1 files changed, 55 insertions, 0 deletions
diff --git a/libc/src/yscanf.c b/libc/src/yscanf.c
new file mode 100644
index 0000000..3d2a488
--- /dev/null
+++ b/libc/src/yscanf.c
@@ -0,0 +1,55 @@
+#include "stdio.h"
+
+struct opaque_t {
+    union {
+        const char * p;
+        int fd;
+    };
+    uint8_t bsize;
+    char backbuffer[3];
+};
+
+static int str_getc(void * _opaque) {
+    struct opaque_t * opaque = (struct opaque_t *) _opaque;
+    int r;
+
+    if (opaque->bsize)
+        return opaque->backbuffer[--(opaque->bsize)];
+    
+    r = *(opaque->p++);
+    
+    return r ? r : EOF;
+}
+
+static int file_getc(void * _opaque) {
+    struct opaque_t * opaque = (struct opaque_t *) _opaque;
+    uint8_t v;
+
+    if (opaque->bsize)
+        return opaque->backbuffer[--(opaque->bsize)];
+    
+    if (read(opaque->fd, &v, 1) != 1)
+        return EOF;
+    return v;
+}
+
+static void scanf_ungetc(void * _opaque, int c) {
+    struct opaque_t * opaque = (struct opaque_t *) _opaque;
+    
+    if (opaque->bsize < sizeof(opaque->backbuffer))
+        opaque->backbuffer[opaque->bsize++] = c;
+}
+
+int vsscanf(const char * str, const char * format, va_list ap) {
+    struct opaque_t opaque;
+    opaque.p = str;
+    opaque.bsize = 0;
+    return vxscanf(str_getc, scanf_ungetc, &opaque, format, ap);
+}
+
+int vdscanf(int fd, const char * format, va_list ap) {
+    struct opaque_t opaque;
+    opaque.fd = fd;
+    opaque.bsize = 0;
+    return vxscanf(file_getc, scanf_ungetc, &opaque, format, ap);
+}