move __string_read into vsscanf source file

apparently this function was intended at some point to be used by
strto* family as well, and thus was put in its own file; however, as
far as I can tell, it's only ever been used by vsscanf. move it to the
same file to reduce the number of source files and external symbols.

src/internal/stdio_impl.h

@@ -60,8 +60,6 @@ hidden size_t __stdout_write(FILE *, const unsigned char *, size_t);
 hidden off_t __stdio_seek(FILE *, off_t, int);
 hidden int __stdio_close(FILE *);
 
-hidden size_t __string_read(FILE *, unsigned char *, size_t);
-
 hidden int __toread(FILE *);
 hidden int __towrite(FILE *);
 

src/stdio/__string_read.c

-#include "stdio_impl.h"
-#include <string.h>
-
-size_t __string_read(FILE *f, unsigned char *buf, size_t len)
-{
-	char *src = f->cookie;
-	size_t k = len+256;
-	char *end = memchr(src, 0, k);
-	if (end) k = end-src;
-	if (k < len) len = k;
-	memcpy(buf, src, len);
-	f->rpos = (void *)(src+len);
-	f->rend = (void *)(src+k);
-	f->cookie = src+k;
-	return len;
-}

src/stdio/vsscanf.c

 #include "stdio_impl.h"
+#include <string.h>
 
-static size_t do_read(FILE *f, unsigned char *buf, size_t len)
+static size_t string_read(FILE *f, unsigned char *buf, size_t len)
 {
-	return __string_read(f, buf, len);
+	char *src = f->cookie;
+	size_t k = len+256;
+	char *end = memchr(src, 0, k);
+	if (end) k = end-src;
+	if (k < len) len = k;
+	memcpy(buf, src, len);
+	f->rpos = (void *)(src+len);
+	f->rend = (void *)(src+k);
+	f->cookie = src+k;
+	return len;
 }
 
 int vsscanf(const char *restrict s, const char *restrict fmt, va_list ap)
 {
 	FILE f = {
 		.buf = (void *)s, .cookie = (void *)s,
-		.read = do_read, .lock = -1
+		.read = string_read, .lock = -1
 	};
 	return vfscanf(&f, fmt, ap);
 }