libc: Wrap low level glibc io calls for stdio

This is much less work and actually works better.

1 files changed, 42 insertions, 0 deletions

diff --git a/src/libc-stdio.c b/src/libc-stdio.c
new file mode 100644
index 0000000..713497b
--- /dev/null
+++ b/src/libc-stdio.c
@@ -0,0 +1,42 @@
+#include <stdio.h>
+
+struct bionic___sFILE {
+#if defined(__LP64__)
+   char __private[152];
+#else
+   char __private[84];
+#endif
+} __attribute__((aligned(sizeof(void*))));
+
+// Bionic standard stream support pre-M Android
+// Post-M it's saner and they point to stdin/stdout/stderr symbols instead
+const struct bionic___sFILE bionic___sF[3] = {
+   {{ 's', 't', 'd', 'i', 'n' }},
+   {{ 's', 't', 'd', 'o', 'u', 't' }},
+   {{ 's', 't', 'd', 'e', 'r', 'r' }}
+};
+
+static inline FILE*
+bionic_file_to_glibc_file(FILE *f)
+{
+   if (f == (void*)&bionic___sF[0])
+      return stdin;
+   else if (f == (void*)&bionic___sF[1])
+      return stdout;
+   else if (f == (void*)&bionic___sF[2])
+      return stderr;
+   return f;
+}
+
+// Wrapping internal glibc VTABLE functions to handle bionic's pre-M crap
+// We define __real_IO_file_xsputn in libc.c so linker will link our library,
+// it's not used however for anything.
+
+extern size_t
+__real_IO_file_xsputn(FILE *f, const void *buf, size_t n);
+
+size_t
+__wrap_IO_file_xsputn(FILE *f, const void *buf, size_t n)
+{
+   return __real_IO_file_xsputn(bionic_file_to_glibc_file(f), buf, n);
+}