"
+
+static void putc(int fd, char c) {
+    write(fd, &c, 1);
+}
+
+static void printint(int fd, int xx, int base, int sgn) {
+    static char digits[] = "0123456789ABCDEF";
+    char buf[16];
+    int i, neg;
+    uint x;
+
+    neg = 0;
+    if (sgn && xx < 0) {
+        neg = 1;
+        x = -xx;
+    }
+    else {
+        x = xx;
+    }
+
+    i = 0;
+    do {
+        buf[i++] = digits[x % base];
+    }
+    while ((x /= base) != 0);
+    if (neg) {
+        buf[i++] = '-';
+    }
+
+    while (--i >= 0) {
+        putc(fd, buf[i]);
+    }
+}
+
+// Print to the given fd. Only understands %d, %x, %p, %s.
+void printf(int fd, const char *fmt, ...) {
+    char *s;
+    int c, i, state;
+    uint *ap;
+
+    state = 0;
+    ap = (uint*)(void*)&fmt + 1;
+    for (i = 0; fmt[i]; i++) {
+        c = fmt[i] & 0xff;
+        if (state == 0) {
+            if (c == '%') {
+                state = '%';
+            }
+            else {
+                putc(fd, c);
+            }
+        }
+        else if (state == '%') {
+            if (c == 'd') {
+                printint(fd, *ap, 10, 1);
+                ap++;
+            }
+            else if (c == 'x' || c == 'p') {
+                printint(fd, *ap, 16, 0);
+                ap++;
+            }
+            else if (c == 's') {
+                s = (char*)*ap;
+                ap++;
+                if (s == 0) {
+                    s = "(null)";
+                }
+                while (*s != 0) {
+                    putc(fd, *s);
+                    s++;
+                }
+            }
+            else if (c == 'c') {
+                putc(fd, *ap);
+                ap++;
+            }
+            else if (c == '%') {
+                putc(fd, c);
+            }
+            else {
+                // Unknown % sequence.  Print it to draw attention.
+                putc(fd, '%');
+                putc(fd, c);
+            }
+            state = 0;
+        }
+    }
+}